Engineering', Research _--_ Development _ and Technology _ Thrust Area ___ R ep ort FY92 Manuscript Date March 1993 Distribution Category UC-706 Lawrence Livermore National Laborato_t UCRL 53868-92 Dli :, Conhm_ Introduction Roger W. Werne, Associate Director for Engineering and Technology Transfer 1. Computational Electronics and Electromagnetics Overview _, John F. DeFord, Thrust Area Leader Parallel Computers and Three-Dimensional Electromagnetics Computational Niel K. Madsen .......................................................................................................................... 1.1 Computational Integrated Photonics Raymond J. Hawkins, Jeffery S. Kallman, and Richard W. Ziolkowski ......................................... t.7 Analysis of High-Average-Power, Millimeter-Wave Microwave Components and Induction Linear Accelerator Modules Clifford C. Shang, John F. DeFord, and Malcolm Caplan .......................................................... Electromagnetic Modeling and Experiments for Dispersive t.13 Media Scott D. Nelson and Carlos A. Avalle ....................................................................................... 1.21 Band Gap Engineering for Infrared Detectors J. Brian Grant ........................................................................................................................... 2. 1.2s Computational Mechanics Overview Gerald L. Goudreau, Thrust Area Leader Solution Strategies: New Approaches for Strongly Nonlinear Quasistatic Problems Using DYNA3D Robert G. Whirley and Bruce E. Engelmann ............................................................................... 2.1 Enhanced Enforcement of Mechanical Contact: The Method of Augmented Lagrangians Bradley N. Maker and Tod A. Laursen ........................................................................................ 2.7 ParaDyn: New Generation Solid/Structural Mechanics Codes for Massively Parallel Processors Carol G. Hoover, Anthony J. De Groot, James D. Maltby, and Robert G. Whirley ..................... 2.21 II Thrust Area Report FY92 4, Engineering Research Development and Technology Contents Composite Damage Modeling EdwardZywicz ........................................................................................................................2.1s HYDRA: A Flow Solver for Three-Dimensional, Transient, Incompressible Viscous Fluid Mark A. Christon ..................................................................................................................... 2-19 Development and Testing of the TRIM3D Radiation Heat Transfer Code JamesD. Maltby ....................................................................................................................... 2.23 A Methodology for Calculating the Seismic Response of Critical Structures David B. McCallen,FrancoisE.Heuze, LawrenceJ. Hutchings, and Stephen P. Jarpe............................................................................2.27 Reinforced Concrete Damage Modeling SanjayGovindjeeand GregoryJ.Kay .......................................................................................2.u 3. Diagnostics and Microelectronics Overview JosephW. Balch,Thrust Area Leader Novel Photonic Detectors RaymondP. Mariella,Jr.,GregoryA. Cooper,Sol P. Dijaili, RobertChow, and Z. Liliental-Weber.......................................................................................... 3.1 Wideband Phase Modulator CharlesF. McConaghy, Sol P. Dijaili,and JeffreyD. Morse ........................................................ Optoelectronic Terahertz Beam System: Enabling Technologies JeffreyD. Morse.......................................................................................................................... 3.9 Fabrication of Microelectrode Electrochemical Sensors Dino R. Ciarlo,JacksonC. Koo,ConradM. Yu, and RobertS. Glass......................................... 3.13 Diamond Heatsinks DinoR. Ciarlo,fick H. Yee, Gizzing H. Khanaka,and Erik Randich.......................................... 3.1s Advanced Micromachining Technologies Wing C. Hui ............................................................................................................................. 3.19 Electrophoresis Using Silicon Microchannels JacksonC. Koo,J. Courtney Davidson,and JosephW. Balch...................................................... 3.21 Engineering Research Development and Technology 4. Thrust Area Report FY92 iil Contents 4. Emerging Technologies Overview Shin-yee Lu, Thrust Area Leader Tire, Accident, Handling, and Roadway Safety Roger W. Logan .......................................................................................................................... 4.1 EXTRANSYT: An Expert System for Advanced Traffic Management Rowland R. Johnson ................................................................................................................... Odin: A High Power, Underwater, Surveillance Applications Acoustic Transmitter 4.9 for Terry R. Donich, Scott W. McAllister, and Charh,s S. Landram ................................................ 4.13 Passive Seismic Reservoir Monitoring: Signal Processing Innovations David B. Harris, Robert J. Sherwood, Stephen P. Jarpe, and Davht C. DeMartini ................................................................................................................. 4.17 Paste Extrudable Explosive Aft Charge for Multi-stage Munitions Douglas R. Faux and Russell W. Rosinsky ................................................................................ 4.21 A Continuum Model for Reinforced Concrete at High Pressures and Strain Rates Kurt H. Sinz ............................................................................................................................. Benchmarking of the Criticality Evaluation Code COG William R. Lloyd, John S. Pearson, and H. Peter Ah'sso ............................................................ Fast Algorithm 4.23 4.27 for Large-Scale Consensus DNA Sequence Assembly Shin-yee Lu, Elbert W. Branscomb, Michael E. Colvin, and Richard S. ]udson ..................................................................................................................... 4.29 Using Electrical Heating To Enhance the Extraction of Volatile Organic Compounds from Soil H. Michael Buettner and William D. Daily ............................................................................... Iv Thrust Area Report FY92 _ Engineering Research Development and Technology 4.31 Contents 5. Fabrication Technology Overview Kenneth L. Blaedel, Thrust Area Leader Fabrication of Amorphous Diamond Coatings Steven FaIabella,David M. Sanders, and David B. Boercker........................................................ s.1 Laser-Assisted Self-Sputtering Peter J. Biltoft, Steven Falabella,Steven R. B_an, Jr., Ralph F. Pombo, and Barnd L. Olsen ........................................................................................... Simulation of Diamond Turning of Copper and Silicon Surfaces David B. Boercker, James Belak, and Irving F. Stowers ................................................................ 6. Materials S.7 Science and Engineering Overview Donald R. Lesuer, Thrust Area Leader Processing and Characterization of Laminated Metal Composites Chol K. Syn, Donald R. Lesuer, and O.D. Sherby ....................................................................... e.1 Casting Process Modeling Arthur B. Shapiro ....................................................................................................................... Characterizing _7 the Failure of Composite Materials Scott E. Groves, Roberto J. Sanchez, William W. Feng, Albert E. Brown, Steven J. DeTeresa, and Richard E. Lyon ....................................................... s.ll Fiber-Optic Raman Spectroscopy for Cure Monitoring of Advanced Polymer Composites Richard E. Lyon, Thomas M. Vess, S. Michael Angel, and M.L. Myrick ............................................................................................................................. Modeling Superplastic s.17 Materials Donald R. Lesuer, Chol K. Syn, Charles S. Preuss, and Peter J. Raboin ......................................................................................................................... Engineering Research Development and Technology _ s.23 Thrust Area Report FY92 V Contents 7. Microwave and Pulsed Power Overview E. Karl Frettag, Thrust Area Leader Pulsed Plasma Processing of Effluent Pollutants and Toxic Chemicals George E. Vogtlin ....................................................................................................................... 7.1 Ground Penetrating Imaging Radar for Bridge Inspection John P. War/ms, Scott D. Nelson, Jose M. Hernandez, Erik M. ]ohansson, Hua Lee, and Blvtt Douglass ........................................................................ High-Average-Power, Electron Beam-Controlled Switching in Diamond W. Wayne Hofer, Don R. Kania, Karl H. Schoenbach, Ravindra Joshi, and Ra!lP. Brinkmmm ..................................................................................... Testing of CFC Replacement Fluids for Arc-lnduced By-Products 7.23 Delayed Low-Pressure Gas Discharge Switching Sh?_hen E. Sampayan, Hugh C. Kirbie, Anthony N. Payne, Eugene Lauer, and Donald Prosnitz .......................................................................................... 8. 7.19 Theory to Mode Stirred Richard A. Zacharias and Carlos A. Avalle ............................................................................... Magnetically 7.13 Toxic W. Ray Cravey, Wayne R. Luedtka, Ruth A. Hawh'y-Fedder, and Linda Foiles .............................................................................................................................. Applying Statistical Electromagnetic Chamber Measurements 7.s Nondestructive 7-27 Evaluation Overview Satish V. Kulkarni, Thrust Area Leader Fieldable Chemical Sensor Systems Billy ]. McKinley and Fred P. Mihutovich ................................................................................... e.1 Computed Tomography Harry E. Martz, Stephen G. Azevedo, DanM ]. Schneberk, and Geolxe P. Roberson ..................................................................................................................... fl.8 Laser Generation and Detection of Ultrasonic Energy Graham H. Thomas .................................................................................................................. VI Thrust Area Report FY92 • Enlglneorln R R(,sealch Developmont ancJ lochnology &23 Contents 9. Remote Sensing, Imaging, and Signal Engineering Overview James M. Brase, Thrust Area Leader Vision-Based Grasping for Autonomous Sorting of Unknown Objects Shin-yee Lu, Robert K. Johnson, and Jose E. Hernandez .............................................................. Image-Restoration and Image-Recovery Algorithms Dennis M. Goodman .................................................................................................................. View: A Signal- and Image-Processing 9.7 System James M. Brase, Sean K. Lehman, Melvin G. Wieting, Joseph P. Phillips, and Hanna Szoke .......................................................................................... VISION: An Object-Oriented Pattern Recognition 9.1 Environment for Computer 9.11 Vision and Jose E. Hernandez and Michael R. Buhl .................................................................................... 9.1s Biomedical Image Processing Laura N. Mascio ....................................................................................................................... 9.21 Multisensor Data Fusion Using Fuzzy Logic Donald T. Gavel ....................................................................................................................... 9.23 Adaptive Optics for Laser Guide Stars James M. Brase, Kenneth Avicola, Donald T. Gavel, Kenneth E. Waltjen, and Horst D. Bissinger ............................................................................. Engineering Research Development and Technology .*,. Thrust 9.27 Area Report FY92 vii Introduction The mission of tile Engineering Research, Deveiopment, and Technok_gy Program at Lawrence Livemlore National Laboratory (LLNL) is to develop the technical staff and the technology needed to support current and future LLNL programs, To accomplish this mission, the Engineering Research, Development, and Tecl_lology Program has two important goals: (1) to identify key technologies and (2) to conduct high-quality work to enhance our capabilities in these key technologies. To help fox:usour efforts, we identi_ teal'lnology thntstareasand seh:K_tK, chnicalleaders for each al_,a. The thn.Lstareas are integrated en_neenng actMti_ and, rather than being based on individual di_iplines, they are staff_:_.tby l._l_nnel ft'ore Electronics Engineering, ML:_hanical Enb_neering, and other LLNL org_liza tions, as appropriate. The thrust area leaders are accoLmtable to me for the quali_ and progress of their activities, but they have sufficient latitude to manage the resources alkv,:ated to them. They are expect_M to establish strong linK,_to LLNL program leaders and to industry; to use outside and inside experts to review tile quality and direction of the work; to use univel_ity contacts to supplement and complement their efforts; and to be certain that we are not duplicating the work of others. The thrust area leader is also responsible for carryhlg out the work that follows from the Engineering Research, Development, mid Technology Program so that the restflts cml be applied as early as possible to the needs of LLNL programs. This annual report, organized by thrust area, describes activities conducted within the Program for the fiscal year 1992. Its intent is to provide timely summaries of objectives, theories, methods, and results. The nine thrust areas for this fiscal year are: Computational Electronics and Electromagnetics; Computational Mechanics; Diagnostics and Micr_21ectronics; Emerging Technologies; Fabrication Technology; Ma terials _ience _md Engineering; Microwave and Pulsed Power; Nondestructive Evaluation; a_md Remote Sensing and Imaging, and Signal Engineering. Readers desiring more information are encouraged to contact the individual thrust area leaders or authors. Roger W. Weme Associate Director.fi_rEngineering and Teclu mlo,_yTraltsfer m I ,,,,,Mlililllil .......... _- i i_-----_ l,lli,,lliliil, iiimiiillill, _-___---_-----_- _ ........ -= .._ .... ............ ...................................... _- : __-:=_- o o __ . . _--__-:_= ........ _= -_ .... .................... 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III Illlll IIJlllllllll Illl II Illll IlnmnllllllllIlll iJlllllllllll IIli,llllllll ....... _ _- illlllllli,Ell: IIIIIIIIIIli Illllllllllll ' = I IlllJllllll II lillllllllllllllllllllliI Illlllllll i, Illlill III II ii; = = = : Coml Eics and i The Computational Electronics and Electrornagnetics thrust area is a focal point for computer aodeling activities in electronics and electromagnetics in the Electronics Engineering Department of Lawrence Livermore National Laboratory (LLNL). Traditionally, we have focu_.-I our efforts ha technical areas of importance to existing and developing LLNL programs, and this continues to form the basis for unstructured conforming grids. The thrust area is also investigating various technologies for colaforming-grid mesh generation to simplify the application of our advanced field solvers to design problems involving complicated gc_metries. We are developing a major c_Kle suite based on the three-dimensional (3-D), conforming-grid, time-domaha ct_.le DSi3D. We continue to maintain and distribute the 3-D, fhaite-difference time- much of o, :r re_,arch. A relatively new and increasingly important emphasis for the thrust area is the formation of partnerships with industry, and the application of our simulation technology and expertise to the solution of problems faced by industry, The activities of the thrust area fall into three broad categories: (1) the developmentofth,_retical,'mdconapulaltionalmt×lels of electronic and electromabmetic phenomena, (2) the development of useful and robust software tt×_ls ba_d on tht_ models, and (3) the application of these ttx_ls to programmatic and industrial problems. In FY-92, we worked on projt_cts in ali of the areas outlinecl above. The object of our work on numerical electromagnetic algorithms continues to be the improvement of tinae-domain algorithms for electromagnetic simulation t..' domain (FDTD) ctx:le TSAR, which is hastalled at ,,_,veral dozen university, government, a_d industry sites. Also, during this past year we have begun to distribute our two-dimensional FDTD accelerator m_Kleling code AMOS, and it is pre_ntly being used at _veral tmiversities and Department of Enerbnf accelerator laboratories. Our principal applications during FY-92 were accelerator components, microwave tubes, photonics, and the evaluation of electromabnaetic interference effec_ in commercial aircraft. Included in this report are several artacles that di_uss some of our activities ha more dett,,il. The topical areas covered in these articles include computational hategrateci photonics, the application of massively parallel computers to timt_'lt_main mtKleling, analysis of pulse propagatioo through concrete for bridge insl._'ction, accelera !or component modeling, and the development of tt×_ls for semiconductor bandgap calculations. John F. DeFord Thrust Area Leader Section I IIIIIIIEIlIIIIlllllll|llllh_ iii ilP iiilillil ililiililii, r_ iiii i1||1111 iiilUUl 'nII'_ ,;;,,, z z iii iiii I ii 1. Computational Electronics and Electromagnetics Overview John F. DeFord, Thrust Area Leader Parallel Computers and Three-Dimensional Electromagnetics Computational Niel K. Madsen .......................................................................................................................... 1.1 Computational Integrated Photonics Raymond ]. Hawkins, ]t_'ry S. Kallman, amt Rict qrd W. Ziolkowski ......................................... 1.7 Analysis of High-Average-Power, Millimeter-Wave Microwave Components and Induction Linear Accelerator Modules Clifford C. Shan,?, John F. DeFord, and Malcolm Caplan .......................................................... 1.13 Electromagnetic Modeling and Experiments for Dispersive Media Scott D. Nelson and Carlos A. Avalle ....................................................................................... t.21 Band Gap Engineering for Infrared Detectors J. Brian Grant ........................................................................................................................... t.2s ParallelComputersand Three-Dimensional ComputationalElectromagnetics o:oComputationalElectronicsand Electromagnetics Parallel Computers and Three, Dimensional Computational Ecs Niel K. Madsen EngineeringReseardzDivision ElectronicsEngineering We have continued to make progress in our ability to use massively parallel processing (MPP) computers to solve large, computational, electromagnetics problems. In FY-92, our primary emphasis has been to produce a message-passing version of the preprocessor, PREDSI3D. In addition, the execution module DSI3D has been ported to other parallel machines: the BBN Butterfly, the Thinking Machines CM-5, and the Kendall Square KSR-1 machine. Our DSI3D algorithm and code, together with the ever more capable MPP computers, give us a unique oppoilunity for significant new contributions to three-dimensional electromagnetic modeling. Two recent applications of DSI3D are presented: (1) full-wave analyses of very-high-frequency optical signals propagating in a weakly guided optical fiber cable; and (2) study of the behavior of whispering-gallery-mode microdisk lasers. - IId:roductioll ume Maxwell's solutions to computational volumes smaller than about 104_.3, where _. is the The solution of physical problems whose behavior is govemtKt by Maxwell's equations has been of considerable interest for many years. The propagation of electromagnetic (EM) signals, such as microwaves for communication or radar pulses for the detection of aircraft, are two examples of such problems that have been studied over long peritKIs of time. More recently, other areas such as the desigll of integrated photonics devices; the design and analysis of electronic interconnects for integrated circuits; and the full-wave analysis of micrt×-lisk or thumbtack lasers have been studied bv numerically _lving Maxwell's equations, 2he computational tasks for accurately ro(Kieling three-climensional(_D)problemsthatareelec_omabmetically large are very challenging. Two iimitations that have been real impediments to the successful solution for these problems are (1) the lack of g_Kl, numerical EM algorithms for dealing with problems with complicated, irregu!ar, and nonorthogonal geometries; and (2) the speed and capacit), of even the largest and fastest supercomputers, Present-day supercomputers, such as theCravYMP, limit full-wave finite difference or finite vol- wavelength of the EM radiation of interest. For a radar cross-section (RCS) calculation, this limits one to the analysis of scattering from only a small portion of an aircraft fuselage at the upper end of the low-frequency regime, thus neglecting the intra-structure coupling effects that can be imporrant under some conditions. The calculation of the RCS of a complete aircraft, which may be of size 100 _. in each of three dimensions, may require as many as lfP grid or mesh elements. Problems of this extremely large size clearly will require computers with capabilities that are far beyond those of current supercomputers. New massively parallel prtKessing (MPP) computers have emerged as the most attractive approach for increasing our computing capabilities to the levels required by large, 3-D, EM simulations. Though still evoMng rapidly and not as yet cornpletely viable as production computers, they havudemonstrated computational speeds that can no longer be ignort._-t. With their very distributed nature (nlemor}.., and CPU's) and lack of sophisticated software development tools, MPP computers present new computing challenges in and of thenlselves. Large Et_g,,_e_,.;_g Resea_cti De_.iol_.:er, t ._Jna Te. ctir_f:_/og_ _.o Thrust Area Report F"'92 1-1 ComputationalElectronicsand Electromagneticso:oParallelComputersandThree-Dimensional Computational Electromagnetics PII_[OtMD Rgure1. A twodimensional sliceof the3-Dnonorthogonaiandunstructured gridused to solve anelectronic interconnect problem With our development over the past _veral years of tile new discrete surface integral (DSI) methods, t the first of the two modeling limitations listed above has been completely overcome, i.e., our new algorithm (implemented in the code DSI3D) has proven to be robust, reliable, and aCCtlrate in solving EM problems with complicated and irregular geometries. The _cond limitation has been the primary subject of our work for the past t, vo years. Previously, we produced and tested a parallel version of the DSI3D execution mtx.iule that performs quite efficiently on distributed-memory parallel computers such as the Intel iPSC/860. withthreestripline conductors. Parallel Rgure2. A two- sors. These processors are capable of performing hundreds or thousands of arithmetic computations at the same time. partitioningthe electronic interconnect problem, simulation problems must be broken into smaller subpieces that can be handled by the indMdual processors. As a result of this decomposition, data must be efficiently communicated among the processors as required by the numerical algorithm. In the next :_ction, we will describe a new technique that can automatically decompo_ a problem into smaller subpieces, and also seems to be effective at minimizing the amount of required conamunication. We will also discuss the performance of our new parallel EM software on one of these newer parallel computers, Finally, we will show some sample results for two optical applications problems and conclude by indicating our future development directions and thoughts, Thrust Area Issues Recognizing the ultimate physics limitations of trying to speed up traditional serial pr(x:essing computers, computer manufacturers have begun to design ,and build MPP computers with hundreds and even thousands of independent proces- dimensional slice showingtheautomaticpartitioning producedby the r_ cursive spectralb_ sectionmethod for 1-2 Computation Report FY92 .:. Engineering Rose#ttct) Development Typically, these MPP computers are distributed-memory computers, i.e., they have very large total amounts of memory, but each processor has rapid direct access to only a small subset of the total memory. For a processor to obtain accessto data not residing in its own memory, some form of communication or message passing among processors is required. This distribution of memory pre_nts new complexities when one desires to soh,e very large problems. Ultimately, the computer's operating system, compilers, and other software tools will automatically take care of the_ additional complexities. At present, however, ali of the_ software tools are in a state of infancy, and so solving very large EM problems remains a challenging task. The efficient partitioning or distribution of the computational tasks and data across the comput-i i er s memory and processors is an area of high interest. A gt×)d partitio|ling of a problem among multiple processors should satisfy at least two criteria: (1) the partitioning of a problem should produce subpieces of approximately equal size; and (2) the boundaries betwtx'n the pieces should be as small as possible. The first requirement is _lnd T_,chnologv ParallelCon?puters and Three.Dimensional Computational Electromagnetics4* ComputationalElectronicsand Eloctromagnetics imposed to make sure that each processor has • about the same amountrequirement of computational perform; the ,second is set towork try to minimize the amormt of inter-processor Rauro3. Parallel .... i:_i_ :::_;:: ': :'i .::?!'_::::: _:,;::::, data com- mtmication. the case that an efficient partitioning of the problem is visually obvious. However, for unstruc- _ Perfect speedup "---,",---"100000cells -- - , - 60000cells tured grids with little predictable structure, a gcxM partitioning is rarely obvious ,/4"/_ and can present a / / ,, problemSferant sizes,°f threeusingdif- / / ,,*' variousnumbers of IPfiC/860. tel ,, i //._;,_.,, I " initial formidable experience problem. withG'l,,;tyear, a very promising we reported new our appreach. Others 2 have recently developed a 'recursive spectral bisection' method that seems to meet both of the above criteria, lt is based upon the construction of the Laplacian matrix of the dependency graph of the algorithm being used. A dependency graph is produced by linking together variables that depend upon each other, through the underlying solution algorithm (in our case the DSI3D algorithm). The partitioning is accomplished by finding the second eigenvalue of the Laplacian matrix and an associated eigenvector, which is referred to as the 'Fiedler vector.' The median ':_:: . ,ac'/ : : _";_: i:!i_!_; ..... Rguro4. -- _ ----,',_ -- Perfect at speedup 128000cells ,_, - .... _- Parallel performance of i:ii_i:::P REDSI3Dp for waveguide roblems 54000 cells ofthr_ 32000 cells es, using various different siz. numbemofproces- value of the entries of the Fiedk. vector is computed, and variables that are associated with Fiedler vector entries that are greater than the median value form one pk._e of the partition, and those less than the median value form the other partition piece. This process can then be applied recursively to partition the entire problem into the desired sotson theIntal IPSC/860. "_) number of pieces, which must be an integral pewerof2. _.:_,_ We have further tested this new, rectwsive, spectral bisection technique and have found it to be quite effective at meeting the desired criteria for a good partitioning, even for very large problems, Figure I shows a two-dimensional cross-section of a 3-D, unstructured intercormect grid; Fig. 2 shows the automatically derived partitioning of this grid cross section into 16 colored subpieces (shades of gray in this rendition), In addition to the partitioning of an EM problem for MPP solution, there is also the difficulty of producing a version of the tmstructured grid code, DSI3D, that runs efficiently on a MPP computer, The primary challenge is to design and implement the passing of data among processors, so that it consumes a small amount of time compared with the time required for computing the solution components. The DSI3D code is really separated into two subpieces: a preprocessing piece, PREDSI3D, which takes the primary grid and the DSI algorithm and derives a dependency graph and update coefficients; and an execution piece, DSI3D, tngJneerlng performance of o$13D for wave_uide / /, -- -'- -- 30000cells ";: :"_r _ which repeatedly uses the dependency graph and coefficients to update the field components in a time-marching manner. In FY-91, we completed the implementation of message-passing versions of DSI3D for the lntel iPSC/860 parallel computer. In FY-92, our primary emphasis has been to produce a message-passing version of the preprocessor, PREDSI3D. In addition, the execution module DSI3D has been ported to other parallel machines: the BBN Butterfly, the Thinking Machines CM-5, and the Kendall Square KSR-1 machine. Generally, we have found that if the problem is sufficiently large, there is considerable benefit to using parallel computers. For smaller problems, it is more efficient to use conventionalserial-processingcomputers.Figure3 shows the performance of DSI3D for waveguide propagation problems of three different sizes, using varying numbers of processors on the Intel iPSC/8(YJ parallel computer. Figure 4 shows the Hesearctl L)evetopment at) rl It?ct_nology ,_ thrust Area k_eport FY92 "1-3 Computational Electronics and ElectromagneUcs .:. Pi-_rolle, I Computers _mdTl_reeOimensiomTIComlouti_tiom_l Electrom_gnetics microns perfornlance of I'Rt_I)SI3D for a similar set of p;oblems, lt is clear from these figures that larger problems run uniformly nlore efficiently than do smaller problems. The preprocessor, I)RFDSI3D, in general runs less efficiently than the execution module, because it requires considerably more interprocessor communication. However, it is run only once for a particular problem, whereas the execution module may be run repeatedly for the same problem. _ 6 microns --_,L.L"_p- F/gum 5. Schemat- ic fora wearerguiaed fiber optical cable Selected Applications The overall purpose of our work using MPI' computers is to be able to easily solve problems that heretofore have not been solvable on conven- with an offsetendcleave, tional serial-processing COlllptlters. ICVhilethe ex- isting MI'P computers are not quite at that h.,velof capability, the next generation will be, and we are now ready to address this type of problem, One area of new interest to us has been the use ,,ffDSI3D to perform full-wave analyses of very- Figure6. rwo-dimensionai planar cut in the center of a fl- w.. I .. Figure8. DSI3Dgrid usedto modal the behaviorof the mb crodisk laser andpedestaL high-frequency optical signals propagating in weakly guided optical fiber cables. In splicing optical fibers, it is desired to cleave (or cut) them in a manner so that the cleave is tent-shaped and centered with respect to the fiber core (see Fig. 5). Due to their small size, it is not always easy to determine if the cleave is appropriately centered. (-hie idea for determining if the proper centering exists is to launch optical signals in the fiber cable toward the cleave, and then to analyze the signal reflected from the cleaved end back down the cable, ifthe cleave iscentered, most of the reflected energy should remain in the cable core in the fundamental mode. if the cleave is offset significantly, much of the reflected energy will be reflected out of the cable's core. DSI3D is well stilted for studying this type of problem. The cleave intersection with the cylindrical fiber is easily handled ber optical cable with a centered end-cleave,showing the using the tlnstrtlctured reflected pulse field fringes, featuresof DSI3D.Figures6 and 7 show the nature of the reflected pulses for a centered cleave and an offset cleave, respectively. The differences between the two reflected signa isare obvious. Another new interesting application has been the use of DSI3Dtostudy the behavior of whispering-gallery-mode microdisk lasers.3 These novel devices have potential for the integrability and low-power operation required for large-scale photoniccircuits. The disks are formed using selective etching techniques in a Inl'/In(,aAsl _system to achieve 3- to lO-}.tm-diadisks as thin as 5007k suspended in air or SiO2on nn hal' pedestal. Optical confinement within the thin disk plane results in a microresonator with potential for single-mode, ultra-hwv tlweshold lasers. Figure 8 shows the Figure 7. Two-dimensional planar cut in the center ota fi- ber optical cable with an offset end-cleave, showing the reflectc d pulse field fringes. 1-4 Thru.,;t Area report FY92 .1. [ tl_,,iJ,,,,rirJj, I_'l,,,i,,Jr, h I)e. tl, l_)t)tT_t,lJl ,_,_11 I_,( hl}f_lo_'_ and nonorthogonal grid Parallel Computers and Three-Dimensional Computational *'. Computational Electromagnetics Electronics and Electromagnetlcs Rgure 10. Reid plot showing the radiated fields from the micr¢_ " disk laser and pede_ tal structure. Plot shows fields In the center plane of the mlcrodisk exterior to the disk. •:'_'_:_, _ -._ _.,- ._ . Figure 9. Field plot showing the M = 8 mode for the microdisk laser and pedestal. I3'313I_)grid for tile disk and pedestal. The grid for the surrounding medium is not shown. Figure 9 shows the excited M = 8 mode for the disk and pedestal. Figure 10 shows the structure of the radi,,ted fields in the plane of the disk. Future Wolrk Our DSI3D algorithm and code, together with the ever-more-capable MPI' computers, give us a unique opportunity for significant new contributions to 3-D EM modeling. We now have the flexibility and capability to solve problems of a size and detail that were previously unimaginable. We intend to address to a mucta greater extent some of the areasofapplication mentioned above, in addirien, we plan to add a charged-particle capability to DSI3D, so that these new capabilities will be available to the plasma physics comnaunity. Lrlgln{_<,rltlg We have attracted the interest of several industrial partners, and Cooperative Research and Development Agreement efforts arc.,underway with these partners to develop specialized versions of DSI3D for use in RCS analysis and for gyrotron design. 1. N.K. Madsen, l)i_,et_,cencc Prescrr,in,_Discrete Sm'/iwc Intc,kr, al Mctho,ts li," Maxwell'.,;Cttrl Equations I.IsittgN(_n-('h'lh_),e,¢ )ttal fit tsh'tlclurcdGrids,l.,awrence l.ivermore National I.aboratory, l.ivernaore, California, UCRI.-JC-I()t)787(It,_tt2). 2. ILl). Simon, Comtmlink,St/sh'ms in t:nNinecrin,, ¢2 (2/3), 135(lt)t,_l). 3. S. McCall, A.l.evi, R. Slusher, S. l'earton, and R. Logan, Appl. Phys. IJ'tl. 60 (3), 28 t) (lt)t)2). L_ R(;s(,r_rch D_'vt'lolJnt_'t_r _st)d T(,(:hl)olog;, .:. Thrust Area Report FY92 1-5 Computational Integrated Photonics o:. Computational Electronics and Electromagnetics Computational IntegratedPhotonics Raymond J. Hawkins and JeffreyS. Kallman EngineeringResearchDivision ElectronicsEngineering We have continued Richard W. Ziolkowski DepartmentofElectricaland ComputerEl_ineering UniversityofArizona Tucson,Arizona our hmovative work in computational integrated optics, a field impor- trait both to programs at Lawrence Livermore National Laboratory (LLNL) and to industry. Integrated optical device design has been our primary research topic. The results of this project have been applied to device design at LLNL, at Bellcore in Red Bank, New Jersey, and at Hughes. A second leading project, device design code integration and graphical user interface development, has also proved to be of great significance, with our simulation results proving to be of interest to a number of companies. IllltroducUon terface (GUI), and have made significant advances in nonlinear FDTD. Computational integrated photonics (CIP) is the area of computational physics that studies the propagation of light in optical fibers and in integrated optical circuits (the photonics equivalent of electronic circuits). The purpose of integrated photonics simulation is to develop the computational tools that will support the design of photonic and optoelectronic integrated devices. These devices will form the basis of ali fflture high-speed and high-bandwidth information-processhlg systems and are key to the ffiture industrial competitiveness of the U.S. CIP has, in general, two thrusts: (1) to develop predictive models of photonic device behavior that can be used reliably to enhance significantly the speed with which designs are optimized for applications, and (2) to further our ability to describe the linear and nonlinear processes that occur and can be exploited in real photonic devices, Our efforts in FY-92 have been focused in three general areas: (1) pseudospectral optical propagation codes; (2) linear finite-difference time-domahl (FDTD) codes; and (3) nonlinear FDTDcodes.This year we have focused on both the development of codes of interest to the integrated optics community, and on packaging these codes in a user-friendly manner, so that they can be used by other researchers in both academic and industrial laboratories. We have developed two new design codes, BEEMER and TSARLITE, with graphical user in- As FTDT becomes increasingly popular for the study of integrated optical systems, the need to include material dispersion and nonlinear effects has forced us to examine these issues. We found a particularly convenient way of including linear material dispersion in FDTDcalc.ulations, and have funded studies ha the inclusion of material nonlinearities in FDTDcalculations. Engineering Our work in integrated optical device design continues to give us our leading role in the design of integrated optical components both for Lawfence Livermore National Laboratory programs and for U.S. industry. This research is of particular interest, since we have predictive codes that significantly reduce the time required to bring a device from concept to prototype. Our work with the pseudospectral optical propagation code, called the beam propagation methcK1(BPM), has addres_Ki the issue of tmderstanding optical field evolution in multilayer, integrated guided-wave detector structures. This work, which previously led to the development of extremely short integrated waveguide/photodiodes with high quantum efficiency, has now resulted in the development of the polarization diversity detector shown in Fig. 11 and the coherent receiver shown in Fig. 2.2 Research Development ,_nd Tect_nology 4. Thrust Area Report FY92 1-7 ComputationalElectronicsandElectromagnetics.'. Comput_t_om_l Integr_tedPhotomcs teta by and for ctmlputational physicists. Ct)nsequenilv, tile BI'M was often admired from afar by TEphotocurrent capability. those who would best benefit ft'ore a hallds-orl To fill the void, _A'C _._'roteBEEMER, a BPM code with a (.,UI that allows corlstruction of ,_ device P+-InGaAsP -I_ TMphotocurrent l-lnGaAs n+-InGaAsP 21 75 lnP.Fe InGaAsP:Fe InP:Fe lnGaAsP:Fe InP:Fe TM Figurel. The Bellcore polarization-diversity photodetector that produces two pho- tocurrentoutputsproportional toguide-inputintensitiesineachoftwoorthogonal polarizationstates.Ourdeviceis significantly(a factorof5 to 20) smallerthanpreviousmonolithicrealizations of thiscircuit. We were also able to helt:_ researchers at Hught.,s undelstand the operation of their phot_.ietectol.'s,since they were ba_'d on a very similar design. C)ur work with [k,llcore was ,_,leck_t as an exampleofleadingworkinopticalinterconnecfions. 3 For several years, BI'M has been the nlethod of choice for ctmaputational physicists studying integrated optical wa\'eguide/device beha\'it_r. Unfortunatei\', the special methods underlying the BI'M that made it so efficient ,also l-Ilade it difficult for nadnv to code from scratch. Distribt_tion of source code reds found, empirically, to be ,ata unsatisfactory alternative, since most codes are writ- layout, simulation, and optinaization, ali within the sa nac windt_v¢ structu rc. Tb,, designer can specifva variety of material paranaeters including gain, loss, and Kerr nt_nlinearitv. Thus, this teel can easily handle design problems from linear plaotodetectors to all-optical soliton-based switches. BEE1MERis written in C and has been compiled successfully on a number of workstations, including SUN, IBM, DEC, and SGI. An illustration of the type of problem that BEEMEl<can handle is shown in Fig. 3. The manual for BEEMER guides the user tlarougla a nunaber of examples drawn from vm'ious areas in optics, to accluaint the tlser with the ].31"Ogl'Ol'll. BEEMER and the nlallLia] htqve been released for distribution oatside of LLNL, and we have installed BEEMEl_,atbotll academic and industrial sites. To meet the needs of a variety of photonics device designs, we have continued our developmerit of FDTD as a tool for integrated optical device simulation, extending our previous experrise in pseudospectral-code-based device simulation. Our FDTD work has provided information on a variety of devices that could not be modeled by any existing codes. For example, we have dctaonstrated the ability to model diffractioll gratings and facet reflections. The FDTD treatment of electromagnetic pulse propagation holds mucla prom- , _'_ TE TM "290 Tapers 177 3 .. 84o __ ..... ' _ Local oscillator ii Optical Gold ,ig,,al .... !_ii_ .... _ /"_:, i " _ii!:_! : Figure2. TheBellcoreultracompact,balanced,polarization diversityphotodetector. Thetwodetectorscorresponding to eachpolarization stateareinterconnected foron-chipphotocurrentsubtraction,whichis essentialforbroadband, balanced operationwithoutmicrowavehybrids. 1-8 Thrust Area Report FY92 .:. t nl:_l,_,_.r_l_ /?_,_.nrch l_t",_'t_l) n;_'_t ,_n_l I_'_ tl_o/_._'_ Computational IntegratedPhotonics*:. ComputationalElectronicsand Electromagnetics ise for tile complete numerical description of integrated optical device behavior, where reflections and/or coherent effects are important. The recent application of FDTD to problems in integrated optics45, _,has indicated that electronic dispersion must be included to treat realistically the broadband behavior of integrated optical devices. The inclusion of m,,rerial disl._rsion (elcx'h'onic or magnetic) in FDTD calculatkwls has _qstofically [_='enquite limittxi. The first formulation ot broadband disF'-,ersion in FDTD w_s pl_:_nt_t in a pioneering palx, r7 that demork,4rat_Ktthat if the electronic su_eptibili_, was expanded as a _ri¢=_of exlmnentials, the treatmerit of dispersion could be rt_.iuco.i to a t_vm.'sive utxiate. The incorbx_ration of thb; update, however, reqtfi_ a substantial rewriting of the standard electric-field update t_uatiorks. More recently, othersS, '_demonstrated a different formulatiort of the linear problem, explicitly soMng the equation of motion for the polarizabiliFigure3. Anall-opticalswitchbasedonspatialsolitons.Lightcomingin fromthe ty using finite-differencing. This alternative for- left is combined intoa waveguide that isplacednextto a nonlinearmedium.If the combinedintensityisgreatenough(asshown),thentheevanescentfieldin thenoninitiation has b_en extended 10to nonlinea r optical linearmediumis strongenoughto forma spatialsolitonthat splitsoff andis subse. propagation. In our work, we have exploited a quently captured by the lower arm. simple causally, argument that enabled us to write dispersion as a simple, recursive, additive term in an establish(xi,thro.,-dimensional (3-D), FDTDcode the common electric-field update equations. This with limited GUI application.]'FSARL1TE hasbeen is of particular interest, since it enabled the treatcorlstructed with the integrated optics comnlunity ment of dispersion in a large number of existing in mind, and thus has desirable features such as FDTDdesibm codes with minimal computational the ability to launch spatially and temporally modification, shaped pulses, and our latest dispersion model. While there has been a great increase in inteAn example of the typeof problem that TSARI_JTE grated optical devices for which only a solution of can handle is shown in Fig. 4. Unlike BEEMER, Maxwell's curl equations will suffice, ease of use TSARLITE does not yet have a manual and has not has not been the hallmark of these codes. To meet yet been released fl_r use outside of LLNL. We this need and to provide ea._ of user access, we anticipate that this will happen in the coming year. have written TSARLITE'_: a two-dimensional With the continuing and heightened interest in FDTD code with a fully integrated GU1. [TSAR is nonlinear semiconductor and optically integrated Figure4. Anopticalcrossbarelement.Ontheleft, theelementis in transmitmode,but thedegreeof confinement of the lightinthewaveguideleadsto significan* lossinthecrossregion.Withthemirrorinpiace(right),thelight iscoupledinto thewaveguide, buttheoffsetofthemirrorfromanidealpositionresultsinsomescatteringlosses. Enl_r_l'erll_ Rc'se,ltch De_'l(_/)m_'nt ._r_l l_,_ t_l_,)i_)J.l_ o:" Thrust Area Report FY92 1-9 ComputationalElectronicsandElectromagneUcs4. ComputationalIntegratedPhotonics devices, more accurate and realistic numerical slmulations of these devices and systems are ill demand. To date, most of tile mt×ieling of pulse propagati m in and scattering from nonlinear media has been accomplished with one-dimensional, scalar models. These models have become quite sophisticated; they have predicted and explained many of the nonlinear as well as linear effects in present devices and systems. Unfortunately, they cannot be used to explain many observed pilenornena, and are probably not adequately modeling linear mid nonlinear phenomena that could lead to new effects and devices. Vector and higher dimensional properties of Maxwell's equations that are not currently included either in existing scalar models or in more detailed material models, may significantly impact the scientific and engineering results. Moreover, because they are limited to slmpier geometries, current modeling capabilities are not adequate for linear/nonlinear optical-component engineering design studies. The successful development of general, linear, and nonlinear electromagnetic modeling capabilities will significantly impact theconceptand design stagesasstx:iated with novel linear and nonlinear phenomena and the resulting optical components, We have developed the first multi-dimensional, full-wave, vector solutio|zs to Maxwell's equations for problems describing the interaction of ultra-short, pulsed beams with a nonlinear Kerr" material having a firdte response time. u These solutions have been obtained with a nonlinear fhlite-difference time-domain (NL-FDTD) method developed by investigators at the University of Arizona. This NL-FDTD methe, i combines a nonlinear generalization of a standard, FDTD, fullwave, vector, linear Maxwell's equation solver, with a currently used phenomenological time relaxation (Debye) model of a nonlinear Kerr material. In contrast to a number of recently reported numerical soluti(ms of the full-wave, vector, timeindependent Maxwell's equations and of vector paraxial equations, the FDTD approach is a tinaedependent analysis that accounts for the complete time evolution of the system, with no envelope approximations. Nonlinear, self-fCx:using numerical solutions in two space dimensions and time that are obtained with this NL-FDTD method, as well as related NL-FDTD results for normal and oblique incidence, nonlinear ir|terface problems, have been investigated. Although these basic geometries are straightforward, the NL-FDTD lpproach can readily handle very complex, rea listic structures. problems highlight tile differences between the scalar' and the vector approaches, and the effects of the fir|lte response time of the medium. The NL-FDTD method is beginning to resolve several very basic physics and engineering issues conceming the behavior of tile full electroma_letic field during its interaction with a self-focusing medium. Ill particular, using the NL-FDTD lpproach we have (1) shown the first back reflect-ions from the nonlinear self-focus; (2) discovered optical vortices formed in the trailing wakefield behind the nonlinear self-focus; (3) identified that the longitudinal field component plays a significant role in limiting tile self-focusing process; (4) performed the first complete full-wave, vector treatment of both the TM and TE models of ali optical diode (linear/nonlinear interface switch); (5) characterked the performance of an optical diode to single-cycle pulsed Gaussian beams, irlcluding the appearance of a nonlinear GoosH_inchen effect, the stimulation of stable surface modes, and the effects of a finite response time of the Kerr material; (6) shown definitively that the linear/r|onlinear interface does not act like an optical diode for a tightly focused, single-cycle pulsed Gaussian beam; and (7) characterized the performance of some basic linear/nonlinear slab waveguides as optical threshold devices. Ill ali of these analyses, we have identified the role of the longitudinal field component and the resulting transverse power flows ill the associated scattering/coupling processes. Future We will continue our efforts hl the desigm of novel integrated optical devices, both for LLNL programs and for industry, lt is our intention to transfer BEEMER and TSARLITE to industry. Our development of linear FDTD applications to integrated optics will be extended to 3-D structures, and our studies of NL-FDTD will continue ill the area of r|onlinear waveguides and couplers. 1. R.J. Deri, R.J. Hawkins, E.C.M. Pennings, C. Caneau, and N.C. Andreadakis, AppI. Phys. Left. 59 (15),1823 (1991). 2. RJ. Deft, E.C.M. Pennings, A. ,_here_, A.S.(,ozdz, C. Caneau, N.C. Andreadakis, V.Shah, L. Curtis, R.J. Hawkins, J.B.D.Soole, and J.-l._mg, I_hotonics 7?ch.Letl.22, 1238(1992). 3. R.J. l)eri, E.CM. l'ennings, and R.J. Hawkins, Opticsmat Phoh_lticsNcu,s(l)ecembeb 19t)I ). S.T.Chu and S.K.Chaudlmri, 1.l.(9,hlwaz,eli'clmol. 4. The cho,_n sample TE and TM nonlinear optics 1-10 Thrust Area Report FY92 • Engineering Research Development _/011_ LT-7,2033(1989). and lochnology Coml3Utatiom_lIntegrated PlTotonics ,_oComputational Electronics and Electromagnetics 5. 6. 7. 8. S.T. Chu, Moih'lliJlg i!f Gllhh'd-Wa_,¢ ()l_tical Str1,'t,r{'s I_llthe FI)7"I) Method, l_h.l). Thesis, University 9. R.M..Ioseph, S.C. I lagnt,ss, ,uld A. rl.llllwe, ()pl. l._'tl. 16, 1412 (ltir) I). of Waierloo (lt)t)()). S.T.Ciau and S. Chaudhuri, IEEE Tra,s. Microwaz,_' TIr'ort/7i'ch. 38, 1755 (1t)t)0). • 10. I_.M.(.;tx_rjian,andA. 'l,lflovt,, Oft. l_'tt. 17, 1412(itr)2). R. Luebbers, F.P. Hunsberger, K.S. Kunz, R.B. Standler, and M. _hneideb IEEE Trans. Eh'ctro,ttN,. Coml_at. EMC-32, 222 ( 1t)q0). C.E Lee, R.TShin, and J.A. Kong, PIER4 Progress in Eh'ctro,ta_netics I,_esearch,J.A. Kong (Ed.), Elsevier _ience l_ublislaing Conapany, Inc. (New York), 415, Engln_.,erlr)g 11. acteristics R.W.Ziolkowski ludkins, "Pn_pagation Ch,u'of U ItraandJ.B, -Wide !?_1 nd w idth l_uI_'d ( ;,1tt_,_i,ua lk:anas,"acceptt'dforpublic,ltionin/()SAA(NtwenaL_.'r1t_)2). 12. Rosearcl) R.W. Ziolkowski and J.B. Judkins, "FulI-W,we Vector Maxwell Equation M_:ieling of the _,lf-Ft_:using of Ultraslaol_ Optical I_ul_ in ,a Nonlinear Kerr Mt'dium Exhibiting a Finite Rt_pon.,_, qim,_',"I()SA l'_10, Dt_vl'lot_m(_nl ,ll)(I l_,cl)nolold;, 4. Thrust Area Report FY92 1-11 An_lys/s ofMIcrowaw _.Components nlTdAc('(_h_'t,ltol Mo(hfleso:.Computational Electronics andElectromagnetics Analysis of HiglAveragePower, MillimeteWave Microwave Componentsand Induction Unear Accelerator Modules CliffordC. Shang and JohnF. DeFord Malcolm Caplan Ma,,Jl,,tic Fusio l'rq,ram Etzgi_tc,'riJl_ Research Divisiolt Eh'ctrolfics Elt_ilteerilt g In FY-92, we analyzed high-average-powel, millimeter-wave microwave components ,;nrf systems for heating fusion plasmas and induction linear accelerator modules for heavy ion fusion. The electrical properties of these structtm?s weir studied using time-dependent electromagnetic field codes and detailed material models. Wt.' modeled gyrotron windows and gyrotron amplifier sever structures for transverse electric modes in the I(X)- to 150-GHz range, and computed the Ivflection and transmission characteristics ft'ore the field data. Good agreement between frequency domain codes and analytic results has been obtained for some simple geometries. Wt' describe t_sults for realistic structu res with Iossy dielectrics and the implementation of microwave diagnostics. For the model ing of ind uction accelerators (electr(_n machines), understand ing the cou piing of the beam to the cavity is of fundamental importance in estimating the effects of transverse beam instabilities. Our accelerator modeling work focused on examining the beam-cavity interaction impedances (impulse l_'sponse of cavity) for sublvlativistic beams in drivers for heavv ion fusion, to better understand longitudinal (n = 0, monopole) and transverse (n = 1, quadrupole) beam instabilities. Results for simple segmented cell configurations show that the pulse power system and induction colvs are largely decoupled from wakefields. meter-wave (mmw) structures; the _'cond involves induction linear accelerator culls. The principle Rt_bustalgorithms for the solution of Maxwell's features in modeling the mmw structures are the equations in the time domain have bt,el'lknown launching of modes, the modeling of Iossy dielecfor some time.l.2Since 19(_,specializations of these tries, and the development of microwave diagnosalgorithms to ilaclude more sophisticated bound- tics. 'l'he fundamental aspects of modeling the are conditions _,4and detailed material models S._, heavy-ion induction culls include implementing have allowed the application of the basic nunwri- realistic, magnetically dispersive material models cal techniques to interesting problems. Further, and computing subrelativistic wake potentials." rt_'entalgorithnl developments,",s for Maxwellsolvers on COlfformingmeshes now allow high geo- Modeling mmw Components metrical fidelity that may be rt,quired for a certain class of problems. 'l"heuse t)f high-power microwaves to laeatthe plasma in a magnetic ftmsionenergy (MFI:,)reactor _SS at the elt'ctrola-cyclotrt)la rt,soll,_tllce t,ala yield a ntlmber (_f bent, fits, such ,as bulk-Ilealing and In FY-q2,we e×amined tw_ sets _f problems, preionization of the plasma; reaction startup; and l'he first set iIwt_h't's higla-average-pt}wer milli- instability suppressit_n. "l'ht,rise of t,lt,ctr(_l_-t'vch_Intcoduction t nl,,_t_'_,t_n/_ /¢_,s_,,it(h I)_'v_'l_l_m_'t_t ,tt_l It',/_lott_l_ .:. Thrust Area Report FY92 1-13 ComputationalElectronicsand Electromagnetics.:. Analysi_ of Microw_we ComponentsandAcceleratorModules tron heating (ECH) in tokamak and stellerator reactors has been studied in many significant MFE experiments, including C-mod at the Massaclausetts Institute of Technology and DIII-D at General Aton'fics in the U.S.; Compass at Culham, England; T-10 at the Kurchatov Institute, Russia; and the Heliotron at Nagoya, Japma. sion. To model gyrotron components requires the launching of transverse electric modes (TE..) This is accomplished by driving magneticcurrents over the beam-pipe aperture. To describe the location of the TE drive-nodes, we rewrite the EM time-dependent curl equations: :)E Operating parametel_ of interest for ECH applications include frequencies in the 140- to V x H = crE+ e-_-- + Js r)H 250-GHz range and output power in the vicinity of 1 MW per bottle, m Currently, the fixed-frequency mmw source available for use in the 1-MW range is the gyrotron. Understar,ding the microwave V x E = -lA _ properties of high-average-power rfsta, ctures is nodelocationon the _: Yeelattlce. !: i' - Ks (2) + ""x O) in the integral form ""'=II crucial to tlae design of gyrotron tubes and an'|plifi- excessive conversion arerfoften limiting fao er devices.mode Dissipation of the (ohmic loss) and tors in the performance mad robustness of the overall device. The_ issues mad others pertaining to mmw devices can be investigated using timedomain electromagnetic (EM) field codes.II Ata advantage of simulation in the thne domain is that EM characteristics can be obtained over a wide bandwidth from a single calculation. Excitation of the frequencies of interest can be obtained by launching modulated pulses driven by magnetic currents. A general feld code such as AMOSI2 can be u_d to launch the pre_ribed m(Ktes at the frequency or frequencies of interest to examine mmw component performanceby numerical integration of MaxweU's equations, Mode Launching.Gyrotron oscillators operate with whispering gallery (WG) m(xies, for which the radial mode number greatly exceeds the axial mode number. Thus, most of the rf is distributed near the beam-pipe wall. As the mtxte propagates near the window, the modes couple into gaps in the window assembly, leading to mode conver- (1) + :_t _ E. d/= - ii(c)H lA_ + Ks )_• dA. (4) K _t|rcecomponen_areco-ltx:ated with H field components on the Yee lattice. I Referring to Fig. 1 and Eq. 4, one can see that di iving the Kr compt_ nent of the magnetic current will excite the proper Ht, Hz and E_,fields. Similarly, 1%currents excite Er and Ho field components. The proper spatial variation of magnetic currents required to obtain propagating WG TE_,2 mtxles are the Bes:_l function J22(x) out to the second zero, and its derivativeJ'22(x),whichdirectiy drive 1% and K.., respectively. The amplitude distribution in time can be a modulated pul_ to obtain the required frequency content (Fig. 2). Field diagnostics for compt|ting the voltage standing wave ratio (VSWR) were incorporated into AMOS by sampling ek'ctric fields at 'numerical' probes and computing the VSWR directly from the field values, lfF If(t)] denotes the forward Fourier transfoma, then the VSWR can be computed from the field data by first co|nputing the reflection coefficient (no mode conversion), He i 0 , : r: _,,,smp(t)] ,_2 I] , :1.0- (5) o where e_mp(t) is the sampled • [_tii_j, :' rt;_:ii,:i-): • • ....... ::;'H_ii:i: : O:_ .... :_" _0 1-14 Thrust Area Report _ FY92 _ :, : ._ IlHr;l_: ,_0 _ Engineering Research , ::H_.,i: 0 i :. ' _ 'downstream' thetime. window, and pm,_t(t) the modulated side pulseof in The VSWR is com-is puted according to the definition VSWR = (1.0 + F)/ (1.0-v). - IHrEz Development electric field on the Results of mmw: High-Power rf Window Analysis and Gyrotron Amplifier Sever. Presently, gyrotrons operate in the I(X) to 140-GHz and - 1-MW regirne. Future performance requiremerlts and Technology Analysis of Micro_ave Components ] 1.20 r zmd Accelerator Modules 7 20 _ 'i o.,o o.,o O_ 1 _ -- 40- / 0 -0.60 40 -- -0.80 60 m 100 300 200 400 I 80, 500 Launching TE22.2 WG mode-spatial and temporal magnetic drive func- /\ Besself and ElectromagneUcs Figure2. /'_ 20-- ,_ -0.20 0 i Electronics 'i 6o 8o_ 0.20 -1.oo i (b) 00 -- ,., 0.80 ._ i 40 (a) 1.00 + Computational 0 I I 10 20 Time (s) x 10 -12 t 30 40 ,,o°. ---- 50 r (m) x 10 -3 will increase power levels to the multi-megawatt range with frequencies approaching 250 GHz. In this scenario, mmw components will be placed under severe mechanical and thermal stress. Until now, ltss demandh'lg performance consh'aints have rendered non-ideal component effects less impof tant. However, understanding these effects is now critical to the operation of the device, We now examine high-order mode scattering caused by various rf window geometries at the exit of the gyroh'on. The VSWR associated with the window can be determined over a broad spectrum of frequencies, using data from a single timedomain run with the technique described in the previous section, In Fig. 3, we find good agreement between AMOS and analytic values I_ for the VSWR of a three-layer rf window. The gyrotron window geomeh'y includes a beam-pipe radius of 5.08 cm with the longitudinal extent of the window at 0.443 cre. The window material has t:..= 9.387, and the dielectric cooling fluid has t',. = 1.797. A .;mali difference between the AMOS and frequency code results is evident, caused by a minor variation in window element thicknesses resulting from the useofa regular grid in AMOS. The gyrotron window structure is grown from a sapphire crystal. The window assembly is expensive and difficult to fabricate, but more realistic window geometries cannot be easily treated analvticallv. In Fig. 4, a realistic window structure with the 'coolant reservoir' is modeled. Compared i I 24 I _-t_ 20 -- I 1 fHI /\ "_-.443 16- 1 I - /.""\t ._ , Analytic _i_ _'_ I %.3 x ct _ 8 -4- t cm 5"0icru _ m 12 -- I 4 o _ I,' _ / --------1 : t000merl t000mer2 t000mer3 t000mer4 _, 0 0 Figure 3. 100 105 110 Frequency 115 (Hz) 120 125 0 0 20 30 40 50 Radius (m) x 10"3 VSWR for idealized 1lO-GHz bandpass, from ana- lyric calculations and from AMOS. The inset shows the gyrotron window geometry, 10 Figure 4. Radial field profile at varying longitudinal Iocalions for realistic gyrotron rf window structures. The inset shows the window geometry. [:r_E_t_'ur .,g R_'._t,,_r_ I, l)v_t,l(,tJ._t._t ,_t_l I_,_ t_n<,t,,i,_ .:. Thrust Area Report FY92 1-15 ComputationalElectronicsandElectromagnotics4. rL_t_')/_'_l,_ ()t COn)l)()t_ent_ ,mUA(x'(q(,tat(,Moduh,s /_'_l(_'l())''_'_(! partMt, beam to pass ur_disttlrL',ed.(.,31interest is _rmanceforberrylla 60/40. - 3" -4 _',_-_ RF,............ _Ih:'rrylia Tli ,I Insert II ' -- .... rad it,s is ()._j5mn 1,w hicl_ is nt,ar lht, cutoff raditls. As before, '1'1!11modt,s ...... !!nlr,lllct.' dk, lectric insert (seeFig. 5) for a varit, tv of Iossv rf I1"1i xtures. I'l_t,beam-pipe wt,re launched by driving magnetic currents al the sever aPerlu re.The material cond u¢livity characlerislics for five berrvlia 3 _'_ 2 x nlixltires were obtained from the availabk, experimental data al 12GIIz. Two matt, rials, berrvlia 8()/20 and berrvlia 6l)/41), 0 berrvlia 6{}/4{)and 80/20 are 4t}.Fq and 17.81, re- -1 -2 -i 1 --3 -- spectivelv,. and the loss tangents are 0.72 and (/.... "_'_ respectively. I.l are representative: the dielectric constants K' for AMOS predicted -40 dB attenuation for a 95-(,Hz'l'l-t i mode propagating toward the st'\'t'l" for the berrvlia 6()/40 nlixture. Iii comparisor|, unacceptably low rf abstwption characteristics for the other berrvlia, mixtures (Fig. 5) were evident. II1 the limit, when the conductivity is large (berrylia 60/4()), the relevant diameter is not that of the beam-pipe, but instead it is the diameter inside the sever section. With cutoffgiven by L.-= 2ml/l.84,a TEll modeatt)5(;Hziswellbeh_wcutoff, andthe fields will be attenuated. This set of calculations can be wpeated when updated berrylia measuremeats in the - I()0-(,l-lz range are available. For the previous class of modeling problem, we plan to examine sinmlatit_n isstles such as the launching of waveguide modes near cutoff. Further, the taper of the lossv sectiim was initially limited to a naininauna of 5'_because of nunaerical limitations -4 -5 "ao- 11 21 3l Time ts)x 10-1° S 41 to the idealized 'vindow, the electric fields near axis highlight coupling to modes through the rf window near the beam-pipe wall. At the multimegawatt range, this amount of rf mar be significant. However, the exact le\'el of power pet" mode awaits further analysis, We performed a second set of calculations in whicla we exarnined wa\'e propagation through a microwave sever, a device for stopping or absorbing microwave energy while aih_wing a charged .... (a) of a shalh_w-angle staircasing of the mesh. "l'lae conftwming mesh algoritlma in C(;-AM(YS t_ will allow exact bt_tmdarv wpresentatit_n, and thus any shallow taper. Modeling Modules Induction Linear Accelerator Wt' have naodeled the beam-ca\'itv interaction impedances for induclic_n linear accelerator cells for ht,,1vv i(_11fusicm. Fhe induction cell works (b) F q 125cm conceptually Figure 6. Segmented pillboxregions, with the Long Short I I i has a pulsed voltage V applied to it. The secondarv loop aroulld the cow will hart, a voltage in- pillbox pill2-J primary voltage, i.e., t:1"Oill Far,ldav's law, V dt,ced ac,'oss'l'he its COle te,'n,inals thatofis WOtllld the sanwmetallic as the :---A dB/dt. consists 53cm ............... much like a I:1 tr,ulsfornler TM010~92MHz TM020~210MHz TM030~330MHz Inductioncore geometry Illustrating [ L TM010~217MHz TM020~497MHz TM030~780MHz 'long' and 'short' glass (M,,tglas), which has good dB/dt characteristics ( 1 to 5 l'/I, ts). In the tlaree-segment COl'eCODfigul",ltioil propt_st'd by I.awv'etlct, I_erkt, lev I ,ab_wa tt,'v ( I Bl ,),each t't _l'e is fed in pa ra IIcl. 'l'he st'Ct}lld,ll'V h_,p t'vlcl(_st'S ali thv't't' C(ll't'S, providing Analysisof MicrowaveComponentsandAccelerator Modules o:-ComputaUodal Electronicsand Electromagnetics 2,_ | 1 2.°°E 1.5o I I I [ I 11:.00 _ _' 0'50 r- 1 dipole modes (TMl,,n) to study tile possible impact of l._eam break-up instability,", in heavy ion _ with analytic calculational results from the drivers. These and inlpc_.tance calcuiations, coupled . BREAKUP beam dynamics ctx:le,indicate controllable beana break-up modes. '7 0.m_ _100 ,).o0 Future Wmtk 03o r'g,_ 7. tmm_'e .,r',,,6_c. , • 1.0o l.s0 2.o0 Ft_,_lUPa_(i-_)x 109 spectrum forthe _ Field calculations show that for the current, heavy-ion, linear accelerator cell configuration, the pulse power system and accelerating cores are 2.so inauctton largely decoupled from wakefields. Although this idealized cell has a high impedance-ge_metry figure of merit, _hemes to lower the Q of the lower- 3 A dB/dt at the accelerating gap. The equivalent shaglecoreconfihmrationwouldro.]uireeitherthree 1-Vacceleratinggapsora 3-V puM_powersystem, Another advantage of the ._gmented configuration is that one part of the core will not _aturate i__fore _'nv other part. in FY ')2, we concentrated on understanding the,_gmented cell geometry and multicell accelerating mtKtules for subrelafivistic heavy ions from a t.veam-cavit_, coupling point of view. Resmts from Accelerator Modeling. For the base case (Fig. 6}, the gap width is 1.5 cre, the radial length is 1.25 na,and the overall cell width is 10 cm. In Fig. 2, the Fourier transform of the lmpul._ n__l._mse (wake potential)" of the cavity due to cbarge bu.ach transiting the accelerating gap shows the beam-cavity coupling (interaction inat.x_.iances) for the monopole fields, The dependence of the inapedance as a function of v, the charge velocity, goes as sinc: (oxi/2v) (tra,_sit time factor), I'' where (0 is the angular frc'quency and d is the gap width. We can .,a.'e,in fact, that the natKit_ at 217 MHz and 497 MHz correspond closely to the TM,,_and TM,20 mt,des of the short pillbox gt._metn.', and the weaker coupling order nat_it._ can be develoF,.<t. We will continue ou! work to model the fully thrc_-dimensional, multi-beam-pipe cell as proposed by LBL for the Induction Linac Systems Experiments. We intend to develop detailed ani_tropic, dispersive media mt_els of Metglas in the coming year. We al_-) will be involvext in research on desibms for the nextgeneration induction accelerator for radiography. In the latter work, ali cavity m(Kleling results will be incorporated into beana dvTmmics ctKtes, with the goal being erld-to-end simulations leading to dosage c_timates. For high-average-power mmw comfx_nents, we have shown how application of feld ctKtes can be u_'d to analyze complex get, metrical aslx-,cts that are not anaenable to analytical techniques. TE mtKh__may be launchc_i in a beam-pipe by use of the dual K term (magnetic current) in the Faraday-Maxwell equation. TM modes may be launched using a similar dual technique.Since the rf impinging on the window (II0-GHz tube) is in the WG mode, it remains to be seen if the approach for extracting usable mtKies wdl invoh,e either (l) converting WG to usable modes external to the of the 92-MHz mtse com_.,sponds to the TM, ml m(Kte of tile 1.25-m radial line (Fig. 7). ] For this simplified mt_.iel, we can _'e that the don finant feature is the gap width, lo detemaine if the segmented core has ge×Kt damping features, we ol._'ned the gap width t_; ,'.5 cna. The field calculations (Fig. 8) sivw,, Iow Q re,,_mances (Q = 3.91) corrt__ponding to the 1.25-m (long-pillbox The final set of results to be discus_'d involves 2.410 _ 2.00 -,', x 1.60 ._ 3,., l.a_-- I Nominal ---- Opened _gum8. Imta_tance spectrum for gap -- _g_p I_qdth. ,.a 0.oo 1J__j I_ . 0"80 The res,ult (Fig. 9b) shows that this is indeed the c,a_'. Similar sinmlations were performed for the ,,ve,,,_,< -- _ 0.40 the stack_M accelerating mt_ulc_ (Fig. 9a). In the absence of inter-cell m(Kles"radial line. interactions, it is expecttM that the imp_Mance of a single cell will add in _,ries. _,_ I Res,,,_,c,_ 0.00 De_t,*ot)me_t _ Frequent3,0"_ (Hz) 1.1_x Ii)_ ,_ re_:_,_o_o/_ .¢, 1.50 Thrust Area Report FY92 1-17 Computational Electronics and ElectromagneUcs .:. 1""1_ Thrust Area Report FY92 .:. I , tt,t,_ ,,, ,_,_ An,-dysk_ of M/ctow_we t,',''_,'a_( _, I),'+._,,;),r,+.t ConlpotTentsand Accelerato_Modules ,+,:,! _,,, t,, ++,,,tI+ Analysis of MicrowaveComponentsand Accelerator Modules o:oComputational Electronics and Electromagnetics Lawson, IEEE Trans. Microwa_,e Theory and Techniqucs 37, 1165 (1989). 16. R.J.Brig_s, D.L. Birx, G.J.Caporaso, V.K. Neil, and T.C. Genoni, Part. Accd. 18, 41 (1985). 14. W. DeHope, Private communication 17. G.J. Caporaso, "Transw.,rse Instability in a Heavy Ion Fusion Induction Linac," lh'oc. Lonyit,dinal 1n- 15. C.C. Shang and J.F. DeFord, "Modified-Yee Field Solutions in the AMOS Wakefield Code," Proc. 1990 Linear Acceh'n#or Co1{f (Albuquerque, New Mexico), (_ptember 14, 1990). (April 1992). Er_glneellng Resei_rch stability Worl,'shot; (Berkeley, California), (Febru,_y t., 1992). Development and Technology 4, Thrust Area Report FY92 1-19 Electrom,w_et_¢ Mo(h,lmg ondE_tg(,mu,nts forD_s/)etsove Me(J/_.:. Computational Electronics andEloctromagnetlcs Modeling and for mve Medm Scott D. Nelsonand CarlosA. Avalle Dqfivsse Sciences Etty, iJteerili_ Divisiolt Eh'ctrolffcs Elzgilwerilt_¢ The G round Penetrating imaging Radar l'n._jectwas established to investiga tc the feasibility of designing an ekvtmmafinetic (EM) radar system to examine the internal structure of concrete structures typically found in the highway industry. The central project inw_ived the c(_wdination of the EM m_Jeling, imaging, code design, and experimentation efforts at Lawrence Livermon? National Laboratory. The modeling effort generated data for EM imaging and enabled the precis, control of individual parameters in the model. nlmn |nb'oduction The modeling effort consisted of three phases: (!) complex permittivity analysis of cement using a coaxial line; (2)model construction and expertmental verification in one dimension, which was represented by a coaxial line in the time domain; and (3) model ctmstruction and experimental verification in two dimensions, which was represented in the model by a slice through a concrete bl(_'k and experimentally byan antenna with a hn beam. _118 ()he-dimensional (1-1)) and two-dimensional (2-1))models were constructed and compawd with experimental data. The 1-1)data served as a preliminarv testofthedispersionalgorithmsadded to the AM(_412-i/2 1)I:I)TI) (Finite l)ifference Time I)omain)electromagnetic(l-M) mt_.|elingct_.le.l'he 2-1) data served as a verification for the concrete model and as a method to create wavetlwms for the image reconstruction algorithms, The following parametric studies were perfornled: I'uls,'r_,htlh: I(X)ps to I(XX)ps CltalI,wch'l_th: I()-mmh) 15(l-mmvoids C'han,,_,e sL-c: 5-mm t()75-mm voids A,\,,vrc'y,a/_' %: I()'!, t()5()",aggregate pmbabilitv I tll_l.e¢'_F I Multi-Receiver: 5-mm to 45-mm spacing (simulates highway speed or prf changes) Multi:l_u;_:et: no targets, I w)id, 2 rebars, 2rebars + 1void, grate, shadowing AirCom'rcic: ! cast' Bistalicdata: I set 1'he parametric studies gave some results that wen.,already hypothesized2,_: (!) the desired frcquency is close to 2 GHz; (2) the corrtvtion tilters have an image 'gain' of a tactor of two; (3)large targets reradiate in addition to reflecting;(4) monostatic data spatially averages out the aggregate effectsforsmall-and medium-sizt_t partich._;(5)bistatic data is more su_:eptible to aggregate effects near the transmitter than monostatic data, which is why commercial systems do not see a lot of aggregate effects; and (6)shadowing is not a significant problem as long as the spacing between the rebars is greater than three times the pul,_, width, and the rebars are not appreciably larger than the pulse width4 (to give the diffracted field time to repair the wave front). 1-D and 2-D Verification Effort A coaxial line was used for the I-1)simtnhlti(m, with thecement sampk, embedded in a removabk, section of 2-in.coaxial line.'l'he I,orentzian param- H_,',e._t,h I)evel(;l_ment ,_nd le_l_ou¢_lol.;; 4' Thrust Area Report FY92 1-21 Computational Electronics and Electromagnetics ,:. ElectromagneticModeling and Experunentsk_r Disperswe Me(ha eters u,'_'d for the initial ca,,_,s are as follows: I-D and 2-D dispersion 2-D verification experiment LLNL Anechoic Chamber ..... was performed in the using a broadband an- tenna (with a fan beam pattern), 'l_t sinh(7,/)} f{Ya,e ,:1 2 ,_1/J, - 7,I + j0J = lI+_ a concrete block, a broadband field l:,robe Ddot probe), and a transient digitizer. The(Prodyne time domain waveforms for the experimental and modeled ca_s are shown /J, + 7,1 + ire ] aggregate, dispersion of pulse the concrete in Fig. 2. Theandantenna beanl effects l._attern, shape ' block were included in the m_.tel. fhe finite size of a I = 1.55.10 m, the bk_:k /ii - 71 = 3,29. lOs, were al_ til + 71: 5.58.lO]°, and the included diffraction around the block in the model. 2-D Concrete Simulation a, = 1,6310_2, /J2-72 = 1.16'1[)1[, /j: +},: 3.62.10i.. Figure 3 shows the received waveform from one of the receiver antennas (1 of 15), with tile indMdual reflection identified for a geometry typ- The results for the 1-D experiment, performed in the I_,awrence Livermore National Lztboratory (LLNL) EM lab, 5 are shown in Fig. 1. Tile 4(X)-MI-lz ripple _,en in Fig. 1 repre,,_,nts tile resonance in tile material sarnple due to its length. The IINo block icai of the project/' In this, there were two rebars and one void at different depths and cross-range distances. Tlle effects of the aggregate in tile pmblem are clearly visible. The aggregate is modeled as di_'rete,_attering [x_.lit,'s of finite size. "File lighter Block i &l- -1 _ ,o, - 0.4 . t Bh)ck __ 0 0,2 -o.4 l{"f I - II . - -0, . 1 I I 2 3 Time (ns) I 4 S -1.o 0 1 2 3 Time (ns) 4 S 6 Figure2. Thetime domainwaveformsforthe 2-D concrete block experiment comparedto the modeledresults. Themodeled resultsarenormalized.Thenegative-goingdoublepeak in the experimental results is comhir : fntoa single negativegoing peak in the modeled results. ElectromagneticModeling and Experiments for Dispersive Media ,,', Computational Electronics and Electromagnetic: (b) Filtered waveform showing return from 2 rebars and ! void Target return signals are in this region, use filtering to isolate _: Figure3. Receivedwaveformsfromoneof 15 receiverantennas.Thefirst waveformshows the receivedtime domain wav_ form fromoneof the receiverelements in the modeledcase with no aggres_e and no dispersion.Theindividualtar_nt r_ flections are identified. Thesecondwaveformshews the effects of the aggregate in the problem.Thereceiverin this case is closer to the transmitter than in the previouscase. Thelighter curveshews the resulting waveformafter the application of the imaging team's adaptivefilter. Conclusions curve in Fig. 3 shows the results from the imaging team's adaptive filter. The reflections from the two rebars and from the void are clearly visible. The parametric study listed above was performed; Fig. 4 shows a typical wave propagation scenario, The 90 ° beamwidth of the antenna, the two rebars, Aggregate sizes less than one third of the pulse width did not create significant reflections at the receivers. Aggregate sizes on the order of the pulse width created discrete waveforms in the received the void, and the aggregate are ali visible. The aggregate radius is one half that of the rebars and represents a 30% probability duty cycle. The earlytime backward-propagating waves are due to the aggregate, signals in the power dispersion was most transmitter .P..i_.eri_a,,,. ..... o R._.Rr_'h ..... the areas around the transmitter where density was the strongest. Due to the effects of the concrete, the aggregate reflective (in a relative sense) near the when the pul_ was still short. Since D.vpln_mpnt. and r_chnoloPv_. _ Thrust Ar_a Report FY92 1"_P3 ComputationalElectronicsand Electromagnatics.'- Electromagnetic Modelingand ExperimentsforDispersiveMedia will be modeled using a section of a typical bridge deck as the target of interest. The transmitter/ receiver designs will be optimized to efficiently use the spectral information in the waveforms. Comparisons will be made to the experimental effort being performed on the 6 ft-x-6 ft-x-1 ft concrete test slab. This effort is already under way. Issues that still need to be addressed are: (1) single vs multiple transmitters; (2) different antenna beamwidths based on distance from the transmitter(s); (3) a single linear array sweeping a synthetic aperture vs a real SAR; (4)optimum receiver antenna size vs receiver density; and (5) the temporal holographic use of the time domain waveforms. AolomwkMJg_H_ts FYgure 4. Fourframesfroma propagating EMwavesequenceshowingthereflectionsfromthevarioustargets. Thetrensratthem is oa the umr surfaceof the concrete, an#thewavepropagatesdownintothematerlal.Thetwo rebarsam oa the right;the single voidis on the left. Note thepo/ar/tyd/Herence betwoentherebareandthe void.Also observe the multi_ ren_tior_ hetwounthe outertargats andthecentertarget. the area around the transmitter also had the greatest power density, then the maximum returned waveform (in an absolute sense) from the aggregate was also seen in this region. This modeling effort demonstrated that the original complex permittivity data obtained in the 1-D case does support large-scale material modeling, as was expected. More important, this effort confirmed the assumptions that were made about the aggregate and its modelability. 7 The size of the individual rocks constituting the aggregate and Thanks go to John DeFord (LLNL) for his advice and timely modifications to the AMOS code and to Robert McLeod (LLNL) for his efforts in adding dispersion to the TSAR code. The imaging team consisted of Jose M. Hemandez (LLNL) and Joe Arellano 8 (Sandia National Laboratory) with assistance from James Brase (LLNL). 1. J.EDeFord, G. Kamin, L.Walling,and G.D. Craig, Developmentand Applicationsof DispersiveSoft Ferrite Modelsfor Time-Domain Simulation, Lawrence Livermore National Laboratory, Livermore, Callfomia, UCRL-JC-109495(1992). 2. K. Olp, G. Otto, W.C.Chew,and J.EYoung,]. Mater. Sci.26,2978 (1991). 3. K.S. Cole and R.H. Cole, ]. Ch,'m. Phys., 341 (April 1941). M. Kanda, IEEE Trans.AntemuTsPropag.,26, 439. 4. their probability distribution were more important than some exact spatial placement for each rock ill the model. This result provided direct 5. C. AvaUe,BroadbandComplex Permittivity Measurements of Cement, Lawrence Livermore National Laboratory, Livermore, Califomia (in preparation). support for the usability of an adaptive filter as part of the imaging effort, to remove the aggregate effects even when individual aggregate particles generate discrete reflection waveforms in the received waveform. The aggregate specifications are known, or at least are specified, for concrete structures. 6. R. Zoughi, G.L. Cone, and ES. Nowak, "Micrc_wave Nondestructive Detection of Rebars in Concrete Slabs," MaterialsEvaluation--American Soci,'ty for NondestructiveTesting,1385 (November 1991). K.R. Maser, "Detection of Progressive Deterioration in Bridge Decks Using Ground Penetrating Radar," Prec. ASCE Conventhm (Boston, Massachusetts), (October 27,1986). _¢@ 8. Work 7. A realistic dispersive concrete model will be introduced in three dimensions, using the TSAR code, and a realistic synthetic aperture radar (SAR) 1-24 Thrust Area Report FY92 4, Engineering Research Development and J. Arellano, "Adaptive Filter for LLNL's Impulse Radar Inspection of Roadways and Bridges," EE373A, Adaptive S_,,nal Processing(Winter 199192). Technology BandGapEngineering fof InfraredDetectorso:oComputationalElectronicsand Electromagnetics eandGapEnneeringfor Infrared Detectors ]. Bdan Grant Engineering ResearchDivision ElectronicsEngineering We have extended and improved modeling codes for strained layer superlattices. Significant improvements include capabilities for reliable subband tracing and multilayer modeling; better vMidation of eigenstates; and the calculation of physical quantities such as wave function and optical absorption profiles and effective masses. I1_ Applications for infrared (lR) detectors include military, civilian, and medical devices with current interest focused on the far lR spectrum (wavelengths greater than 10 _m). Small band gaps corresponding to this range push the engineering parameters in commercial IR detector techilology, which is alloying Hgt_×Cd×Te. This process is not only very sensitive to composition, but toxic and volatile too. While a switch from alloy to superlattice technology would relax the conditions on exact composition,| an even greater benefit is obtained from a switch to III-V semiconductors, 2 where internal strain can be used in designing band gaps. Recent advances in Gel-×Sbx alloy fabrication provide another alternative, -_which is less s_,nsitive to alloy composition. Severe lattice mismat :hes prevent the formation of Ge/Sb superlattices. Of particular interest are superlattices c f GaSb/ modeling of non-perkKiic, finite-sized strucbar_. Computational speed is further enhanced by use of the k.p theory, which expands bulk wave functions in terms of those at the Brillouin zone center. Because interest is in the lowest conduction and highest valence, i.e, in bands near the Brillouin zone center, only the eight spin split s- and p-wave ftmctions of the bulk are kept. L6wden perturbation theory is used to extend the range of accuracy by including effects of other wave ftmctions to first-order. A significant portion of our project has focused on extending and improving existhlg modeling codes.4, s By combining several codes into a single package and by reducing and simplifying required ................. 0.7 _ lattice mismatch, the source of internal strain. The major tradeoff is reduced optical absorption beIn l_xAl×Asin which the alloy composition controls o.6 cause the superlattice is type II, i.e., the conduction and valence states are principally confined to dif- O.S]-_\_ i_ Iw\v\ la_ersl' ] _ 0"4[-\'_"_x----k\ ,_ ] _,_,'_X 2 _x= 0.1 =0.2 - consequently increasing wave ftmction overlaps. The modeling of strained layer superlattices is _0.31 _] --._ x = 0.3 "4- x = 0.4 _ Englneer_ng Research compositioneffects - - x = 0.0 ferent material layers. Thirmer layerhlg and strain help toovercome thisby increasing ttumelingand proaches, which must model each atom in the periodic structure. The matrix approach al_ allows Strain and on _ndgap. t__bld5 perhaps best achieved through the use of interface transfer matrices. These matrices identify how wave functions in one bulk-like material are transformed into those ofthe theexcessive next. While thissize idealizes interfaces,ap-it eliminates basis of tradition_ FTgum Z. --_ _'_ _____KN_ 0.2I--__,Nlk_"N" _ _ ' _N_,._,Z,q+ _ 0.1 _::___, _, / .... "l-'?_, _O ] I ] ] ] I ] I I ] a S 7 9 lZ la is 17 19 21 d (layem) Development anti lechnolog), 4o Thrust Area Report FY92 1.2_ ComputationalElectronicsand Electromagneticso:oBandGapEngineenng for InharedDetectors Figure I shows a sample calculation for SBRC -- = -- -- -- .--._- --, ¢,_..-- -Ga l_,ln,Sb superlattices. . _ _ - w_C---_ %Transmiss_ ,_ _C_ _ __i_ % % _,, % _:0 _V_.. __ _ _V,_,. BulkInAS _._ / " _ BulkGaSb Gradedlayerln8 Figure2. Percenttransmission asa functionofelectronenergyrelativetothebulk conduction(C)andvalence(V)bandedges.SlopeofbandedgesIndicatesanal> pliedvoltage, input, the ease of use was greatly improved. Further, the resulting sis code was made truly 'user friendly' by building an X windows _xt interface that wraps around it. The incorporation ofcapabilities for automatically locating subband-edges, as well ,as for reliable energy subband tracing, has aisoenhanced the code's versatili_,, Other significant inaprovernents include better validation of eigenstates and allowance for calculation of a variable number ,,; bands. Both help to alleviate the numerical in: .tabilities introduced bv the inclusion of extrel_aelv weak, but finite, tunneling wave functions sometimes required for accuracy. Significant capabilities were ,added to the sis code toallow multilaver superlattices Previousiv, only two layers could be modeled. Further advantage was taken of the interface-matching approach by allowing the non-periodic boundarv conditions of a finite-sized superlattice sandwiched between two semi-infinite bulk materials. Calculation of various physical quantities were alsoadded. Anat_ngtlaenaoreinalgortantarewave function and optical absorption profiles, and iengtla of 12 l.tm wouM require very thick layers of haAs without alloying = ().()),but that (alloy) only Iand 1or that demonstrates the (x effects of strain 12 atomic layers would be required for a cor,ap,_sition where x = 0.4. In addition to the band gap, SBRC is interested in the actual position of the conduction band with respect to the claemical potential (Fermi level) and the optical absorption as functions of the same parameters. Similar plots can be made of those values. Values of effective masses calculated by the sls code can also be used for add itional calculations by SBRC. Modeling for programs at Lawrence Livermore National Laboratory (LI_,NL) has been based on graded-layer superlattices that slowly accommodate large band offsets. Externally applied voltages then provide a rather constantenergy cor_dtiction band throughotlt the structure. The sis code easily identifies acceptabletransmission energy ranges, as shown in Fig. 2, as well ns resonant tunneling states, which build up nauch larger electron concentrations between barrier layers. While this code is unable to provide self-consistent estimates of current densities, the information available can provide a guide to superlattice grading, and quantitative estimates of the necessary external voltages. FutureWork This project has included software development and improvement, modeling, and teclanology transfer. The result is a rather complete and usable strained-laver superlattice code. Relations with SBRC are continuing, supported in part by the Physics Department,at LIgNIn. I. 1).!..Smith, "I.C.Mc(;ill, and I.N. _taulnaan, AtV_I. 2. I'hlls.I.,'tt.43, 18(1(!t)83). I).K. Arch, (;. Wicks, i.Tonae, and I.-!.. Staudt,rmaann,/. At;pi. I'lnls.58,3t)33(1985). effective masses. 3. Atlother significant t?onlponent of this project was technt_lo_' transfer. Working with Bill Ahlgren of _anta I_;arbaraRt_,arch Center (%BI_C),a subsidi,u_, 4. of l-ltlgllt_, we engaged in ntlmerotlS mtKieling activitit_. Illeslstrw.k, ha,, l.×_,n transtem__l t_SBRC for s. l:tlrther 1-26 Thrust Area Report tl_, dnd c(intilluct_ FY92 .'_ /l_/t:,,_._.,,r_l: S.M.I.t,e ,llld W. I'aul, "l.]t.ctronic B,ind (;ap Measttremt,nts ot IC,lkMetastable Crvstallint, ; ;t'l ,Sn, Alloys, ()<_x <_: 0.31! "prr, print. C. Mailhiot and ILl.. Smith, Crit. I<('r.5,_lidStair Ma/,'r Sri. 16, 131(!t)tll)). I).[ .. Smithand(..'. Mailhiot, I@_,. _V/_1,_d. l'hil_. 62, 173(Itjtj()). L] colla[_lrations. .q't.-.t',lt_ 1_ [)l'_l,¢(,_Jt.i.tll Note that a target wave- ,l_tl Jl't htl(_l Ipt Computational Mechanics TheComputationalMechanicsthrustarea sponsors research into tile underlying ,_lid, structural, and fluid mechanics and heat transfer necessary forthedevelopmentofstatL_ff-the-artgeneral purpose computational software. The scale of computational capability spans office workstations, departmental computer servers, and Crayclass supercomputers. The DYNA, NIKE, and TOPAZ ctx:les have achieved world fame through our broad collaborators program, in addition to their strong support of on-going Lawrence Livermore National _,'i Laboratory (LLNL) programs. Several technology transfer initiatives have been based /" on these established c(Kles, teaming LLNL anaJysts and researchers with counterparts in industry, extending c_xie capability to specific industrial interL_stsof casting, met- alforming, and automobile crash dynamics. 'file next-generation solid/structural mechanics code, ParaDyn, is targeted toward massively parallel computers, which will extend performance from gigaflop to teraflop power. Our work for FY-92 is de,_ribed in the following eight articles: (l) _lution Strategies: New Approaches for Strongly Nonlinear Quasistatic Problems Using DYNA3D; (2)Enhanced Enforcement of Mechanical Contact: The Method of Augmented Lagrangians; (3) ParaDyn: New Generation Solid /Structural MechanicsCt_.tes for Massively Parallel Prtx:essors; (4) Composite Damage Modeling; (5) HYDRA: A Parallel/Vector Flow _iver for Three-Dimensional, Transient, lncompressible Vinous Flow; (6) Development and T_..,sting of the TRIM3D Radiation Heat Transfer C_Kte; (7) A Meth_x:lology for Calculating the _ismic Respon,,_, of Critical Structures; and (8) Reinforced Concrete Damage Modeling. Gerald L. Goudreau Thrust Area h,ader Section -- _____ 2 2. Computational Mechanics Overview Gerald L. Goudreau, Thrust Area Leader Solution Strategies: New Approaches for Strongly Nonlinear Quasistatic Problems Using DYNA3D Robert G. Whirley and Bruce E. Engelmann ............................................................................... a.1 Enhanced Enforcement of Mechanical Contact: The Method of Augmented Lagrangians Bradlet/ N. Maker and Tod A. Laursen ........................................................................................ 2.7 ParaDyn: New Generation Solid/Structural Mechanics Codes for Massively Parallel Processors Carol G. Hoover, Anthony J. De Groot, James D. Maltby, and Robert G. Whirley ..................... 2.11 Composite Damage Modeling Edward Zywicz ........................................................................................................................ a.3.s HYDRA: A Flow Solver for Three-Dimensional, Transient, Incompressible Viscous Fluid Mark A. Christon ..................................................................................................................... a.J.9 Development and Testing of the TRIM3D Radiation Heat Transfer Code James D. Maltby ....................................................................................................................... 2-23 A Methodology for Calculating the Seismic Response of Critical Structures David B. McCallen, Francois E. Heuze, Lawrence ]. Hutchings, and Stephen P. Jarpe ............................................................................ 2.27 Reinforced Concrete Damage Modeling Sanjay Govimtjee and Gregory ]. Kay ....................................................................................... a._ Solution Strategies: New ApproactTes for Strongly Nonlinear Quaslstahc ProOlems Using DYNA3D o:o Computational Mechanics Solution Stmtegles: New oaches for StronglyNonlinearQuasistatic ProblemsUsingDYNA3D Robert G. Whidey and Bruce E. Engelmann NuclearExplosives Ellgilleerillg MechaJfical EJs_,iJleeri_lg The analysis of large, thr___-dimensional, strongly nonlinear structures under quasistatic loading is an important component of many programs at Lawrence Livemlom National Laboratory (LLNL). The most widely used formulation for this type of problem is an implicit solution process with a linearizafion and iteration approach to soMng the coupled nonlinear equations that arise. Our research investigates an alternative approach, in which ml iterative solution method is applied directly to the nonlinear equations without the use of a linearization. This approach alleviates some of the difficulties encountered when linearizing nonsmc×_th phenomena such as mechanical contact. The first iterative method explored is the dynamic relaxation method, which has been implemented into the LLNL DYNA3D code, and combined with software architecttu_, and computational mechanics technology developed for explicit transient finite element analysis. Prelimina_,, analysis results are presented here for two strongly nonlinear fftf' approach. quasistatic problems to demonstrate Introduction Many programs at Lawrence Livermore National l+aboratorv (I.LN[+) use nonlinear finite element structuraf analysis to guide engineering projects. -\pplications include the determination of weaD)n component response to a variety of structural and thermal environments; the study of stres_,s in nuclear fuel transportati_n casks; and the simulatit}n of the forming of sheet metal parts to optimize pnaes.sing parameters and minimize waste. fhese applications share the common feattlres of being tllree-dinlensiollal (3-1)),quasistatic, and stn,lglv nonlinear, and illustrate wide use of this type t_fcomputer analysis, Nonlinear finite element structural analysis metht_ds may be divided into twt_ categories: iraplicit mvtl-ltKtsand explicit meth(_ds. Implicit metht_ds are typically used ft)r quasistatic and ](_w-frt'qtit'l'lC\' dynamic prt_blenls. The I,I.NI. N1KE2D I anLi NiKE3I) 2 c_des are ba._ed on an implicit l:ormtllati_.l. This appr_ach uses a small the promise of a linearization- number of large increments to step through the simulation, with the increment size cho_,n by the anah, st to satisfy accuracv and convergence requirements. An implicit analysis code must solve a coupled svstem of nonlinear algebraic equations at each step, usually by a iinearization and iteration procedure. This linearization leads to a coupied system of linearalgebraic equations that must be solved at each iteration of each step in the analysis. Typically, the iteration process is continued within a step until some convergence measure is satisfied, then the solution is advanced to the next step. Explicit methods are typically used for highfrequency dynamics, wave propagation, and irapact problems. The I,I_NI_, DYNA2D 3 and DYNA3D 4 codes are based on an explicit fomlulation. In contrast to implicit methods, explicit meth()ds usea largenumberofsnaallincrementstostep through a problem, with the increment size chosen automatically tosatisfv stability requirements. This stability requirement essentially dictates that t r,_{_*_e_ t _g Re,,e at_h DevelOl)mer_t anti lc.(hn(_lug; .'. Thrust Area Report FY92 2-1 Computational Mechanics _ Solution Strategies: New Approacl)e._ tel St/onglv Non/meal Qu,)_istatlc P/obl(;tn._ Using _YIVA3D the time increment size must bN smaller than the time it wouM take a stress wave to propagate across the smallest dimension of the smallest elemerit in the mesh. An,xplicit code does not solve couph.'d equations at each step, and therefore the update ft'ore step to step is much faster than in an implicit code. In practice, implicit meth_x'lshave worked well for strongly nonlinear quasistatic problems in two dimensions, but have encountered difficulties on 3-D problems. These difficulties can bNattributed to thrt_' primary factors. First, large 3-19 contact problems, espt_:iallysheet-formi|lgproblenls, llave large matrix bandwidths due to the large contact area between tile sheet and tool surface. This large matrix bandwidth translates into high computer menlory requireme|lts and expensive li|lear solutions at each iteration of tile nonlinear solution process. _'cond, strongly nonlinear problems often contain di_'ontinuot|s phenomena that are difficult to linearize. For example, in a contact problem, the interface pressure abruptly changes frt_m zero when two bodies are separated to a finiW value wlaen tile bodies come into contact, Obtaining an accurate linearization of such abrupt changes is difficult, and this is manifest in the code as slow convergence or nonconvergence of the linearization and iteration prtx:edure within a step. Finally, when solutior| difficulties are encountered in a large 3-D problem, it is nluch nlore difficult to troublesht×_t the model than it would be in a similar two-dimensio|lal model. Ofter| there are few clues to suggest why the iteration procedure is having difficulty converging to a solution. The developn'|ent of a more robust soltttion strategy for strongly nonlinear quasistatic problems is the primary objtx:tive of this effort, One approach to improving tile performar|ce of implicit methods for large, 3-1), strongly nonlinear quasistatic problems ftwuses on the solution of tile large linear svstern that,arises ft'ore the linearization and iteration a,pp:',;_,_ch.An iterative method, such ,astile use of a prt_'onditioned conjugate gradient, is one approach to solving the linear system. This approach was investigated in the LI_NL NIKE3D cocle,_ and culnainated in tile development of an iterative solver r|ow used in the prtx:luction code version. Although this approach reduces menlory requiren|ents and may reduce CPU costs for tile linear equation solutit,1, it dtws nothing to improve tile convergence of the nonlinear iteration. An alternative apprt_act| ftu"difficult quasistatic problems is to use an explicit transier|t dynan|ics code, and apply the loads so slowly that tile dynamic effects are negligible, and therefore a quasi- 2-2 Thrust Area Report FY92 • Lnglnee,ltlg I?p,.;e,Jt¢l_ I)evt, lopmpnt _tatic solution is obtained. Although this approach isoften used by engineering analysts, it does have _,veral disadvantages. First, the best rate of Ioacl apF, licatiotl to minimize dynamic effects while keeping the analysis cost tolerable is not known a priori, and often requires some experimentation. Also, ii is important to minimize artificial oscillations in tile solution when history-del.x'ndent material models such as plasticity are included, and this further complicates tile choice of analysis parameters. Finally, this approach obtains only an approximatequasistatic solution, and the amount of error due to dynamic efft.'ts requires some effort to quantify. These observations suggest tile alternate appmacll followed in our work. The basic linearization and iteration paradigm is abandoned, and an iterative solution metht_.t is applied directly to tile nonlinear equations.This rnetht_J iscombined with much of tile computational naechanics ttx:hnology and software archiWcture developed for explicit transient dynamic analysis to prtwJuce a ctx.|e that solves the nonlinear problem directly by ,_sing a large numl,x,r of rather inexpensive iterations, and without solving a ct_upled linear system. The esro,ntial dements of this approach and its development in the Ll.Nl.l)YNA3l)codearede,_ribed I.x,low. I:_._ h| FY-q2, we developed an iterative quasistatic solution capability in DYNA3I), basex.! on the dynamic relaxation (I)R) method. In addition to tile implen'|entation of the basic I)R procedure, a load ir|crenlentatior| frar|lework has been incorporated into DYNA31) that allows a true quasistatic soltttion to be obtained at a load level before the load is if|creased for tile next increment, in addition, a spectrur|l contraction algoritllm has been implemerited that greatly improves the efficiency of the method. Also, extensions have btx, n developed for the rigid-bt_ly mechanics fornat|lation and the treatmerit of boundary conditions to accornmodate n:)nlinear quasistatic problems withir| the DYNA3I_) framework. The t'esulting code is now being used as a testbed to evaluate the overall robustness and efficiency of the DR method, and to study iraprovements in the forr|lulatior|, contact algorithnas, and adaptive dampingprtwedttres. Overview of the DR Approach in the I)R method, the equatit,ls governing a quasistatic analysis are first transftwrned into those governir|g a dvr|atnic systenl. "l'he nt_nlin_,ar tori- and l_,,-hnolt,,i,_ SolubonStrategies:NewApproachesfnrStronglyNonlinearQuaslstatlcProblemsUsingDYNA3D.:"ComputationalMechanics p(x0) = f, ( 1) requiredforconver. ._ 1 malized iterations . themagnitudeoft,._e from stress :-rates in the finite elements; x_)is the ntKtal displacement .,_lution; and f is a vector of externally applied loads. An associated dynamic problem mav be writte_ :ts damping factor in " the dyrmmicrelaxnti_ method. 2 Mi_ + Ck + p(x) = f, (2) where dots denote clifferentiation with respect to time. With the appropriate choice of mass and damping matrices, M and C, the solution of the d_lamic problem as th]le gets large approaches the solution of the quasistatic problem, i.e., lim x(t) = x,. (3) The iteratix, e scheme is defined bv applying hhe explicit central difference methtK-! to integrate the dynamic equations in time. The success of thedwlamic relaxation iterative methtKl to _)lx'e highly nonlinear quasistatic probleto.s depends on many factors including the specification of mass and damping, as ,,,,,ell as the development of an incremental loading strateg,y. Spectrum Contraction The efficiency of the DR roeth(×'i may t_, irapnwed by contracting the spt.K'trum of the global c_.]uations. This is easily accomplished by proper choice of the mass matrix M in Eq. 2. The construction of the mass matrix should not dominate the computation, and thus it should be based on convenientlv available quantities'. In our algorithm, the mass matrix is cor,_,4mcted from an assemblage of element contributions. The mass matrix of each element is scalt_:l so that ali elements have a un/form critical time step, and thus information flows throughout the rr ,:_h at an optimal rate 0 0 500 Cantilever Elastic Plate Example To demonstrate _)me essential features of the new quasistatic solution capability, in DYNA3D, an elast;c cantilever plate was subjected to an applied moment on the free end. The problem was _lved with two magnitudc_ of applied load: one \\ Damping t(,_\_l_\x ,_r_g,r_eer_t_g 200 300 400 Damping factor(lO-s) estimates must be usecl for the lowest eigenvalue, which can va_, greatly throughout a nonlinear simulation. When ic ufficient damping is used, iteratc_ will oscillate around a solution and reacl-, it very :_low!y.Too much damping will dramatically' retard conx,ergence, especially for problems that include large rigid-btKty motions such as the motion of the sheet in sheet-forming simulations. Resuits thus far indicate that adaptive damping approaches, ba.,_d on the evolving physics of the problem, may prove most effectix'e for highly nonlinear problems. Figure I shows the variation in the number of iterations recluirecl to converge relative to the magnitude of damping in the DR algorithm. The graph depicts the strong influence of damping value on the number of iterations required by the DR methtKt to converge to a solution. The automated detemfination of the optimal damping value is a subject of ongoing investigation. proven quiteiteration u_ful prcKt._s. in accelerating the converduring the This technique has gence of the DR meth_×'l. The type and amount of damping can also significantly affcx:t convergence. For linear svsterns, optimal damping depends on the ooth the highc.,st ,and lmvt__t eigenvalues of the svstem, Although bounds on the highest eigenvalue are reat_iIx"available from theelement eigenvalue inequality, 100 x \ \' _ x _ _ _ I / j t _', • .;_ \ x_ _ i , , I i , _/"//////7 r_tnt_mdtinata_r(mn___rar..n_ver __gwe2. _ to an ena_. Theu/_a_rtt&Weeonesp(_lstoasn_k)a_, and_e_.er_i_retoal._erk)ad, r_ r,aut_ to e,_ o¢_ _m_ was_ taango, tyone _a_ment _ thelX__in DY_aD. R_',_',_rct_ Devetot_me_t i_.(I 7_.(h,_otold,_ .'.. Thrust Area Report FY92 2-3 ComputationalMechanics.:- SolutionStrategies:NewApproachesfor StronglyNonlinearQuasistaticProblemsUsingDYNA3D " i:lil'- i.3 T_ _", r : I ." ! [ '.... Figure& Initialgeometry forhydroformingsimulation, showing the punch, blankholder, andsheet.The punch and blankholderaregeometricallyrepresentedby &nodecontinuumelem_ and are treat_ as rind bodes. Thesheet is represented by4-node thinshellelements andismodeled as anelastic-plasticmaterial, that causes a small deformation of the plate, and one that causes an extensive 'roll-up' deformation, The initial geometry and the two final deformed shapes are shown in Fig. 2. An interesting obserration is that the DR algorithm required approximately the same number of iterations to converge for both load cases. This is in contrast to conventional implicit solution techniques, where the number of iterations required to converge increases quickly with the degree of nonlinearity. This illsensitivity of DR to the degree of nonlinearity is a powerful advantage of the DR method, Sheet Metal-Forming Example formed shapewith thatpredicted by numericalsimulation. Thecircledareasin thenumericalresults indicateregionsof largestrains,and thesecorrespond closelywiththe tearsobservedin the realpart. 2-4 Thrust Area mize dynamic effects, ali approach requiring approximately two hours of CPU time. More recently, this problem was solved using the LLNL implicit code NI KE3D, but it required somewhat more computation time. Using the newly deveioi.KKiiterative methods in DYNA3D, this solution has been obtained in approximately 20 minutes of CPU time. Further improvements in contact algorithms, adaptive damping algorithms, and code optimization should enable solution of problems such as this in even less CPU time and without trial and error. Although much remains to be done, the_ initial results indicate tile promise of the iterative quasistatic solution method in DYNA3D. Ft_re Wock One major application of the quasistatic solution capability developed in this research is the numerical simulation of sheet metal-forming processes. These problems pose a real challenge since they involve large strains, material nonlinearities such as plasticity, and extensive sliding contact F/gure4. comparisonof actualde- with addition, thin difference sheets havebe-a wide friction. spectrumIll due to tiletilelarge _,een in-plane and bending stiffilesses, thus making them even more difficult for an iterative solver. Figure 3 shows the finite element model for the numerical simulation of an aluminum hydrofonning process. Pressure is applied to the upper surface of the sheet to hold it against the blankholder, and the punch is then advanced to form the sheet into the final shape shown in Fig. 4. The good comparison between the computed results and the shape of the actual part, including the failure locatkms, is illustrative of the power of a versatile quasistatic analysis tool. This problem was first solved at LLNL in 1988 by running DYNA3D in an explicit dynamic analysis mode and applying tile loads slowly to mini- Our research in FY-92 has led to the development and implementation of a DR iterative strategy for quasistatic problems in tile LLNL DYNA3D code. Four general conclusions can be made from our experience thus far: (1) overdamping in the (bl , (a) ._ l _._ _..... Report FY92 4. Eng'neerlng Research Developtnent and recht_olog_ SolutionStrategies:NewApproachesfor StronglyNonlinearQuasistaticProblemsUsingDYNA3Do:oComputationalMechanics DR method significantly slows the convergence rate, especially for problems with large rigid body motions; (2) the convergence rate of DR appears insensitive to the degree of nonlinearity in many problems; (3) the rate of load application within an increment is important, and a step ftmction is probably not optimal; and (4) adaptive damping algorithms work extremely well for some problems, and are clearly desirable. More study and development will be required, however, before these algorithms can be used for general production analysis. Our research efforts in FY-93 will explore the promising directions discussed above. We will refine adaptive damping DR algorithms and develop optimal load application schemes for a range of nonlinear quasistatic problems. We will also investigate new contact formulations to eliminate the solution noise introduced by the current penalty-based procedures. In addition, we will evaluate the utility of the nonlinear conjugate gradient algorithm for the problem classes of interest. Finally, the results of this effort will be optimized for vec- Acknowledgements The authors wish to ackalowledge Dr. Brad Maker of the LLNL Methods Development Group for sharing his early experiences on sheet forming with DYNA3D and for providing the finite element model and photographs for the sheet forming example. 1. B.E. Engelmann and J.O. Hallquist, NIKE2D: A Nonlinear, Implicit, Two-DimensionalFinite Element Code.forSolM lHechanics--User Mamml, Lawrence Livermore National Laboratory, Livermore, California, UCRL-MA-105413(1991). 2. B.N. Maker, R.M. Ferencz, andThree-Dimensional J.O. Hallquist, NIKE3D: A Nonlinem; Implicit, Finite ElementCode.forSolidand Structural Mechanics--User Mamml, Lawrence Livermore National Laboratory, Livermore, California, UCRL-MA105268(1991). R.G. Whirley, B.E. Engelmann, and J.O. Hallquist, DYNA2D: A Nonlinear, E._t_licit,Two-Dimenshmal Finite Element Code for SolM Mechanics_Llser Mmmal, Lawrence Livermore National Laboratory, Livermore, California, UCRL-MA-110630(1992). 3. tor computers and implemented into a future production version of the LLNL DYNA3D code for general use. In addition, the algorithms developed 4. R.G. Whirley and J.O. Hallquist, DYNA3D: A Nonlinem, Explicit,Three-DimensionalFiniteElement Code for Solid amt Structural Mechanics--Llser Mamml'LawrenceLiverm°reNati°nalLab°rat°ry' Livermore, California, UCRL-MA-107254(1991). 5. R.M. Ferenez, Element-By-Element Ptvcondithfing _,clmiquesfor Large-Scah',VectorizedFinite Element Anaysis in NonlinearSolidamt StructuralMechanics, Ph.D. Thesis, Stanford University, Palo Alto, California (1989). L_ in this project will be implemented into the ParaDyn project to allow the solution of large quasistatic problems on massively parallel computers. Engineering Research Development and Technology 4. Thrust Area Report FY92 2.5 Enhanced Enforcement of Mechanical Contact: The Method of Augmented Lagrangians o:oComputational Mechanics Enhanced Enforcement of Mechanical Contact: 1he MeUmd of Aed ans Bradley N. Maker NuclearE.xplosivesEngineering MechanicalEngineering We have introduced the method Tod A. Laursen Duke Universiht NorthCarolina of augmented NIKE2D and NIKE3D. This approach penalty method for enforcing contact accuracy is determined by physically penalty parameter. Lagrangians into our stress analysis codes, provides a simple and effective enhancement to the constraints. Also, by using augmented Lagrangians, motivated convergence criteria, independent of the |gtroductkm distributions obtained. Contact between deformable bodies occurs commonly in mechanical systems. Stress analysis codes that are applied to multi-body systems and assemblies must accommodate this contact to be useful to design engineers. Our NIKE and DYNA finite element codes have a widely recognized capability to capture the mechanics of contact in complex systems, as the models in Fig. I demonstrate. The results of this research effort have further enhanced our contact algorithms by introducing the method of augmented Lagrangians into NIKE2D and NIKE3D. This simple example highlights the nonlinear nature of the contact problem. Indeed, the deformarion of each body may be large, generating both geometric and material nonlinearities. But the more fundamental nonlinearity, in the contact problem ari_s from the discontinuous manner in which the contact area evolves. Since the surfaces are faceted, the contact area grows or shrinks in discrete increments. These abrupt changes in contact area are sharp nonlinearities, which complicate the equilibrium search process. In the finite element method, bcxties are discretized into as_mblies of elements whose bound- Progress aries are described by a set of node points. In this context, mechanical contact conditions act to constrain the node points of one body from penetrating the boundary surface of another. Figure 2 represents the di_rete contact problem in two dimensions. Driven by the action of externally applied loads, a single node point from the 'slave' body penetrates the boundarv of the 'master' body. This penetration is identified by a _'arch algorithm, and activates the constraint enforcement algorithm. As the contact constraint is enforced, penetration is minimized, and stress and deformation are induced in each body. This deformation may cause other slave nodes to penetrate the master body, which in turn activates additional constraints. As this iterative process reaches equilibrium, the proper contact area and pressure The constraint algorithm used to minimize penetration in most finite element codes, including our own, is the penalty method. This simple but effective approach introduces penalty springs betw___enthe two bodies wherever penetration occurs. As the penetration increases, the springs are stretched, generating forces that oppo_ further penetration. The springs act unilaterally, i.e., when the bodies separate, the penalty springs are removed, allowing gaps to open. One obvious drawback of the penalty method is that penetration must occur before any constraint forces are generated. Thus, in the equilibrium state, where each penalty spring is properly stretched to balance the applied loads, the two bodies are interpenetrated, and the exact contact condition is violated. Engineering Research Development that balance the applied and Technology • loads are Thrust Area Report FY92 2-7 Computational Mechanics .:. Enhanced Enforcement of Mechanical Contact: The Method of Augnlented Lagrangians .... results are dependent upon the vah.he chosen for the penalty stiffness. This effi.,ct is demonstrated in FiB. 3. Clearly, as a larger stiffness is chosen, the bodies are driven further apart, and the contact area and/or pressure changes. This arbitrariness motivated our work toward an enhanced constraint algorithm. The augmented Lagrangian method is an effective and intuitively obvious enhancement to the (a) penalty method, and proceeds as follows. Using the penalty method as a kernel, equilibrium is obtained in the usual manner. With known penetration depth and penalty stifflless, the contact force may be computed. This force is taken as the initial value for the Lagrange multiplier. The Lagrange multiplier defines a static load that is applied to the slave node, and the equilibrium search is then repeated. In the presence of the Lagrange multiplier load, penetration is reduced. The new penetration distance is then used to compute a new increment in contact force, the Lagrange mul- (bl Figure 1. Examples of NIKE3D contact algorithms applied to engineering problems: (a) the belted superflange and (b) the Kestrel bulkhead, To minimize this peneh'ation, the penalty spring stifflless may be increased, generating a large contact force through a very small penetration. This approach works well in theory, but in practice introduces poor numerical conditioning, and inevitably numerical errors. But a more fundamental deficiency of the penalty method is that the tiplier is augmented bv this increment, and the iteration process is repeated. This equilibrium search and Lagrange multiplier augmentation k×_p proceeds until convergence is obtained. But now convergence may be defined in physically meaningful terms. Forexamph:, the augmentation loop can proceed until the contact force (Lagrange multiplier) stabilizes to within 1'% or until the largest penetration is less thana user-specified distance. ii Pressure (ai (b) Slave Fl=kd vF 2= F1+ kda,F3= Fa+kd 3 Master Figure 2. Enhanced enforcement of mechanical contact. (a) A search algorithm detects penetration of the master body by the slave node point. The penalty method introduces a spring of stiffness k between nodes S and M. When stretched, the spring generates Interface force F = kd. (b) The augmented Lagrangian method applies F as a static force on nodes S and M, and iteratively augments this force, i.e., Fn+1 = Fn + kd n until a convergence criterion is satisfied. 2-8 Thrust Area Report FY92 .:. Fr_,g,r,e'_*r_r_f', Re,'-,¢',ltt tp [)_'_,_'loIIt_l,'_!f ,I,,1t II', tl,_,,,i,!:_ Enhanced Enforcement (a) Default penalty . F,, lb oi Mechanical Contctct: 1he Method of Augmentc'd Lagtangtans (b) lO,O00xpenalty " o:- Computational Mechanics (c) MAL,0.1% F. 7,0OO.lb F. 69,00Olb Figure 3. Using the penalty method, results vary dramatically with penalty stiffness. In this example, a contact interface is defined between two flat plates (arrow). The lower plate is fixed at its lower edge. A downward motion is prescribed to the upper edge of the upper plate. Erratic stress distributions result using NIKE3D's default penalty stiffness (a). Increasing the penalty stiffness by 104 produces a more untfonn stress distribution (b). The augmented Lagrangian method gives the most accurate solution (c) using a convergence tolerance of 0.1% on the interface force. This same answer was obtained for pe_ alty stiffnesses ranging from 1@2 to 10 4. The new method therefore provides an insurance policy against errors from a poorly chosen penalty parameter. The new method has several advantages. In the limit ota large number of augmentations, equilibrium contact force is obtained without penetration. Further, thesolutionisindependentofpenalty parameter, since augmentations proceed until the (physically based) convergence criterion are satisfled. The exception to this independence is the case where the penalty stiffness is cho_n so large that the original penalty method (the kernel of the new method) will not converge due to numerical conditioning. This case is obviously m_x}t, since both methods hil. The obvious drawback to the augmented Lagrangian method is that an additional iterative I_p is introduced into the solution pr_:ess. For a very soft choice of penalty parameter, this iteration loop can be slow to converge. However, _._tlrJillplementation allows fl}r immediate convergence with no iteration if the penalty stiffness is ck,verly (or luckily) chosen to satisfy convergence criteria in the first step. The method is therefore an insurance policy against a poor choice of penalty parameter, which before would have yielded an inaccurate result. The final and perhaps most dramatic advanrage to the new method is that the l,agrange multipliers are preserved ft," use ill the next loading step. Thus, fi_ra problem in whicll load is applied I ngltl_,(,tlng in several steps, the initial guess at contact pressure is the converged value from the previous step. This history information often speeds convergence of the equilibrium ,_,arch in the secorld and later steps in the problem, and can result in an overall reduction in CPU run time for a complex problem. The augmented Lagrangian method provides a simple and effective enhancement to the penalty method for enforcing contact constraints in NIKE2Dand NIKE3D. Accuracy is determined by physically motivated convergence criteria, and is independent of the penalty parameter. F'U_I_ Work The method of atigmented l.agrangian also of_ fers a new mathematical framework for considering the frictional COlltact problem, which will be pursued in future work. Adf,_lOwl_l_o_ We gratefully acknowledge the extensive collal:_ration of l)r. Bruce l'_ngelmann in the algorithm developmentand NIKI-2l)implenwntation,and Mt,'ssl,s. M.A. (;erhard, I).J. '['rumrller, and E.A. I_latt for the suD,rflangeand Kc,'strelexampk,'s. LI t?_,5(,,11ch I c'v('l_l)nl_'tlt ,l_lll l(,(llll,Jll,l{; ":" Thrust Area Report FY92 2-9 ParaDyn: New Generation Solid/Structural Mechanics Codes for Massively Parallel Processors o:oComputational Mechanics ParaDyn: New Generation Solid/ Structural Mechanics Codes for Massively Parallel Processors Carol G. Hoover NatiollalEneGn j Research SupercomputerCellter Comtn_tatio_z Directorate James D. Maltby NuclearTest Engineering MechanicalEny,iJweriltg Anthony J.De Groot EngineeringResearchDivision Eh,ctronicsEngineering Robert G. Whidey Nuch'arExplosivesEngilleeriJlg MedzanicalEngineerilzg The objective of this work is to develop DYNA3D for massively parallel computers. In this last year, we have worked with the DYNA2D program on a Tl-finking Machines CM-5 computer to develop strategies for distributing the data and parallelizing the finite element algorithms. We are using the experiences gained with DYNA2D to guide the parallelization of the algorithms for the much larger and more complex DYNA3D. We have measured performances comparable to Cray Y-MP speeds for a DYNA2D test problem on systems with as many as 512 processors. The performance restflts show moderately large commtmication times relative to computing times, pmt-icularly for the global force assembly (scatter). We attribute this performance to the early developmental releases of the CM-5 software. computer is a 16-procc_,_r system with a peak perfomlance of I GFLOP per proc___sor.The motivation Recent advanc___in microprtx:essordliptedlnolofor developing a l.,arallelizecl version of the _lid h,y and parallel computer archit_._tu'es are revolumedl,mics prod,rams (DYNA and NIKE) is the potionizing the concept of supercomputirlg. Vector tential in the next three to five years for running supercomputer architectures have reached technoioapplicatiol_ that are larger by two or thrt'e orders of Kwlimits that preclude the orders-of-magnitude l._rma_litude than are I.x_sible on vector supercornpub fonnance improvements expected for the massively ers. This wotdd allow simulatiol_s of hurldreds of parallel ard'fitectu_.l A m,'t,_sivelyparallel computmillions of elements rather than a few hundred thouer ks an arrangernent of htuldreds to thou_lnds of _lnd elements with DYNA3D. microprocL.--_rs interconnected with a high_p_ Figure I illustrates the speed and storage reinternal network (a.m'ently up to 250 megabytes/s), quirements for typical advanced applications in Typical mi_a'oprocessor peak Sl:_-_dsrange from a metal forming, materials science, earthquake slmlow of 10 MFLOPS per processor to a high of ulations, and crash dynamics. Notice in Fig. 1 the 10(3MFLOPS per pr(xze_sor for pipeline_J (vectorincreased complexity of the models for points in like) processors. Performances between 10 and the upper right portion. These applications are of I(X)GFLOI_ are l_X_,_iblet¢_lay on systems of 1(X/0 high value in government research and for their pr_xzc__,_rs.By compaff,_n, the latest vector superimpact on industrial competitiveness. I_¢tllOIm Engineering Reseatcl_ Developm¢,nt and Technology ,:. Thrust Area Report FY92 2.ii Computational Mechanics 4" ParaDyn: New Generation Solid/Structural Mechamcs Codes tor Massively Parallel Processors F'roltess The DYNA3D progran_ is nearly twice the size of DYNA2D, and the thrtv-dimensional algoritlmls (e.g., for contact between slide surfaces) are more elaborate. Our strategy is to experirnent with conversion techniques, paralh.,I lanDmge paradigms, and algorithm parallelization with I.)YNA2D rather than with DYNA3D. 7:_i The development of a parallelized version of a larD., vectorized program necessarily proco,,ds in steps. The first and most tedious step is the conversion of array storage. The storage allocation for a distributed-mernory massively parallel computer is dramatically different than fora common-mem()r_ ._rial computer. Careful analysis of reused storage, detailed conversion of array layout, and parameterization of the element vector block length absorbed well over one third of our effort. A bene- Figurel. Advancedapplicatlons for maesively parallel pro. ceuors. The data represents systems as follows: E : earthquake simulations: (a) bridges, buildings and oth- er structures, and (bl full Bay Area earthquake simulations, C : crash dynamics simulatic_: (a) automobile com_ nem simulations, (b) automobile/barrter simulations, (c) multiple automobi_ crash simulations, and (d) aircraft cr_hslmuiMiomm.M:_tal_aingap_llcatlons: fit of this work and of the following timing analysis has been the insight we la,we gained into teclmiques for greatly reducing this same effort for the DYNA3D conversion. (a) twocllmm_lonalsimulaticns, and (b) thr_dimonsional simulations. T: tribology and nanometer-scale machining The computationally exl:_,nsivestep in the DYNA algorithln is the element-by-element ft)ria.,twaluation. The vectorizA.'dversion of this element proct_ il'lg trarlslatt_ readily into the data parallelparadigm oil the CM-5. We have complett_:! a data parallel version of the force Ul.Xtateand time integration for simulatiotm: (a) laege4cale 100 million atoms) m_ lecular dynamics simulations (10 withtono electronic structure (ab initio) calculations, and (b) hybrid molecular dynamics and continuum mechanics models with billions of particles/ zones and electronic structure calculations with mUllah par. ticle moleculardynamics.Projectndtimesforthenextget_ erations of systems are given along the top of the plot. Table 1. Timing for the 7 cycles of an elastic/plamtic bar Impacting a rigid wall. There are 32, 768 elements In the 64.×.Et12 mesh. Results are for a 512_roceJmor CM.5. f The gather time Is associated with the block processing for multiple material and element formulations. The scatter time is amsoclated with the global force assembly step. The parallel reduction time accrues for calls to an intrinsic parallel library routine. i Processor i Gather/._atter Parallel ............ ......................................................... ........... CPU time time Reductions Front-end 20.8'_,, 33.8% 24.5'!,i, ().8'_',, to processor tirne "[otais CM-5 elapsed 29.3% (].7"/, 36. I% 183.7 s 54.0% ().t)62 s time for 7 cycles: Time per element-cycle 2.03 s (November It._92): q I.ts for the 512 processor 6 t.ts for the Cray The above software. results results I)ischlimer ftmc hvnaltlt¢ Fcrlorntmtl 0 '1 _ Thtu;t Araa Roport FY.. the use of vector At the time of this printing for the CM-5 per element t do not include Machines and lib' h_ol., ncc¢_e.artl ¢ our timing have improved to .Z 2 _ls time step. In.I "lhinhin,II _' lunnt\, CM-5 Y-MI' and, _mt_.cqt.'nthl, f;;g;r:cc':':;E Cotjtoration, h_ bc,_ln h'_Imk' I'he_.¢, rl'_ldl., arc btu.cd iq_on ct h'_,l i,m.,tmlt,! lhc( 'A,I q ii'tilt i'('Flor tnttl'.. i,. tlol tl_'cc.4..arlh/ rvprc._¢nhll ¢_...... ,:;;:t; 12_:;,::;:;::;:_'::'. ivc lq Ila' pvrlornlml( ,::::: the .,tqh'l'm¢ wlh'rC I/li' ctnplla',t_, iva., oil I,rm'idm,k' Iln_. ".ql wmc rch',l_,¢ hm, taq had lhr I_eth'ltl oi _lqtnn::alton _' oJ lht' lull i,er.,lon '¢r:.':::;:;_;;i_; tq lhr..,_ql.,mc m PafaDyn: i i NP_ Generi_tmn Solld,, Structural Mechanics Codes lol Mass_vely Parallel Processors i i iii (a) 0:. Computational Mechanics i (b) Figure 2. Partltio_ ing of a standard three.dimensional mesh for an automobile piston; (a) the unstructured, three. dimensional finite el. ement mesh, (b) the partitioning of the piston mesh for two processors, (c) the partitioning of the piston mesh for four partitioning of the piston mesh for eight processors, (d) the processors. x (c) _z both elastic and elastic/plastic material m(_:lels.We chose a standard t___tca_,, a bar impacting a rigid wall, for timing and [x'fforrnance analysis, Balancing the parallel and scalar calculation time with network time is essential for efficient use of a massively parallel computer. An unbalanced problem with communication times exceedingcalculation times prevents the desirable linear speedLips predicted by Amdahi's law. (.Th_ the CM-5, the performance analysis tool, PRISM, has been effectire in providing the breakdown of hardware times. The most \'aluable feature of PRISM is the avail- The communication timt.s we have measurt, i are still exctssivelv high for a balanced cak'ulation. We have coilaN_rat___.twith computational analysts at "lllinking Machin_..'sto analyze the imbalance in the timings for this tt.'st problem. The devdopment of system ,_vare such as compilels and communication librarit_.,sfor massively parallel systems is in its infancy. We find that the newer alpha-t_.st vel_ions of the sffb,vare, u.,.:,t_.t now by thecompany analysts, will change th_.._, r_.suits up to an order of malofitude. This _vare may Ix, available to us within the next thro., to six months. With the new velsions of the ability of timing data throughout the program, from tipper level subroutines down to indivMual FORTRAN statements. Two timing analyses are shown in Table 1. The perh)rrnance difference in the two runs is a combined effect of hardware/ software changes at the Army High Perf(}rmance Computing Research Center and several programruing changes inspired by the i'RISM statistics, 1-'he speed achieved for our most recent run is 9 microseconds per element-cycle, which is con> parable to the one process(lr Y-MI _perfln'n_ance i_f 6 microseconds per element-cych.', ._,<are, w'eexl.xvt to exceed single proo_s,_." Cray C-90wrf(_rmanc__.'sforasinglenlateriai problem with a regular tol.x}log3,.At the time of this printing our timing rc_.,sultsfor theCM-5 have improved to.7321.is I.x,relement timestep. _,veral techniques have been developed for balancing the computational work among processors while minimizing the communication time. We are testing a recursive spectral bisection technique 2 with three-dimensi_,lal meshes. We have de\'ehiped a meth_)d fin \'isualizing the results, as shown in Fig. 2. Computational Meehanles • ParaDyn: New Generation Solid/Structural Mechanics Codes let M_ssively Piltilll(.,I Processors _'ltlll_l_ W_'k element, at least one shell dement, one contact We will continue to u._ DYNA2D to experiment with algorithm parallelization, in this next year, we plan to inw.,,stigate: (1) mes,_lge-passing and data-parallel versions of,_lected contact algorithms, (2)a data-parallel and mt,'s_lge-passing hybrid system mftware mt_,iel available in the next year from Thinking Machines,' and (3) parallel table kx_kup and mrr algorithms, which are appropriate for contact algorithms. We will begin the conversion and parallelizafion of DYNA3D and develop kernel algorithms for DYNA3D for further evaluation of parallel programming paradigms and architectures. DYNA3D is an 8I),(XX)line analysis program including ten finite element formulations (solid elements, shells, and _.ams), 35 material m_.teis, _._luations of state for hydrodynamic models, ,_,veral algorithms for contact at arbitra O, interfaces, and a list of additional boundary conditions and mechanics algorithms, ali of which make the program one of the most widely tl,_d t_x_lsfor nonlinear structural mspon,_ simulations. Our plan over the next three years for demonstrating a prototype massively parallel version of DYNA3D include_ implementing an eight-node mild (continuum) 2-14 Thrust Area Report FY92 4, £nglneerlnl_ R(tse;iil¢:ll I)ev(,Iol)nlf, i)! algorithm, and solid/structural mechanics capabilities needed for thn,_,,large-scaledemonstration problems. The demor|stratio|l problems include the simulation of a nanoindentation problem, an automobile/barrier simulation, and a weapons penetration application. Adl(_lOWl_lll_allll_ We gratefully acknowledge the Army High Performance ComputingRe,_,archCenterforpmviding CM-5 computer time for this work as part of their General Plan for Developing Structural Analysis l'rograms for Adwmced Massively Parallel Computers. Funding for cornputer time was supported by, or in part by the Army Re,_,arch (.)ifiec contract number DAAL03-Hg-C-(X)38 with the University of Minnesota Army High Performance Computing Research Center. We thank Earl Renaud from Thinking Machines Corporation for his advice and c_,_peration. I. 2. i_l)(l B.Bhoghosian,Comput.Phys.4, I (1990). tI.D. Simon, Computing Sysh'nlS in I:nxilleerin,y2 (2/3), 135(1_)91). L_ Ie,(:hn(JlotI ; CompositeDamageModeling,0, ComputationalMeehanlcs Comiske DamageModeling EdwardZywicz Nuclear E.x7_losives Engineering MechanicalEngineering A progress damage model for continuously reinforced, polymeric-matrix composites is being developed and implemented in the implicit finiteelement code NIKE3D.The constitutive model replicates the discrete laminae with an equivalent homogenized material prior to the onset of damage. Failurecriteria eventually trigger damage evolution laws that track individual failure mechanisms within each lamina and degrade the stiffness and strength of the laminated composite. Failure criteria and damage evolution laws are currently being developed, as well as numerical procedures, to efficientlyaddress the multilayer nature of laminates. This work will allow analysts to simulate the redistribution of load as the composite materials degrade and, therefore, to design minimal mass composite structures. iii iii IIII I IntlnlxJ_lctI_ Continuously reinforced, polymeric-matrix composites offer substantial weight savings over conventional materials, such as steels and alu- ual life and strength. At the same time, the material model must be numerically efficient and resolve the complex lamina behavior within each laminate region modeled. minums, and at the same time provide equal or superior mechanical properties. For example, at Lawrence Livermore National Laboratory, continuously reinforced graphite/epoxy (Gr/Ep) composites are used in lightweight earth-penetrator weapons, advanced conventional munitions, and enhanced nuclear safety systems. Commercial applications of Gr/Ep composites include high-speed aircraft, automobile drive shafts, bicycles, and tennis rackets. Currently, components manufactured with continuously reinforced, polymer-based composites are designed very conservatively or must be tested extensively, because the failure response of the material is not fully understood. To overcome this barrier, a composite damage model is cur- A continuum-based framework has been assembled to represent composite behavior. The approach uses conventional 8-node, solid isoparametric, 3-D elements with conventional 2 x 2 x 2 Gaussian quadrature. Element stresses and stiffness are calculated in the usual way at each Gaussian point; however, the constitutive evaluations use homogenized material properties that are calculated uniquely for each element. During initialization, the 'virgin' elastic properties of ali laminae present within each element, which can vary between one and two hundred, are homogenized and stored along with element-level, strain-based, failure criteri- rently being developed and implemented in the implicit finite element code NIKE3D.I A progress composite damage model permits analysts to simulate the complex three-dimensional (3-D) response of composite components in both subcritical (e.g., dings in an aircraft wing) and catastrophic (e.g., car crashes) loading environments. Tobe useful, thedamage model must accommodate a wide range of fiber on coefficients. Throughout the analysis, the small-strain, finite-deformation (total-Lagrangian)-based constitutive relation continually updates the element stresses, using effective stiffnesses and monitors for failure initiation, prior to the onset of damage. Element-level failure triggers an in-depth lamina level or microanalysis. The microanalysis checks for failure, and tracks and evolves indi- layups, track damage evolution based upon indMdual failure mechanisms, and predict resid- vidual damage mechanisms for each lamina present in the element. Furthermore, it degrades Engineering Research Development and fecl]nology _ Thrust Area Report FY92 2-15 ComputationalMeGhanics• ComposaeDamageModehng the individual lamina stiffnesses and calculates a material tangent matrix. The upc'ated stiffllesses and tangent matrices are then hot,,ogenized for u_at the element level, The _,o-tier hornogerfized apprtoch provides a rational and preci,_ mecl'_anisnl for tracking and integrafingthecomplexrespon_,ofdamagedlaminatt_i comD_sitt_. For undamagt_J material Dfints, thehomogenization tedmique, which incorporak.,s bending and coupling effects, yields accurate _lufleas at a substantial computational savings, since laminate integration is performed only in initialization. Traditional methtxts u,_ single elements or integration points for each lamina or homogenized material property and neglect bending and coupling effects. Efficiency in the undamagc_.i region is very importar|t since, in general, only small regions of typical composite components reach critical load levels. To date, the element homogenization technique, a con_,rvative, element-level, strain-ba_,_d failure criteria for fitx'r-direction strain to failure, and a micro-lamina-level sttbintegration _heme have been developed, implemented, and verified. any twosystems for a specified displacement field. The kinematics assumed in theeffective long wavelength solution are, with the exception of the through thickness shear strains, identical to art 8-node, rectangular, isoparametric brick element for small strains. Therefore, the finite element solution reflects the same behavior assumed in the homogenization. Thus, the effective properties repre,_nt preci._ly the varying lamina orientations, and the stacking _,quence relates behavior, i.e., the bending and coupling responses. Equation I allows approximate, but very accurate, element-level integration with conventional Gaussian quadrature. Witll 0c ---0.25, the maximum normalized error in any sillgle stiffness or force term is less than 8.4 x lO-3. Although smaller valt|es of _ reduce the integration error, they ir|troduce other undesirable numerical problems. By restricting ir|dividual laminae to be orthotropic, only 19 coefficients per pair of Gaussian poir|ts are neces_lry to de_ribe C 11(z),independent of the number of laminae pre,_nt. Element Homogenization Representation Accurate, strain-ba_,d, element-level failure criteria minimize computational costs by postponing, as long as possible, the use of expensive microlevel analysis. Criteria must be con,_rvative to ensure that failure initiation is not raised within any of the sublaminae, and thus, a criterion is needed for each failure mechanism. Laminate strengths are inherently limited by the extreme stres_ and strains that the individual fibers and matrix can sustain. Since fibers arc.,typically brittle, one convenient and commonly u_,d criterion ba_s damage initiation or failure upon the minimum and maximum fiber direction strains. 4 A conservative, element-level failure criterion ba,_d upon fiber direction strains was formulated. Tensile and compressive failure initiates when and Homogenized stiffness functions 2 are u_d in the element to repre_nt the total sub-laminate respond. Within an element, the homogenized local stiffness CII(z) is given by C"(:) = C_! + c p: + c_r cos(u :), (1) where con, cp, and c_a are element-based stiffness matrices, z is the normalized distance frorn the element's central plane, and (_ is a constant used to minimize element integration error. To determine c__, cp, and c__, ali laminae present in an element are identified. Next, using the closed-form long wavelength solution of Paga- Failure Criteria lt'li cd' no, _through the current the element lamina stiffnesses thickness, are yielding 'integratthe effective extensional (A), coupling (B), and bending (D, matrices of the element. Ti'tis approach treats eachsa me element as a uniqueproced sttblaminate. Using the long wavelength u re, Eq. 1 is integrated. The resulting extensional, coupling, Thrust Area Report FY92 4. Eng, lneer_n,q R(;sc, alch D(,vel(JIJment • + b max 0,- +! / r"-L ir_.L/ 41_-1 [ _maxc, r,r ,"2 v_. J = _ (2) and vious ones and manipulated to yield c_I , cl I , anti nlatrices are equated with tlae preand bending c{t directly in terms of the actual lamina properties and local geometry. Thisapproach, aswellavenoted,2enst|reside|l tical net mid-surface forcesand " nloments between 2-16 t'22 a max o, _ a min ]} ;tn(I _rc.t_nolog_ ( 0, --etl [ _-I, rain 0 , C22 ( ] r} /j-_ }} [ r t ]j: _ _l _ rain ,'mr_---Z2 "_ -]( r_ ' " r___L]] r_ 41_--! 4lfr ' (3) CompositeDamageModeling4° ComputationalMechanics respectively, where r-----T- a = max{cos20i } (4) b = max{sin"Oi} (5) _gum 1. 3-0 finite elementdlscretiz_ tionof theintemally preuurizedthick. walledcylinder.A represented here. "1 = max max O, (_ c, = rain rain 0, " (6) . (7) i -('( i Ill these expressions, _l l, t'_2,and t'i2 are the inplane strains, expressed in the element's natural coordinate system; t.tt. and _ii represent the composite's tensile and compressive fiber-direction strains to failure, respectively; and Oi is the angle " quartersectionis between the fiber direction (in the i-th lamina) mid the 1-axis of the elements' natural coordhlate. The ar(r = valueof_positk_ns the failure surface and isLx_tmded by 1/2 < ]3 < 3/2. For arbitrary layups, the optimal value is ]3= 0.785. Equations 4 through 7 are evaluated ush_g ali lamina present within the element, hl 8-mKie brick elements, the failure criteria, Eqs. 2 and 3, nc_ed be checked on only the 'upper' and 'lower' element surfaces. Ba._line 3-D 3-D* ar(r = rg) r 1) 1.112x 10-4 l.l12x I0-I 1.110x 10-4 8.294 x 10-4 8.297x 10-1 8.264.)x 10-4 FUIIW@ Work To demonstrate the new mtKiel's abili .ty to predict the elastic response of a laminated composite material, a thick-walled composite cylinder subjected to an internal pressure was analyzed. The Additional failure mech,'misms are necessary before component responses can be realistically tracked beyond initial failure. This requires that an element-level failure criterion as well as damage evolution relationships be developed for each mechanism. The lamina-level constitutive laws must ensure _iution convergence with mesh refinement, include ali mechanisms, and permit interaction between the various modes. In the cylinder was axiallv constrained and had an inside-to-outside ratio of ri/r0 = 3/4. There were 72 GrEp plies randomlv oriented with their fibers in either the axial (0°) or ht×}p (90°) direction. The 3-D quarter model used, shown ill Fig. 1, contained immediate ftlture, development efforts will focus on the predominant failure m(_,tes, namely, tensile and compressive failure, delaminafion, and inplane shear failure. Development of the evolution laws will use both micromechanical models and only 60 elements, i.e., 12 circumferentially mud 5 radiallv oriented. Radial displacements on the inner [Sr(r = ri)] and outer [Sr(r = r0)] surfaces were compared to a baseline solution and are listed in Table 1. The ba._line solution was obtained with non-traditional I. B.N.Maker,NIKE3Dl.lser'sMamml,LawrenceLivermore National Laboratory, Livermore, California, UCRL-MA-105268(1991). an axisymmetric, two-dimensional 2. E.Zywicz, Int. ]. Num. Meth. En,e,.35, 1031(1_92). tained 1152 elements in the radial direction, lt modeled each lamina with 16 elements. Calculations were performed with and without incom- 3. N.J. Pagano, "Exact Moduli of Anisotropic Lamihates," Mechanics of Composite Mat,'rhfls 2, Academic Press (New York,New York),23 (1974). pafiblem(Ktes.(._'erall, thereisexcellentagr___,ment between the axisymmetric ba_,line and the 3-D homogenized solutions. 4. R.M. Christensen, (19c)0) Internally Pressured Thick-Walled Cylinder mcx.lel thatcon- EnglneetJn/g TaMe 1. Baseline and3-0calculated radialdisplac_ ments. *With'i_ compatiblemodes' turn,Ion. Rcs_arct; Dei elopmt, experimental results. nt and ]. Compos. Mater. 22, 948 LI T_chr;olog} o:" Thrust Area Report FY92 2-17 H_DRA, ,_t l(_l_,S(dw,/ h)t 1hto,c, D//lt('n,',.)ll,ll, h,m._tl't_t,hu'oml_r_,._._lh/i, F'l_co.s /Iol_ .:. Computational Mechanics HYDRA: A Flow Solver for ThreeDimensional,Transient,Incompressible Viscous Flow Mark A. Chdston NtMcm"E.vt,losi_,cs l:'Jsk, iJmerilt,v, Mechmfic_tl EJ4k, ilmerilt,k, This addressing artich" describes the the incompressible class very-high-resolutiorl meshes. riti'ml-to-architecture mapping examph., pre,_,nted problem showing to demonstrate curr,.,nt The effl_rt code issues a high-performance transient development involved the application the class to develop of complex-geometry in both of the current of problems being flow fl_w problems solver that efl_rt is described in ternls vtvtl," and parallel stlpercomputers. code to a streamline for require of the algoAn submarine hull is considered. i I__Hi_ll port,mt lhis work is pnrt_ffn colla[x mltive eff_rt inwdving the Mtvh,mic,d l:.ngincering,md I'hvsic.-s ! _.,pnrtmenls, and Milit,uw Applicntions <lt lawrence I.ivennorv Nntionnl la[x,utorv (I,I.NI,). The development i_fa high-l.x'rtorm,uwe, thm,.'-dimension,d, tr<msient, iucomprt,'ssible, vi._'ous flow c_te is Ix,ing undert,lken regil_ns of sep,lr,lted flow, which directly influence vehicle lift ,rod drdg. In nddition tl_ the high degree of spntial discretizntion, file te,nptmfl resolution is also dem,mding, requiri,]e, the efficient mapping of the fl_w-solution nlgorithm t_ ctlrrt,nt vt,t'tor ,rod parallel supercomputer nrchitectures to make such simulntions pr,lctic,_bh'. primarily t_ study submarine I.x,rfom_ance in n fluid dvn,lnlit.-'./, ._,n.'-_'. I'Jleefftvts ()t tltlw _'pnr,_tion and v_,'ticih' utx,_ vehicle lift, dlvlg, <lnd ultimately steeril_g,,u't'tlfprim,u._,mtertst. I'hefin,dgt_,fl is to provide n dt_ign simulntioi_ ti_l th,lt will help ti_ rttJtlCC'the For the solution of the time-dependent Stokes t,qu,ltions with complex ge_mletl'y, 111dtt,d that computers with memt,'v si/es to i(),(X){)inillioi_ words and pt, rftlrnl,lnct, Iii iii IIXX)(, ;1:! ,t )l>'s (I t i1:1,t)l > _ I billion c_stlv sLibn_,irine design cycle, While this eff_l't ,iddressl,s one iii the N,ltillll,ll t ii',md t'hallenge._ _f Clln_puting, sinlulntii_g flow fields ,lbout vchich,s nnd ii_ iurbllnlilchillt,rv, this pllint i _pernti_ns per secilnd) will be reql.Ii rt,d. I'lld,lv, ,1 fully cllnl°igured CRAY t'-gii vl,t'lor supercoi]_ptitt, r provides ,i peilk pt'i'fllri]l,ulct, inte tit lh (;l:l.t)l"swith,i nlt'nlorvsi/t'_lf2._6nlillilli_wtlrds. ctln_putiltitln,ll fluid dvii,imic._ (Ct:I)) cilp,lbilitv is unique br'chi.isr' it ,llsll finds ,q_plicntioi_ within inultiplt, divisions ni IJ.NI., the I)ep,lrtmei]t tli I{ilt,rgy, <llld iii I_J.,_.il_dush'v. Applic,lti_ns ilWItidt, Iii clll_h',isl, ,1 fully tolyligt|red p,lrnlll,I cllinputt,r such ,is the lhinking M,lchil_t,s CM-.5 prlwides ,l pt,,ik perttlrm,uwe rntt, til 121)(,;l:l,(,)l"s with 4l)96 Illil]ion f_l-bii wtlrds (li Illt'llltlrv. !lr lllCtlSil_ig till the study lit cnsting pr(t't,sses, he,ivv gns dispersitln, ill]ct flow iii the plill_t't,lr), blltll_ddl'V I,Ivt'l. the r,lpidly evl_lving p,lrnllel c_ln_puling pl,ltfllrn_s ,ind ill,lkill_Ll_,ot,ldVill_ct,d I_unlt,i'ic,li,llg(irilh111.% I'here is <llsl_ immedi,_te ,ipplicntioi_ in iilctustrit'._ criticnl Ii) U._. c(m_pt,titivt,i_ess in the wt_rld ec_nl_nw, such ,is the,]utllm(llive ii_dustrv wilt,rf t't:l)is lhr, gll,ll of r,_pid sinltililtilll_ (ltclllllplt,x gt,(Inlt,ll'v flow simul,lti_li_._ ft_r dt,sigi_ ni,iv L_t,,_chit,v,iblt' il_ the lit,dr ttllurt,. being used to ,lu_nlt,ilt t,i]_illt't,l'in_ ft,<ltures such ds vortices ,rod N,wierit is esti()f I(XX) I',ltt,s tit fhl,ltil_g dr'sign in lhr' ,ll't,,ls _)t vehicle ,lt,l'()dvl_iiilllit'.% he,_ting ,illtt ,iii" cllnd ili_ in ing, nnd t,l_gillt, ,li ld ulid t,l'l-il lt ld t(ll ilii_g. I:llr the full-blld\', flow-field tr<lllsit,ill lhlw sinltii<ltillil tll,i lhe stlblllilrillt,, ii i._,lnlicip,lted lh,li ul_w,ii'd_ (ii lint, milli(in t'lt,nlt, nts will ht, rt'qtiirt,d t(i I't,slllvt' illl- I ,,i:,,,,,,,,t:_tt _SS lt,',._' currl'nl finitl' t,lt,nlt,i}l clldt, tlu" s(llving the N,l\'it,r- ,%t(ikt,st'qthltillllS is b,lsed prinl,lriI.v tlp(ill the w(irk til (;l't,,_hll i'/_l#.,I .I ill,lkili_ ii._(, iii ,icl- l,, t, I_ i_,l,,V,,_,.,it ,_,_,1 _,., t_,,.,e,,tl i ..'. Thrli.f Area Report FY92 2-19 ComlmtatioemlMechami,'AI .'.. HYDRA.A RowSolverfor Three-Dm]ensional, Transient.Incompressible ViscousFlow 2 2-20 Th ul_t Area vanced solution algorithms for both implicit and explicit time integration. In the case of the second•)" aer fractional step algorithmX4 (implicit), a consistent-massp_ictor in conjunction with a luml.'_'d masscorrector le#timately decouples the velociW and pressure fields, alerebv reducing both memor,' and CPU requirements relative to traditional, fl.dlv coupled _iution strategies. The consistentmasspredictor retains phasespeed accuracy,while the lumped rr.asscorrector (projection) maintains a divergence-h'ee velocity field. _th the predictor and the corrector steps are amenable to solution via direct or preconditioned iterative techniques, making it possible to tune the algorithm to the computing platform, i.e.,parallel, vector, or superscalar. The second-order proj___'tionalgorithm can accurately track shed vortices, and is amenable to the incorporation of either simple or complex (multi_]uation) turbulence subm(xlels appropriate for the driving applications, The explidt solution algorithm]2 sacrifices some of the phase-speed accurac'v of _he fractional-step algorithm for the ._akeof minimizJng memo D, and CnU requiremenLs. However, the momentum equations are still decoupled in the explicit algorithm, While both the diffusive and Courant stabilit3, limits must be resFK_ed in the explicit algorithm, balancing tert._r diffusMtvJ2 is used to )c_,sen the restrictive diffusive stabilit\' limit in the explicit algorithm. This, in combination with single-point integration and/K_urglass stabilization, makes the explicit algorithm ve_, efficient computationally, and because of this, the explicit algorithm was chc_--mn,-,._the initial fcx-us of tafionofthecodesuitableforthelaminarflow regime. In the case of the vectoriztxi version of the c(Kte, element operations are bl(x:_.i intogroupsofcontiguous, data-independent operations bv using a slmplified domain-decomD_sition strat_._/to group the element. This approach results in a c(_e that is completely vc_.'torizc_,yielding Performance comparable to DYNA3D for the time integration of the momentum equations. However, the solution to the pressure PoLssonoperator limits the overall pefformanceof thecode, taking up to 95%of the CPU time per simulation time-step in problems with strong pressure-vekx:i_ coupling. Becausethe element datastructun__s for thevectoriz_.,dversk)n of HYDRA are adjustable,they are als() used for the SIMD (CM-2/CM-5) implementation, where element-level operations are Performed in a kx:k-step parallel fashion. For theCILAYarchiterture, the vc_or bl(x:k size is configured as 1.,28(twice the length of the vector pipeline). In the case of the CM-2/ CM-200, the element bl(Kk size is configured as a multiple of the minimum virtual processor ratio (4) and the numberofavailable pr(x_,asingelements. For the CM-5, the block size is configured as an integral multiple of the prtK_;,sor v__vtorpipeline length and the number of available prcKc*&sorsenabling proc(._,_r pipelined operations in conjunction with SIMD parallelism. In the SIMD (CM-2/CM-5) version of the c(Kte, data dependence in file element bl(Kks may _' resolved usinghardwarc_-p_K:ificcommunication/combining operations for the parallelizect assembh/of element data to nodal data. Instead of data del:x_-n- the paralleliz.ation effort, The fractional step and the explicit algorithms both rely upon the implidt solution of a linear system arising from an elliptic operator. In the case of the fractional step algorithm, this solution is used to prcgvt an intermediate velcK-i_, field to a divergence-free space. In the explidt solution strata,g}', the elliptic operator appears in the procure Poisson equation, which is used to advance the pre_sure field in time. B(.__aLLse the linear system solver Lsa kev component of the algofi_m-to-architecture nmpping for both algori_ms, it h-ts been necessan' tu develop modifled, conjugat_.Dgadient iterative _lvers _*'that minimiz_ethe impact on memory requirements and a/low the r_ltural data parallelism of element-level pr(x:essing to Ix, exploited. For both the explidt and the pr(gvtion algonthms, no additiork'd storage is required for the elliptic operator iLself,making the tmrrent conjugate gradient _/ver c_.,_'ntiallyrnatrix-fr¢__,, During the past year, our efforts have Ix__-'n dir___ecl primarily towards the vector and data-parallel or SIMD (Sing;le lnstructi(_n Multiple Data)implemen- denc}', the constraint on domain decoml:x)sition in the SIMD implementation requirc.'sthat theelements be grouped in a spatially contiguous manner to minimize the deleterious effects on performance of offpr(x:_,sor communic.ation. However, because the same data structures are used for the v__vtorand SIMD versions of HYDIL&, it is/:x)ssible to appropriately reconfigmre the block siz/efor each architc_.-'ture for the sake ()f performance. In effect, the element grouping strat__%D "' provides a mechanism to account for variati()ns in granularit3., acrt_s supercomputer architectures ranging from v___or to SIMD t()Multiple Instruction Multiple Data (MIMD). Many alternative domain-dc_:omp(_sition a/gorithms are available, including meth(x.ts that consider the graph of the finiteelement mc.'s.h7 when suixlMding the physical domain, and are not r_._tricted to k_._call.vn_%,;ularmesh___.By matching the domain dcx:()mt:x_siti(_nstratc%_'to the superc()mputer architc_'ture, it will IX,I:X_ssibleto maintain ¢_ptimalpefformance ¢_nreg.-tor,SIMD, and MIMD machines. t-]YI)IL,\ has Ix'en written using standard, UNIX Report " F','9',_ ",, E-fi "ce" "g M #ese;_': _ 3:e.,: t::"(-'' ;_,,: _',..:_' : c#', H /DRA: A Row Solver tot Three-Dimensional. mftwar_ievelopment tt×_is,enabling the ctx.le to IX' simultaneously developed in FORTRAN 77 and FOr,- Transient, Incompresstble Viscous Flow o:o Computational (a) TILgN tYdby making UL':,e ofcompile tirne confibjn.lrafion of thesoftware ThLsapprt_achhasmade it l.x_sibleto provide HYDRA in a foma suitable for computing plaffomls including work,;tafions, and CRAY vcvtor Figure1. Results calculations per. .J---x Y ,agethat makes it p(_sible to peffoma d,aan'dc memo- ¢0, rv alltKafiondesibD on a ofsingle processor workstation, requin.n.ithe a memory management packmulti-prtvessor CRAY, or on the pr(x:_._orsof the CM-2/CM-5 with a single interface definition. '_ Currently, initial calculations are beinl.:performed Application on a range of simplified submarine-hull configurations. The top frame in Fig. I illustrates the mesh t_'d (¢)Y'Lx I-EdNA-- -J _'7..':_-'[mL ,_F y. 0.SZ i .......................... ,,_j_' ........ _ / _....... , 0 -1.74 _ of the x-veloclty. (b) ieoeurfaces of _as0 i Z scalability in temas of the rnesh rc_lufion, multigfid acceleration can provideenhanced convergence rates by effectively damping the low-m(_.ie error comlmnents via coarsegrid corrections, lt aim fits well in the current parallel-ctx.le architcKtum. While the current, vL_or-bkx:king, domain-decoml.xrsition algorithm is adequate for w_,ctorsupercomputers, robustdecoml.x_sition tr."chniques yielding elenaent-to-ptxx.'es_)ra.,_,_ib,mmentsthatminimizecommunications overhead are nLvessary to achieve peak performance ratL.,son both SIMD and MIMD parallel ardaitLvturt_. The rt_vursive sp_vtral bi_vtion 7 algorithm, which ttst_the_'condeigenvt_orofthem{.sh connL_livity graph, kscurrently being invL_tigated as a candidate for performing domain dtKomp(,sition. 1. l:MGn__ho,S.T.Claan,R.l..l_ee,andC.D. Upmn, h_t. I. Numer.Met/ads HuMs4, 557(1'484). back of the straight _'ction of the hull correSl_)nd to locations where the fluid has Ixrenaccelerated to track 2. PM.(;rt_ho, S.T.Chan, I{.l..ix__.,and C.D. Ups)n, htr. 1.Numer.Melh(_tst:Tuhls 4, 61(4(1t)8.-l). the contours of file vehicle hull. At the surface of the 3. I:MGrt.'sho,Int.]. Nm,te_:Metta_tsI:luMs11,587(ltN()). hull'ntwslipLx)undaryc°nditi°nshaveLK_'nimlx_sed" 4. PM Grt_la. and S.I_ Chan, Int. 1.Numt'r Meth(_t.', 5. thdds11,587(199()). fLS.lkvkman, '"Flat,_)lution of IJnearlkluationsby theConjugateGradientMethod,"MathenudicalMeth(_ts./brl)ik,italO,npuh'rs 1,62 (1t)65). y....L.x W_l'k the acceleration of the _lution to the linear system, arising from the pressure PoLs._nloperator; and the inclu- 6. sion of the recursive, sp_vtral d()nlair_-dtvoml.w,_sitic)n strateg,y for SIMD architt.vtures. The pressure computation currently relits Ul_Xma data-parallel, element-by-element diagonally scaled, matrix-free conjugate gradient.,_-)b,or. While this approach offers Eng_nee,,_lg the computation of the flow field; pressure; and (c) i, osu_es t in the computation of the flow field around a streamline submarine hull at a Reynolds number of 830, ba_.i on the hull diameter. A 1/4 symmetry m(x:tel has been tL_.t, resulting in a mesh with 18,0(X)ntKtes (16,rX)0elements) or 72,0(.)0degr___ of freedom. Towtank conditions were imp(_<i on the computational domain to sirnulate the ca_ when the vehicle is moving straight ahead, Lst_suffact__of prL.-'ssureare sho_a hl the middle frame of Fig. 1 for the initially divergence-free and Imtential flow field. At the leading edge of the vehicle, a stabgaation l.x_int Ls apparent, with the prt_sure dL_reasing in the streamwise dirLvtion along the hull of the vehicle. Near the trailing edge of the submarine, a low prL_sure 'bubble' is pre._nt due to the acceleration of the fluid as it tri(._ to tuna and follow the streamline surface of the hull. In the bottom frame of Fig. 1, i._uffaces of the x-veh_K'it3.' are shown. At the inlet to the domain and the ht-field Ix_undaw, a uniform x-velocity h&s Ix,en inll.X_-;edto simulate tow-lkank conditions. The bubblc_ at the front and Future efforts will address ha,o kev issuc.,s: of /orins/on simplified submarine-hull configurations,showing (al the mesh used in z and Thinking Machines SIMD superconaputers. The tol._iovm desib_land bottom-upimplementation have Mechanics 7. Re, sear¢l_ RM. Firencx,t:.h'mvnt-by-Fh'ment I_n,(t,ldilh,mlg7i.chniqu(_ltirl_o'k,('-Scah', Ve('h m izcd Finih'I".h'm(,nt Anahlsi., in N(,}linem" .'.qolid andSh'uc'htn_lMechanics,l'h.l). "l;laesis. Stanford University,I'aloAlt(),California (198q). H.I). Sire(m, "Partitioning of Unstructured l'robIt,ms for l'arallel I'r(_cessing," C(,nputin.,4511,'_h'lll5 in t:.n_inc('ring2 (2), 135( 19t)l). Lm, Devetopme_t_¢ ,_i¢! T_,_h,_¢_/o12_ "." Thrust Area Report FY92 2-21 Development and Testingof the TRIM3DRadiationHeat TransferCode . ComputationalMechanics Development and Testing of the TRIM3D Radiation Heat Transfer Code James D, Maltby NuclearTestElzgi_weriJzy, MechaJfical Engineerillg We have developed a new code, TRIM3D, to solve radiative heat transfer problems involving a participating medium. The code u,_s a Monte Carlo fomlulation to solve problems with absorption, anisotropic scattering, and specular boundaries, lt is desibmed to work with other codes to soh'e coupled radiation/conduction/thermal stress problems, and has been verified against known analytic solutions. I_dj¢l_l Radiation heat transfer problems invoMng a se,-.|i-transparent medium that participates in the radiative exchange occur often in areas such as high-power optics, crystal growth and glass manufacture, coal furnaces, annealing ovens, and analysis of fuel fires. Unfortunately, the_' problems are often difficult to soh'e due tr) the complex nature of the radiative transfer equation. A Monte Carlo approach to radiation heat transfer problems without a participating medium has proved very successful, resulting in the computer code MONT3D. 1,2The objective of this re,arch was to develop a Monte Carlo code to analyze radiation heat transfer in the pre._nce of a participating medium. Lawrence Livermore National Laboratory (LLN L). The cu rren t working version of TRI M3D soh'es three-dimensional (3-D) radiation heat transfer problems in absorbing, emitting, and anisotropically scattering media. Problems may be soh, ed that are non-homogenous and nonisothermal, and material properties may vary with wavelength. Boundaries may be diffuse, specular, or mixed, with directional reflectMty and transmissivity. The code has been verified against a ,_ries of analytic problems with ab_)rbing or _attering media and specular boundaries, with agreement within the statistical accuracy of the simulation. Currently, no other code exists that can handle participating media problems of this complexity. The resulting c(_Je, TRIM3D, represents the state of the art for radiation heat transfer analysis, and is also the first production code with detailed participating medium capability. The addition of TRIM3D to our code suite allows the solution of coupled radiation/conduction/thermal stress attainable. problenls with a le,'el of detail not l.we,,iously Theoretical Formulation TRIM3D generates a matrix of direct exchange areas (DEA's) that de_ribe the radiative interaction among ali surfaces and volumes in an enclo..... I INGRID ; I TRIM3Dcode Rgutel. flow.Temperatureoutputfrom TOPAZ3D is passedthrough REMAPto During FY-92, a working version of the computer code TRIM3D was developed and given preliminary testing and verification. The TRIM3D code is f()rmulated in a similar manner t(_ the successful MONT3D non-participating medium heat transfi.,r code used by programs at fnglneer_lJp, R_;seart. NIKE3D forsolu- tionofradlation/ conduction/ thermalstress prouem. h De_elt;pm,_nt iirl(! le(hnol_JI4_ ": Thrust Area Report FY92 2-23 Computational Mechanics 4. Development and Testing of the TRIM3D Radiation Heat Transfer Code any two surfaces sure. The net exchange between ' or volumes may be described: :, _, -.. = 0 si g i (Ti 4 - T_) (surface to volume) = c gi gi (T_ -Ti4 ) (volume to volume). _ Qq=osisj(T__T;)(surfacetosurface):_, This matrix is then passed to TOPAZ3D for solution of the coupled radiation/conduction problem. Since the matrix of DEA's is temperature-independent, boundary conditions and temperatures in an analysis may be changed without re-running TRIM3D. This approach has been very successful with MONT3D and TOPAZ3D, resulting in a large savings in computer time. The temperature output from TOPAZ3D may then be passed through REMAP to NIKE3D for solution of radiation/conduction/thermal stress problems. The code flow during the solution of such a problem is shown in Fig. 1. The mesh generator lNGRtDandpost-processorTAURUS are also used. TRIM3D simulates thermal radiation byemitting a large number of monc_nergetic photons from each surfaceandvolume.Thesephotonsaretmcedthrough multiplereflectionand/orscatteringeventsuntilthey are absorbed in another surface or volume. The DEA's are then calculated from these photon tallies. For a given rowoftheDEAmatrix, si si gi si = Ai _i Nii / Ni = 4 v_ ai N 0./ N_ , where Nii is the number of photons emitted by element i and absorbed by element j, and Ni is the number emitted by element i. _rption. i',',!:_i, i:iil;ii?_it _ TRIM3D ----- Analytic "\ \ x N 2-24 Thrust Area Report N _ _ _ N '0;8 . 1,0 : FY92 -_': :: .'_ Figure 3. Analytic verification of TRIM3D for isotrepic scattering. If the material properties changesignificantly with wavelength, as is typical with gas-radiation problems, a band-wavelength model is available. This model splits the wavelength range into separate gray bands, with a separate simulation per band. Surfaces consist of 4-node shell elements, degenerating to triangles. Volumes are repre_nted as 8-node bricks, with triangular prisms and tetrahedra as subsets. Both surfaces and volumes are designed for mesh compatibility with INGRID and TOPAZ3D. Material properties are assumed constant within a single element, but any number of materials may be defined. In this manner, nonhomogenous problems may be solved. Analytic Verification ...... , Engineering Researct; Development through- out the entire range. Some of the results of this verification are shown in Figs. 2 and 3 for pure absorption and isotropic scattering, respective- _ ': ' ::' _ ........... lytic solutions are one-dimensional, they were simulated with a 3-D geometry with specular mirrors on four sides. Optical depths from 0.1 to - . _ 'iI 0:4:-:: ._ 0,3, , ,:.......... : _!!:i;.:, 10 were tested, with good agreement 0_6_1--; '" :i0J [- . .. :: _ • __ .: /: TRIM3D forpure ab. TRlM3DAnalytic TRIM3D has been verified against a series of participating medium heat transfer problems with known analytic solutions. Though the ana- Figure2. Analytic veri_atlonof -- : ly. Agreement with the analytic solution in both cases is very good. An additional result from this verification was that the speed of the code appears to decrease only linearly with optical depth, and that even at an 'optically thick' depth of 10, the speed is practical onaSUN worL,_tation. and Technology Development and Testingof the TRIM3DRadiationHeatTransferCodeo:oComputationalMechanics Future Once tile c(_.ie is released, we intend to collabo- Wolrk One of tile difficulties ill verifying a participating medium code is the small number of problems with analytic solutions that exercise ali the code features. To address this problem, a symposium was held at the 1992 American Society of Mechanical Engineers Heat Transfer Conference to assess the current capability, for solving non-gray, anisetropically _attering, multidimensional radiation problems. Thirty-four benchmark problems ranging from one to three dimensions at optical depths from 0.1 to 10 were specified. 3These problems will be solved using TRIM3D and should provide a good platfoml for verification of the code features, Additional features are planned for the production version of the code to simplify the solution of large problems and make the code more 'user friendly.' A complete u,_r's manual, including test problems, will be produced for TRIM3D. In addition, ali the solved analytic and benchmark problems will be organized into a quality assurance manual for code validation purposes. rate with groups inside or outside LLNL to test the utility and accuracy of TRIM3D on experimental problems. This will provide valuable feedback on code robustness and performance on large problems, as well as on which features are most useful to the analysis community. l:k_cau_, TRIM3D uses a Monte Carlo formulation, it is very well suited to the new class of massively parallel computers. A test version of TRIM3D will be developed for whichever parallel computer becomes available at LLNL, and its performance will be assessed. If successful, it should provide a good example of a production-parallel application. 1. 2. 3. J.D. Maltby and I!J.Burns, Numer. Heat Transti'r9 (2),(1991). R. Siegel and J.R. Howell, Thermal Rad&rien Heat Transti'n4th ed., Hemisphere Publishing Corporation iBristol, Pennsylvania), 1992. T.W. Tong and R.D. Skyocypec, "Summary on Comparison of Radiative Heat Transfer Solutions for a Specified Problem," Developmentsin Rad&tire t4eat'Fransfi't, HTD 203 (New York), 1992. Lm] !l Engineering Research D(,,velopment and lecl_nolog_, _o Thrust Area Report FY92 2-25 A Methodology for CalculatingtheSeismicResponseof CriticalStructureso:oComputationalMechanics A MeOwxlolol for Calculating the of Critical Structures David B. McCallen NuclearTestEl_gineering Mecha,ficalEngineering FrancoisE. Heme, Lawrence J. Hutchings,and Stephen P. Jarpe EarthSciencesDepartmellt We are developing a methodology chain that will allow estimation of tile seismic response of critical structures to large earthquakes. The methodology consists of three distinct steps: generation of synthetic bedrock motion at the structtu'e site due to a postulated large earthquake; nonlh_ear finite element analysis of the soil profile at the site to transform the bedrock motion to surface motion; and linear/nonlinear finite element analysis of the structure based on the predicted surface motions. Progress in ali steps is reported here. Our ultimate goal is to allow accurate, sitespecific estunates of structural respo_zse for a specified earthquake on a specified fault. i |nttoductioll Our computational simulation of the _ismic respon,_ of a critical structure is illustrated in Fig. 1. To envelope the motions that might be obse_,ed at the structure site, the seismological portion of the methodology develops a suite of possible earthquake rupture Kenarios for each hult that can contribute significant grotmd motion at the site. Field instrumentation is placed on bedr(x:k at the structure site, and over a period of time, bedrock motions due to micro-earthquakes emanating from the causative fault(s) are recorded. These recordings ser_,e as empirical Green's functions, which characterize the motion at the structure site location due to slip of an elemental segment of the fault. By appropriate summation of the responses due to each element of the fault rupture zone for a given rupture scenario, the bedrock motion due to slip over a large area of the fault (corresponding to a large magnitude earthquake) can be estimated, By considering a standard suite of 25 possible fault rupture models, which characterize the different manners in which the fault rupture can propagate across the total fault rupture zone, a suite of 25 acceleration time histories are generated. The suite of time histories is representative of the maxirnum ground accelerations that could be expected at the site for a given size earthquake. Hutchings 1,2,_and £t_glneellnR his coworkers have led the development of the empirical Green's function technique and demonstrated the utility of this method using Loma Prieta earthquake data; The transmission of earthquake motion from bedrock through the soil to the soil surface can result in significant modification of the bedrock motion. Traditionally, the nonlinear behavior of the soil under strong ._ismic motion has been modeled with 'equivalent linear' methods, which iterate with a linear model to approximate the nonlinear response of the soil deposits. The classical computer program SHAKE 4 has typically been u_d to perform site-response analysis. SHAKE is operational at Lawrence Livermore National Laboratory (LLN L), but such equivalent linear models cannot describe the evolution of pore pressure and predict liquifaction; i.e. they cannot perform "effective-stress" analysis which we deemed essential for this project. So, the effective stress nonlinear finite element program DYNAFLOWS has been obtained from Princeton University. As part of the meth()dolobn/development and validation, the DYNAFLOW and SHAKE programs will be applied to the Loma Prieta earthquake data obrained at Treasure Island, California. The Treasure Island site consists of saturated soils that exhibited liquefaction during the Loma Prieta earthquake. Site-response calculations are being perfl_rmed by Resealcl_ De_,elol)met_t and fe( t) nulogV o;, Thrust Area Report FY92 2-27 Computational Mechanics .:. A Methodology for Calculating the Seismic Response of Crilical Structures (a) Figure 1. Comput_ (b) _ _ tlonal simulation of the seismic re. _ ................... sponSestmctureOfshowinga critical tem and (b) the (a) three-step the physical comput_ sy. tional model. 2. Finite element soilmodel for _,,-....... -: :'_, ture zone for large quake _, _:sponse _ _ _ 81" BEI. o.00 AI V II _.:a" l- !1"" I soil response / 3. Finite element structural model for structural El. -300 Iio"" - - I _• I _ for microquakes Aft i I _! Estimated Rupture zones fault rupture zone for large quakes functions for bedrock motions a nunlber of researchers, anti a portion of our model validation efforts will consist of a comparison of DYNAFLOW and SHAKE results with measured Treasure Island response data for the Loma Prieta earthquake. No|llinearstructural-responsecomputatio|lsare being performed with nonlinear finite element software developed at LLNL. The implicit, nonlinear, trar|sportatio|l structures in California. The first structure is the Dumbarton Bridge, which is the southern-most crossing of the San Francisco Bay. The Dumbarton Bridge study was initiated by LLNL at the request of the California I_'partment of Transportation (CtX)T). The second study is concerned with the seismic analysis of the Painter Street Bridge in Rio Dell, California. The Painter Figure2. Location of Apr, 1992 Petrolia earthquakeepicenters and Painter finite deformationprogramNIKE3LY, is being used to model structures and the nonlinear near-field soil. N1KE3D has a number of nonlinear constitutire models and advanced contact-surface capabilities for modeling gap opening and closing, The seismic analysis procedures arm capabili- Street Bridge study is very important from the standpoint of validation of our methodology and procedures. This study is the focus {}fthis report. The l_ai|lterStreet Bridge, wl|ichhasbee|lheavi ly i|lstrumented by the California Department of Mines and Geology (CDMG), provides an excel- Street Bridge site. ties under lent case • development are being applied to two study. The high rate of occurrence ..... o --'_- 0 10 Miles Painter Street overcrossing, Rio Dell, California Pacific Ocean _t [ _ Thrust I M=6.0 aftershock , 2-28 I Area M = 6.5 aftershock Report FY92 .:. I!nglll_,tltli: t?(,.,;t,,_1_';_ Dp_,l_)!)m(,t_t ,ll_t l('(ht_ol()Ht. of ,4 Methodology for Calculating "_"Computational the Seisn)_c Response oi Critical Structures Mechanics Shear wave Figure 3. velocity graphs showing measurements by CalTrans) Bridge superstructure T Photo- (a, b, and c) expertmentation and field work for the Painter ' Street Bridge site; and (d) Illustration of finite element model. Approach embankment (a) soil (d) ........... Seismic instrumentation • .,., j .'_'_'_ _' _ "A:.. 1 L..I [] packa8 e placement Bedrock 9rilling of four bore holes (performed by CalTrans) (b) (c) earthquakes in tile seismically active region of northern Ca lifornia has allowed the measurement P_ of response of this bridge to a number of significant earthquakes. In April 1992, three large earthquakes occurred within close proximity to Rio Dell and the Painter Street Bridge location (see Fig. 2). During the largestof these shocks,the l'ainter Street Bridge structure was shaken quite riolentlv, with lateral deck accelerations on the order of 1.23times the acceleration due to gravity." These As a resultof the April quakes, the LI.NL efforts at the Painter Street site have been scaled up signif- I]lL'aSLIl't'd accelerations re[gresent tile Rgure4. "_:!_i_.i:,:._,_:,.:_{,:_7_:i:,_ ,-<............ _.._:,, :.:>:_,,,.: :_!<_:_:_:::!:,_ : :: :;:i:::,!_!'{! ? ::: ::" largest accel- _ earthquake, Callen, Romstad, l'rior and to the Goudreau-had Ap'ril earthquakes, constructed Mca detailed finite element model _,fthe Painter Street bridge/abutment system (see Fig. 3) and had performed cletailed parameter studies on the dvnamic resp_)nse of the system. Since an extensive modeling effort had already been initiated on this bridge, the latest set of quakes event for our project. ::.::,_::, _;_a:,:_'.,,! _:;_:: !;';_:_:_ _!£!.}i:};_}ii!,?, ::ii: , _;:_;i,v_.> :_ :, ,@ was a fortuitous L_g,:)et'_,_)_; :i Eureka Region of aftershock locations of (location Green's functions. Humbolt Bay decommissioned _:_tt,_:_;,.:_i::.::*_:-_]7:!i:" ,i":i_di: ,_,::' : : nuclear power used for measure- plant) • ii;:;:i;i :_ ( /.,/ {)evL'l_)lJll)_'_)t After shocks to 3) (M = 2 , " i : 17¢'_,(',.1_(/) • Arcata . ,,'.. 0 " _ o/)d [Z=ZZZZ__I Miles l('( h_iul_)_ ._o Thrust 1|) Area Report FY92 2-29 Computational Mechanics .:. A MetlTodologyfor Calculating the Seismic Response oi Critical Structures _"::':_:':": ............ Fault mptu_ , Li ' plane _, Ix'en measu rc_.tf_u"t,ight nlicl',_,a rthqua kt._ emanating ft'ore the fault I_.-ations indicak'd in Fig. 4. I}a._J on the empirical Green's functk_ns obL,i_l_,d from thr ,_.a. , measurements, synthetic N_d rt_-k-gct _und-motion time historiL_ have recently [xvn generah._t by Rupture Model MPE00 0.6 0.2 •-0.2 :7-.;'1 ;:';.;..::!i::7 I S _ 7,'. :r:1.71;:!:::;7:;.., , " I 10 I 1B ] 20 J 25 ] 30 Hutchings and .larl.x, for a numtx, r of earthquakt_. _m3plt._ of l'ainter Strt%'tslit, synthetic time historit.,s, Rupture Model MPE03 each ba_J on a different In parallel to the seismological 0.6 •,_ 0.2 _ -0.2 ;:_::: ;.... ment -i.0 5 -0,6 10 15 20 25 __'i !, ' [ ! 5 pl.0 I nonlinear 0.2 .....,. ??.j . :. :-. ,"'. 7.-?{:;, ....... I 10 l 15 I 20 i 25 mass. 0.2 type I 15 I 20 I 25 behavior of the soil embank- svstem was Loallow incorporatioll Traditional finite element models for this Of bridge, which are used in bridge design and analysis calculations, neglect and the soil stiffness is represented ] 30 tic, amplitude-independent Rupture Model MPE04 _0.6 •._ 0.2 _ -0.2 "_ -0.6 hvsteretic the bridge/soil -0.2 -0.6 I 10 of the Painter Street bridge/abut- imporh-illt factor in the dvIlalllic respollse of the merits has been 'j,lil experimc'ntally asof a Ctlllvery bridge system, The pril-ilarv identified obiective structil-ig a detailed, three-dimensional model of [ 30 Rupture Model MPE08 -I.0 [ 5 finite ele- bankmerlt soil masses have been modeled as shown in Fig. 3. in this t.vpe of bridge structure, Rupture M_de_MPE_6 ',t modeling work, regirne.system For nonlinear time history analyses, the merit has progressed into the noiliillear stiperstrLiCttlre, pile fOtlildatioFi, and approach eta- 30 ;. .... • " "¢" fault rupture propagation approximately tion, and apply springs. the soil mass, by litlear elasWe decided the original ground surface ele\'athe surface ft'ce field motion direct- FigureS. Fivesamplefaultrupturesce_ narios resulting Painterwith Street time icantly. At the request of Heuze, s ltle CDOT i'ecently drilled fotlr bore holes at the l'ainter Street site (see Fig. 3) and performed down-hole, shear- " ly to the base of the model at this elevation (see Fig. 3). This approach neglects potential soil-structure interaction effects between the piles arid soil below this level, and prevents radiation of energy vertically back into the soil. ]-]owever, interaction between the soil and piles typically occurs in the top portion of the piles, and energv loss throtlgh histories, wave-velocity nleastlrelTlellls. _il samples were retrieved from the borehoh_'s, and HeLizc, has contracted with the Departrnent of CMl Engineering at (UCB) to perform iaboratoIT tests on the soil samples. The field shear-wave-velocity measuremerits and the laboratory soil testing will provide quantitative soil properties for use in the site soil response calculations and the structural model calculations. Two of the boreholes were drilled to radiation will be small relatM., to the el'iergy dissipared by the nonlinear hvsteretic behavior of the, soil embarlkrner_ts. Until the experimental tests are completed at UCB in January 19_3, there is only sparse quantitative data on the soil properties for the l'ainter Street site. The srnall-amplitude shear moduli fi_r the approach embankments and original grade soils have been estimated li based on P and S wave bedrock (a depth of approximately 80 ft), and two seismic irlstrumentation packages were placed, one at the surface and the second at the bedrock surface refl'action measurements which were performed. To represent the nonlil-iearitv til the soil in the bridge/abutmenl finite ek'reel-lt model, the depth of 80 fi (Fig. 3), The package at bedrock depth is Cl.lrrel-itly being used by seismologists to I]-ieastlre enlpirica] (]reen's ftllll_'tit)l-is for nlicroearthquakes emanating from nearby faults, si-l-tall-strain shear moduli i_btaint,d from these meastlrelllellts were tlsed with standard soil m(}dtlltls degradatiill-i alld damping4 ctlrvt,s. 12|1} i't,prest,l-it the standardized modtiltls degradatkln and damp- < -1.0L ..... : S I 10 Todate, l_ainterStrtt'tsite 2-30 Thrust Area Report FY92 .:. [_lg_#leur_ug I I 15Time(s)20 [xtirock Res(,,lr(h I I 25 30 rtsp(In_s have l)(,_.l_/i)lllllt, tll illg curves in the NIKIq31) fiilite t'lt'inen[ ,iii(/ li,( ll#lf,_ol{; program, A Methodology for Calculz_tmg the SeismicResponseof CriticalStructures.:. ComputationalMechanics a simple Ramtx, rg--Osgtx_d constitutive model was u_'d to moclel the soil. Tilt, material parameters were set such that the Ramberg--Osgood hysteresis loop would yield modultls clegradation and daroping curves very simila r to _'ed's 12stand ardized curves. The prt_:edtwe for determining the Raml.x,rg--Osgc××i parameters to approximate given modulus degradation and damping curves was developed by. Uel_a, g and Chen. , I_ The, m_Mulus and damping curves obtained from the Ramberg-Osgt×}d constitutive model fit with Ueng and Chen's -- L /Appro;4ch /emb_,kment Figure6. Simple nonlinear seY char. acterizatlon for I -, 'L _ l.O _ _, nal curves of Seed. The shear stress-strain behavtechnique are shown in Fig. 6 along with the origi- _ ior generated with the fitted Ramberg--Osgood model in the NIKE3D finite element program is f_ 0.S - also shown in Fig. 6. A number of time histow, analvses, have been carried out with the detailed bridge/abutment model shown in Fig. 3, as well as with simple reduced-order stick models of the bridge. 4 The bridge instrumentation records for the April 1992 Petrolia earthquakes have not yet been completely _ I I 'X "_,_,_• ",Q_ -- -% - - - Ramberg-Osgood _ Seed-ldriss sand curvem°del I 1,0"s 10.4 30 I I 10"2 10-1 Shearstrain(%) 1 I lO I prcx:essed by the CDMG; thus, the measured free field motions were not available to apply to our model prior to this report. However, free field and model ---- Seed-idriss sand curve ,./,_ _ 20 -,/,,')" -- bridge-respond, data for a mab,mitude 5.5 earthquake of November 1986 were available and were used to examine the accuracy of the finite element "i ._ _, The 1986 frLw-field acceleration --o Ramberg-Osgood // / /' ,// ] time histories were used as input motion to the ba_ of the bridge nlodels of the bridge system. system models. The model respon._ predictions were compared to the actual bridge respon_ data measured bv the CDMG bridge instrumentation array. Since tile details of ali of the respon._ predictions art, given elsewhere,14 only an illustrative example of the response predictions is provided here. Tile detailed model response predictions fur _10-0 _ 10.4 _--I l 1 10"2 10-1 Shearstrain (%) Soll stresHtrain behavior I I I 3.0 -- 2.0 -- _ shows the response of the detailed model when a linear elastic soil model is used, and mass- and j _ 0.o -- Rayleigh damping is used 1.0- -1.0 - toprovide approximately damping in the first transverse and longitudinal5%modes qf the bridge system. For the linear analysis, soil properties were set equal to the small-strain soil properties estimated bv Heuze and Swift from field measurements. -2.0 -- ...... d .rf,e'zc,'_'r'_ ---NIKE3D (Ramberg'Osg°°d model) / / / -,,,._ _ j / /i -- jt / I / / S _[ /:_" / -- _ -3.0 I -O.OlO -0,005 Two observations can be made: (1) the frequency content of the bridge model is significantly too high when the small-stra in soil properties are u_'d; and (2) the amplitude of the response predtction" is too large relative to the measured response. The bridge response prediction using the detailed model with the nonlinear Ramberg-Osgood soil model f"'d":r: [ lO lO-s the absolute displacement at channel 7 (transver._ motion at mid-span) are shown in Fig. 7. Figure 7a stiffness-proportional finite element model. [ 0.000 I O,OOS O.OlO Shearstrain(rad.) r-'""','Jc"d'::""t :':::: rg':t:,'::":-'g; + Thrust Arca Repc_rt FYB2 2-31 Computational Mechanics i .:. A Metllodology for Calculating t/tc Sc.tsintc Responso of Critical Stfuctu/os [!1 iii I III n_,, 7. _,,_o,,,_ c,_16 Cb,10 Cb.8 (b) nonlinear mod_. i 7 ' Free !t i _--Ch. c, ,;" [ Painter Street slesmic November ':,.si I 2.0 E I ("' ._ 1986 earthquake I -------.... 1.0 F -0.5 [-1.5 0.0 ] _ |l,__ 12 I ' 1 selected ,_ i'a" t" with , 5% i1 modes) ii !1_ I_Jo damping i I . West _ Cb. 3 - instrumentation i '1 in ':'.s 2.0 1.5 -- -7 ---i I [ 1.0 --_ll 0.5 -- 0 1986 earthquake /November 'l respons'_ -- I I I 1/ 2 3 (2.47,0.89) J I I I 4 "5,, Time ts) I ._ - _..* --- 1, I 6 " 1986t earthquake /November 1.5 I model) ... I ,I _ with Ramberg-Osgood / ... ,'_ ..._, (2.47,0.89) -i I response -------- - - Ch. Ch. 7 (measured) (detailed model I],, -1.s-- " I i (b) -1.0 Time ts) 1986 earthquake 0.0 -1.s - i layout I --1 ___ -LO / ! November Cb. 7 (measured) (detailed model q, ' c,,., i ch.=o Ch. 1 response I' II III C_.6 Cb.S Cb.19 ':,cb.9 H Ch. 13 \ field--- III I . -- 7 8 .. response -- (2.48,1.127) 1.5 o.0._ _ /.'in.p_. , 7%, _ , _] yT,,,_, ,1_ ._, 1.0__ O.S_ o.o ,, , "i,,,A,, 1.0[__ 0.5 ,'_ -0.5 -1.0 I-1.5 ._ Lr 2.0 _' "_'-"_l---, I (2.6b,-0.64) (2.hl,_0.09) I 2.4 / I 3.2 (s) 2.8 Time J --I 3.6 Future Work Significai_t prog._'ss Street of the seismok}gical el have been generated model completed, with has been made ovt, rcr()ssing both in the nlod- (2) Ba_,d nlodel, and laboratory elenlent model of tilt' bridgt_,/abi.ltnlellts. Thrust Area Report FY92 "." £r,g ,:_,ctsn._f Ro_,,*sch Dv_*,lopm_'nf bridge/abutnlent Green's functions, nltx;tel will generate time historic.,s h," the Apt'ii (3) retile _'is- a final suite of Zq lqq2 I'etrolia magni- 'lhel_x_Jrock-n_otit}ntimehistt,it.'swilllx'tlansfornlctJ to surfact' analysis,and the The fnt.astlred ,i_(l lol lI_lot,jt;,l nlotioll tlle.stiile will tx' c(inlpal't'd site-still characterizatitln will als(_allow site-response 2-32 4.0 tude-7 ea rthqtla kt,. expc, rinlental ill predict on nleasured inological field mea- data will improve lhc. s()il characterization finite to accurately ts seisnlological 3.5 span.'%'. have been Add itional 2.5 3.0 Time (s) 2.0 analysis to transform bedrock lllOtiOll to soil SLit'face motion. Specific tasks that we intend to perform during tile next vear inclttde: (1) U_> of the nonlinear m(K-lelof the bridge/ abutment svstem to prL_iictthe r¢.'s[._n_,of the bridge to the April !c/-)2Ih.,trolia earthquake. lhc predictt__t rc,'spon_' will t×' compared to fl_eactualbiidgei_..'sD)i:_emc,astll_'dbyCDMG. Thisearthquake should have r¢.'sultedin significant nonlinear tx,havior of tilt' bridge/abutmerit systenl, and this analysis will allow i.tsto further \'eri fy the abilih, (if the nt)nlhlear lntx:lel study and the structural and calculations m(_dels. 1.5 site. C(}nstl'tlctioll of (7;reen's fu ncti(llls fix ml fti ill ro lll iCl'l)earthquakes will ctnltinue t(i eilhance the site su reillen -1.s 4.0 is shown in Fig. 7b. This lllodei also Ll:'_.'d lllaSsproportional l?,ayleighdanaping, in which thedamping in tile first transverse nlode was set to I()%. The nonlinear model exhibits significant improvement over tile linear model. The nonlinear model displays appropriate softening and energy dissipation in tile system, such that tile frequency content and amplitude are more representative of tilt, actual structural response. of the Paii:ter -1,0 / with a site-i-c,>spon_ , of stlrt_lct' tilllo historit._ to tilt' actual frc_.,fieid illoti(in at tilt' silt, by C'I)M( ;. A Methodology for Calculatingtlm SeismicResponseof CriticalStructureso:oComputationalMechanics (4) The suite of preclicted hz'e field r_..'Sl.X_lz_.'s will [_.,mn through the structural m_:lel, and reSl.X_rkse st,ltistics will L-_., compart_.t to the actual rL_l.X_l_sefrom the April 1_#-)2magnitude-7 earfl-Nuake. The ultimate goal of our project is to allow accurate site-specificestimatesofstructural response for a specified earthquake on a specified fault. For practical applicafiorLs of this meth_Ktology, it will be essential to decide how the structural engineer ma}, best use the infomlation provided by the suite of time histories developed by the seismological portion of the study, lt will generally be impractical to perfoml 25 time history analyses (or more if multiple faults/multiple rupture zones are considered) for a large structural m_,x.-lel, lt is necessal T to consolidate the informatkm obtained from the time histories into a simplified fore1 (e.g., a representa- fornia, Berkeh,v, California, Report I:.t!RC72-12 (1_72)" 5. I.H. Prevost, DYNAt'I.()W, User'sMare,al, l)epartment of Civil Engineering, I'rinceton University ( I_)92). (_. BN. Maker, R.M. Ferencz, and J.O. t-lallquist, NIKE3D: A Nonlinear, Implicit, 1Jm'e-l)imensional FiniteElementC,)d,'.fbrSolidandStructural Mechauits, l_ls,'rlVhmual,l.awrence l.ivermore National l.aboratorv, Livermore, California, UCRI_-MA105268( 1_J_-_ I ). five respon_ spectrum and corresponding single time histor},) to achieve practical application. The Painter Street site study will allow a critical 9. evaluation of the accuracy of the method that is being developed, and a demonstration of our technology in ali ,_gments of the methtKlology chain. lt will also provide an opportunity , for interaction between structural analysts and seismologists, so that appropriate proceclures for using the earthquake grounci motion in structural response calculations can be developed. 1. t.. Hutchings, Modeling EarthquakeGround Motion 2. with an EarthquakeSimulation Prowam fEMPSYNJ Thai LltiliaesEmpMcal Green'sFunctions,Lawrence l,ivermore National Laborator}; Livermore, Callfornia, UCRL-ID-105890 (199_1 "" L. Hutchings, Bull.Seism.Soc.Am.81 (5),(19_,q). 3. l,. Hutchings, 1.Geophy.Res.95(B2),(19_J0). 4. P.B._hnabel, H.B.R'ed,arm J.Lysmer,SHAKE-A Computer I)rowam./brEarthquakeResponseAnahlsis _)1Horizontally Layered Sites, Earthquake Engineering Research Centel; University of Cali- Engineering 7. 8. D.B. McCallen, K.M. Romstad, and G.I.. (_,oudreau, "Dynamic Response of a Reinforced Concrete Box-Girder Bridge," En,_ineering Research, Developmeul,and _'chnology,Lawrence Livermore National Laboratop,, Livermore, California, UCRL53868-91,2-12(1995). Per_}nalcomn'mrfication between E Heuze(lJ,Nl,) and Kenneth Cole (CIXTF)(lt)_-)2). J.C. Wilson, and B.S."lhn,ASCE ]. End,,.Mech. Div. 226 (8), (1_)_)0). 10. S.D. Wemei;J.L. Beck,and M.B.Levine, Earthquake F_n_.and Sh'utr. Dyn. 15,(1987). 11. EE. Heuze and R.I: Swift, SeismicRqf}'actionStudies at the Painter Street BridgeSite, Dell, Cal!lbrnh_, Lawrence Livermore National Rio l,aboratory,Livermore,California, UCR/A D-108595(1992). 12. H.B._.,d, R.T.Wong,i.M. ldriss,and K. Tokimatsu, Moduli andDampin_Factors.lotlhlnamic Analysis (!/ Cohesionh,ss Soils,Earthquake Engint_.,ringRe_,arch Center, University of California, Berkelm, California, Report EERC-84/14 (1c)84). 13. T.S. Ueng, and I.C. Chen, Computational Procedure for DeterminingParametersin Ramber_,,-OsRood l',lastoplasticModel Basedon Modulus and l)amping Versus Strain, l,awrence l.ivermore National Laboratory, l,ivermore, California, UCRI,-ID111487 ( 1_,lc}2). 14. D.B. McCallen and K.M. Romstad,Dynamic I@. sponse (!/ a ReintbrcedConcrete, Box-GirderBridw, Lawrence Livermore National Laboratory Livermore, California, UCRIAD-II0640(19_,I2). k] Rt_se_tr( h D¢_elolJment and fe(',qoolotj_, .'.. Thrust Area Report FY92 2-33 Reink)rce(ICom:feteDam_geModelingoi. ComputationalMechanics Reinforced Concrete Damage Modeling SanjayGovindJeeand GregoryJ. Kay Nuclear Explosives EJtgineering MechaJfical Engineering The mt_:ieling of reinfl)rced concrete structure.s is currently performed by empirical codified formulae and linear elastic calculations. This state of the practice, however, can lead to both noncon_rvative designs on the one hand and to over-designed and costly structures on the other This wide range of outcomes arises from the lack of an adequate constitutive ro(Kiel to describe the behavior of concrete as it cracks under applied loads. This report briefly de_ribes work at Lawrence Livermore National Laboratory in the development of an appropriate constitutive model for concrete damage. ii ii ii iiiiii I__l:iem In the mtKieling of reinh)rced concrete structures, the current state of the practice involves the use of codified empirical h_rmulae and linear calculatio,as. While the._ methods are very u._ful, they can also produce unwanted results. When using empirical formulae, there is risk invoh, ed iea applying them to a sittmtion that is not absolutely identical to the tests from which they were dcduced. In particular, formulae for limit loads Kale in a rather non-linear fasiaion and must be applied with care and experience to avoid a non-con._rvative design. (-hl the other hand, one d(K's not want to have to over-build a structure and hence make it overly costly becau_ of uncertainties in modeling, A vast improvement to the design cycle is obtained if some of the empirical formulae currently u_'d are replaced by analytical models. The main unknown that most of the empirical formulae try to address invoh,es the behavior of the concrete it._if as it cracks under various loading conditions with different reinforcement patterns. Thus, the thrust of our work has been to develop a constitutire model that describes the behavior of damaging concrete, lk'cau_, this work is being performed for the Computational Eartlaquake Initiative at l.awrence IJvermoreNational laaboratory(H.Nl3, the level of complexity of the model has been cho_,r_ to be comnaensurate with that needed to model critical sections ()f large reinforced concrete structures under seismic loading conditions. This requires the constitutive model to be table to track l?r_g_noeiIng i i the progression of damage induced by arbitrary three-dimensional (3-D)loading histories in complex 3-D geometries, lk'cause of the.'_' requirements, the model has been developed as a 3-D damage theory that is suitable for large-scale finite element calculations. Such thinking is not new to the modeling of reinforced concrete structures.IThis original work, and almost ali that has followed since, has been confined to two-dimensional (2-D)problems. Under _,isnaic excitations, however, one must l(_)k at the more general situation that includes 3-11)effects, be,cau_ of the high likelihood of complex loading paths. There dtn_,sexist a handful of 3-D models. 2.,_,4However, none of the_, models is suitable for the pre_'nt problem. The first tw() models and others like them are only suitable for isotropic compressive type behavior, and the third, while promising, still requires some development. The pre_,nt model takes advantage of the insights and developments of this previous work and extends them to a new framework for damage modeling, The framework we have developed most closely resembles the framework proposed by Ortiz. "_ Progress l>rogress for FY-92 has been made on many different aspects til: the problem: choosing an appropriate class within which to develop the roodel; developing the features ttr inct)rporate into the model; developing appropriate nunaerical algorithms to efficiently perform finite element calcu- f?e, stri_tch Dl, vt, lol]tlJ(,tll iltld l(,,chllc_logy *'¢ Thrust Area Report FY92 2-35 ComputationalMechanics.:. ReinforcedConcwteDamage_1odehng lations; and deternlining how reinforcing bars should be mt_tel|.'d in co||junction with the cracking concrete. Model Classand Features M_.iel class refers to the basic style of the roodel: plasticity-like or damage-like, in plasticity-like models, material unloading takes place elastically with a stiffiaess equal to the initial elastic stifflaess of the material (Fig. la). lr| a damage-like model, material unh_ading takes place elastically with a degraded stiffiat,'ss(Fig. lb). The plasticity-like roodels have strong appeal fora at|tuber of reasons, but mainly becau.,a.' their algoritlamic properties are reasonably well understtx_i and are known to be suitable for finite element calculations. The true behavit_rtffcrackingctmcrete, laowever, re_,mbles more closely damage-like model behavior, Nevertheless, at the beginning of this project, we used a plasticity-like model to examine some of the numerical and theoretical issues that are unique to materials displaying softening behavtor like that shm'¢n in Fig. 1. The main use of this naodel class was to examine the issue of ill-pt_sed boundarv-value problems. Materials displaying iiiii ..... .... ............ Hill J ta) plasticityqike erallaypt)tlat_.'stffcontinuuna naechanicsl|avel.x_,n um,d instead to generate a complete mt_.tel. The basic premise of the model is that the damage state of the material will be represented by the rank 4 stiffness tensor of the material. Hence, ,as is knt_wl'l to occur in other damaging systenls,- the 'elastic stiffness' of the material is allm,,'ed to evolve with the loading history. To determine the evolutitm law for this degraded stiffness, the notit)n _t: maximum dissipation is used. To use this idea, one first pt_stulates restrictions on the ad missibh, stress or strain states of the material. For the collcrete, two restrictions ta) Figurel. Material unloading in stress-strain behavit," like that in Fig. 1 often generate ill-posed l_tmndarv-value p|'obh.'n_s.'_ While there are st,veral waw artmnd this issue, for concrete the most physically, realistic one is the notion of ctmstrairting the amot|nt of energy dissipated in tilt, system on a per-unit-volume basis to equal thai dissipated on a per-unit-area basis when opening new crack faces. This type of constraint results in the appearance of a characteristic length in the model ft_rmt|latitm. For the deveh}pment of the present naodel, the continuuna ft}rmulation _' was used to render the present ft_rnmlatio|l weil-posed for both the plasticity and damage model classes. In the domain of damage models, there is a wide variety of rnt_lel choices. 1"ochtx_m' the appropriate one usualk, requirt.'s a fair amount of insight into the micronaechanical naechanisms of the ohm, eyed damage and their reh_ti(mship to the free energy densi b, of the material. In the cam, of concrete with Mt_|e 1-,I1-,and Ill-type crack% such informatitm is not available. Therefore,_,veral gen- and(b) damage-like modelclasses, are postulated. Thf first restriction states that the nornaal tractions across cracks in the system ti t i.-,.- mt|st be beh}w a given critical value and that the critical value evolves ,Is the damage increases. Thf second restriction states that tj:'., shear tractions a given acrt_ss critical cracks valtle, in the which system alsomust t,,'t_lves be behwv with to (.'rdcks asStlllled pr_gressing damage, are nucleate in the material when the maxirnurn principal stress ,lt a point exceeds a given valtle. Using these two restrictions and the concept of maximum dissipation, an t,volutitm law can be derived for the rank 4 stiffness tensor of the ('o) I material tla,_tgives lilt, ctwrecl anis(_tr()pic sti'tlcture to the damagt,d stiffness tensor. lhr, other d_mlinant phentmaenoh)gical features of cracking c()ncrett' thai I_avt, betT_ inctwporated inh) thf m_)ttt'l are: Strain _'3_ Thrust Area Report FY92 4. t t_l:I.l'l'r_t/._ (I) H_''.(,,tt_h D_'_.I't(,l,.l(',lt ,l,*_l t,', Tilt' choiCt' (_t rt,stricti,uas (u_ the admissibit' stress states in tilt, na,lterial pr(ividt's h_,.i,,/,_ ReinforcedConcreteDamageModeling-:"ComputationalMechanics (2) (3) (4) (5) for Mode ,-, 11-,and lll-t3,pe crack growth (damage evolution). Tile notion of crack closure has bc_en included by monitoring the tractions across crack fact_. When the traction across a Reinforcing Bars crack face becomes compressive (negatire) and the shear tractions are below their critical value, the material behaves as though it is undamaged (tip to the compressive yield limit of the concrete), The notion of shear retention is built into the mtKtel b.v limiting the amount of shear degradation allowed in the system, The softening evolves with an exponential character, b4.<,ndevoted to rebar issues. Our results are, however, slightly non-conservative. To address this, ,,_mle prelimhlar 3, work has b_:_2ndone on rebar releas,e methods. Force-and damage-based slideline release meth(Kts have been u_,d, as have bondlink elements. The damage-based slideline release has been found to be superior to the force-based model and the bond-link element for accuracy againstexperimentaldata. However, the best overali robustness for these methods (after the fixed The damage evolution is anisotropic, rebar m(Ktel) is [_','en by the bond-link element, which is a node-on-ntKte contact element with a Sit,,., using fixed rebar bars (i.e., compatible displacements between concrete and rebar) gives reasonable results, to date only a small effort has Algorithms displacement-based The algorithmic imp!_ mentation of the pro F _i m_x:tel in a finite element _tting has involved the developm.ent of several novel algorithrrts. Of foremost iml_x_rtancefor .'_fftening rn{Ktels has _en the development of a characteristic-length ir|terpolation _qleme for _D problems. While an interpolation _,a:heme for 2-D prob!ems has been presented," a straightfonvard extension of this method to 3-D leads to singular d-_aracteristic lengths for certain crack orientations. In our work, a new interl:x)lation meth{_.ihas been developed that d{_,,s not have thc,_se singtdarities ,and vet remains fa;thful to the original dlaracterLstic-length idea. The other algorit!:,nic issues that have been addressed deal with iocal and global integration algorithms. On the local levol, a concave (as opposed to convex, as in metal plasticity,) optimization problem governs the stress point calculation. Because of the concave nature of the Examples Two examples are shown to partially demonstrate the proposed model. The first example involves the 3--point bending of a lightly reinforced beam; the second e,,ample involves the 3-point bending of a heavily reinforced beam. In the first example, the beam is 12 feet long with a 8 x 20 in. cross section that contains two #8 rebars in the lower fibers. The load deflection curve at mid-span is shown in Fig. 2. Overall agreement is seen to be quite g_xxi. At point (A), the concrete starts to crack, and load is transferred into the rebars. Cracking progres,_s up through the cross section with more load being transferred into the rebars until at point (B) the rebars yield. These obser-vafions from the simulation are consistent with experimental observations? problem, a unique answer to the stress point 411[ with one being inadmissible. However, bv pick" calculation does not exist; there ar two answers, algorithm can be made to always produce the admissible answer. On the global level, the nonlinear ing a balance suitable equations starting value' of the boundary-value the stress p°int problem have multiple bifurcation paths that lie - = ,'xtremelv close to each other and cause global con\ergence difficulties. To circumvent these well-known convergence difficulties, an aggressire, automatic time-stepping scheme has been teveloped. The scheme t_ses logarithmic-based time step control in conjunction with a special oscillating norm check. The combination of these tw_ idea,_ greatly enhances the ability of the global solvers to achieve equilibrium. release lav,,. i I / '1 I I F/gure2. LoaOcl_mid.6pan _rbeam with twocurves #8 rebars flection at in BA/_'___ damage initiation point (A)andthe _I _ _ 20 p _ ..a [ I . potntofyleld(B) thelower111_m. Tl_ are /A marked. /" A '°L? ' A__ 01 0.0 J 0.1 a Data Simulation t I I 0.2 0.3 0.4 Deflection!L-..) 0.5 _ Lr, g_neer_ng Resf_,arct, De_o,_oO'ner_r a_d lecf_r_oiof,_ "*" Thrust Area Report FY92 2-37 ComputationalMechanics.:oReinforcedConcreteDamageModehng | I Figure3. Loaddeflectioncurvesat withfourWgrebars in theIowerlfbers andtwo #4 rebarsin mld.spanforbe.m I damageInitiation _, 125L i00 _ / _ ! _.| facefailureInitiation ,. the upperflbers. The I FIuIture Work stress point algorithnl more robust anti efficient. In addition, a few new features will be added, such Ft,turf' work w,,, f(_L,S on making the ,ota, as compressive f!ow of the concrete and crossing cracks. ..,,.._ ../_." iFA Ill 03) I ./_.AAA, / ' . Ii _/AA Z pointmarked.(B) are I I 0,1 --Simulation ata I I 0.2 0.3 Deflection (in.) _ I 0.4 0.5 In the second example, the beam is 12 feet long with a 12 x 21.75 in. cross section that contains four #9 rebars in the lower fibers of the beam and two #4 bars in the upper fibers of the beam. Additionally, there are #2 stirrups every 8.25 in. along the 2-38 Thrust Area A--w.... of The LLNL, Prof. wish R.L. to Taylor of the University authors acknowledge Dr. B. Makerof California, and Prof. J.C. Simo of Stanford University for their help and interest in carrying out this work. 1. Y.R.Rashid, Nuc. Eng. Des.7, 334 (1968). 2. D.C. Drucker and W. Prager, Q. Appl.Math. 10,157 (1952). 3. EL. l)iMaggio and I.S. Sandier, ]. Eng. Mech. 97, 935 (1971). 4. M. Ortiz, Mech. Mat. 4,67(1985). length of the beana. Figure 3 shows the load deflection curve at mid-span for the experiment '_and the calculation. At point (A), the concrete starts to 5. L.J. Sluys, Wave lh'opay, ation, h_oflizalhm and Dispershm in S(!fieningSolhts,Ph.D. Dissertation, Delft UniversityofTechnology (1992). crack, and there is a large load transfe.r to the #9 rebars. The #4 rebars do not carry much of the load. Vertical cracks develop along the span and grow upwards and towards the centerline of the beana. At point (B), the calculation deviates from the data because rebar release was not included in the sinaulation. 6. J. Oliver, Int. ]. Numer Meth. En,%,. 28,461 (1988). 7. S.Govindjee and J.C. Simo, ]. Mech.Phys. Solids39, 87(1991). 8. N.H. Burns and C.P. Seiss, University of Illinois CMl Eng. Studies SRS No. 234, (1962). 9. B. Bresler and A.C. Scordelis, ].Am. Concl. lust. 60, 51 (1963). [_ Report FY92 .:, Engtneertng Research Development and Technology Diagnostics and Microelectronics _! _' The Diagnostics and Microelectronics thrust area conducts activities in semiconductor devices and semiconductor fabrication technology for programs at Lawrence Livermore National Laboratory. Our multidisciplhlary engineering ,and scientific staff use modern computational tools and semiconductor microfabrication equipment to develop high-performance devices. Our work concentrates on ffu'ee broad technologles of semiconductor microdevices: (1) silicon and III-V semiconductor microelectronics, (2) lithium niobate-based and III-V croelectrode electrochemical sensors; (5) diamond heatsinks; (6) advanced micromachining technologles; and (7) electrophoresis using silicon microchannels. In FY-92 construction of the new Micro-Technology Center was completed. This new state-ofthe-art facility includes 7,500 sq. ft. of Class 10-1000 cleanrooms and three large dry laboratories. The building was specifically constrtlcted for the Laboratory to exceed ali federal and state safety codes and regulations. Ali toxic gases are stored in autopurge gas cabinets located in separate earthquake semiconductor" based photonics, and (3)silicon-based micromachiningforapplication to microstructures and microinstruments, In FY-92, we worked on projects in seven areas, described in the reports that follow: (1) novel photonic detectors; (2) a wideband phase modulator; (3) an optoelectronic terahertz beam system; (4) the fabrication of mi__ !_ 104' r. resistant vault. Ali air handling machinery is mounted on a separate foundation vibrationally isolated from the cleanroom laboratories. The dry laboratories are used for microscopic inspection, packaging, and electrical and optical testing of devices. While the Micro-Technology Center is primarily a solid state device research facility, the emphasis of the thrust area is to solve problems for internal and external customers relating to diagnostic and monitoring instrumentation in a variety of scientific investigations. Joseph W. Balch Thrust Area Leader 130' i Light lab Process equipment [ZZ] Clean room UHP gas vault B153: Micro-Technology Center Section 3 3. Diagnostics and Microelectronics Overview JosephW. Balch,Thrust Area Leader Novel Photonic Detectors Raymond P. Mariella,Jr.,GregoryA. Cooper,Sol P. Dijaili, RobertChow,and Z. Liliental-Weber.......................................................................................... s.1 Wideband Phase Modulator CharlesF. McConaghy,Sol P. Dijaili,and JeffreyD. Morse ........................................................s.s Optoelectronic Terahertz Beam System: Enabling Technologies ]effi'ea d D. Morse.......................................................................................................................... s.9 Fabrication of Microelectrode Electrochemical Sensors Dino R. Ciarlo,JacksonC. Koo,ConradM. Yu, and RobertS. Glass......................................... s.xs Diamond Heatsinks Dino R. Ciarlo,fick H. Yee, Gizzing H. Khanaka,and ErikRmldich ..........................................s.ls Advanced Micromachining Technologies Wing C. Hui ............................................................................................................................. s.x9 Electrophoresis Using Silicon Microchannels JacksonC. Koo,J.Courtney Davidson,and JosephW. Balch...................................................... s.21 Novel Photonic Detectors o:oDiagnostics and Microelectronics Novel Photonic Detectors Raymond P. Madella, Jr., GregoryA. Cooper,and Sol P. Dijaili EngineeringResearchDivision ElectronicsEngineering Z. Uliental-Weber L,nvrenceBerkeleyLaboratory Berkeley, Cal_,'llia Robert Chow MaterialsFabricationDivision MechanicalEngineering Tl'fis project had two parts for FY-92: (1) to fabricate a photocathode that could respond to infrared (lR) light; and (2)to fabricate a di(xte laser that would function as an x ray-to-light converter. Although IR-sensitive photocathodes are not available commercially, there are numerous Lawrence Livermore National Laboratory and Department of Defense applications for such devices, including a 1.3-pm streak camera and radiation-hard lR sensors. The key part of our work on an lR-sensitive photocathode is the use of molecular beam epitaxy (MBE) to grow high quality semiconductor layers that can absorb lR light and transport the resulting charge carriers to the opposite surfaces of this electrical device. During this last year, as part of a separate research project, we discovered a new kind of photocathode and, thus, we centered our activities for both projects on fabricating and testing devices that incorporated it. Little data had been published on the direct effects of x rays on diode lasers, and our idea was to use the absorption of x rays within the gain medium itself to modulate the optical output from a diode laser. The advantage of this device was expected to be that it should have picosecond response times since, at least in a simple double-hetemstructure laser, there would be no time delay due to carrier transport. To test the device experimentally, we u_d a pulsed x ray source, which was a plasma that was created by a pulsed laser focused onto a metal surface. Although we did observe the direct conversion of x rays to optical output on a fiber optic, we were unable to make an accurate determination of the ultimate time response of the device. Introduction Photocathode Of ali materials tested, p-type GaAs, coated with cesium and a form of cesium oxide(hereafter we shall simply refer to this as 'activated'), has shown the highest quantum yield, q, for detection of visible and near-infrared (lR) light; state-of-theart commercial GaAs photocathodes can have q = 10% for wavelengths ()Lit to 0.9 pm. For light with longer wavelengths, however, the GaAs is essentially a transparent material, and its use for Englnec'ring direct detection of lR light is not practical. While allsolid-state detectors with high values of q exist for light wavelengths longer than 0.9!urn, photocathodes offer greater radiation hardness and are wellsuited to photon counting and two-dimenskmal imaging when used in conjunction with electron multipliers, such as microchannel plates. A radiation-hard detector with sensitivityto 1.()6-pmlight is desirable for LIDARapplications;atmospheric viewing can be achieved in the 1.3-to 1.8-pmband; and a photocathodewith sensitMty to 1.3-1urn light would find application in a streak camera that could be used for rernote monitoring of physicsexperiments. Research Development and Technology ,:. Thrust Area Report FY92 3.1 Diagnostics o:. Novel Photonic Detectors and Microelectronics p,type substrate .... : [ 1_ ' lI _' _ _ pl _e _ Gradedbandsap ' emitter . light L'TT'_ L_] absorber / ]_ light, create ek'cb'on-hole pairs, and (under applied electrical bias) _parate and move the elech'ons without kx-;sto ata activated surface for emission. This is promotes an electron from the lower energy level (the valence band) to the upper level, the conduction band. Since the conduction band of the layers on either side of the lR alp sorber is higher than that of the lR absorbar, thisunblasedde- shown sdaematically in Fig. 1. We startxxt investigating strained-layer lnyGal.yAs OFIGaJks substrates with lnx(AlwGal.w)l-xAs as an emitter, but becausethiscombinationwas intrinsically limited in itslong-wavelength resl.x_nseto atx_ut 1,3t.un mid t'_cause we had recently invented a new photocatht×ie (GaAISb), we concentrate:_l on this latter system, which we are ha the process of patenl_ag. Phot(x:atht_.ic_ of Gai_xlnxAs or GaAsi.xSbx (for small values of x) have smaller bandgaps thma GaAs and can absorb longer-wavelenbeth light and have l_x, en hbricated elsewhere, but their values of 1"1fall very quickly as a function of x. These photocathtKles, in which a single material functions as both the lR .... (al 1.8-kev x rays ............... Aluminumo,3_m GaAs O.Ipm AIGaAs 0.TB_tm GaAs0._/am AIGaAs 0.75 I.tm (b) X-rayradiation . . ....... Light OU| _. N Diode laser Figure 2. of the physical structure oi Simple representation x ray.t_lightconverter. (a) Schematicdrawingof the layersin thedeviceandcalculationsof absorption of the 1.8-keVx Report rays. (b) Sketch of device, FY92 .1. X ray-to-Light Converter In the r___seardl area of x-ray dia_aostics, one dc'sirable feature of a detector is to enc(Kle the temporal information atx_ut tidehatensities directly or|to a coherent optical beam, which is b'ansmitted ota ata optical fiber for remote recording. Ch'_eapproach, ori_nally proposed by J. Kt×),lhad been to combine a solid-state phot(x:ondtJctor with a diode laser, where the electrical carriers generated in the phot_onductor would l.x_ used to m(Ktulate the output of the laser; this was successfully testc_.t.2A limit to the high-spc_'d response of such a detector Lsthe time it takes to move electrical carriers into the gain region of the dk_.ie laser. We propo_,d rising the excess carriers, whicla are generat_xt by tide ab_wption of x rays in the gain region itself, as the source of mtKtulated laser output. This has the advantage, at least for a simple doublehetemstructure laser, that no time is k}st for carrier transport. Since the time for the 'hot' x ray-generated carriers to thennalize has i_'en calculated to [_' l_:_s such a device should Ix, limited only by the stimt|lated '_ Area (lnP). This two-part approach has been what we have fore, contain a material that could absorb the infrarL_.] _gurel. Schematicdrawingot the _nd structureof anlRphotocathoOe.Thesmallerbandgapregionabsorbsthe lR light,to whichthe su_trate is transparent,tl_t absorption vice cannot transport the electron out of the lR absorber, Thrust ed by Varian EOSD, was to use a two-part semiconA more advanced concept, ductor photocathtx.ie, with one originally part as thedemonstratIR aba_rber (GalnAsP) and the other part as the electron emitter Infrare 3-2 absorl._r and the electron ernitter, have not shown tLseffdsingle-shotsensitivity to light with wavelengflls t. tlg_n(,(,tl_ g Re_;_:/_t(;h Develol_mt:,;t than one picosecond, the overall time rc.'spon_ for emission lifetime of the carriers, whidadifficulty can easilyinbe few tens of pic(_'conds or It:_s.The de-a signing and fabricating such a device is that the x rays must pass through the top cladding layer of the lair before they can Ix'ab_w[x,d in the gain regi()n to crea tc, u_ful electron-hole pairs to m{_.tulate the optical output (Fig.2). if the x rays have little absorption in the cladding, they will al_ have little ab_)rptiola in the gain medium. Similarly, if they are intensely ab_)rbed in the gain meditma, they will N, inten_,ly ab_r['_,d in ;_1(I I('chrlolo_',k .:. Diagnostics Novel PholonJc Detectors and Microelectronics iii cladding and will not reach tile gain meditlnl. Penetrationdeptks of x rays vmT rapidly with x-ray energy, _ we exl.%'ctc_.t our devicc_to L_,_nsitive to only a rather narrow ener_,_,rangeof x raysin the low the " _10 --- I [- I 10-_ I _ ,., _j "_ keV enerbw range. This is a range commonly prr>d LICL_.iby flx:u.,_t-la_,r plasmas. [ I l I ] Figure 3. Plots of photoresponse for a variety ofGaAsand GaAISU photocath- _ LLN L AIGaSb w/grid 10-2 -_; _-' l0 -3 -- " I LLNLGaAs II LLN L AIGaSb --- odes that were ._ '"e_ 10-4 _ E_IO [] -s- - _ our grOWnandactivatedinOn our MBE -- testapparatus. - lo-7_ Photocathode ao__ 1. I 0 I I I I I I 1B lC lD During FW-92,we u_.i our molecular L_am el:fttaxy (MBE) system to grow heteroepitaxial structurc.'s w,ifla InJAl,,Gal_w)l_×Asemittet.'s and InvGal-vAs aL> m_rL_r,including superlattice tx,_,een the GaAs strained-layer substrate and file lR ab_rt_,rbufft.,ls with elecb'onemitter. Ik'cau:_acfivationand tt._tingofphotocathtx.tcs is a slow proct._%we began concentrating our effo_ on GaxAll._Sb (x = 0.3) emittel:s as _x_n as we diKovered that it worked about as well as GaAs (Fig. 3). The main appeal of the Ga_All_xSbemitter is that it is lattice-matched to single-crystal lR ab_wl__,ls, whicla span the range of waveleng-ths from (1.9_.tmto more than 10 luna.GaSb absorbs out to 1.7luna, haAs I J 3A 5A 6A 6B 7A 7B Run index placementoftheF(.)proximaltotheenaitfingfilcet.We then mounto.t the assembltM la.,a.,ron a vacuum flange with a fiber-optic connection through the flange. Using x rays ft'ore a focu_,d-la._r plasma, we did ob._rve the direct conversion of x rays to coherent optical light, as hoped (Fig. 4). ik_cau._ the la_,r puM,s were multi-nan(ysecond in duration, we could not determine the shortest time rc_pon_,of our deter:tor. However, we did learn that the pul_'-to-pul_, variations in x rays that were generak_i by the f(xTtl_K'lla.,a.,rcatL, a_'d far more variation in the outpLit of our dettx:tor than in reaches 4 lure,and inAs/GawlnvAIl_v.,,Sb SUl:_.'rlattic- the simple photoconductive detecto_.'s.This, again, is c.,shave Lx_enshown to ab_)rb out to 12lure. We have due to the fact that our absorbing region is 0.8_.[m grown, activatc_.i, and tcsto_i numerous photocathtx_neath the sLn'faceof the lair (().7-_Jm-thickcladding (_.ic_of Ga×AI__,Sb,and we have grown suwrlatticcs with 0.1-_.tm-thickelectrical contact layer). ot lnAs/GaSb, which we expert to absorb in the 0.9-to The data shown in Fig. 4 reprc_,nt the average of 2-lure range. We are still invt_tigafing doping levels in 100 laser pulses. When we tried the same experifl_e various layers to minimize dark currents. Dark ment with a subpicosecond x ray source with less currents degrade the perfomaance of thc_, devicc_, total f IL,.ncc, , "' We were not able to detect x rays. X ray-to-LightConverter Future Work To fabricate ata appropriate device, we u._'d OtlP We are patenting the new GaxAll.xSb/ll,_-abMBE to grow a simple DH la._r with 70V,,alLuninum serber photocath(_de. An Engineering Research in the cladding. This high alunainLmacontent increa_'d the overlap of the optical L-v,_,a m with the carrie_sin the 0.08 .... t I I I I gain region and al,_ allowed more x rays to pass start of through Llaecladding and enter the gain region for abc)rpt/on. BecaLISe Otll"simple turK/cling showc_.i that our devicc_, with ().7-ium thick cladding and ()._.tm ,,, thick gain region, would exhibit peak _,nsitivib, for = x rays with energies of a few keV, we had to cii._ontinue using our nom_al top-side metallizx_tion ¢)ftitanium/plafinuna/gold and substitute pure alunainum. ,_ (-Ihe gold and platinuna would have ab_wbed virtually ali of the dcsirc_.tXrays.)This requirc_J(_urdeveloping a new metallization pr(_:edure and a wire bonding pnx:edure for the aluminum c(_ntact. We al_} designed and built a heat sink to mount this dcxice, and the heat sin k had to Ix'dt_igned _ )the t the epoxy that we tL,-edfor I:-0 pigtail/rig wt_uld nt_t flow onto the la_w face,t, yet would allow accurate t n,q_n,,¢,_/np, tVc.,,(,,iz(h 0.06 -- x r, zs " -- l Figure4. Plot of la- ser output vs time for our x ray-t_light cotF verter,averaged over lO01aserpulses. 0.04 0.02 -I ] 0.00 -0.02 40 II(,_,t, ] 50 foptn_.nt t 60 ,_tid [ [ 70 80 Time (ns) I_'( hn ,l(_l.!V .:. [ 90 Thrust 100 Area Report FY92 3-3 INall_mltlosand Microelectronics4, NovelPhotonicDetectors Division project at Lawremce Livermore National Laboratory is working on its development and seeking an industrial partner. The x ray-to-light converter is not currently being pursued further. 3-4 Thrust Area Report FY92 4, Engineering Research Development 1. J.C. Koo, Private communication, Lawrence Livermore National Laboratory, Livermore, California (1988). 2. C.L. Wang, Appl. Phys.Left. 54,1498 (1989}. and Technology L_ Wideband PhaseModulatoro:oDiagnosticsand Microelectronics VKleband PhaseModulator ChadesF. McConaghy, SolP. Dijaili,and JeffreyD.Morse EJ_gineerin S, Research Division Electronics Lithium National Zehnder En_qneeriJ_ niobate integrated Laboratory, modulators optics work has been an ongoing (LLNL) for many with bandwidths effort at Lawrence Livermore years. We have delivered completely packaged Machto 20 GHz, extinction ratios over 40 dB, and losses as low as 4 dB, to LLNL programs. These devices have traditionally been used to intensitymodulate laser sources hl high-speed analog links. During the past year, we have been doing research on a very broad bandwidth, integrated-optic phase modulator. Such a device would have immediate applications to stimulated fibers and glass amplifiers. In addition, these pulses from long or even cw laser pulses applications is new, what is unique here is used to implement these techniques. Brillouin scattering suppression in both optical devices can be used to generate very short optical (pulse compression). Although neither of these the efficient, integrated-optical phase modulator in generath'lg bulk optics, Vn can be reduced to 10 volts or less. Higher electrode voltages can be achieved for a given drive voltage by ushlg resonant electrodes. We have been working to achieve a Q-factor on the order of 100 in a microwave transmission line reso- picosecond optical pulses usually involves large, expensive table-top laser systems, which greatly restricts the applications of these systems. A picosecond, compact, inexpensive pulse compressor suitable even with cw laser sources can be built nator designed in an integrated fashion with the optical waveguide. At resonance, the voltage applied to the electrodes is approximately the source voltage multiplied by the square r_x)tof the Q-factor. We estimate that bandwidths on the order of with an ultra-high bandwidth, LiNbO3 phase rnodulator together with a dispersive element such as a grating or a fiber. In fact, these optical pulse generators can be built at any wavelength where suitable optical waveguides can be built. Previous atternpts to compress and generate picosecond pulse trains using phase modulators used bulk devices and, hence, required many kW of microwave power to achieve picosecond pulses and optical bandwid ths of 6(X)GHz. I One other a uthor 500 GHz can be achieved with microwave power levels on the order of several watts. Using a dispersire elemen t, this bandwidth can give rise to picosecond pulses from optical sources. For a transform lilmted pulse, the minhlmrn pulse width obtainable is given by .8/(bandwidth). Therefore, for 5(X)GHz of bandwidth, 1.6 ps pulses can be obtained. Figure 1 shows the concept for pulse compression. has tried a guided-wave device. However, a low drive power and an inefficient electrode structure limited the bandwidth to 12 GHz. 2 Stimulated BHllouin Scattering Suppression The bandwidth of a phase modulator is directly proportional to the drive voltage and inversely proportional to VTr,which is the voltage required to produce a phase change of 180° in the optical carrier. By using integrated optics as opposed to Stimulated Brillouin scattering (SI3S)is a nonlinear optical effect that limits the maximum optical power that can be transmitted in both glass amplifiers and glass fibers. For example, at 800 nra, experimental evidence exists that shows optical power I__011 Pulse Compression Current commercial capability Engineering Resealch Development _an(l Technology ._. Thrust Area Report FY92 3-5 Diagnosticsand Microelectronics":" WidebandPhaseModulator -- illlll II I li|li I lE I Microwave signal Figure1. Optical pulsecompression witha wideband phasemodulatorto chirptheincoming laser. I ] Dispersive grating pair Pulsed laser At Electro-opticcrystal Time domain t Ato= 0.71_d o IEI2 Afl =0'4/Ali Frequencydomain [ , ,, f P_ The goal ot FY-92 work has been to design and fabricate a high-Q electrode structure. We have _ ..... _ 0 (b) measured reflec. riencoefficient,S:ll. -1.0 --1 -2.5 -3.0 3.5 0 _ -1.0 -- I .... I I I 4.0 4.5 5.0 5.5 Frequency (109) I I I 6.0 -_ 6.5 I -2.0 _-3.0 -5.0 -6.04.0 Report gone through three iterations of electrode design this year. To maximize the overlap of the optical and electrical waves, the microwave electric field must be confined to a gap of about 10 _tm. A tight gap electrode structure can be limited in Q since the microwavecur|'entbundlesir_thecor_ductorsclose to the gap. We have both modeled and built microwave resonant electrodes frorn symn|etric coplanar and asvrnmetric coplanar lines. We have studied shorted and open-ended lines. In addition, we have studied how the microwave energy is coupled to the resonant electrode. In our fir,'s:titeration, hre electrode structurc_ were packaged in one t×_xfor tc._tpurp(_;t_. We diKovered that the microwave ene|'hO,excited not only the electr(_Je of intert_t, but the additional electrtxte ira Lhe FY92 _vond iteration, swaametric linc_,'s were u_'d for Lx_th the input coupling line and the rip,hater. Thc_ devicl.,'swere testt__.iwith higla frequency rf protxs and a nehvork analyzer. Network analyzer naeast|remenLs of th__,_structurts indicatedm_ieling _'o D×lrly rt_,'sollarlcc,-.;. Further computer withdefined a corTlrnercial elfftTonaagnetics program (_nnet EM) indicated that rt_nanct,,s were achie\'ed at slightly different fiequencit__ for wa\'es on either side of the rc._,nant elt._:trc_te.This was probably due to the perturbation of symmetry,, from the center ft_'d point on one side of the elt_:tr(Kk,. Another electrode pattern that was identical except that it had a l()0-#jm gap, did not have this problem, t l¢_wever,the wide gap is incompatibh: --4.0 Area f ,"_qllle ¢_ -2.0 Thrust A_ '--tl_ Lx_x. The fi_t iteration u.,aMNith an asymmetric lineand an asymmetricinput-coupling,_heme. In our -0.5 -1.5 3-6 _ - saturation at abotlt lO0 nlW in fiber. The fiBS is inverseh, proportional to optical linewidth. Therefore, it is more difficult to obtain power h'ansmisskin with a narrow linewidth laser'. To suppress the negative effects of SBS, the linewidth can be widened with phase modulation. Experiments are planned to see how the wideband phase modulator can be used to minimize the SBS problem, Figure 2. Plots of (a) calculated and IE_ I 4.4, .:. [ l 4.8 5.2 Frequency(109) I t_l_tpt'_'rs_,.'_ R,._,_.,_t( [ 5.6 6.0 with building a high t,fficiencv m¢_dulator. The third iteration produced a well defined notch in the retlection coefficient. "Ibis indicated that the electrode was indeed resonant stantial amt_unt t_t:input ['_t)\VUI" !_ t_,_'¢_,l)me¢_¢ ,_,! ?,,_ h_t,/(,__{_ and that a subct)ulgled to it. WdS I/V1deL_and PhaseModulator.:. Diagnosticsand Microelectronics near the tiglat l()-J.tnlgap. Currently, the modified asymmetric Figure3. Currentdistributiononelectrodeat resonance, In this electrode design, the input coupling consisted of a symnaetric coplanar line, and tlae resonant electrode was an asymmetric coplanar line. This alleviated tlae problem tlaat existed in tlae completely symmetric resonator, Figure 2 shows i.x_ththe calculatt_:land measurect reflection coefficient, SI I. llae rt_nance laas a Q of aN_t|t Zq,which ctwrt,,sponds to a _timts voltage enlaancenaent, llae depth of tlae notch is no greater tlaan 5 dB, indicating tlaat al._ut one-third of the incident power ix not coupk, d into the rt_wlant ek'ctrt_:le. A new mask with a wider coupling gap has improved this notch depth to about 1(IdB or q)"_, coupling. The slight differenct_ in notch depth and rt_nant frequency t_'twcen the mt_ieled and measured data can probably Ix_,accountt_i for by the fact the m_x.ieling ethic ix hvt_iimensional and dots not take into account the effect of ek,ctr_x:iethicknt_ss. electrode structure shown ila Fig. 3 is being electmplated on top of an 80()-nra optical waveguide. Once fabricated, thedevices will have ttaeirbandwidthsevaluated witla an optical spectrometer. If sufficient bandwidth, in the neiglaborlaood of 50(/GHz, is achieved, the clairped pulses will be compressed with a grating to aclaieve picosecond optical pulscs. In related integrated-optics work, we are expiot'ing the use of modulators at superconducting temperatures. We would like to explore the possibility of bt|ilding one of the resonant electrode plaase modulators with niobium electrodes to determine what type of Q can be acilieved ,at superconducting temperatures. 1. T. Kobavaslai, !t. 5ao, K. Atnano, Y.t:ukuslaima, A. Morilnt}to,and E Sueta,It?f!F101"24 (2),382(10_). 2. B.It. Kolnt,u AFI,I.Phtls.la'lt.52 (14),11_ (1088). O_)toelectron/c Ter_ltTertzBeam System: En,iOI/ng leclmologtes 4. Diagnostics and Microelectronics Optoelectronic Terahertz Beam System: EnablingTechnologies Jefhc_yD. Morse EJtgipleeriltg ResearchDivisiolt Eh'ctrolficsEJte,ilwerillg In FY-_)2, we investigated the photoelectronic properties of semiconductor materials and structures for implementation as photoconductive dipole antennas in a terahertz beam system. We have measured optically generated electrical pulses propagating on-chip having temporal resolution as short as I ps. Furthennot_e, our devices have been used in a terahertz beam system to generate and detect electromagnetic pulses traveling through free space, with durations as short as 5(X) fs. i Introduction antenna With the advent of sub-picosecond laser sources, optoelectronic switching devices can be used to emit broadband electromagnetic (EM) pulses into free space. Integrated metal-semiconductor-metal photoconducti\'e devices are capable of radiating EM pulses from monolithicaliv integrated antenna structures. 1,2The basic svstern concept is illustrated in Fig. 1. A static electric field is stored across the electrodes of the highly resistive, photoconducting antenna structure. When an optical pulse of intensity E,,ptis incident between the electrodes, the conductance of the photoconductor increases, and the relation between the radiated electric field and the static electric field strength is described by _ will that retains high mobility for the of the antenna Pump static electric acrossof the ductor, and (_,fieM is the applied conductivitv the photoconphotoconductor due to the photogenerated carriers. The conductMtv is described by pulse k /\ '_ (1 - this research The power radiated by the phot(_:onductive antenna element is directly related to the electronic transport properties of the semiconductor materi- material, q0 is the free space impedance, E, is the O's = q//efr Therefore, focus on optimizing the mobility of materials used as photoconducting antenna structures, which are suitable for compact arrays of emitters for ultra-wideband radar and remote applications. The advantages of using integrated optoelectronic antenna structures include ultrawide bandwidth, high power, excellent directionality, low cost, and compact, durable elements conducive to large, photonically controlled arrays. rlal where t" is the dielectric constant element. r) Eop t /h v, yb L_ /1, Terahertzradiation _ Photocurrent _J /X j, - "J- T LT-GaAsemitter and detector k \ diagram of photocorv ducting antenna emit. ter anddetector. (2) where q is the electronic charge, r is the reflectivitr, _J,., is the effective mobility, hv is the photon energy, and E,,pt is the optical energy density. • " Frorn Eqs. 1 and 2, it can be seen that the effecfive mobility of the photoconductor material directlv relates to the effMencv of the radiating Flgurel. Schematic Probe pulse Diagnostics and Microelectronics .:. Optoe/ectronm h,n/_ertz &?,,, St,stem: E,_,,.)/.JF_ le,'/,n>/o_.,s i i i!i Rgum 2. Autocom_ tures Probe pulse Pump pulse 4 ps, 532 nm 4 psr 532nm lation circuit conflguration, f -_ (ILM ' to 400 C) inh'oduces l)uring thermalranging annealing tilt, epitaxial at tt,rnperaturt,s from of58() to 8()()"C, laver the extess arsenic diffuses to forrn precipitates, l)epend- 2 pm LT-GaAs ing Oil the anneal time and tenlpt, rature, the resu Iti nga rsen ic preci pi tares ha ved ia meters ra nging ft'ore 2 to 20 nm and spacings ranging fronl 5 to .q0 nnl. lt is believed thai these defects are metallic in nature, _behaving GaAs substrate I 1,0 I 0.8 -- me&sutedbyteflectlveelectro-optic sampling. responseof Ll_als _ ._ 0.6._ _ . 20 _ 'I _ 10 20 Time (ps) LT GaAs J t 4 6 Time delay (ps) Report bv MBE at 190_C. rills circuit uses and 10-1.1mseparation. With an electric field apof the plied two 'sliding' across balanced contact the coplanar copldnar configuratit_n," lines, lines with all which electrical 5-1.li11consists width lransient signal can then be launched onto tile lines by shorting tile gap between them with an optical pulse. The phottwtwiductive pulse can be gerleratcd <atanv point ah_ng tilt' ct_planar lines, henct, 'slMing' contact. This is especially u,,,a.,ful for ctlai'acterizing -- sanlpling i'll'nit'ni is positioned ailing lull, til tlw lines iri the ctlplanar pair (Fig. 2). l'ht' sanlpling can be either pht)ttwonductiveor t,lectro-optic, s Bv varying tilt, relative, delay between tilt, generat- I 8 tilt, dispersive effects of the coplanar 10 6 S 82()-nra waveleng, th, and tile signal has propagated approximately 10l) t.tm on the transmissit_n technique." The optical pulse wMth is ~ 6IX)tsline. at I 2 10 _ ,ii Calibration optical,at half intensity gives The rc,spoilsc'of istile < 1incident ps full wMth lllaximLIIll. 2 - 120 cna /Vs, an estimated 0,5 1.0 Frequency (THz) carriers whilt, 1,5 prti\'iding 2.0 fast rv- c-tin-lbil'iation lifetimes is desirable. In gc,nt'ral, thr,st' iwl) eledr()ilic prilpertit,s cilnflicl. Recelltlv, ii has been fllund thai tilt_,gr(_wth tfr(, ;aAs b\' ill(llc, cLilar beam epitaxy (MBIi) at h_w substraie it'nlpera- Area to higher ing and sampling t_ptical ptllst,s, tiw phtltocoridtictivt, transit, ni I'tt_ptilaSt' is Illt'aStll't'd. Figure 3 illustrates tilt, electrical ptllSC, II/C,aSUl't,d ftu" this material, bv the reflective electro-optic sampling i 0 phtfftigenerated Thrust translates -- -_ 0 0.0 3-10 which l'hot(t'onductive atih_corrc, hitit_n circuits, iilustta/cd in Fig. 2, have beento alternative fabricated frt)m LTsensitivity ill Ct)lllparisOla materials 30 -10 il, is exhibited, GaAs grown 0 d mobility / 1 0,2 li 0,1 0 _ 0 (b) corresponding centers for picosecond photoconductivity. _ 90 tectedwlthLT-GaAs detector in terahertz beam system. I ii Rgure4. (a) Waveformand as fast recombinatitln and resulting in sub-picosecond photoconductive responst, times. Furthermore,, since lilt' epitaxiai LT4]aAs retains e×cellent crystalline qualib,, higher . photoconductor concentra- Sampledsignal to lock-in amp V: Figure3. Impulse large tions()f D)intdeftvts t()thecrvstai structure thr()ugh the incorporatit)n of excess arsenic into the lattice. l FY92 ,:. f-i; _l_._,,_,_#f Hl,,-,(.<l_#_ [)(._t.l,,t_+_!l.t!t which to I() tin les mobilityis a factor fllr thisof 4material of larger than thai of otht, r materials used for picosect)l'ltTIphotocorlductivitv. 7 lilitial int'asurt'lnelltS (_f ()ur devices in a terahertz be<ma system have been c_)nducted bv researchers <ii Ci)lumbia LJili\'ersitv. iii Rc'suits from tilt,se t,xpt'limc,nts have demonstrated thai (itll" devices are capabh, (ff dell,cling trailsient electric fic,lds ha\'illg amplitudt's in t'×ct,ss of I kV/cm w;th tt,ml_tlral i't,s(llulitli-i cit 600 fs. Ihe measurc,d ,t!,,s Ii, _*I,<, <,t_l Optoelectronic TeraflertzBeamSystem:EnablingTechnologies+ Diagnosticsand Microelectronics response is illusa'ated in Fig. 4a, tile corresponding frequency domain response in Fig. 4b. From these results, it can be seen that these pulses laave useful frequency content beyond 1 THz. This renders terahertz beam systems useful for further applications such as far-infrared spectroscopy, iraaging, and ultra-wideband communications. Polytechnic lnstitute),J.T. Darrow (Raytheon), and DI'. D.H. Auston (Coltmlbia University) who provided terahertz beam system naeasurements. 2. Future 3. X.-C.Zhang, B.B.Hu, J.T.Darrow, and D.H. Auston, AppI. Phys. Left.56,1011 (1_)90). This research has demonstrated the suitability of our devices as high-performance, photoconducting antenna elements. "llae next step is to irap!ement photonically controlled phased arrays 4. EW. Smith, H.Q. Le, V.Diadiuk, M.A. Hollis, A.R. Calawa, S. Gupta, M. Frankel, D.R. Dykaar, G. Mourou, and T.Y.Hsiang, Appl. Phys. Left. 54, 890(1989). based on this technology. This will be done by implementing integrated optics technology as the active system component to embed the rf signal, 5. A.C. Warren, J.M. Woodall, J.L. Freeouf, D. Grischkowsky, D.T. Mclnturff, M.R. Melloch, and N. Otsuka, Appl. Phys. Left.57, 1331(1990). mad phase modulation on the optical carrier to achieve beam-steering functionality. The combination of these technologies will make this system extremely useful for airborne and space-based ap- 6. M.B. Ketchen, Appl. Phys.Left.48,75l (1986). 7. D.H. Auston, in PicosecondOl_toeh'clronic De_,ices, C.H. Lee(Ld.), Academic Press (London, England), 1984. plications. 8. J.A. Valdmanis, G. Mourou, and C.W.Gable, Appl. 9. Phtls.Lett.41,211 (1982). L. Min and R.J.D. Miller, AppI. Phys. Lett. 56, 524 1. Wol'k Acknowledgements This work would not have been possible without the contributions of Dr. Raymond Mariella (Lawrence Livermore National Laboratory) and Dr. Michael Spencer (Howard l.Jniversity) in naaterials growth, and Dr. X.-C. Zhang (Renselaer A.I: DeFonzo and C.R. Lutz, Appl. Phys. Left. 51, 212(1c)87). C.H. Fattinger and D. Grischkowsk); Appl. Phys. l.ett. 53,1480 (I t)88). (1990). 10. J.T. Darrow, X.-C. Zhang, D.H. Auston, and J.D. Morse, IEEE ]QE QR-28 (6), 1607 (1992). i En[J, lt, eerlng Reseatct7 Development i_:_d Tc, c/_t_ology .1. Thrust Area Report FY92 3-11 Fabrication of Microeiectrode Electrochemical o:oDiagnostics Sensors and Microelectronics Fabrication of Miccoelectrode Electrochemical Sensors Dino R. Ciarlo, JacksonC. Koo, and Conrad M. Yu EngineeringResearchDivision ElectronicsEngineering Robert S. Glass MaterialsDivision Chemistn!andMaterialsScienceDepartment We are using integrated circuit technology to fabricate microelectrode electrochemical sensors. These sensors have improved performance compared to those that use a single macmelectrode. The near-term application for these new sensors is for environmental monitoring, especially for heavy metal contamination. i IcCaodu,Yd_ An electrodlemice'd sensor consists of a p_r of dissimilar electrodes immersed in a solution containing urMlown ions, as shown in Fig. 1. The relationship between the current in the working electrode (lw)and applied potential (Vw) referenced to a reference electrode, depends on the ions in solution and on the composition of the electrodes. This sensor is particularly well suited for the measurement of heavy metal contamination and pH as needed in environ1,2 _ mental monitoring. The goal of this project was to use integrated circuit (lC) microfabrication technology to fabricate mulfielectrode electrodlemical senmrs) The advantages of ttsing micrcxelectrodes in electr¢x:hemicM sensors are: (1) immunity from un- This past year, we used the photolithography and vacuum evaporation capabilities available in the MicroTecl'mology Center of Lawarence Livermore National Laboratory to fabricate microelectrode electrochemical sensors. Figure 2 shows a computer drawing of the,sensor electrodes. In one design, silver was used for the reference electrode, platinum for the counter electrode, and the four working electrodes were platinum, platinum, iridium oxide, and silver. In one application, the iridium-oxide working electrode is ttsed as a pH sensor: one of the platinum workingelectrodesiscoatedwithamercurythinfilm m 0 : " m m k : ; 1 : ;:I/_4_ :2 m _ _'_m]_ _ _ _: _ ' _ :_ i!_!.:_:4;Gi')!._ Flgurel. Typical ;_;':i>_{_ sensor arrangement. _:<,<, _::,_::*!_: Therelationship higher sensitivity; (3)higher sib_lal-to-noise ratios; (4)the potential for extremely fast experiments; and (5) the extension ,_f nomlal electrochemical background limits. _ Englneortng Research _i{', betweenthecurrent Iwand the applied _I_' potentlalVwdepends _,:_ ontheelectrode _ Counter elect. Ref elect, Working AgCl lr, lrO 2 elect, Ionsinsolution. i!!iii materlalsandthe '_ii::i: Pr, Ag, ".... Pt i!ii_ :_ :i_ '7, io_ :_:: ' . ...................................................................................................... Q. . : compensat_i resistance effects because of low currents used; (2) high rates of rnass transfer and hence In addition, the ttse of a matrix of different electrode materials improves the ilffon_ation content of the measurement. Also, bc<ause of the mass-production capability of microfabfication, reproducible senSOrscan be produced inexpensively and used in a disp(_-lble fashion. _ lr : Solution Development containing and unknown Technology + Thrust Area Report FY92 3-13 Diagnosticsand Microelectronics+ FabricationofMicroelectrodeElectrochemical Sensors Sincethematerials u_.ifor this _n_r fabrication .... configuration of the ing, we had to deal with new problems of film adhecracking, and compatibility. Originally, we hic_i an etdl proc(_<tureto define tile _n_)r material, btit this was difficult becatLseof file incompatibility of the sion, micmelectrode electrochemical sensor, Reference electrode Platinum (silver) Iridium oxide Iridium to detcvt lead, cadmiunb zinc, arid copper ions; the other platinum working elcvtrc×te is coated with a polymer to detect heavy metals; and file sik,er working electr(x.ie Lsu_'d to detcvt chlorine, We devotL_i considerable effort to tile develoi> ment of a reliable hbrication process. Silicon wafers, l-toni-thick, were tk'-<'das subsh'atL_ _ that converttional IC processing equipment could be u_,d. Tile thickalcss was chomn _) that riley would be robust enough to allow handling without breakalge, and _) that comnlercial connecR)l,'s could L_ LL'-_cKt tointerface the ._n*)lS with the proc(:ssillg elLvtronics. A conlbination of _XX)A of thermal oxide plus 20(X)_ of silicon nitride was u_d to electrically i_late tile _n_r filmsfl'om thesiliconsubsh'ate.Two_nsorswere fabricated on each wafer, and we could process six wafels at a time in tile vacuum system. When con-ipleted, the mn_rs were cut with a dicing _lw to their final size of 0.5 in. x 1.5 in. Figure3. Photographoftwocom, pletedmicroelectrode electrochemical sensors.Thepadsat thetopinterfacetoa commercialconnec- rt:,'sistwith ,,_)me of the etclles. In addition, it was diffio.flt to completely etch away the fihl_, and this catL_'d _mle conductMty between the various electr{_es. We eventually _,ttle_i oil an all-lift-off procedure for the ,_l'k_r fabrication. With this approadl, openings are patterned in the photoresist layer, the senmr material is then evaporated onto the entire wafer, and the tlnwantc_cl material is lifts,vioff by dissolving the rL_ist in acetone. This eliminated the need for any chernical etdling. After tlle,_nsor materials were defin_i in this manner, a phot(woensitive layer of polyimide was appli_i to the wafer and pal*emcKi with the ol.mnillgs rc_.luired for the sensor elck-_Tc×iesand the connector pad area. The typical circular area of the exp( "_:eclworking electr(x.ie had a diameter of 50 pm. Figure 3 is a photograph of two completc_i sensors. Following fabrication, the ._rtsorswere interfaco.i to a data collection system, and experinlents were wrformed. In l_ny cases, a 'textbcx_k' rc_pon_ was obtain¢Kifrom the sensors for the iolzs of interest. FIItUl'Q Wolrk Future workwill involve experimentswithelectrodes ilaving different sizes and shapes, to try to optimize the performance of tile sensor. We will also work with other sensor materials that are more specific to the ions of interest. The fabrication process will be refined to improve tile overall yield of useful sensors. We will also modify the vacuum evaporator so that we can simultaneously fabricate 24 instead of 12 sensors. Finally, we will start working with an industrial parhler, since some early versions of this sensor appear ready for commercialization. I. R.S.Glass, S.P.l-'erone,and I).R.Ciarlo, Anal. Chem. 62,1914(1oX)()). 2. R.S.Glass,K.C.Hong, W.M.Thompson, R.A.Reibold, J.C.Estill,D.W.O'Bfien,D.I,',.Ciarlo,and V.E.Granstaff, Eh,ch'odmmical Array Sensorsft," Plati#4_Wash'Sh'cant Monitoring,I_awmnce IJvermom National laborat(;ry,IJvermore, California, UCRI,-JC-10881q(lC_-)2). 3. R.S.(_;lass,S.P.i'erone, D,R.Ciarlo,and J.EKimmons, "Electrochemical Sensor/Detector System and Method," U.S,l'atent #5,120,421,June9,1992. tor. 3-14 Thrust Area Report FY92 .:. Englnc, r_l_/._ t?_'s('a:ch Li_'v(:/(*l}m('n_ and Tecllnotogv DiamondHeatsinkso:oDiagnosticsand Microelectronics DiamondHeatsinks Dino R.Ciado, JickH. Yee,and GizzingH. Khanaka Edk Randich M_tcri_lsDivision Chemistny and Materials Science Department Engineering ResearchDivision Electronics Engineering We are studying patterned diamond films for use as heatsinks to coolsolid-state laser diodes. We have etched coupled plasma diamond slabs using our chemically assisted ion beam etcher. An inductively torch has been set up for the high rate deposition (> 50 p/h) of diamond films onto patterned silicon wafers. Our modeling sions for both types of heatsinks. effort was used to design the optimum dimen- InlmmJlucf_on P_s For some time, Lawrence Livermore National Laboratory has been using silicon microchannel heatsinks to cool solid-state laser diodes. Very intricate microchmlnels have been etched into the surface of silicon wafers to provide paths for cooling water. The packaging has been designed so that diode bars can be stacked together to maximize the radiated flux.l In some designs, aheatdissipationapproaching3000 W/ cm2 has beenachieved, During FY-92, we worked on three aspects of the diamond heatsinks problem: modeling, etching, and film deposition. The modeling effort consisted of refining a code, originally developed by Landram,2 to make it more user friendly and more efficient for analyzing silicon and diamond. Figure I shows the heatsink configuration used ill the modeling work. In tl'fis Figure, a heat generating device is shown bonded to a microchal_lel heat- To expand our heatsink options, we have been studying the use of patterned diamond as a heatsink material. Diamond makes an excellent heatsink because it has the highest thermal conductivity of any lqlown material at room temperature, i.e., 20 W/cm°C vs 1.5 W/cm°C for silicon, lt is also an excellent electrical insulator (1 x 1016 f2-cm ) and will not corrode. Until recently, diamond had not been used extensively for heatsinks because of its high cost. However, recent advances in the deposition of diamond films using chemical vapor deposition (CVD) techniques haslowered its cost.These CVD films are now commercially available from several vendors and are being used as heatsinks, The thermal conductivity of CVD diamond is somewhat lower than that of natural diamond, i.e., sink. There are five thermal impedances in this structure that limit heat flow: (1) _[spread (_[sp), the spread of heat from a point source generator; (2) PbuJk(Pbu),the flow of heat through the bulk of the heat generating device; (3) Pinterface(Pin), the flow of heat across the eutectic bonding material; (4) _tconvectio n (_tconv), the flow of heat from the eutectic bonding material to the cooling fluid; and Figure1. Cross soc- tion of a solid-state a microchannel heat. device bonded to sink. 14 W/cm°C vs 20 W/cm°C, but it is still high enough to make the material very attractive. All of the commercially available diamond is in the form of flat slabs. Our emphasis is on patterned diamond slabs. The patterning can be used for water flow channels or for slots into which laser diode bars are inserted. = = Engtnee,-,ng Research Development and Technology .'.. Thrust Area Report FY92 3-16 Diagnosticsand Microelectronics.:. DiamondHeatsinks " Rgure2. Crosssectionofa microchan- W,v of 20 H, It is - 700 IU.If these values could be achieved, the diamond heatsink would out-per- Cover parameters, nelheatsinkillustrat- Fin-base _ _W height, however, is rather impractical frorrl a fabrication point of view, but otlr nlodelir_g has shown fOr thatlllifthe diamond silicon heatsinks hea tsin ks were b y a fabricated fa cto r of fowith klr .Ththe is _ W_ ing the design I_I --_I_Hw_ -[dB I Base _ _ _ same wall height as silicon, the therm,ll impedance would be lowered by a factor of two. _ T°createfl°wchannelsindiam°nd'we'l:_erformed a number of etching experiments using q = W/eta= our chemically assisted ion beam etcher (CA IBE). The diamond was purchased ft'ore two different (5) blc,m,,.ic (IUs.,,0, the removal of heat by tile cooling vendors. One vendor supplied free-standing slabs fluid. Our modeling effort concentrated on I.tc,,n,., that were 5 x 5 mm and 0.3-mm thick. The diawhich concerns the optimunl design for the micromond was deposited by CVD. The other vendor channels. We were able to compare microchannels supplied diamond bonded to a 1.5-mm-thick tungfabricated ft'ore silicon and diamond, sten carbide substrate. This film was 600-bi thick, Figure 2 is a cross section of a microchannel and the diameter of the part was 26 mm. lt was heatsink illustrating the parameters used in the deposited by a hot pressed technique and then modeling. The model calculates the thermal lm- polished smooth. We deposited a 1000/k-thick pedance for the microchannel heatsink, Iu_-,m.. chmmitml film on both types of parts, patterned Knowing Iut,,n,, we can immediately determine the chromium using photolithograpily and a wet the difference between the average temperature of chemical etch, and then etched the diamond in our the cooling fluid and the temperature of the fin- CAIBE. The etching experiments followed work base, as identified in Fig. 2. This temperature dif- by Geiss. 3 In this experiment, the diamond is bomference is given by AT = (iu_,,m)*(q),where q is the barded with xenon ions that Ilave been accelerated heatfluxappliedtothelleatsinkinW/cme.Thus, a to an energy of 700eV. At the same time, the low value for IUs:,,,,is desired, and the optimum sample is flooded with a source of oxygen, such as \,aluesfl_rthedimensionsofthemicrochannelsare N20 or NO2 gas. The bombarding xenon ions determined by those that give the lowest IU_,,,_,. promote chemical etching and, since they are coiliFigures 3a and 3b are three-dimensional plots mated and directional, the etching proceeds in a of the thermal impedance h_rsilicon and diamc)nd directional nlanner. Under these conditions, an microchannel heatsinks. Both are for a channel etch rateofapproximately200 _/min is achieved. width (W_.)of 20 IU.For silicon heatsinks with a When the xenon ion energy was increased to wall thickness (W,,,) of 20 IU,the optimum channel 1800 eV, the etch rate doubled to 400 _/min. Unheight (H) is -180IU. Beyond this, not much is fortunately, thechronliummaskalsoerodesawaj, gained. For diamond, also with a W_ ot 20 Iuand a limiting how deep one can etch. With a 1000 A(a) (b) 0.016 0.016 0.014 0.014 0.008 0.012 _ 0.008 0.010 0.006 0.006 _0.012 0.010 0.008 0.006 0.008 0.006 0.010 _ 0.004 0.004 0.004 160 120 H(p) 200 240 0.010 0.004 0.002 0.002 0 400 H(I.t) 600 Ww(p) 80_ 40 50 Ww(p) Figures3a and3b. Three-dimensional plotsof thethermalimpedanceof(a) siliconand(b) diamondmicrochannel heatsinks.Thechannelwidthis 20 _lin bothcases. . 3-16 Thrust Area Report FY92 4, I]r_gtn_,t, rll_t: R¢,,_¢,,tt¢ l_ D_,_t'tol) m_'nl ,111_1 /f,_llr_/_t',_ Diamond Hea_tsinl,s + Diagnostics and Microelectronics thick chronliunl mask, we could only etch to a depth of 0.5 pm. We are looking at other mask materials such as oxides that may be more durable to tile ion beam. We also studied tile deposition of diamond films onto patterned silicon substrates. The plan was to deposit thick diamond onto a silicon substrate that already had deep flow channels etched into its surface. Tile silicon could then be etched away, leaving a patterned diamond film. Figure 4 shows cross sections of the silicon wafers prepared for the deD_sifion. The etcll_i gr_×wes are ali 204.t wide, on 404.tcentels. The depth-to-widfll ratios u_.i were 20/20, 40/20, 100/20, and 200/20. In May of 1992, we gained access to an inductively couphM plasma (ICP) torch to t._ u_.i for the diamond film depcrsition. This _xluipment has bc_enus_.i by others to deposit diamond films at rates as high as R) p/hA The high-vekx:ity directional flow of the ga_ should make this technique ideal for the deposition of diamond into preformc_d grc×wes. Figure 5 silows a diagram of this madline, lt uses argon, hydrogen, and methane as _mrce ga_ and is power_t by a _)-kW, 4-MEtz generator. From May to Octo[_r of FY-92, we work_:l on tile gas control system, and built crx_ling chambers and wafer hoidels. A number of calibration mns were made to adjust the plasma operating conditions. Actual film depositions are plann_.t forearlv FY--93. Groove depth/width:20_J20_ Groove deptldwidth:40_/20_ Groove depthlwidth:lO0_120_l Groove deptldwidth:2O0_/20_ Figure 4. Scanning electron microscope cross sections of silicon wafers to be coat. edwith thickdlamondfllms. Future Work Our modeling effort needs to be extended to include the other four themlal impedances discussed above. This will help designers optimize the complete diode package instead of only tile i the ICP torch used Figure 5. Diagram of for high-rate diamond film deposition. Cooling water in Hydrogen/methane Water cooled substrate holder Argon _ 4 MHz 50 kW Cooling E/lt_,lltrz¢.'tl/ll_ f?eseiirch D(,t_,tl:li) ui(,rlt ilrJ,l water out ll, llllol(lt!_ .:* Thrust Area Report FY92 3-17 Diagnosticsand Microelectronicso:oDiamondHeatsinks heatsink itself. Experiments need to be conducted with other mask materials ill our CAIBE to find thorn with low etdl rates _ that we can etch deel_r stnlctures. Finally, and most importmlt, we need to use the ICP torch to deposit thick diamond films into silicon grooves and then etch away the silicon. If successful, 2. C.S. Landram, An ExactSolution.ti,rConjugateLon_,,iludinalFin-Fluht Heat Tran.sft'rin Internal Fh_w Including Optimization, Lawrence Livermore National Laboratory, Livermore, California, UCRLJC-103249(1990). 3. N.N. Efremow, Geiss, ].D.C. Flanders, G.A. Lincoln,and N.EM.W. Economou, Vac.Sci.andTectmol. B3 (1),(1985). 4. M.A. Capelli, T.G. Owano, and C.H. Kruger, ]. Matel: Res.5 (11),2326 (1990). LI this will be the first report of a diamond slab with deepverticalchmmels. 1. G. Albrecht, R.J. Beach, and B.Comaske); Enel_,Cy and Tedmology Review, Lawrence Livermore National Laboratory, Livermore, California, UCRL52000-92-6,7 (1992). = 3-18 Thrust Area Report FY92 .:o Engineering Research Devel(,pmc, nt _Jnd lechnol(_g}, mE Advanced Micromachining Technologies o:oDiagnostics and Microelectronics Advanced Micromachining Technologies Wing C. Hui Clwmical Sciences Division Chemical and Materials Science Departlnent and Engineering Research Division Electronics Engineering We have developed several ilmovative micromadlinhag tedaniques that will hcilitate the future development ofhigh-tech microtechnologies, sud! _ microelectrorti_, micrtrstructur_,'s,microactuators, microsensors, and microinstruments. The Comer-Protection Technique will p_xxtuce sharp convex comers and dear scribe lines in any aJKsotmpic etching process. The Ci_tular Etching Pmce_ alone, or combined with Selective Wet Chemical Etdling for Boron Nitride Film, can be u_d to fabricate numerous forms of new, round features that were previotusly unatt._nable. i i i i ..... li (a-l) (a-II) (b-I) (b-II) __ Over the last two decades, single-crystal silicon has been increasingly used in a variety of new applications besides microelectronics. Single-crystal silicon is not just a good semiconductor material; it is also an excellent mechanical material for rnicroscale devices, such as microstructures, microactuators, microsensors, and microir_;truments. To facilitate the development of these new hightech devices, newer and better micromachinhlg technologies have to be created for the fundamental fabrication processes. R(_emtly, we have develot._ several new micromachining processes. Tlaese new processes will allow LLSto make microscale feattm._ that were previously unattainable. The Comer-Protection Technique will allow us to make preci_ shmT>corner features, without rounding the comer by undercutting. The Circu- ; lar Etching Prtx:c--ss,which uses isoh'opic etching with boron nitride as the masking film, is well engineered to fabricate circular thin film mernbrane windows or circular microstructurcs. Combined with ,_lecfive Wet Chemical Etdaing for Boron Nitride Film, this Circular Etdaing Princes can build clear circular microstructures with or without additional films. Pro_, Figure1. Comparisonof the LawrenceLivermoreNational Laboratory(LLNL)Corner-ProtectionTechniqueandthe reg. Comer-Protection Technique uiaretching technique on the anisotropic etching of a (110) silicon wafer: (a-I) the clear 109.4 corner etched by the Microscale features on silicon wafers are very often achieved by means of anisotr()pic wet chemical etching. However, most of these etching pro- Et_[.Jtt]eering Rcrseatch LLNLtechnique; (bq) (a-li)the theundercut sharp 70.6 corner etched bythe LLNLtechnique; 109.4' corneretched by the regular technique; and(b-lOthe undercut 70.6 comer etched by the regular technique. Dev_,lol,,ment ;ttt¢l [_echnolo,ql ._. Thrust Area Report FY92 3-19 Diagnosticsand Microelectronics.:. AdvancedMicromachining Technologies Figure2. An exampleoftheroundfeaturesetchedbythe CircularEtchingProcess. cesses have a severe undercutting problem at any convex or outer comer of a chip or device feature. This undercutting problem will limit the compactness and effectiveness in the overall design. We have successfully developed a novel method for protecting these convex comers with very, little space. This technique can produce shm'p convex corners and clear scribe lines at may desirable etchirlg depth, lt can make many previously impo_ible geometries possible, diskafterSelectiveWetChemical Etching;and(b) thefoggy, small,roundsilicondisk afterdryplasmaetching. This year, we extended the technique to (110) silicon wafers. Figure I compares results with and without the Comer-Protection Technique. This successful demonstration has provided a possible licensirig opportllnity with Endevco, a designer and manufacturer of instrumentation for vibration, shock, and pressure measurement, thin film windows arid other rotu-id microstructures were hbricated in this way (Fig. 2). For this drcular etchirlg techniqLle to be more useful as a tool when making round features for general applications, it is son-letimes desirable to remove the masking boron nitride thin film. Conventionally, the boron nitride film can L_ remcvo.t only by dry plasma etching. However, plasma etching is not very selectivc_---itals() etcht._ silicon rlitride film, si licon-baso:l substrate or film,and even gold tihn. Our contribution to the solutiorl of fllis problem is the development of the fii_twet chemical pr(x:ess that will .,_qectivelyetch only boron nitride, but not coatings or substrate-s"of silicon, silicon nitride, and silicorl dioxide. The etcharlt is a very strorlg oxidizing reagent of sulfuric acid and hydrogen peroxide, lt can remove the boron nitride film rely _lc'ctively and smc×_thly, without leaving any over-etched su rfact.'s,as the plasma etching procc.>ssdc_.'s(Fig.3). Thisrn(x.tifiedround-etchingpr_:t.,sswasal_demonstratc_.i to be very u._ful il'lthe development of the microcapillaries for the Miniaturized (;as Chromatography Project ofConrad M. Ytiand the auth(ir. LI Most micromc-v.hanical devices rely on traditional anisotropic KOH etching for fabricating the microfeatures. This etching technique will produce only features with straight boundaries. Since it is desirable to have round features ha many applications, we have put a great deal of effort into the development of spedal circular etdaing technique_ to create new and unique microstrtictures, First, we carefully engineered an isotropic etching process with HF/HNO3./CH3COOH to produce even etching in all directions. _)ron nitride thin film was used as the etching mask becau._ of its chemical compatibility with theetdaant.Circular boron-rlih-ide 3"20 Thrust Area Figure3. Comparison of the boron nitride-coated, round sil. icondisksetchedbyLLNL Selective WetChemicalEtching andDryPlasmaEtching:(a) theshiny,small,round silicon Last year,we demonstrated the tedmique on (100) siliconwafers to make narrow-flame thin film merebrane windows, also h'town as 'thin-wall windows.' Circtdar Etching Process : i Report FY92 o:, Engineering R(.'s(:i_rch Dvvelopnlont and lecht_olog_ L Eleclrophoresis UsingSiliconMicroct_anne.ls .:, Diagnosticsand Microelectronics Electrophoresis Using Silicon Microchannels Jackson C. Koo, J. Courtney Davidson, and JosephW. Balch EJzgiJweril_y, ResearchDivisMt ElectroJlicsEjz_iJleeri_Ig We are developing elechophoresis techniques in microchannels that can be micromachined in substrates. We have developed a model of electro-osmotic flow in fl'ee-solution capillary electrophoresis when an external electric field is applied to the walls of the capillm T. Also, we have begun development ot gel-filled microchannels to be used for electrophoresis of biological materials. |l i • iu Introduction Progress Electroplloresis is the separation of charged ions or molecules in a solution based on their differential migration in an applied electric field, lt is widely used in modem analytical cllemistrv to separate charged particles in ionic solutions, and in biochemistrytoseparatebiomolecules.Theemergence of the biotechnoiogy industry hasgreatlyincreased the interest in various electrophoresis methods, Our objective is to develop methods for novel electrophoresis of liquid ionic solutions and charged biological material, in microchannels in silicon and other substrate materials. Silicon microchannels for electrophore.-,_s have potential advantages over conventional quartz capillaries due to (1) enhanced thermal dissipation of heat generated during electrophoresis, because the thermal conductivity of silicon is nearly 1()()times that of quartz; and (2) the construction of a higl>clensity array of microchannels on a single substrate in silicon and other materials, tlsillg modem microfabricati(_n technology. Silicon-based microfabrication technology also provides a promising way to incorporate field plates around an electrophoresis microchannel tocontrol theelectr(_-osmotic flow of solution in fl'ee-soluti_n ek'ctrc_phc_resis. Control of dectro-osmotic flm.v in free solution electrophtu'esis is a promising means to inlpr(we separation resolution and to allmv separatit_n of solutes in relativelv shortcapillaries(i.e., 1to I(1cm). (-)ttr previous efforts ] demonstrated control of electro-osmotic solutkm flow in round quartz capillaries and rectangular silicon microchanneis, by applying an external electric field perpendicular to the inner walls of the electrophoresis capillary or rectangular channel. The electro-osmotic flow of the solution is caused by the force of an axial electric field upon a diffuse, dipole charge sheath in the solution adjacent to the capillary wail. This sheath is created by the electrostatic attraction of charge surface states of the capillary wall on solrated ions in the electrolyte. As the mobile part of the sheath is mo\'ed along the capillary wall by the applied electric field, the soh'ated ions of the dig fuse layer transfer momentum to the remainder of the electrolyte solution. Therefore, the whole solution moves with the diffuse layer, and plug-like flow is created in the capillary. We can control the mobility of the electro-osmotic flow by applying an external electrostatic field perpendicular to the capillary wail, s(_ the diffuse dip(_le layer in the electrolyte is modulated orelim:nated. Figure 1 shows a typical experimental result we obtained previously for the electro-osmotic mobility in a quartz capillary as a function of the external voltage applied perpendicular to tile capillary walls. Our experimental setup was quite similartothatoftheUniversitvofMarvland, where two concelltric quartz tubes each filled with dec- { nt:,n¢'elJn,,* /?_,s_',_r, IJ l){,_eli_l_mt'nt ,,n,I l_,_hnol_:_ *',* Thrust Area i Report FY92 3-21 Diagnostics and Microelectronics .:. Electrophoresis Using Silicon Microcl)annels ............... 1.8 1,6 ' I Figure1. Measured electro-osmotic mo- ... bilityofan electrolyresolution (2 mM ,V, 1.4 -- I -- - 1 concentration) ina 1 '= 1._5-0.24821X I_ 1.2 _ 1.0 -- r- = 0._m2 0.76816-0.10834X -- the thickness and dielectric constant of tile quartz wall, the surface state density of the quartz wall, and the applied voltage that controls the electroosmotic flow. From these equations, we are able to relate the change h'l electro-osmotic mobility as a ftlnctioll of applied voltage (i.e., the slope of the curves in Fig. 1) to the density of stirface states on 0.2 __ the quartz wall for a given eh_'ctrolvte concentra_ 0N _ -tion. For experimental results such as shown in -0.2 -I-" _"-_ Fig. 1, our analysis shows that when the anion -0.4 I l 1 0 2 4 6 8 10 traps are replaced by cation traps, there is a si_fifiVoltage (kV) applied tocontrol Electroosmotic Solution Velo¢lly cant change in the density of the surface state pet" volt, while the total surface state densities per trolytes were used.Z:_ The inner tube was for the square centimeter (Ns) under the two different electro-osmotic flow; the outer tube was used to conditions are nearly the same. This indicates that provide the external bins electric field. In our exthe total number of active surface states, Ns, on the perirnent, we continuously increased the bias voltsilicon dioxide are determined by the initial chemage up to 10 kV. At about7 kV, the electro-osmotic ical conditions, and the active sites are bipolar in flow changed its direction. Here, we noticed that nature.Thecalculated value(2.4x lO'2crn-2)ofthe the rate of change of the mobility was not exactly a _ ,....... _ linear function of the externally applied voltage. However, we could fit the curve with two linear lines: one when the mobility is positive and anoth- 50Tlminternaldlam- etercapillary asa function of voltage applled across the 167.5_tm-thlck .... cap- illary wall. _ 0.8 ._ 0.6 0.4 R2 = 0.988 -- - er when the mobility is negative. This is expected because, as the direction of electro-osmotic flow changes, the moving anions. cations are replaced R,,o with '-- C Model for External Electric Field Control of Electro-osmosis __ ._+ This ),ear, we developed a theoretical model of external electric field control of electro-osmotic flow to gain additional ir_sight into the physical - - the quartz wall and the ionic concentration of the electrolvte. Our model of the capacitive and interface-charging phenomena in a conductor-insulator-electrolyte capillary structLu'e is adapted from a model widely used for similar pl_enornena in Metal-lnsulator-Senficonductor capacitors used in microelectronics. 4This type of model can easily be 3-22 Thrust Area in terms of an electrical equivalent ---'_+ V ,,di,, CT " "c -% mechanisms of electro-osmosis. This model allows us to relate the functional dependence of measured electro-osmotic mobility \'s the applied external voltage, to the density of surface states on interpreted C_o Rsl - - c_ _L T C.i _ --'---T ---'T_+ Figure 2. The electrical equivalent circuit model of two an- nularcapillaries, eachfilledwithelectrolytes. Theoutercap illary is used to apply an external electric field to the walls circuit. Figure 2 shows this model's equivalent of the inner capillary to controlelectro-osmosis in the inner capillary. Ceorepresents the capacitance of the electrostat- circuit for our experiment, where two concentric capillaries are each filled with electrolytes. In this eqtfi\'alerlt circuit, the externally applied voltage is shared among a series of capacitors, An extensive set of equations was deri\'ed that relates the various elements in the equivalent circuit to hnportant phv_;icalquantities such as cleotroh'te concentration, viscosity of the electn_lyte, ic diffuselayerbetweenthe capillarywalland theouter aqueousinterface.Cc represents thecapacitanceofthein- Report FY92 .:. Lrlg_lP('etlrlg Rebl',JIcit L) t'_l'lIIl_ftlt'tJ_ ner capillary tube. Cel represents the capacitance electrostatic of the diffuse layer between the inner capillary wall and the inneraqueous interface. Rsi and Rsoare surface re_ sistances for the inner and outer surfaces, respectively. The surface capacitances Csoand Csl represent the surface state densities per volt on outer and inner surfaces of the capillary. _tlll lt'ctll_lJtll/:_ Electrophoresis UsingSiltconM/crochannetso_o DiagnosticsandMicroelectronics surface state densities is, however, mucla smaller _- - ..... .... than that normally ,accepted (5 x 1014cre-2). This is SObecause the \'alues measured are the nunaber of 2,t active sites, which tare shown to be dependent upon not only the surface condition but also the 20 16 - From experimental 12 - experimental data, I we calculated the values conditions l I } I 4 i_' sO J l _1[, j I_ '_ l0 60 llO_ 160 Electrophoresis '_ 12 10 This year, we also began an investigation of electrophoresis of biological materials in gel-filled silicon microchannels. Gel electrophoresis is wideIv used for separath-lg biological materials such as DNA fragments. Almost ali clinical, molecular, or forensic projects that involve the characterization 8 of DNA are dependent upon the separation and/ or purification of DNA fragnaents by one or more methods. By far, the most common method is based upon electrophoresis. Since the DNA double-helix backbone is negatively charged, fi'agments 0 of DNA migrate toward the anode when placed in an electric fieM. If the DNA is caused to migrate through a sieving matrix such as agarose or polyacrylamide, fragment mobili b, is a function of fragment size, i.e., the smaller fragments migrate faster than larger fragments. In our experiments, we filled microchannels that had been etched in silicon substrates, with agarose gel. Figure 3 shows the results obtained using a standard 4-mm-thick agarose gel compared to those for a thinner gel supported in a 1-nam-tlaick etched silicon channel. These results indicate that not only is it possible to separate the fragments in a structure of these dimensions, but more important, both the resolution and speed of the separation are enhanced. We expect that the significantly higher thermal conductivity of silicon, compared to that of standard glass materials used in conventional gel electrophoresis, will enable electric field separations to be done at much higher electric fields to achieve faster separation. More experimentation is required to verify the I I l I / I I ...... 51 lOl 210 260 I I - I 310 36t1 410 I I I 460 I _t _ Sl0 '" I _ _ J_ 6 4 2 1 151 _ q_.., _ d _ 201 2s! 301 351 401 Ttme (arbltraryuntts) 1_ _ t_._:_' 451 501 Figure 3. A comparison ofDNAfragment separationresultsobtained for(a)mmthick a Mandardagarose slabgel,4 mmthickand4 mmwideand(b) anagarosegelI and4 mmwideas formedbyanetchedsiliconchannel.Notetheincreaseinboth peakresolutionandspeedofseparationin thethinnergel supportedbythesilicon substrate. trend in improved resolution and speed in even narrower gels, down to 0.25 mm. However, difficultT arises in proper and repeatable sample injeclion in these narr-weer gels. This warrants further research and development in novel, F_"teclse,"" highdensiO,,small-sanaple-volumeinjection. 1. .l.W. Belch, J.C. Davidstm, and J.C. Koo, "Capillary Zone Eiectrol.,horesis Using Silicon Microchannels," l.aborato(llDirech'd Researchand DevelopnwntFY9I, Lawrence IAvermore National Laboratory, I_ix'ermore,California, UCRl,-5368991,4(.1(1091). 2. C.S. Lee,W.C. 131arlcliard, and C.T. Wu, Anal.Chcnt. 62, 1550(1990). 3. C.S. Lee, D. McManigill, C.T. Wu, and B.Patel, Anal. Chem.63,1519 (It)t)I). 4. S.M.Szc,"Metal-hasulator-%'miconductorl)iodes," Physicsi!fSclllit'ollductorDevices,Wilev-lnterscience (New York),Chapter 9, 196q. " [._ expected improvement in separations by going to smaller (i.e., thinner and narrower) gels. We have perfomled experiments that indicate the definite Enfllne_,tltlg I II .......... ... I the same order of magnitude, but increased close f°rNsand that theasvalues °f Ns under to one order f°und of magnitude the electrolyte concentration increased from 1.5 naM to 50 naM. Materials I - _! similar to ours were of of Biological ..... Re_,_,,Itch I) evulol3merlt acid l_'th¢lolog_ .I. Thrust Area Report FY92 3-23 Emerging Technologies Ihe mL,<sionof the Emerging Technologi_ thrust area at 12ro,rance Livermore National 1211xmltoryis to help individuaL_ es'tablish technolog 3, are, ts that have national and commercial impact, and are outside the _ope of the existing thrust areas. Wecontinuetoencoumge innovative ideas that bring qualit), l't_ults to existing progmnts. We aL_}lalke as our mission the encouragemeat of hwestment in new tedmolog)' areas that are im_x_rtant to the tvonomic competitivent_s of this nation. . ;_.: In fiscal year 1992, we have focttsed on nine projcvts, summariz_xt in thLsrel.x_rt: (1) Tire, Acddent, Handling, and Rc_ldway Safet3,; (2) EXTRANSYT: An Exwrt System for Advancl_i Traffic Management; (3) (Xiin: A FlighPower, Undem'ater, Acoustic Transmitter for Surveillance Applicatiolz_;; (4)I'assive _ksmic P,t_,rvoir Monitoring: Signal l'r_x:t_,;ing hmovatiorLs; (5) Paste Exh'udable Explosive Aft Charge for Multi-Stage Munifiolzs; (6) A Continuum M_x.ielfor Reinforo.__t Concrete at High Prc,_stu'esand Strain l_lt_,'s:Interim Rel_x_rt;(7) Bendmlarking of the Criticality Evaluafian CcKie COG; (8) Fast Algorithm for hlrge-_ale ComenstLs DNA _luence Assembly; and (9) Using Electrical Heating To Enharlce the Extraction of Volatile Orgm_icComl.x_unds ffomSoil. Shin-yee Lu Thrust Area Leader Section 4 4. Emerging Technologies Overview Sltin-yeeLu, Thrust Area Leader Tire, Accident, Handling, and Roadway Safety Roger W. Logan.......................................................................................................................... 4.1 EXTRANSYT: An Expert System for Advanced Traffic Management RowlandR. Johnson ................................................................................................................... 4.9 Odin: A High Power, Underwater, Acoustic Transmitter for Surveillance Applications Ternj R. Donich,Scott W. McAllister, and CharlesS. Landram................................................ 4._.3 Passive Seismic Reservoir Monitoring: Signal Processing Innovations David B. Harris,RobertJ. Sherwood,Stephen P. Jarpe,and David C. DeMartini ................................................................................................................. 4.17 Paste Extrudable Explosive Aft Charge for Multi-stage Munitions DouglasR. Faux and Russell W. Rosinshy.............................................:..................................4.21 A Continuum Model for Reinforced Strain Rates Kurt H. Sinz ......... :: Concrete at High Pressures *and Benchmarking of the Criticality EvaluationCode William R. Lloyd,JohnS. Pearson,and H. PeterAlesso ....4.23 COG 4.27 Fast Algorithm for Large-Scale Consensus DNA Sequence Assembly Shin-yee Lu, Elbert W. Branscomb,MichaelE. Colvin, and RichardS. ]udson ..................................................................................................................... 4-29 Using Electrical Heating To Enhance the Extraction of Volatile Organic Compounds from Soil H. MichaelBuettner and William D. Daily ............................................................................... 4.31 Tire, Accident, Handling, and Roadway Safety o:oEmerging Technologies Tire, Accident, Handling, and Roadway Safety Roger W. Logan NuclearExplosivesEngineering MechanicalEngineering We are developh_g technology for an integrated package for the analysis of vehicle handling and of vehicle impact into roadside features and other vehicles. The program involves the development and use of rigid-body algorithms and the finite-element codes, DYNA and NIKE. Our goal is a tool for use by highway engineers at the Federal Highway Administration and state Departments of Transportation that allows good quantitative results at the workstation level. Our work has involved integration of handling and deformation codes, development of material and tire models, and comparisons of our results to test data. I_d_Oll Our Tire, Accident, Handling, and Roadway Safety (TAHRS) project at Lawrence Livermore National Laboratory (LLNL) provides technic_ advances to be used in an externally funded program for VehidelmpactSimulationTechnologyAdvancement (VISTA), to begin on a small sc_e hl FY-93. The goal of the TAHRS initiative is to develop the technical capability to accurately model vehicle/bander crash and post-crash behavior (Fig. 1). An improved analysis capabil'ity will improve highway barrier (and possibly vehicle) designs to minimize risk to occupants, and the hazards due to post-crash vehicle motion. These technical developments will become an integral part of the VISTA program. The goal of VISTA is to integrate the entire state of technology, including DYNA3D, Z NIKE3D, 2TAHRS, and other worldwide developments, into a user-friendly highway design ttx_l useful at various levels of expertise. The current state of the art in barrier design and post-crash dynamics involves a mixture of actual testing using instrumented vehicles, and empirical/numerical modeling using small, personal computer-based codes. These codes have been developed over many years; their empirical aspects have been tuned against crash test data. They are u_ful tools, but their relative lack of physics leaves them open to technical or legal doubt when extrapolation is involved. As an alternative, LLNL's three-dimensional (3-D) NIKE and Engtneerlng DYNA codes could be used separately or coupled to analyze the vehicle/barrier crash interaction. Recently, a Federal Highway Administration (FHWA) contract on this topic concluded that DYNA3D is the code of choice on which to form a VISTA program. The incentive for VISTA is quite strong, shlce about 40,000 traffic deaths occur each year in this country. As a direct consequence, about 40 billion dollars worth of lawsuits are active at any given time. Often state Departments of Transportation (DOT's) are the targets of these lawsuits. More than half of the fatal accidents typically involve only one vehicle. Thus, the ability to model and analyze barrier crash and post-crash motion with physics-based tools like NIKE, DYNA, and an integrated real-time handling (RTH) capability, could provide a strong supplemental tool for sorting out areas of responsibility. The TAHRS technical efforts are organized into four overlapping areas: (1) vehicle handling and interfacing; (2) roadside features and component modeling; (3) vehicle models and integrated analysis; and (4) test data and validation. Highlights of progress in each area are summarized below. Vehicle Handling and Interfacing This technical area involves developments in the simulation of vehicle handling, linkage of RTH Research Development and Technology .:. Thrust Area Report FY92 4-1 EmergingTechnologies.:. hre, Accident.Handling,andRoadwaySatet_ iii i i i Figure1. Illustrationofthe total handling/impact scenariotobe addressed bythe TAHRS technology andVISTApackage. Pre-crash (undamaged vehicle) Crash-vehicle/barrier(damagedvehicle) Post-crash(damagedvehicle) and finite dement 4"2 Thrust Area mesh (FEM) codes, and devel- vehicle dynamics L_,fore and after the contact, and opment of an intk_rmati\,e tlser intert:ace, In preparation for the linkage of RTIt and F!!M codes, a steering Ik_rceboundary condition is being added to NIKE31). The lateral forces generated by each tirecan becomputed by the incltision of a tire model subroutine in N IKF.3D. l'he vector diagram in Fig. 2a illustrates how NIKE31) computes the lateral load on the tire. Simulating the road as a stone wall, NIKI'.'31) first determines the vertical load on the tire. Then, tising the user-input driver steering angle, 0, the vehick' orientation direction, A, and vek×:itv, V, NIKli31) determines the tire stlb_'qtlent deformations of the vehicle. Ui.x_ncontact deto,:tion, data ft'ore tile nx×DI is paK,._'dto the finite element o_.|e, which simulatc.'s the dvnamk.'s of the vehick, during fix,collision. If theaccideitt is such that the vehicle di,_,ngagt_ from contact with the barrier, tile new, defoi'med vehicle configuration and the dynamic conditions can tx, pas_.t back to the rigid-Lx_,tym(Ktel ft}i"continuoJ simulation. The ve hicle configuration is fully .%1),rigid-tx_:ly, with i() degwt.'s of freedom, l'here is one spruitg ma_,_and four indeD, ndently susD, nded unsprung mas_,s (wheels). 'l'ite wheels, which air connected to the slip angle, ox.NIKE31) then uses a complex tire model to determine the lateral load, L, as a function of these variables. Figure 2b slxwcs top views ()f a cal" model durillg twil sinltllatillilS. Identical dl'ivc,r inptll is tlst,d: the wheel is ttlrnt,d first to the left, tllen to the righi. l'he 2rq-mph simulation restilts iita circular path; in the 45-nrpb case,tilt, car skids into an ui_stable(wei'sh.,ercondition, Wt, ha\'t, als(_de\'t,lo[xtta rigid4x_lyvehkit'handling tilde calk_t AU'I'OSI.I!I) to dt,monstrate tilt, linkage lx_th to NIKli, I)YNA, and the tlst,r ink, rface, 'l'his c_.te and olht,i_ can Ix, used to simulate the sprung mass with a spring and daml:_,r, are constraint,d tomoveD, it_,ndiculartothevehich.,.Another ._'t of springs and daml,X,l_ are tl,_.| to rn_,x.|eltilt, deftwmatiollofthewhtvls, which are l:reeto leavethe grt_tllld stlrfact,.The grotlnd, htlwt,vt, l',is Iimitttt to a flat plane. The vehicle \,ell_:ity can Lk' coi_ti'ollt'd by sDtil_,ing driving foi'cts ora dt,,sir_.tvek_:iiy. Sltt,ring can Ix' accomplisht_Jeitht'r by stxvifying a table _f slt_.,ringangles or by dt.'signaling a path thai the stt_.,rhlgcontrol will atien_pl h_follow.'l'his rt.'sultsin a II)-dt,grt_._-olLlro.tti,n ml_,tt,I, willi each StlS|X'ltsionelenleill reprt_,nlttt by a springand dain|x,r, as Report FY92 o:. t n/t:nu+,/in/{ tPe,,,_,,_'h l)#,lt,l_)llml,_l! ,ind l,'</_n_f_,lJl Tire, Accident, Handling, and Roadway Safety is each unsprtmg mass. Tile tire forces ,_ modeled _ tLsing the Dugoff tire m_.tel and ,_ limited tLsingthe friction drde concept. Control of the vehicle during a rtul is currently accomplished by completing tables hl ......... ..-- .,'_ ,..-. :: adata file.Vehicle vel_ity can be controlled by specilying a desired sl.-_ or by inputting a table of driving forces vs time. Stee_lg, likewise, can be controlled hl two ways. One way is to st:_ffy a table of steering angles vs time, anti tile other is to specify a table ofx-y coordinate pairs representing the desired path of the vehicle. An imbedded steering controller will then attempt to follow the path _ closely as possible. To provide the interfaces among the user, AUTOSLED, NIKE, and DYNA, a simulation program has been developed to read an output file from AUTOSLED, and display pertinent information in an interactive graphics environment. A typical session using this simulation program is shown in Fig. 3. In the upper left comer of the window, an oval racetrack is shown with a rectangle representing the car. Tile user has the option of displaying or not displaying the racetrack. In addition, outlines of some of the car's previous positiol_s are shown. The frequency with which these outlines are shown is another option controlled by the user. This view displays both position and yaw of the vehicle. To the right of the track are four gauges. These display suspension forces on the tires as the car follows the path. Next to the gauges are friction circles, which convey information about the normal, longitudinal, and lateral forces experienced by tile tires. A constant diameter circle is based on initial forces on the tire when the car is angles are shown. At the lower left comer, a rear view of the car is shown, giving the user information about the roll angle. To the right of this, a stationary. Below this, vehicle steeringspeed angles and slip speedometer displays in miles per hour. The maximum speed on the speedometer is during the simulation. A pop-up shell next to the speedometer lets the user create strip charts using based on the maximum speed the vehicle reaches any of the 48 variables from the AUTOSLED output file. For example, one could plot lateral forces at tire Ivs pitch of the vehicle. In the figure shown, the y coordinate of the center of gravity is plotted against time. Roadside Features and Component Modeling Before embarking on a 'big picture' analysis of vehicle and roadside barrier under linked handling and impact conditions, it is necessary to consider the FEM deformation analysis of Engineering ::: .... o:o Emerging Technologies ::, ; :::>> _ra 2. Implementation ofsteering algorithm and lateral tire force In NIKE3D. 7:::,e_,_:i,: _7%1;:::>:_:::::5v>_:C::::,,_ : _:J:! :;_e_ :71 st_rl_lls_ deg_/eft at t = 0.2s, then20 _eos r/_t at t : 2.0 s. Vehicle respondsdifferently as a function of vel_. 7':_':¢'_ ! :" .'(. _! _:_:_¢_: v( 'i_i.i v,_,;_ ,;:,,;> _::_v i :, • _:, :;i_,: • • •. •i :_-i '_'i _ , k r " _ smaller components. This work was begun with an analysis of a rigid bogey developed through a collaboration between the California Department of Transportation (CalTrans) and the University of California Davis. The bogey has a crushable steel box-structure front end resembling a coarse honeycomb, as modeled with DYNA3D in Fig. 4. This analysis was run at slow velocities to approximate the static crush test conducted on the actual structure. The mesh was kept coarse in the spirit of workstation level Research Development and Technology .:, Thrust Area Report FY92 4._ Emerging Technologies o:. Tire. Accident, Handling, and Roadway Safety iiii ii ao, ii I I # #t S 20 -- 10 t 0 o /./ /i e I -- DYNA-EI-PI DYNA-FL' ..... Test data I . s Deflection I 1o 15 (in,) Figure 3. User interface for AUTOSLED handling program. Information includes position, speed, roll angle, original and current friction circles, normal and lateral tire Figure 5. Load deflection for bogey crush into pole. Static test data matches DYNA3D if FLD failure model is used. loads,andslipangles, but is still of value in learning the techniques and meshing needed to match real tests. Another matching exercise at the component level involved a small car hitting a modifled bullnose median barrier. Crash test data .... Figure4. WorkstatiorHevel DYNA3Dmesh of bogey front crush for a Honda Civic hitting a modified bullnose mediar, barrier head-on at 60 mph are documented by a report prepared by the Southwest Research Institute for the FHWA. 4 This test was chosen for simulation both because of the areaon impacting rigldpole, availability of test data and because damage to the car was relatively small, allowing a simple car model and a focus on barrier deformation. Since modal size and run time were limited, models, and load deflection was compared against the test data, as shown in Fig. 5. Timefirst runs with DYNA3D used an elastic perfect-plastic material model. This type of material behavior givesa numerically well-posed problem that is not too dependent on the mesh size. However, the calculated load-deflection (DYNA-EI-PI line) is too stiff during early stages of time crushing process. Use of the augmerlted Forming Limit Diagram concept3 with rate-dependent flow and failure allows a match to be achieved (DYNAFLD) with the test data. The effectiveness of advanced material models under de\,elopment at LLNL is demonstrated here for isotropic flow and failure. Related studies invoh, e timeintegration of anisotropic flow and failure theories for analysis of metallic and non-metallic materials, such as deep drawing steels or chopped fiber composites. The type of simt|lation in Figs. 4 and 5 is neither predictive nor post-predictive, 4-4 Thrust Area Report FY92 "P Engln(_er_ng R(:sealc:h Developm(.,nt and since many model parameters (especially material properties) had to be estimated, the model is simplified and contains many estimates of relevant parameters. Figure 6 shows time DYNA model and a sequence of plots as the car plows into the barrier. The car was modeled as rigid. The barrier nose slit was not modeled; r,_ther, the car was 'caught' by constraining the vertical displacements of the front bumper a_d the bottom edge of the bullnose. The zigzag cross section of the thrie-beam rail was appr(,ximated by a rectangular strip with the same m ,ment of inertia and weight-perunit length as time thrie-beam. Since time deforming rail kinks at time posts where it is fastened, sl,:.rt lengths of thin, 12-gage strip were used near the posts to capture this kinking. The posts were modeled with tie-breaking slidelines, so that they broke off at ground level (as they did in the test), with a region of elastic-plastic material just above ground level and Technology Tire, Accident, Handling, and Roadway Safety o:0 Emerging Technologies i to allow some energy breakage. dissipation during post . (a) t=0,, Seconds With the additi°n °f self'c°ntact and an aP" proximation of the plastic hinge development at the posts, it is possible to match the vehicle trajectory to the test data, as shown in Fig. 7. However, predictive or even post-predictive analysis will / ..... ' (/';z ._ _: ' _ - - _ t _ require further study of the thrie-beam and post (b),t:=O.2secOnds approximate, coarse-mesh models shown here provide behavior consistent with more detailed mod- components We to ehow arn to make els, without having computational requirements. Vehicle Models to deal with and Integrated increased • Analysis • ._ formed A forertmner this year in of aanalyses joint effort to involving follow wasLLNL, per- .ii:!i. i i,ii ii. i.i.i i .i/ . !: _: _ developed a working model of a 1991 domestic the FHWA, and University of Alaska faculty._ We sedan. ::,,,: .i!i. li:.:i'!;r. :_i:i!!!iiiii_ii:!_i iii:ii_"'i"'i.i:il " !, "i' "!,;i I: 'i ' i.aili: ii!_ : :y:,,:., Our goal was to define the car in sufficient detail to capture its pre-crash, impact, and post- :_:_:! ._-: crash behaviors, and yet keep the model simple enough for analyses to be run overnight on a workstation. .:.. In the light pole impact example i",.:: ,.,:,z...;:v:._.,_._,r,, .,., ,: i:":i_ii::_. I_ firewall. (Fig. 8), the Underhood car model features is rigid material are modeled aft of the as simple rigid bodies. The vehicle model consists ,( of 20 parts, 2406 nodes with six degrees of freedom at each node, 10 beam elements, 1575 plate elements, and 224 solid elements. This is one :_-.,_.!:i.. (::.i_::_i" :ii:i ;_ i (ej"|._iiOiss_i)nds..:._.., __ ....... ":. -. '. " " .... , .... • .. . i _ and roadside features, with possible coupling to vehicle handling, in a workstation environment. The model above was then used in post-predic- a]]i Engineering -_ i _ , . : ;. :,i.i_ _ example of problems we hope to eventually run routinely: large deformations of both vehicle tive mode to demo]xstrate DYNA3D's crash roodeling capabilities. These analytical predictions are compared with crash test results obtained from the National Highway Transportation Safety Administration, where this 1991 domestic sedan was impacted against a rigid wall at a velocity of 57.5 km/h. Although all major structural components of the car were accounted for, the soft crush characteristics of the bumper area were not accounted for in the vehicle model used here and in Fig. 8. To compensate for that, a clear distance of 0.5 m between the structural bumper and the rigid wall was allowed. Figure 9 compares DYNA3D prediction and crash test results of the time/acceleration history of the engine block (upper plot) and rear seat area (lower plot). Given the coarse FEM of the model, the agreement is remarkably good. ::r"i' Rgure6. Time sequence of Impact of simplified vehicle into modified bullnose barrier. Meshing is again at the workstation level. Test DataandValidation A vehicle model of a Ford Fairmont is being constructed. An instrumented test of this vehicle is planned to demonstrate the potential for and effectiveness ofanintegratedprogramofanalysis, measurements, and vehicle testing. This may lead to further tests or parts of tests at LLNL. I_tllll_ Work This year, we have demonstrated the effectiveness of integrated vehicle/barrier impact analysis at the workstation/FHWA/DOT level, and have identified the needs for additions and refinements Research Development and Technology ,;. Thrust Area Report FY92 4.5 .:. Tire, Accident, Handling, and Roadwa) Safety Emerging Technologies i _ __ 12.s I '" I 1 m i ii I 101(a) i i '(' i illl ,. /_'1 ' 1 " I .._" 10.0 Figure 7. Vehicle temporal position for Impact into bullnose _ of Fig. 6. Although _ not a predictive mode, DYNA3D is I i | li -40 I'-- '..0 _ very coarse simple model. _ 2.5 II--/ ------- Simul_ion DYNA3D [ rediction -- '- 50 I --! -lo o 0 0.25 0.50 0.7S 1.00 1.25 1.50 Time (s) -20 -2S ._ "35 F .*40 _ -0.05 Figure S. Time sequence of YNA3D prediction , [ , 0 0,0,_ iCrashte:tdata -- 0,1 0.15 0.2 • 0.2.q Time (s) domestic sedan impacting luminaim support. Pole failure is modeled with LLNL 's SAND technology, :. ii' : " Figure 9. Acceleration history of vehicle model of Rg. 8 for a 3Graph rigi_wall impact. Comparison to NHTSA supplied data is done in post.predictive mode. Agreement is good for only a 2000.node vehicle. leading to a complete package. Our goals for the future focus on the four technok_gy areas established. We will work toward full linkage of the AUTOSLED RTH code to N|KE and DYNA, and development of compatible tire models for ali the codes. Continued study of both roadside and vehicle structural sections will continue at the component level to ensure that model simplification is efficient yet accurate compared to more refined meshes. A more complete suite of vehicle models and roadside hardware will be developed, making u_, of material model improvements for flow and crush of aluminum and fiber composite materials, including features such as anisotropy, forming limit, and composite damage. These will be used in future lightweight designs such as Calstart's Neighborhood Electric Vehicle. We will continue the • close integration of our analysis package with test data obtained at LLNL and elsewhere. Acknowledgements The author wishes to acknowledge the many contributors to the TAHILS/VISTA program this year. Of special note are the contributions of B.N. Maker (Fig. 2), D.D. Dirks and M.C. _,ibel (Fig. 3), and S.J. Wineman (Figs. 4 and 5). The author appreciates the close c(}operation of Prof. A. Frank 4-6 Thrust Area Report FY92 o:o EtlEtn_,'crtnt_ R_'sc,_lrch Dc, vc'lOl),)_,nt ,:_nd lochnology Tire,Accident, Handling, and RoadwaySafety o_oEmerging Technologies at tile University of California Davis o11 tile bogey analysis (Figs. 6 mid 7), and of Prof. J. Wekezer of the University of Alaska on the domestic sedan model 1. 2. 3. R.W. la_gan, Imt_lemcntation ¢!ta I'rvssure aM Rate Dependent tOrmiuy,-IJntit Diagnlnl Model inh_NIKE and DYNA, Lawrence Livermore National Laborator_; IJvermom, California, UCI_,lMD-I[)576[) (1992). 4. L. Meczkowski, A Thrie-13eanlBullnose Median "7)'ealmerit, U.S. Department of Transportation, Federal Highway Administration l'ublication Nos. FHWARD-88-004 and FHWA-RD-88-005 (1987). J.W. Wekezer, M.5. Oskard, R.W. Logan, and (Figs. 8 and 9). R.G. Whirler, D YNA3D: A Nonlinear, Explicit, Thn'eDinlensiona[ Finite Eh'nlent Code tbr Solid and Struttural Medlanics--Llser Manual, Li'lwmnce IJvermore National Laboratory, Livennol_,, Calikwnia, UCRLMA-107254(1991). 5. B.N. Makeb R.M. Ferencz, and J.O. Hallquist, NIKE3D: A Nonlinnu; hnplMt, Three-Dinlensional Finite Eh'nlent Code.for Solid and Structunli Mechanics_l_lser Manual, Lawrence Livermore National Laboratory, Livermore, California, UCRL-MA105268 (1991). Englnee¢lng E. Zywicz, "Vehicle Impact ]. 7i'ansportation En% (in press). R(;seatcll Develol)¢t1(3nt and 1(:,ch¢1o1_)_ Simulation," [l .:, Thrust Area Report FY92 4-7 EXTRANSYT." An Expert System for Adv_nced Trathc Man_?gem_nl ¢, Emerging Technologies EXTRANSYT: An Expert System for Advanced Traffic Management Rowland R. Johnson EngineeringResearchDivision ElectronicsEn#na'ring Coordination of traffic signal systems is carried out at present by a signal timing plan that uses a relatively primitive computer program, TRANSYT. To deal with the difficulties in using TRANSYT, our project is developing ali expert system called EXTRANSYT that encodes the kalowledge of an expert TRANSYT use1: The project is a collaborative effort among (l) Lawrence Livermore National Laboratory, in the lead emd providing the computers and computer science expertise; (2) fl-_eUniversity of California Berkeley, Institute of Transportation Studies, providing the TRANSYT/traffic engineering Department of Streets and Traffic, providing i expertise; and (3) the City of San Jose, Ca li fornia, the testbed for the system. ul i|1 |ntroductJoll (although the drivers perceive no apparent reason) until a platoon arrives that they can merge Coordination of traffic signal svstems is the pfimao, means by which congestion, pollution, and fflel consumption caused by city traffic is reduced. A coordinated system can be either a single arte_ or a grid mid O'pically consists of between 10 and 50 intersections. An interaction phase is the time duration for which the traffic lights at the intersection remain fixed. Each intersection has a controller that causes the intersection with. Usually travel time is the same, and a reduction in pollution and fuel consumptk_n is realized because of the reduction in acceleration/de-acceleration cycles. Signal timing plan design is usually done by using a computer program called TRANSYT that can (1)simulate the operation of a coordinated system, and (2) find the optimal signal timing plan based on some combination of congestion, poilu- to cycle through its set of phases, C(x:_rdination is achieved by the use of a signal timing plan wherein the controller at each inter- tion, and fuel consumption. en a green light as it arrives and passes through the intersection. Platoon progression also has the psychological benefit of drivers perceMng that thev faster through the strategy for efficient preventing multiple svstem. Another • coordination is achieved by acceleration/de-acceleration cvcles. For example, vehicles should be delaved Enf_lnoer_t_g a traffic Incident: planned _ction in the system has the same cycle length. That is, there is a background cycle during which each intersection cycles through each of its phases, The signal timhlg plan also specifies the offset for the beginning of each phase at each intersection. One strategy for efficient coordination is . achieved b', gcx)d platoon progression. Platoon progression is the situation whereby a set of closely spaced vehicles (i.e., a platoon) progresses from intersection to intersection, and the platoon is giv- are moving Typically, Traffic or _ .._ unplanned operations center / ceP_l:lliaeetr_eP;_e, 1_ unizsity 1_ / _ planned construction,etc. 1_ ( ._]___) New link capacities, vehicle counts, etc. New signal _ [ EXTRANSYF Figure 1. ] timing plan . Real-time incident response. A traffic incident has occurred on a city street and has been reported to a central traffic operations facility. Operations personnel determine the impact on vehicular flow capacities and vehicular flow demands. This information is then routed to EXTRANSYT, which quickly determines an appropriate signal timing plan and downloads it to the traffic light controllers. Re;se_,rch De_(_lopnlent _Jnd [_,t t_t_ol(p,,_ o:. Thrust Area Report FY92 4-9 EmerginlTechnologies..'. EXTRANSYT: An ExpertSystemfor AdvancedTrafficManagement engineer will provide a description of a set of intersections and streets as well as traffic flow capacities and traffic flow requirements. The TRANSYT model is then calibrated against actual traffic flow conditions, followed by file search for the optimal signal tinGng plm_. TRANSYT has several limitations that are described below. However, the reality is that it is the only analysis tool of its kind and is likely to remain so for at least five years, TRANSYT was originally developed in the 1960's when input to computer programs consisted of a punched card deck, and the output device was a lineprinter, hl response to the primitive nature of TRANSYT, several peripheral programs have been developed that make it easier to use TRANSYT. However, these efforts do not appear to be adequate shlce we have formal that 30 to 50% of the 'fielded' signal timing plans have errors, Since the original development of TRANSYT, there have been several advances in intersection control- specification of the grid is reduced to an undirected graph. A particular undirected graph will have an infinite set of realizations in Euclidean 2-space. Therefore, it is impossible to present the traffic engineer with the two-dimensional (2-D) layout of the intersection_ and streets that yielded the TRANSYT input. This fact results in many input errors that are never discovered. hl practice, TRANSYT users usually use one of several intersection/street numbering schemes. EXTRANSYT uses heuristics to determine if such a scheme is being used and the Euclidean hfformation derivable from it. Other heuristics about likely intersection/street configurations (e.g.,a city street is tu'flikely to pass over another city street) are also used. As a result, EXTRANSYT is able to determine a likely 2-D layout. In practice, this layout is almost always close enough to the actual intersection/street configuration that the traffic engir_eer can easily discover input errors. EXTRANSYT also uses another set of heuristics ler hardware that are not directly modeled by TRANSYT. However, it is possible for an expert user to derive useful results from TRANSYT about coordinated systen_s that u_ the newer controllers, The difficulties in using TRANSYT results in an error-prone, lengthy process to develop a signal timing plan for a coordinated system. A traffic engineer not accustomed to using TRANSYT can require up to four months to develop a signal timing plan for a moderately complicated grid. Furthermore, the resulting signal timing plan will often have errors that need to be 'tuned out' in the field, resulting in more time required and a sub-optimal signal timing plan. to discover probable errors not related to the geometry of the grid. For example, the situation where the speed limit in one direction on a street is not the same as the speed limit h-_the other direction on the same street is flagged as a probable error. As another example, many existfllg TRANSYT input sets have errors pertaining to the existence, non-existence, and direction of one-way streets. EXTRANSYT has proven to be very effective in finding these types of errors. Future developments in EXTRANSYT will include heuristics to determine phase sequenchlg for each intersection. For example, should a particular approach be given the left tuna before or after through traffic is allowed to move. Also included will be heuristics to determine which intersections should be in a coordinated system. Closely related to this will be heuristics to determhle if an intersection should be fully actuated, semi-actuated, or non-artuated. As _escribed above, TRANSYT is used to design signal tirning plans. Potentially, TRANSYT could also be used to respond to an incident occurring on a city street. As an example, consider an accident that causes the capacity of a street to be reduced and, further, that reduced capacity will exist for one hour. A modified signal timing plan based on the reduced capacity due to the accident would (1) take advantage of reduced demand downstream of the accident, and (2)accommodate extra demand on the alternate routes chosen by drivers upstream of the accident. The problem with this approach is that the modified signal timing plan must be derived quickly. Typically, 15 To deal with the difficulties in using TRANSYT, our project is developing an expert system called EXTRANSYT that encodes the knowledge of an expert TRANSYT user. The project is a collaborative effort among (1) Lawrence Livermore National LaboL,_ory (LLNL), in the lead and providing the computers and computer science expertise; (2) the University of California Berkeley, Institute of TraJlsportation Studies, providing the TRANSYT/traffic engineering expertise; and (3) the City of San Jose, California, Department of Streets and Traffic, providing the testbed for the system, The input to TRANSYT specifies a set of intersections, streets connecting them, and the length of each street. It does not specify _he location of each intersection. That is, the original Euclidean 2-space 4-:LO Thrust Area Report FY92 .:, Engineering Research Development and Technology EXTRANSY T: An ExpertSystemfor AdvancedTrafficManagemento:oEmergingTechnologies minutes are required to first download a signal timing plan and then switch to the new plan. Ill this example, to obtain 30 minutes of improved traffic flow, the modified si_3al timing plan must be derived in 35 minutes, F_l_r6 Work The current version of EXTRANSYT has been installed at Deparhnent of Streets and Traffic in Engineering the Ci_ of San Jose, California for the purpose of developing a real-time incident response system. The deployed system in San Jose is linked to the development system at LLNL via high-speed modem lines. EXTRANSYT is being used to help analyze existing traffic si_lations in San Jose. This in rum is used to provide a better understanding of how to implement the heuristics d_cribed above. A real-time incident response version of EXTRANSYT will be operational in October 1993. I_ Research Development and Technology 4. Thrust Area Repurt FY92 4-11 Odin:A High-Power, Underwater,AcousticTransmitterfor Surveillance Apphcations.:. EmergingTechnologies Odin: A High-Power, Underwater, Acoustic Transmitter for Surveillance Aplications Ten3 R. Donich and Scott W. McAIlister Dt'f_'nseSciellct_EngineeringDivisioli Chades S. Landram NuclearTestEn%qneerillg MechanicalEngiJleering The Odin project staff has performed ma engineering assessment of an underwater acoustic projector using impulse-driven, split-ring-projector technolobD, in an ocean surveillance, antisubmachae-warfare application An Odin projector system could be engineered to meet the system requirements for output power and acoustic beam control; however, the final projector size raises serious issues about its compatibility with existing deployment platforms. _[his problem mad the fact that the submarine threat has changed have led the project team to defer further work on this application and to f(_us on the air-deployable, impulse-driven projector being funded by the Navy. |__1:[1_ Split ring projectors (SRP) are acoustic trm_smitters for underwater use in active sonar systems to detect submarines. In FY-90, Lawrence Livermore National Laborato D, (LLNL) developed the idea of ushlg the combustion of chemical fuels to drive a SRP element. When a chemical fuel combusts i1_ide the cylinder, the resulthag inward pressure pulse drives the shell outward, loading strain energy into the split rhlg shell. The split ring shell 'rings' down, converting the strain energy into acoustic enerb_,,, as illustrated in Fig. 1. 'Impulsedriven split ring projector' is the phrase used to describe this system. The chemical fuel-driven SRP overcomes the acoustic power limitation encountered when piezoelectric ceramics drive the split ring shell. At LLNL, our capabilities in numerical modeling of combustion anda detonation and in structu::a] eling give us unique capability to assessroodthe feasibi]itv of impulse-driven SRP's.| In FY-92, we were funded to assess the"feasibility of the impulse-driven SI_P concept, scaled to a ship-towed surveillance system, as illustrated in Fig. 2. The hypothesis put forth ill the reviews was that impulse-driven SRP technology could create the acoustic power required by the surveillance community in a reasonably sized, hydrodynamic Engineering package that could be towed with greater ease thm_ the existing projector arrays. The basis for the hypothesis was twofold: (1) package size would be reduced, since the direct conversion of chemical energy into strain energy was more efficient than converthlg the chemical energy into electricity, conditioning that electricity, and creating strain enerb_y with magnetostrictive or piezoelectric materials; (2) the SRP, being long and slender, provided a more hydrodynamic shape than other piezoelectric or magnetostrictive projectors. This project comprised four tasks: (1)the enhancement of our fluid-loaded SRP codes, SOFA 2 for the frequency domain and SOTA 3 for the time domahl;(2) a parameter study of surveillance-scale f _ _O__ ......... . ....... _ Rosearct_ :' 7"_ ..... •i:_.:_: ----!. ! ..., " fuel N ! .!:. - Figure1. Thecycle fora drivenchemicalfuelSRP element. , _ " ,__2_ "_l._-}_,. enersy'inLbsheil Shell rinss out convertinS strainenersy into acousticenersy Development and lechnolog_, o;, Thrust Area Report FY92 4-13 Emeqllng¥echnolol_es.:. Odin: A High-Power. Underwater. AcousticTransmitterfor Surveillance Applications SRP's; (3) an assessment of the feasibility of the projector parameters in an actual application; and (4) marketing actMties for this project and related " projects, Cbjr parameter results: J .| ¶ ,_I . • study yielded the following of the surveillance environment from deep water to shallow water; and the transition of surveillance platforms ft'ore vulnerable ships to air-deployable dispo_ble systems. The Navy is not able to fund this project irl FY-93. (1) The optimal radius at 20 l--lzis 1 m; the corresponding shell thickness for this frequency is 24.4 cre. The shell material is steel, (2) The chemical-to-acousticenergyconversion efficiency, is low (---1.5% for L = 20 m). (3) Acoustic powers of = _3 kW or 226.4 dB are attainable with an input of 310 MJ of chemical ener_,. The peak stress is within the elastic range for high quali_' steels, (4) The projector acoustic output has the temporal characteristic of P,,c_`t sino)t. Our experimentally validated analytical model predicts cs.= 0.095 s-1 for this shell radius and projector frequency, From our engineering assessment, 4 we determined that in an array of these large SRP's, the 2c_ indMdual projector timing specification must be 0.005 s. This specification is rea)izable from an engineering point of view. lt will take approximatelv 60 s to recycle a projector after it fires. This time includes the time to purge the exhaust and reload the fuel/oxidizer for the next shot. LLNL staff were asked to witness a Navy test series off San Clemente Island to assess the performance of the current generation of surveillance projector technology., t' This information has been used to submit additional white papers fl)r reimbursable work for the Navv. The Office of Naval Research (ONR) has expressed interest in the techniques used in SOFA and SOTA, our two fluid-coupled split-ring m(Kleling c_Kles. A white paper has been prepared, on the basis of the ONR interest, to assess some of the fundamental questions that ari.,¢, when modeling the acoustic radiation from a complex stiffened structure. 7 In summaD,, although the Odin projector concept is feasible from an engin___2ringpoint of view, a large funded project is precluded b_x:ause of the major redefinition of the missions of surveillance communities. However, our marketing has uncovered other potential funding _urct_ for related projects. '_ A five-element projector array with a per element power of 226.4 dB will enable detection rangL,s - _A-3 in excess of 144)nautical mlle.i. Five 2-mKtia-x-20-m-long projectors are massire enough t_ question the ability of existing platforms to recover such an an'a,,'. Our marketing activities are influenced by the status of the Navv surveillance community. Re,3efinitions of their mission include the transition AakllOWle__ We thank the staff of LLNI/s Military Applications and Advanced Conventional Weapon Svsterns for their support. Our thanks, also go to Tom Reitter for his numerical computations, using CA LE to determine the pressure time histories generated internal toan underwatercvlinderbv an explosive charge; to Ensign Hal Perdew for his work in the ¢. 4-14 Thrust Atel Repot', FY92 4. fr:g r_ee* '_ g Res¢.a,c_ D(-,_,' .':,;-*er" ,_,: ,' 7p..- ........ :'E. Odin: A High-Power,Underwater,Acoustic Transmitter for SurveillanceApplications *:" Emerging Technologies systems studies of SRP arrays; to Barry Bowman for marketing assistance; to S. Christian Simon_m, Robert Tipton, and Rich Couch for computations; to Kent Lewis for mt_.ie conversion; and to Clark _me_ who formulated the equation for non-explosive energetic material. 4. 5. of state 1. C.S. Landram, 2. C.S. [xmdram, "_)TA," 3. T.A. Reitter, "CALE Calculations of Small-Charge Explosions in Underwater Pipes," TF92-M, April 2, 1092. 6. "SOFA," 1991-1992. 1991-1992. Englnet:rlng H.G. Perdew, "Timing Requirenlents on Split Ring Projector Arrays," August 1992 H.G. l'erdew, "Perfomlance Assessment of Split Ring Projector Arrays in Shallow Water," September I_)2. S.W. McAIlister,"Ix,'s_ns Ix,amed From NCCOSC, NRAD Tests ofg/i6/92 and 9/17/92," ,c_.,ptember 18, I_N2. 7. C.S. l_mdram, "ONR I'roposal on Mt×le Conversion," TF-92-76, .._'ptember 21, 1992. 8. S.W. McAllister, "Electrically Initiated - Frequency Dispersive Sources, A Requirements Dtx:ument," October 1,1992. k] Rese_ar(:h Development and Technology • Thrust Area Report FY92 4-15 Passive Seismic Reservoir Monitoring: Signal Processing Innovations 4. Emerging Technologies Passive Seismic Reservoir Monitoring: Signal Processing Innovations David B. Harris and Robert J. Sherwood EngineeringResearchDivision ElectronicsEngineering Stephen P. Jarpe EarthSciencesDepartment David C. DeMartini ShellDevelopmentCompany Houston,Texas We have extended our matched field processing capability in mapping acoustic emissions associated with hydraulic fracturing. In our new approach, we generate elastic matching fields for a range of source types, and match _ _ best linear combination of these fields, against the observed data. We have begun work with Shell Development Company, applying our methe_ts to data from their monitoring wells. I_ctioR Hydraulic fracturing is a widely used well completion technique for enhancing the recovery of gas and oil in low-permeability formations. Hydraulic fracturing consists of pumping fluids into a well under high pressure (1000 to 5000 psi) to wedge open and extend a fracture into the producing formation. The fracture acts as a conduit for gas and oil to flow back to the weil, significantly increasing communication with larger volumes of the producing formation. While typical treatment costs exceed $100,000 per well, hydraulic fracturing may double or triple production. Such returns justify extensive use of the technique. In the interval from 1949 to 1981, more than 800,000 treatments were completed. I In tight gas sands and diatomite oil reservoirs, 2 virtually all new wells are hydraulically fractured. Field engineers need diagnostics for the height, length, and orientation of fractures to design the proper spacing of wells in the field and to design indMdual fracture treatments. The diagnostics must be inexpensive (10% of treatment cost), fast, and reliable. Diagnostics that are available in a few hours can be used to plan successive stages of a Er.g;ncer_ng multistage fracturing operation in a single well; diagnostics that take minutes could be used in real-time controls of pumping rates and fluid composition. The best diagnostics that fully map a fracture use transient microseismic signals emitted from micro-fracture events along the fracture surface.3,4 These signals are detected by sensors placed in adjacent monitoring wells or in the treatment weil. The arrival times of the signals are measured (usually manually), then used to triangulate the sites of emission. The 'cloud' of locations for several hundred discrete emissions delineates the fracture. This method is slow due to the need for manual picking of arrival times, and has potentially limJted application when an insufficient number of high signal-to-noise ratio transient signals are detectable. We have adapted matched-field processing methods to the problem of imaging fractures, using continuous microseismic emissions. In FY-92, we extended our earlier results,5 which used an acoustic model for propagation, to the Research Dcvc;o_;n, cn: or d Tcc",no:oE, y ¢, Thru_-t Arc_, Report FY92 4"17 Emerging Technologies -:. Passive Seismic Resetvolr Monitoring: Signal Processu_gInnowittons I R_re I. Source andarrayconfigur_ tion formatched field processingtest. Theshear wave velocity as a function of depth is displayed on the left. Onthe right are two sources adjacent to a me_ surementarrayof vertical geophones. Thetop source is a horizontaldipole (intended to simulate a pulsating crack), and the bottom i i i i .......... Velocity (ft/s) 2200 2900 210 {t _ .- _ _ source is a double couple (intended to simulate a micr¢_ earthquake). -f 0 _j_ ltl 150ft @ @ ' Se,,h sio- @ case of full elastic propagation. We have developed two elastic field sinlulators; one to produce test data, and anothe|" that is a highly efficient narix)wband code to generate matching fields ft)r strategy for situations where the source type is unknown. Figure 2 shows the fields generated by the opening crack and the slip type sources. The two sources radiate energy away ft'ore the source the array of sensors. The latter code involves innorations in paraxial wave field extrapolation," that have potential application to oil prospecting and rx:can acoustic modeling. We have also developed a matched field ptx)cessor with the ability to match a wide range of source types, t-lydraulic ft'actui'e nlicroseismic sources may come in a variety of forms, such as an opening crack caused by pumping, or micrtwarthqtiakes caused by slip between It_:ation with very diffcrent patterns as a function of direction. The signals received by the array are correspondingly unique. This presents a problem if the matching field is not chosen appmpriatt, ly, as shown in Fig. 3. Tlae first two rcconstructioi'|s of the two-source test cast' arc reconstrttcted with theoretical fields corresponding to a single source type. In both cast, s, one of the sources is missing in the rccoilstrtiction. adjacent bitx:ks in the prc-stressed medium. Wesimulated these two types iffsourccs fi_r the source and sensor configuration, shown in Fig. 1, (.)ur tvsponse to this problem was to develop a modification of the matched field processing approach, which we call multiple-field matching for a mediuna intended to approximate the conditionsin th,,Shell Bch'idgeoil field. 7 Figure 1shows a vertical array of vertical-axis geophones in a morlitor weil, and two simulated Sotlrces 15() ftvt away. The array l-las 15 geiiphtil-lCS spaced at 3()-ft intervals, which is similar to the Shell Beh'idge (MMFI)). In this approach, we generate matching fields fi_r a range of possible sotn'cc types, and match the best liiwar combination of these fields point for point in the search regions, against the observed data. The rcsult of MMFI > for our tesi casc, shown in Fig. 3, is an image containhlg both sensor ctlnfigtiration. The vclocity strut'ttlrc is 11t111- st)l.ll'CCtypes. uriiform, consisting of a gradient with slwar wave speeds |'ai|ging from 2200 ft/s to 29()()ft/s cwer the aperture of the array. The fields radiated by the two source types are markedly different and require a new processing 4-18 Thrust Area Report FY92 '¢. # nl,'_l_,t,i_n/.' Hr,.,t.,it, h I)l. l r, li_pn,_,rlt Future W(14'A Wt' have entered inlo an agrcement with Shell l)c\'clopmel_t Ctlmpany to apply Inatt:hcd field ,llP,l l_'_ hrJ,,_Ol',t Passive Seismic Reservoir Monitoring: (a) Signal Processing Innovations .:. Emerging Technologies _!:: (c) (b) _ii! " ii lip d: Figure 3. Three reconstructions of the source distribution made from the sum of the two sources shown in Fig. 2. The reconstructions are for the search region outlined in Fig. 2. Reconstruction (b) uses a double couple field, and mi_es the horizontal dipole source. Reconstruction (c) is the MMFP reconstruction that uses a best linear combination of both fields point for point in the search region, and picks up both sources. processing methods to their Belridge hydraulic fracture data set.7 The Shell data set is the best available data for testing hydraulic fracture imaging diagnostics, lt includes two multi-stage ft'acture operations recorded by three monitor wells, The vertical geophone sensors were grouted into the wells, largely suppressing the tube waves that Engineering confound hydrophone recordings in fluid-filled monitor wells. Preliminary analysis of the data has shown us the necessity of using the multiple field extension of matched field processing with rea _ data. We anticipate that our analysis will provide a definitive test of the value of matched field processing in the coming year. Research Development and Technology ,'_ Thrust Area Report FY9_ 4-19 Emerglnl Technologies .:. Passive Seismic Reservoir MotTitoring:Signal Processing Innovations 1. B. Waters, l. l)et.'l_'t'h,1416 (August lt)81). 2. "Frac Attack," ChevrouWorht Spring/Summer, 24 (I_0_)I)' J.Fix. R. Adair, T. Fisher, K. Mahrt't, C. Mulcahy, 3. B. Myers, J.Swanson, and J.Woerpel, L)evelotmteut (?t'Mi_:tvseismicMethods To Lh'tetralin' Hydraulic Fraclure Dimcusious, Teledyne (;_x_tech,Garland, Texas, 'T'eclanicalReport No. 8t)-(.)116(1080). 4. 4-20 Thru|t Area 5. 19.ttarris, R. Sherwood, S. Jarpc, and I' I larben, Maplfitag Acoustic t'missious.t)vm l lydmulic Frm'tm'e 'lh'atmeuts tisin_ Cohereut Array I'mcessiuv,: Co,-. cet#,l,awvence I,ivermow National l,aboratory, ltirermore, California, UCI,',I,-II)-108262 (l_)t)l). 6 I).B. Harris, Wide-Auv,h' l.'om'ierWm,_fiehtl::xtmt_ohztots .for l_#eralh/ t h'h'rogem'ous Media, in prvparation. 7. H. Vinegar, l'. Wills, D. I)eMartini,.]. Shiyapot',.,rsky, W. l_,g, R. Adail, J. Wc,.wpel, J. Fix, and G. _wrels, ]. l_et. T_'ch.,44 (!) 28 (January ItN2). B. Tl'_orne and H. Morris, SPE l:'orm. Eval., 711 (l_,_'october 1988). Report FY92 ¢, Eng_t)e_tsng Roso,atch Devolol)mo_tt ,ll_(I lt,chtlolol4v PasteExtrudableExplosiveAft ChargeforMulti-StageMutations o:,EmergingTechnologies Paste Extrudable Explosive Aft Charge for Multi.Stage Munitions Douglas R. Faux and RussellW. Rosinsky NuclearExplosivesEllgineering MechanicalEngineering Our development project for a paste extrudable explosive (PEX) aft charge is a multi-year effort with the goal of demonstrating the tecl'ulology in a multi-stage mtulition. In FY-92, we studied PEX borehole fill characteristics mid PEX hlitiation schemes. i i |__111_ Multi-stageconventioz_tlmunitionstypic,'fllyt'ulve a two-stage warhead: a forward-shaped charge that pr(Ktuces a borehole in the target, and an ,fit charge that enters the borehole and then detonates, destroying the target. The aft charge is usually a steel-encased explosive that either enters the borehole by its own kinetic energy or is 'driven' into the borehole by a rocket or vekK_ityaugmenter. To hlcrease the ver_tility mad reduce the weight of a portable, multi-stage munition, a paste extrudable explosive (PEX) aft charge that injects PEX into the borehole formed by the forward charge replaces the steel-encased aft charge. The PEX aft charge can be used with a smaller borehole and provides greater coupling of the explosive with the target. modeling of the PEX extrusion through a nozzle and of the borehole fill process has been completed and will be validated by forthcoming tests. The two-dimensional hydrodynamic code CALE has been used to model the PEX borehole fill process (Fig. 2). The complete simulation required the coupling of a DYNA2D analysis of the PEX extrusion through a nozzle, to the CALE analysis of a borehole fill. Nozzle shield Aft charse The PEX Aft Charge project is a multi-year effortwiththegoalofdemonstratingthetechnology in a multi-stage munition. The PEX aft charge is a proposed, pre-planned product improvement for the penetration augmented munition (PAM) currently being developed for U.S. Special Operations Forces and future multi-stage munitions. Figure I illustrates a conceptual drawing of a standoff destruct munition (SODM, or 'flying PAM') using a PEX aft charge. Our FY-92 development work on the PEX aft charge involved two areas: PEX borehole fill characteristics and PEX initiation schemes. Computer EngJne_.'pJng Forwardcharse Flgurel. Conceptual sketchofa SODMwitha PEXaft charge. i Figure 2. Resear(;tl CALE l)evul()l)m(.nt Simulationofa PEXborehole fill. ,irJ_t Tu(:tlnolrJHy .:. Thrust Area Report FY92 4-21 Emorl_lng Technologies4* PasteExtrudableExplosive Aft Chargefor Multi.StageMunitions FUture Work Four tests are _heduled: two tests will evalu- ate PEX flow characteristics during borehole fill and potential sympathetic detonation of the I'EX; two tests will investigate PEX initiation schemes, 4-22 Thrust Area Report FY92 ,:, Er)glneertng Resoarch Dovolopmont Tile first initiation scheme involves tile use of a detonation chord and carrier vane to pull tile detonation chord into the borehole with the PEX; the _cond initiation schenae involves the use of three chemically delayed detonators that will flow with the PEX into the borel'lole. LI _n(I Tochnology A Continuum ModelforReinforcedConcreteat HighPressuresand StrainRates ,;o EmergingTechnologies A Continuum Model for Reinforced Concrete at High Pressures and Strain Rates Kurt H. Sinz EarthSciellcesDepartment We are studying tile behavior of concl_ate at high pressures (200 kb) and strain rates (104/s) and report on a computer model used for this purpo_. Applications include a predictive capability for the damage done to concrete when it is subjected to attack by demolition munitions or penetrators. .,_. INtroduction Concrete is one of the most common building materials in the world. In 1992, the U.S. alone used an es'timated 265 million cubic yards.I Con_quently, the need ari,_,s for occasional demolition or perhaps even destruction, such as i11the event of armed conflict. Recent advances in small-scale munitions make it possible to consider the effects of a .,:.uccessful point attack against concrete even when it contains heavy steel reinforcement ('rebar'), as in bridge piers or bunkers. The damage mechanism is very different from that in seismic events or in ground shocks induced by nuclear explosions where damage results from large-Kale flexure and h'acture or rebar pull-out, munition to be more effectively optimized, and the survivability of penetrators could be calculatcd. Development time of new munitions would be shortened and would require fewer experiments. The resulting cost savings and product improvements areobvious. Problem The problem we pose is to develop a continuum model for concrete that explains the results of experiments performed tk_rthe penetration augmerited munition (PAM) program. A rebar-cutting charge for the PAM has been designed to specifically attack concrete and to cut near-surface • ") rebar up to No. 11 in size.- The minimun_ diameter of this size rebar (when ignoring any ribbing) is Payoff of Predicting Concrete Damage between 3.3 and 3.4 cna. Data from rebar-cutter tests exist that do not seem to be obscured bv "lo date, no computer model exists that can predict the damage envelope in concrete resulting fnml an interaction with a demolition munition or a penetrat{m A calctflational model that predicts the damage done to concrete subjected to point attack is highly desirable for a number of reasons, With the help of such a model, experiments could be more effectively designed to yield specific information, thus increasing the'leverage' ofexperiments that are performed. Aspects of experiments and tolerances of design that are not 'laboratory perfect' could be evaluated by computer. This might include non-ideal standoffs, oblique angles of incidence, and structural peculiarities. This capability in turn would permit the design of a new complicated hydrodynamic motion, inhomogeneities are small compared to the effects of scale, and rebar spacing is of the order of the damage scale. The configuration is therefore amenable to analysis by a two-dimensional (2-D) l,agrangian continuum code such as DYNA, 3 and rebar-cutter experiments are especially pertinent to this effort from the standpoint of providing data as well as filling a need. fr,_,_r_ee,_r_l_ Concrete Properties To construct a continuum m_tel, we n__,_.tto know available prowrtits of concrete. A great deal of attention has tx___,n devoted to the tmdel,'standing of R(.s_.,Jtr h De_elolJm_'nt ,jt_! [_,_.hnol¢_l{_ + Thrust Area Report FY92 4-23 Emerging Technologies 0_o4 (?ontmuum AI(_t(,/l_, th,uH<_tc'_,(l(?_,_ct_,tl,,ii t-lq;h t_l_,._._m_,._ ,u_t ._;/t,,n f¢,tl_,.,; A Continuum Model for Reinforced Concrete at High Pressures and Strain Rates o:. Emerging Technologies from the crater bottom ,and travels along the crater wall. Furthermore, it appears this signal travels though material that is already dynamically failed and therefore is not reliably characterized. There is some indication that if the signal were well resolved by the zoning, that tensile hilure would matter somewhat in this region. We should note, however, that the calculated bore hole is large enough to admit foUow-through charges of current design so that the resolution of these questions, while highly desirable, may possibly not be central to our first objective, lt is most interesting that tensile stresses were not found to matter anywhere in the problem except possibly right on the crater wall and then parallel to it. Reflections from the experimental sample block's boundary did not contribute appreciable reflections m'_dtensile waves for two apparent reasons. The first reason is that the porosity in the concrete is a g(xx-!shock attenuator and only low-level signals reach the botmdary. The second reason is that a release from the target surface follows the main shock and contributes to its decay from behind, SincewearelimitedbytheconstraintthatDYNA is a 2-D code, two different attempts were made to estimate the importance of the rebar. In the first attempt, the rebar directly under the impact area was ignored, and the remaining rebars were represented as rings with radii of the rebar spacing (Fig. 1). The rebar was hardly displaced and had virtually no effect on the failure envelope. This result stems from the porosity-induced attenuation in the concrete and is consistent with experimental observations where the rebar is linear as blow or crack off when a PAM is tested against a sample block of reinforced concrete. Model We now give a brief review of the model we use. The m(_.iel combines the effects of pore crush, shear failure, and tensile failure. The aspect of pore crush is represented by a hysteresis model with a tensorial model for shear failure. This basic model has been used in TENSOR 4 for a number of years to calculate the behavior of earth materials when subjected to high shock pressures. The model, with some improvements, 13 has been carried forward to KDYNA. I° Numerical data for the model are obtained from Gregson's Hugoniot, which also accounts for the pore crush in loading. The pressure at which total crush of the porosity occurs is assumed to be 100 kb. There is a perhaps fortuitous match between Gregson's Hugoniot and the Hugoniot for fused silica (SiO 2 or Dynasil) at the high-pressure end. We follow this suggestion and assume the Hugoniot for fund quartz to be applicable to dynamically full), crushed (pulverized) concrete. This assumption seems reasonable, since concrete is mostly quartz. The pore crush model works by letting a piece of the material load along the Hugoniot. Upon release, the unloading does not simply reverse the loading path; instead, hysteresis is approximated by interpolating a release path from the Hugoniot between the elastic portion of the loading curve and the Hugoniot for fully crushed material. The opposed to circular. In the ,second estimate, the rebar was represented as a solid slab of steel, three centimeters thick, which was backed by concrete i !_ _ i and covered with 6 cm of concrete (Fig. 2). Plastic strains of lC% in the steel were observed to a i $;$ i T radius of about 3 cm. This result makes it plausible that a three-.dimensional calculation would give some amount of gap in the rebar using our current model and its parameters. This, of course, is the objective of the rebar cutter. Another interesting phenomenon was observed in this latter calculation. The concrete cover of the rebar absorbed sufficient momentum in the radial direction to continue to 'peel' off the rebar (the solid slab of steel). The occurrence of this phenomenon distinguished this calculation from those without any steel. We assumed zero bonding strength between the steeJ and the concrete, _., ,., lt seems p]a USl- Engineering ' I I. ........... [............ Overlay ofrel_r cut by the mlmr-ctrttor charge and a calculation. The scales are only approximately the same. In the calculation, the rebar is approximated as a sol. idslabofsteel. Tbe lines of lO% plastic straln in the steel R_'ure2. ble that this general phenomenology of the concrete cover peeling at a plane of weakened bonding I ! I, I are shownas a suggestion Research may explain why ali the concrete cover seems to Development wherethelimit ofcalculatedfail- and £_chnologk ureInthesteelmightbe. • Thrust Area Report FY92 4-25 Emeqlhll T_hnologleo _, A ContinuumModp.I for ReinforcedConcrp.t_; _t HighPressures_mdStrmnR_ttt;s hysteresis is of course ,! repre.,a.,ntation of the pore crush that is fully pre_,nt and accounted for in the Hugoniot. At any point in this space, the pertinent bulk mt_:lulus is inferred. The resulting bulk roodulus is thus a ftmction of pressure that is related to strain rates in shock regions. I'ois_m's ratio is obtainc_:i as an extrapolation of Tang's work s so that the shear rnoclulus is al_defined. To complete the mt_.tel, we mxxt values for the shear strength of concrete. "l'he most extensive ,_:t of clata at this time still api.wars to be that of Cl'|iru'| and Zirnmerman, who give values of shear strengths of cylindrical concrete _m_ples for mean nomml stres.,_,s up to 7.5 kb. 5 More recent data obtainecl by the Waterways Experiment Station (WES) validated the older data but ran_csonly • . up Acknowled_enlellts We thank Russell W. I,'osinskv for providing analvtic design data and Robert M. Kuklo for proriding experimental details on the rr,bar-cutting charge ftu"the I'AM. ...................................................................................... I. National (.,oncrete Ready-Mix Asstwiation, I'rix'ateCtmuutuficatitm,Sih'erSpring, Maryhuld ((_.'tobtu"lqq2). 2. R.W.Rosinskv,"An Anntflar I_t,bar('tdtingL'hargt, ftu"thf I'enetratiotl Augmentt,d Munition," A'hmilions+l;'chn<_l(Ny l)epelotuut'nt!990,F,andia National I.aboratt_rit, s, Albtlqtlurqut,, New Mexico, SANIY.10.11tH(I_.)I). 3. I.O. I iallquist, /./ser's Mmnml /i_rL)YNA21}....an Fxt_licit"l,+,o.-dimensional llydn)dynamics Code ,,ilh Inter+lctivt'Rezonin,,¢mid GralJIlicall)ist,lay, Lav,'n.,nce! ,ivt,rn',ort, Natitu'_ali.aboratory, l.ivt,muu't,, Califiu'nia, UCII)-1875b, I_t,x'.3 (1088). ing to WES, concrete "...is capable of a surprising amount of plastic defomaation .... "7 Con_'qt|ently, we cht_.}._ 10% plastic strain as the criterion for 4. V.(;.(;rt,gson, Jt:,A Shockl, Vm,eSh,h/_!/'l'omht-t't.tre WA-I mtd a Concrete,General Motors 'lbclanical Centel, DNA 27q7 F (February Iq72). maximum failure. This completes the rudimentary mc_.telwe u_,. More _)phisticatc_.t mt_telsexist, but the paucity of data dtws not warrant the intro-duction of any more 'adjustable' parameters. One such variable might be to intrtx:luce rate dependencies for yield strengths, 5. J. Chinn and R.M. Zimmerman, I_dtm,icu" q/Phmt C0,cn'te tinder Vm'h_ttsi/Nh "l)'htxhflComl,'t'ssion I.omtinN Couditi<ms, University of Ct}h_rado, WI. TR ¢_J,-11+3 (Augttst 1%5). N.C. l lolnlt,s, l'rivate conanaunicatitm, I.awrtulct, l.ivernlore National I,abt_ratory,I+ivt,rmort,, California ( It_-)2). PulurQ 7. to 3.5 kb.7To complete the tensorial mtMel, a guess is made for the yield strength of failed concrete of about a tenth of the virgin yield strength. Accord- WoIk Our near-tema plans are to insert the above concrete model into a ctwle with an Et|lerian capability such as CALE. This would perrnit us to calculate the effect of a munititm that penetrates the concrete more dt_eply and is probably n'_uch more complicated laydrodynamically than the rebar cutter. "The ea,_ of perfomaing calculations wc,uld be greatly improved, and parameter studiea such as a study of the possible importance of rate effects would be greatly facilitated. A rtvalculation of the rebar approximatitms should make it pt_sible to demonstrate major shear displacements at failure surfaces. Furtlaermore, the details of the surface crater formation and its resulting width could be reexamined, with the question of zoning definition of the crater wall removed from consideration. The result might provide additional insight into the spall of the fi'ont surface of the concrete in the vicinity of the bore hole. If our results continue to be encouraging, this will constitute a first version of a design tool that can calculate complete systems of mtmitions and targets _,lf-consistentlv. 4"_ Thrult Area Report FY92 • _. Lng_n+,t,_+ng Re_+,,l_ch I)+'_'_,_ " _,nt B.D. Nt't'le._5M.I. Hanlnlotls, and I).M. Smith, T/tc l_)evelot,nentand Cltar+tcterizatiott _!IConvenlh)nal5tre,:cth mn/ l t_k,h-.qh'+',,_ctlt /)+wilt,tdCe,r',l Concrete Mixtures .Ibr l'rojectih' I'enetration Studie:, Waterways l:.xperiment Station, Technical Report Si.ql_15(lt)ql). H. T.Tang, lh'lint,torolConcreh' tlt,h'r 1)!/,,mtic I.oadiny,I'h.D. l)is_,rtation, Universityof Florida ( It_'J()). t). Waterways t!xperiment Station, I'rivate comnutnication, _'icksburg, Mississippi (Marcia ltlq2). !0. !.1..I+evatin,A.V.Atria,and I.O. I lallquist, Kl)YNA User'sMmmal,I,_w_t,nct,l+ivermtu'eNatituml I.abt_ratorv, I,ivernatu'e,California, UL'I,U+-II)-Ii)bI()4 (lqq()'). II. I).F..Burttua,I..A.I.t,ttis,!r., I.ILl_lrvan,and N. Frary, l>hq.qic.,; amt Numeric.,;+!I "l'l?l_'S( )R Co, t+',I.,_wI't'l_lft ' i.ivermort, NationaltheI+,_btu'attwv, I.ivt,rnatu't,, California, UCII)-Iq428 (iq82). 12. R.I!.Tipton, CAI.E _L..;er's Mmn,tl, Vtu'si_u_ t)20721, I.awt't'FIce [.Jvul'lllOl't' Natitmal I.aboralt_rv, I .ivermtwt,,Califtu'ni,_(It)t)2). 13. K.II..";in:, "A Ctuasislt,nt li.,nsilu I:,filtm, 'li'eatmt'ht ttw I Ivdrtwodt,s", tnapublished (Iq87). ,_n,/ '+,, t_n<,l,_l, _ Bet_chmarking of the01tic_#it.V EvaluationCodeCOGo:oEmergingTechnologies BenchmmNng of the Criticality Evaluation Code COG John S. Pearson HealthaJutSatehDivisioJ_ Ha_u'dsCalm'oiDepartn.'llt William R. Uoydand H. Peter Alesso FissiollEllergyrout Sl/stemsSate'h,/Program The purpose of our technology transfer project is to benchmark the Lawrence Livermore National Laboratory computer code COG for nuclear criticality evaluations. COG is potentially the most accurate computational tool available for these evaluations. Introduction Assurance of subcriticality is the most important element in any nuclear facility operation involving special nuclear" materials. A good understanding, of the detailed nuclear fission process is the only way to assure subcriticality, Today, this assurance is provided bv using an analytical computational tool to evaluate and analyze ali possible scenarios and geometries, The reliability of the evaluation results depends upon the accuracy of the computational tool in representing the realistic condition of the operation in questiol_. Proof of the accuracy of the computational tool in turn depends upon the proper benchmarking of the code against actual nuclear fission process experiments I (criticality experiments) similar to the operation beingevaluated. The applicability of a code to a specific geometry and condition depends on whether a benchmark has been done for a similar type of experiment and how accurately the code predicts the result of the experiment, Thecriticalitv evaluation codeconmlonlv used in both government and industry today is the KENO-\'a code with the four cross-section sets available to it on the SCALE system,- ali develaped at Oak Ridge National l,aboratorv (C)RN 13. Development of KEN() began in the Mathematics Division of ORNI_ in IO58. In the 1970's and lOS()'s, the Nuclear Rey,ulatorv Commission funded the development of the _4CAI.F. system, a modular code system for performing standardized computer analyses for licensiny, evalu- Er_,_l_,_,tlrl_, ation. KENO, written more than 20 years ago, used methods as exact as was possible at that time. Today, much better physical data are available, but these data do not fit the forms used by KENO. Development of C(K; 3 began in 1983 at Lawrence Livermore National Laboratory (LLNL) as a shielding code. The principal consideration in developing the code was that the resulting calculation was to be as accurate as the input data provided to the code. Cross-section data were presented by evaluators in the 1980's as point-wise data; i.e.,as a series of cross-section points as a function of neutron energy, for example, with the understanding that interpolation between adjacent points produces results as good as the data. Cf_X; was written to use this form of the cross-section data directly. The angular scattering data are likewise presented and used as the evaluators present them. No approximation has been made that would compromise the accuracy of these data. The geometric description of a problem for input into a criticality code should be as exact as possible. COL-;permits specification of a surhce defined by input analytic equatit_ is containing terms up to the fourth degree. Objectives C(X, was developed on LI_NL Cray Computers using the New IJvermore Time Sharing Svstem. COG is being moved from Cravs to workstations that include the Hewlett i_ackard (!--II_) 9()00/73() and a SUN computer using the UNIX operating system for greater availability. t?¢,s_,,_r, h I)_,_,topmt,t_t ,1rill le,_'hr_l¢_£,_ o_, Thrust Area Report FY92 4-27 EmerltingTechnologies..'. Benchmarking of theCriticalityEvaluationCodeCOG COG and its cross-section set are being benchmarked against at least 250 criticality experiments to understand the bias of COG, in a range of criticality situations. The transfer of COG fi'om LLNL to universities, industry, and other Department of Energy laboratories will be accomplished by placing it in the Nuclear Systems S,'ffety Center (NSSC). Criticality and shielding services using COG can be offered from this system, COG geomeb'y input prep_ation can be tedious for complicated geometrical systems. The three-dimensional computer-aided-design (CAD) software Pro/ENGINEER and the LLNL code Pro/COG will be used to generate geometry input forCOG. COG has 160 subroutines that include 47 geometry subroutines and 86 cross-section subroutines. In May 1992, COG was compiled, assembled, and run on an HP 9000/730 computer. Further detailed checks of capabilities in COG, such as Russian roulette, path stretching, and importance weighting, were initiated on the HP 9000/730. Preparation of 100 critical experiment models as input to COG were completed and run on LLNL Cray computers using LLNL Evaluated Neutron Data Library (ENDL) cross sections. The Evaluated Nuclear Data File/B-V (ENDF/B-V) was converted from its parameterized format to a point-wise format suitable for use with COG. Techniques developed in this work will also permit conversion of other evaluated neutron libraries, including ENDF/B-VI, the Japanese Evaluated Neutron Data File-3 (JENDL-3), the Joint European Filed (JEF-1), and BROND-2 (a Russian file). Benchmarking activities will provide criteria for unifying these evaluations into a single nuclear data library. Output from the CAD software Pro/ENGINEER was combined with LLNL's Pro/COG to 4"_8 Thrust Area Report FY92 4, Engln_,_,rlng R(;searcl_ Development produce some C(_X3 geometry of nuclear fuel rods. Future input k)r arrays Work COG currently runs on an HP 9000/730 workstation with a UNIX operating system. Conversion of COG to run on a SUN Microsystems model S10MX is planned. Completed testing of the deep-penetration and code-optimization features is planned on both computers. The ruruling of models from at least 250 benchmark critical experiments is planned for the SUN and HP workstations. Continued use of Pro/ENGINEER and development of the LLNL code Pro/COG to produce COG geometry input for arrays of fuel rods, the torus, and the sphere are planned. Establishment of the NSSC is planned to provide a mechanism for exporting COG to other laboratories, universities, and industry. jli_lllOW__11111_lllt_ The authors wish to recognize the individual contributions of C. Annese, R. Buck, D. Cullen, P. Giles, S. Hadjimarkos, D. Heinrichs, R. Howerton, D. Lappa, E. Lent, D. Resler, T. Wilcox, and R. White. 1. B.L. Koponen, T.P. Wilcox, Jr., and V.E.Hampel, Nuch'arCriticality Experimentsfrom 1943to 1978,An Ammtated Bibliography,Vols.1-3, Lawrence Livermore National Laboratory,, Livermore, California, UCRL-52769(1979). 2. SCALE: A Modular Code SystemLicensingEvalufor Pe_Jrmin._ StandardizedComputer Analysesfor atio,, NUREG/CR-0200, Revision 4 (ORNL/ NUREG/CSD-2/R4), Vols.I,ll,,-md111(1991);available from Radiation Shielding Information Center asCCC-_5. T.I! Wilcox, Jr. and E.M. Lent, COG---A Partich' TransportCodeDesigJledToSolvethe Boltzmann Equati(m ti_r Deep-Penetration (Shieldi,,_) Pn_hh'ms, Vol. l-User manual, Lawrence Livermore National Laboratory, Livermore, California, M-221-1 (1989). L_ 3. an(I Technology FastAlgorithmfor Large.Scale ConsensusDNASequenceAssembly.'. EmergingTechnologies jodmmforLcde Ctomemus DNASequen=e l.u Ej_qna,'illgRtu'archDtvisiol_ Eh'ch'olfit_ E,,',nJ ,,_'illS Michael E. Colvinand Richard S. Judson Ce_#er.tbr ComputatioJlalEngilwerilzg SmtdiaNath_tallsTboratonl Livermore,Cal(fonfia _zettW. _._ Bh_medical S_L,la_Dk'ish_11 A major CdITent objective of the Human Genome Center at Lawrence Livemaore National Lalxwatorv is complc_on of the physical map for d_)m(_me 19. In the coming years, more empha,;is will be _ven to completely sca.]uencing stretdles of DNA and to analyzhlg these sequemces. The gt_al of our effort is to develop algoritlamic and comput,ational tcx)L,;needed to meet new d',allengt_ that will arL_, frol n this shift of emphasis. -(hi_ article dt__-a_T_'L_'s." our approadl, calk__.t'key-seatfll,' to DNA _quence assembly. The computational complexi_' of the kev-search algofiflml is nearly dirc_-tly p.rol.x_rtionai to the number of DNA ba_ to tx' a._,_mblt__.i.Wt, [aave complett_i the implen lentafion of the algorithm. We are now testing our a._nabiy prt_,-ran:, tk_,ir_ga data _t pro\'id(.Kt by the National Institute of Health. ii The prtK'ess of DNA sequencing is _,pically accomplished by using a .,_)-callo.i 'shotgun _'quencing'appn_,_ch.l'hemeth_3 involvt.,s_'quencing randomly overlapping small fra_,maents(2(X)to _X) ba.-,c pairs) taken from a much larger piece (e.g., 4i),(XX)ba.,a., pairs), toa 5-to 10-fold redundanev; i.e., the total number of ba_, pairs _,quenced is 5 to 10 timt_ the siz,, of the original piece. The original large m'quence can be recovered in principie by pasting together fragments that share common sub_'quenct_, _.lUoace assembly Lscomputationaily difficxflt ft_r two rea.,,on.,,.First, then-' an.' a large, numlx, r of traNnnen_ {IIXX)or gn-,ater); a dire'ct comparison of every pair to detemaine which pairs a)ntain c(_mmon su[.-_t_.]uenctsi._vr,rv slow. [lie _'cond problem afist> [x_.-au_,of emirs iradata collc-cting,imwrfo:tions in the fragmentation pn,.-es,,(_, and the statistical nattm, of fragnnvnt _,k_-tit)n. lqxisting methtKls u._' _'qt_ence alignment pr(vgrams to detemaine overlap tx,b,veen fragments, and optinaization methtKt.,, to paste overlapping fmgmen_ t(,gether.-lqv.._' meth-- _ - _:ls generally do not peffom_ well for assemblh_g large _.tt|ence's. Wehavedevelopedanewapprt_'_datoflaeassembly problems, using a 'key._arch' meth(Ki b,_so.-ton the computer science idea of hash table's. We first enctKteeve_, l_ba_segmentofevery fragment into ,-a int_er called a kt,,,,.Tlat:_ keys are _rte_3 and stored in a table, together with l_×fintersto the ft'agments in which t,_ev we_, found and the kx:ations alongtht_;efra_nen_.Skartingfrornanykey, onecan detennine the adjacent key (e.g., to the fight) in the original _'quc ,ce by examining ali of the frab,maents that contain the current key (i.e.,bast,_ 1to 15),generating a corcse_tsus for fl_enext ba._ (i.e.,ba_' 16).The nextkeyisgeneratedfronaba_2tol6.Tlaeprtve'ssLs rel.x'ated kev by kt.,)'until an end condition ksdetected. Similarly, we can revonstruct the _'quence to the left of the starting key. Figure I illustmtc's the basic concept of thLsapproach. F_xtensions suda as using con_,nsuscaiculationateachba_,f()rautonaaticerror com_.-tion, and meth_Kis for n-._fix'ing the confusion that may l.x,cau_sJ by motifs, I.X,fitKiic patterns, and long n-'[.x,ats art, added to incn-,a_' the n)busb'lt.'ss of the assembly program. Emerging Technologies .:o Fast Algorithm for LargeScale Consensus DNA Sequence Assembly i (a) Original sequence (b) I:ragments (c) Keys ACGCTCGGGCGT ACGCTC GCTCG GCTCGGG GCGT ACGC ACGC GCTC GCTC GCTC CTCG CTCG TCGG CGGG GCGT oftnekey.seamhappreachto DNAse- q_,,_,_,,,,_: i (a)aDNA Rgum,1.. Thebas/cs ._u,,,x.,(b)_ _t.,.,_o,_ __,(c)_r. baseke_aname encon_ocm,_ ke__l_ merits,(d) a sortedta. I ble of all the keys, (e)a_re- constmctkmproce. dure,and(0 finalre. _. Coding (d) Ilash table 00011001 01100111 10011101 10011101 10011101 01110110 01110110 11011010 01101010 10011011 00011001 01100111 01110110 01101010 10011011 01110110 10011101 10011101 10011101 11011010 1,1 1,2 3,2 3,4 4,1 2,2 1,3 2,1 3,1 3,3 (f) Reconstruction le) Key search i I Key _,ey Key 3 T . G GCTGT ACGCTCGGGCGT Vhe major advantagc_ of our appn,,lch are its compL|klti(,laiefficiencyand itsl_)tentia]fi)rgenerating mort., reliable reconstructions.(k."meth(w.tcan generale a complete tx)n._nsus _'quence, the exact kw:ationat which each fl'agment rt_idt_ along the COII.'_L'FISLIS Stk.]tlel'lCt', and locationswhere em_mrx'cur. This infi_rmationprovidt_ nect._,_ll T data fi)r a statisticalt.'stimationofconfidencein the reas,,_,mbk_t .'_.'tlt_eF}ct'.l_iol()gists consider such t.'stimationcritical for their applications, and often fault cun'ent ase, mblv metht_Jsfiw lacking the ability to pnwide confidence tstimati(,_, a SUN SpareStation II.We al_ tt_tt_lthe program with fragment data ._'tscorr_l:x_|ldingto h..'s,_ coverage,at7-,8-,and_)-fi_ld.Asthecoveragedec|'ea.,._.'s, the reconstruction Call Ol'l]V _t, llt, l'att, islands, Lx,cau.,_, ,,_mlemgi()ns(fftheoriginal_'qtlencearen()tcoven.'d in the fragment databa_,. Ba._'d on Monte Carlo simulation, l()-fiddcove|'ageistht,|lfi|li|m||n|_.,quin._J to coverthe entire.,_'quence. Our current task is to reconstructa large _'qt|enct' from an actual fragmt,nt data .,_'tprovided to us by the National Institute of ! lealth (Nil-t). The Nll l databa_, has a relatively h_wc_v,'t,rag¢of 5-to(.,-fold, ._ we anticipate findinggaps inthe original.,_lUenCe. I hwct,ver,the rtvonstruction c_k. is able to generate _,vt,ralislandsin the ¢-,(XX)to l(),(WX)-ba_'-pair size, range,fora total.,-a.'quer_ce of approximatelyM,(XX) ba_, pait.'s.The rtvonstructi_n rt_ultwill[x,evaluatoJ by biologistsat the I lum,m ( ;t.n(,ne C'entt.rat Iro.vrenct,I.i\'t'rm(,'eNatit,_all._N.'atorv (I,I.NI.). We havecompletedthe implementationof the kev-_,archalgorithm and tt.,steditona known I)NA _'quence ()fapproximately 33,(1(1() ba.,_'pai_ to vaildate the appr(_ach.A fi'agmentatit_nprogram that simulatt_ shotgun ._Nuencing and gent'ratt,'sa syntheticfragnaerd databa.,a:was implenlentt_d. We typi- _ WoItk callva_,_umt,I()-f()ldc(wc'ragt,,2(X)-t_)4(X)-ba_'-pair fragment lengtl_,and random cutting sitt.,s.We then I,_t, al fragmt,nt data sets art, ct'rtr'htlv being corrupt the _'qut, nce with t,rrtq,'s,1ta rt,alisticrail' gent'rated at the I,I.NI. I luman (.;t.ll(}ll'lt,(.'enter. ba.,_,d_,a publislat,ddata. I']'n,.'sincrt.a_, t'xp(,at.n- Wt. will lt.stthe ,_sst.mbl\'pr()gram ()ntilt'st' dat.}. tiall\' along thr' length _f the fragment, from I".. ft," Wt, will als_ con_part' t_tll" I't'C{Wlstl'tlCtit_ll rr'stills It'ngths [x'h_w20(1ba_' pai_.'slo 7'!,,at _X)ba_, pait.'s, with tt,st_ltsgt'lat'rdlt'd bv t_tht'ra\'ailabh, stHlwart, (.)ur as_,mblv ph)gram st_ct't.'ssfullv rtv(_r_strt_t'ts the c(_mplt'tt' _'tlt_t'nct', t'xct'pl flwa rtsitttml t,rnw rah, _t al'_ut 2",,.Thc rtv(_nstructit_n u.,_ It.,sstht,n 4()mint)n 4-30 Thrust Area Report FY92 .:" I _,H_*'¢'_,t_y I¢_'',,',_ t* I),'_(,*,,t)m,'t,t packdgt,s st_th as lhc st,tlttt,_lct, a_alvsi,s s(fflw,]l't, tnm_ It_h,lligt, nt,tics, Inc., ,mtt lhr, .qladt,n p,_ckagt, tn_m (',_mbridgt, LJtaixt,rsit\. ,_t,_l l,', _",'/,'li; UsingElectricalHeatingToEnhancetheFxtractionof VolatileOrganicCompounds from Soil .:. EmergingTechnologies Using EleclbricalHeating ToEnhance the ExbacUon of Volatile Organic CompoundsthromSoil H. Michael Buettner and William D. Daily Ellghzeerhzg Researclz DivisioJ1 Eh'ctrollics Ellgilleering We have developed a method of using electrical soil heating in combination with vacuum ventirlg to enhance tile removal of volatile organic compounds from contaminated soil. The results of two engin_._ering-_ale tests show that this technology has great potential for environmental remediation at both government and private facilities. |llltroduction The problem of contamination of ground water and _il by volatile organic COml.x_unds (VC)C's) is widespread in this count_,. VaLxlum venting has long been tL_.ias a rem_iiation method in such ca_. We prol.x_.;ed that ekvtfical soil heating (joule heating) could [_ u_.t in combination with vacuum venting to enhance the removal of VOC's. We de,<fibe hem the rL.'sultsof work to demorkstrate ek<'trical heating of the ground in engineering-,<ale ttsLsfor u_' as an adjunct to vacuum venting or cyclic steam injection for the removal of VOC's from _il. We performed two engineering-scale tests. The first of these, in September, 1991 at an uncontamihated site, Sandia National Laboratories, Livermore, California, proved that soilscanbeeffL_:tiveiv hea ted using powerline-fl'equency energy. The _,cond test, from May to July, 1992 at Lawrence Livermore National Laboratory's (H_,NL) Site 3()0, which is contaminated with trichloroethvlene (TCE), proved that electrical heating can enhance V(X__removal from soils. Our purposes were (1) to Iea m about the practica l aspects of electrical heating such as ._lection and sizing of electrode materials and wires, and maintenance of low contact resistance between the electrodes and the ground; (2) to compare actual heating rates with those based on simph., calcula- _ fngsn(,et_ng tions; (3)to provide data for _aling the experiment up for application at other contaminated sites; (4) to provide data for estimates relating to tile economics of electrical heating; and (5) to demonstrate that electrical heating enhances extraction of VOC's and to quantify tile effect. For our first engineering-_ale field test, at an uncontaminated site, we u,_d a pattern of six heating wells equally spaced on the circumference of a circle with a diameter of 6.1 m (20 ft). The electrodes were made of stainless stt_el tubing _,ctions, and the contact resistance was maintained at a low value by saturating the sand pack around the electrode with water via a feed tube. The heating wells were powered with 3-phase, 400-V, 60-Hz power supplied by a 125-kVA generator. Fixc_.tthermocouplL.,s were u_.i to monitor the tem_x?rature as a flan_on of time during the trot. We ran the t¢.'staround the clock for 10.76 days. then during the day only for four additional days. The CtllTerlts to the eh.vtrc_.ies,and themlocouple temperaturts were monitored on a regular basis. At the end of the 24-h/day heating period, the temperature in thecenter of the pattern (thecoldt_t Ix_int) ata depth of 4.88 m (16 ft) r(zse from a starting value of 19°C to _'C. During the daytimc_nly heafin D the temperature r(_,? to 44°C. At this l.x_int,the l_x_werwas tumt_.i off, and flip teml.x,rattlre contilltled to ri,_ to 54'_Cin a likiay b_,rilKi,after which we stopl_xxi teml_mrature monitoring. ()tiler thennocoupic_ nearer to the l.x'-riphery read as high as 73°C. ThL._ exl.mfimental rtsults agrt_ clizsely with very simple calculations Research Development _1¢_a rechtlolog, y .:, Thrust Area Report FY92 4-31 _q Technolhl_es • Using Electrical Heating To Enhance the Extraction of Volatile Organic Compounds F_re l. TCEcon. centraOoa_ time before,_ring, and aff_t_all_il _na' at LLNt.'s / .-- Autosampled ITCE] + Syringe sampled [TCE] S/lte 300. ] / Hypothetical concentration \ from Soil \ 4" / !: / data #.,,,_/ + / Begin heating / + / Inadequate sampling: water condensation in lines Stop heating • 'k Iqk based on a two-ciimensional model, assuming homogeneous electrical and thermal properties. Over the duration of the heating phase of the experiment, the total energy dissipated in the ground was about 15,(X}0kWh. For our second test, at a site contaminated with TCE, the heating wells were also located on a 6.1-m circle. A vapor extraction well was located in the center of the pattern. The heating wells were powered with _phase, 480-V, 60-Hz power supplied by a 100-kVA generator. Again, the contact resistance of the electrodes was maintained at a low value by saturating the sand pack around the electrode with water via a feed tube. We ran the test during the day only for 40 days. The currents to the electrodes and thermocouple temperatures were monitored regularly. During the heating phase of the experiment, the temperature of the vapors extracted from the central well rose from 16°Cto_°C, and continued rising thereafter to 39°C, when we stopped collecting data. The TCE concentration in the collected vapor decreased steadily as vacuum was applied to the central well during the period before heating, toalowofabout60ppm.Once electrical heating began, the concentration increased. The concentration rose to over 140 ppm during the heating period, and then decayed to v_ues of less than20 ppm. Restflts are shown in Fig. 1.The amount Thrust Area Report FY92 ._ t-nl_t_e¢l_,g iT_v¢ifc, h Dc;_c:c_,.-:.c::t __ The lessons learned as a result of this work have been applied to a much larger and highly visible project at LLNL, the Dynamic Underground Stripping Project. 1,2This project seeks to clean up approximately 17,000 gallons of gasoline from the soil and grotmd water at an old gasoline station site. In this demonstration project, steam injection and vacuum extraction are used to clean gasoline from the sands and gravels, while electrical heating drives the gasoline from the clay layers. FUture Work The technology we have developed has great potential for the Department of Energy (DOE) and for the private sector. LLNL is at the forefront of this work. We are actively seeking partners inside and outside DOE for further development and/or licensing of the technology. For example, the technology is being considered for remediation work at the DOE's Rocky Flats, and for facilities of British Petroleum of America. 1. 2. of electrical energy depositecl in the ground was about 96(D kWh. 4"_ + ::':d R.Aines and R.Newmark, "Rapid Removal of Underground Hydnx:arbon Spills," Ettt't_¢]/ attd Tech;zolo,_,,y Review, Lawrence l..ivermore National Laboratory Livermore, California 0uly 1992). "Ground water cleanup researchers make headway," Newsline, Lawrence IJvermore National Laboratory, Livermore, California (October 2, 1992). LI r_'.'_"(_l_ Fabrication Technology The mission of the FabricationTechnology thrust area is to have an adequate base of manufacturing tectmology, not neces_lrily resident at Lawrence Livermore National Laboratory (LLNL), to conduct the future business of LLNL. Our specific goals continue to be to (1) develop an understanding of fund,_nental fabrication processes; (2) construct general purpose process models that will have wide applicability; (3) d(x:ument findings and models in journals; (4) transfer technology to LLNL programs, industry, and colleagues; and (5) develop continuing relationships with the industrial and academic commtmities to advance our collective understanding of fabrication processes, resources both to maintain our expertise by applying it to a specific problem and to help fund further development. A popular vehicle to ftuld such work is the C¢×_perative Research and Development Agreement with industry. For technologies needing development because of their future critical importance and in which we are not expert, we use intemal funding sources. These latter are the topics of the thrust area. Three FY-92 funded projects are discussed in this section. Each project clearly moves the Fabiication Technology thrust area towards the goals outlined above. We have also continued our merebership in the North Carolina State University Precision Engineering Center, a multidisciplinary research and graduate program established to pro- The strategy to ensure our success is changing. For technologies in which we are expert and which will continue to be of future importance to LLNL, we can often attract outside vide the new technologies needed by high-technology institutions in the U.S. As members, we have access to and use of the results of their research projects, many of which parallel our own precision engineering efforts at LLNL. a Kenneth L. Blaedel Thrust Area l_x'ader Section 5 5. Fabrication Technology Overview Kemleth L. Blaedel,Thrust ,4reaLeader Fabrication of Amorphous Diamond Coatings Steven Falabella,David M. Sanders,and David B. Boercker........................................................s.1 Laser-Assisted Self-Sputtering Peter]. Biltoft,Sta_en Falabella,Sta,en R. Bryan, Jr., Ralph F. Pombo,and Barry L. Olsen ........................................................................................... ¢_ Simulation of Diamond Turning of Copper and Silicon Surfaces David B. Boercker,JamesBelak,and Irving F. Stowers ................................................................ s.7 Fabricationof AmorphousDiamondCoatings4. Fabrication Technology Fd:ricalion of mamondCoangs Steven Falabella and David M. Sanders MaterialsFabricationDivision MechanicalEngineering Amorphous diamond David B. Boercker Con&nsedMatterPhysicsDivish)n PhysicsDepartment is a hard, electrically insulating, inert and transparent form of carbon that has the sp 3 bond character of crystalline diamond, but lacks a long-range ordered structure. The potential applications of amorphous diamond (a:D) are many. This material has several important advantages over conventional chemical-vapor-deposition diamond coatings, making it a more attractive coating for applications such as cutting tools, tribological surfaces, spacecraft components, and medical implants. In FY-92, we produced carbon coatings with hardness rivaling that of natural diamond, and began to evaluate the use of this material in practical applications. We have produced amorphous diamond films on a routine basis, and have produced coatings up to 8 pm thick on carbide tool bits. The combination of extreme hardness, low atomic number, smoothness, low friction, and low deposition temperature make a:D unique in the world. coating causes delamination subs[rate. Intbroduction The physical properties of diamond make it an ideal material for many critical applications. However, natural diamonds are rare, expensive, and too small for many applications. A substantial amotmt of work is being done to produce diamond coatings on less expensive substrates, to take advantage of the properties of diamond without the need for large diamond monoliths. There are four critical problems that n___edto be solved before diamond coatings will be practical: (1) Temperature of deposition. High process temperatures eliminate aluminum, tool steels, glasses, and polymers as possible substrate materials, limiting the usefulness of the coating. Also, heating and cooling of substrates adds time, complexity, and expense to the coating process, (2) Adhesion to substrate. Thin films rely on the substrate bir much of their mechanical integrity, depending on adhesion tothesubstrate for support. Failure of adhesion usually means unpredictable and rapid hilure of the coated part. (3) Stress. Internal stress limits the permissible thickness of a coating when the stressin the El_glne¢;isng or deforms the (4) Smoothness of coating. In tribological applications, sm(×_thness is essential for low friction and long life. Also, for optical coatings, any coating roughness will degrade the performance of the optic. Diamond films produced by chemical vapor deposition have difficulty in ali four areas. The adhesion is poor; deposition temperature is generally above 800°C; thermally induced stress is often excessive; and the polycrystalline films produced Lave high surface roughness, requiring expensive polishing. The situation is very different for a:D. Amorphous diamond coatings are prtKlticed by the condensation of carbon ions on cooled substrates (at room temperature or below). They also replicate the subs[rate surface finish, and can be very adherent. We fcel that only adhesion and stress are still problems, and may exclude- the use of some substrate materials. However, an adherent interhce can be created in several ways: a thin layer of a binder material can be deposited before coating with a:D; or, since the process is ion-based, substrate biasing can form a diffuse, adherent interface. Stress can be lowered by several means: Rese,itct_ Develol)mc, nt ,1hd Tt, chnology .',, Thrust Area Report FY92 5.1 Fabrlr.atlon Teehnology ,O, Fabrication of Amorphous Dian)ond Co_-_tmlgS increasing tile incident ion energy by rf-biasing tile substrate during deposition; increasing the substrate temperature; and incorporating impurity elements it| the film. The_, methods to reduce bladt,'s, rt_ludng ttx'ovefy timt.'s (and htmpital ctmts) for many surgical prtxxxturt.,s. 'l'he high cost of diamond _'all:_,ls(,,_,veralthou_lnd dollm.'seach) isnow b,:,main limit totheiru,,._'. stress and improve adhesion may also reduce certain qualities of the coatings, so tradeoffs will need to be made. We have identifiett four areas where the extraordir|ary properties of a:D can have a large impact. The first is the coating of ttx_lbits for use on diamond tunring machir|es to exploit the toughhess, adhesion, hardness, and wear resistance of a:D. If successful, this process will h.,ad to cost _'wings where the surface finish and precision required is less than that prt_.iuced by diamond tumirlg, yet better than can be produced by conventionai cutting bits. At pre,,_,nt, the firfish obtained on a part is limited by the edge quality of our coated carbide bits, which in turn is limited by current polishing methtKts. If a better method can Ev,.,found to form the tip radius of a coated bit, geometries and precision not practical with |'|ab Jral diamond could be achieved, _,cond, the surfaces of metrology blocks, callper faces, and precision slides can be coated ar|d polished to provide hard, sm_x_th, and wear-resistant surfaces that will not change dimensions or _ratch the parts under test. This will allow more confidence in the contirmed accuracy of the t_x_ls, save re-calibration time, and prolong the life of the equipment, Third, there are applications that would b,'"wfit from the triboiogicai properties of a:D, in air and in vacuum. The friction ctwfficient for a:D i, measured to be 0.2 or less in ali conditions. Thr, re art, several important areas where a long-life solid lubricant could have prevented the failure of mechanical systems on spacecraft, and would enable new mechanisms to be practical in spacecraft. A repre,,.a.'ntative example is the (;alileo probe's main antenna that failed to deploy due to the failure of the MoS2 lubricant on its opening med|a|fism. Coating both disk surface and heads will reduce the damage caused by 'head crashes' arm may enable magnetic recording media of higher der|sitv by allowing smaller head-to-disk distance, Finally, there are_,veral applicationsofa:l) in the medical field. [)tie to the wear rt_istance and bitx:ompatibility of a:l), the potential is great for creating _'ali.x,ls, replace|nent-ioint wei.lr surfact_, and other implanted parts. If a suitable ttwhrfique is dex,elt_l_x,d to allow a c()att'd bladt, a_achieve the shalpnts,_ of a natural diamond _'al|x,I, theFn_tentialLx,nefitswould tx, tn.,mendous. Incisions made by diamo|ad .,a.'all.x, ls heal up to five tinat._fastertha|_tlat_, made with stt_.,I _'_ Thrust Area Report FY92 4, [.t_;_n_,_,_ng R(,,;_,dtcl# I)¢'velul_m_'_t In FY-92, we produced carbon films with our filtered cathodic-arc system, whichwasdeveloped in previous years. The cathodic-arc source produces a carbon ion beam from a graphite target, in a high vacuum e|wironment._ Our goals tbr ti'w year were, to investigate the conditions under which a:D is formed, to improve adhesion to various substrate materials, to model the deposition protess using mok'cular dynamics (Ml_)), and to reduce residual stress in the films, which is rt'quired to deposit greaWr thicknes,,_.,s. We installed a ctx_led and bia_lble holder to control the substrate temperature durir|g deposition. Initially, the holder was ten,led by liquid nitrogen, but we found that water cooling produced equivalent results. By using a i'dgh-voltage bias for the first few _-onds of coating, we have produced coatings on cemented carbide ttx_l bits with adhesion above 111kpsi (limit of the _,bastian pin-pull tester). We are ir|vestigating metht_.ts that will measure adhesion to higher values. We were able to achieve hard cari.x_nc¢_ltings that are low in hydrogen content.'llle hardne,'ss of cart_n films is inversely related to the l'|ydrogen content; e.g., 10 to 20% hydrogen in a cartx_n film (known as diamond-like-cartxw|, or DI,C) veduct,,s the hardr|e_,_ by a factor of four. The hydrogen contt, nt of our coafinh,,swas measurt_'l to rx, lt_ than ().I'Y,,,,using forward recoil ,_attering (Fl,kq).We dek'nnin_J the density of our films from the areal der|sity obtair|t'd, using Rutherfo|d backscattering (Rl_kq)and the film thicknc_,_. We nleasure the density of a:D to rx' 2.7 + 0.3 g/ce, which is [x,tween graphite at 2.2h g/ce and diamond at3.5 g/tc. (.)he of the most appealing properties of amorphousdiamor|d isitsextraordinary hardness. However, standard hardness tests made by indenting are generally difficult to interpret wl|en the coating is thin and harde|" than the substrate material. To get a true measurement of the coating hardhess, the indent depth must be less than 7 to 20'7,,of tlwcoating thickness. 2Quantitative hardness tests are in progress with an ultraImicrt_ha|'dness tester, which uses sucla a small indent that the measuremerit is n(_t influenced by the substrate. A startdard Vickers indent of a tungsten carbide tool bit coated with 8 _tm of a:l) with loads tip to 500 g gives a hardness of I[),[)(X) ± I(),",,, the same as ,_od It,_h/t_)lol_t. F_brlc,11ion oi Amotpl)ous natural diamond. At 5[_)g, the indent depth is 17'!,. To put the severity of this test iraperspective: "_............ 8, the stress put on the film at the 5(X)-gload is over 17 x !(_' psi. For thinner coatings, the Vickers test a' I "_---- (25 g) and then decreases, as the load increases to roughly the substra te hardraess value (ha rd hess of tungsten carbide is _ 2t_)0 He). To get anotlaer as,_ssment of the laardness, we used an abrasion _ S;- that we produced, by abrading various hard materials a coated We were polish test. against We as_,s,_,d the plate. hardness of the able a:D tr) coatings facets iraali materials attempted, including natural and synthetic diamond, indicating that the coating is approximately as hard as diamond. This may 2 1l Diim)ond Codhngs o_*Fabrication _ I _ J- O Without nitrogen • With nitrogen - -__ - T T -- _ I I 100 21111 Blas voll_se 00 point to vet anotlaer application, i.e., the surfacing Figure1. Theintrinsicstress Inamoq_ous diamondfilms of ceramic, or even diamond ttx_ls, vs bias voltage. Stress Is reduced substantiBlly by the addl. The greatest difficul_ with a:D films is their tlon of blas during deposition, and even further by the addb high intrinsic stn.,_s. (_.," fil tero.|cath(_:lic-arc.,_)urce tlon of nitrogen. Data taken with no nitrogen during deposiproduces a fully ionized beam of carbon with a tion are in open circles; data taken with a nitrogen raaeala erlergv of 22 eV 3, arid prod uces stress levels background are in solid circles. In both cases, the stress reaches its lowest value around 150 V and is roughly co_ of 6 to 10 (,Pa. This can De reduced by increasirlg stant above that value. the incident ion energy impinging on the substrate. We usecl a 13.56-MHz rf supply to prm'idea bias during deposition. Since the fihns produced ,are non-conductive, rf bias is required to maintain the potential ,at the fihn surface during coating. We have reduced the intrinsic stress irao:D films bv a factor tfr twt) using bias alone, and by a factor of five using a combination of bias and tlae incorporation of 7% nitrogen ira the films. A plot of the residual stress vs bias voltage on the substrate (IX_7 level) is shown,areinshown. Fig. 1. Coatings and stress without nitrogen Altht)ugh with residual is reduced bx, the addition of nitrogen, the mea- ] 1 I I I I 1 , ii 0 sured hardnessof the films is reduced tr)- _) He, ,as noted above. Residual stress was inferred from the bowing of two-inch silicon yeafers. (.hacarbideforming materials, the adhesion is sufficient to produce thick coatings, witht_ut delamination of the coating caum, d by the c(mlpressive stress, ns long dS the bias voltage is kept above i 50 V during deposition. The 8-).tm-thick coating procl uced on ,l tungsten carbMe t_x)!bit was limited only by source material depletion, The fine strtlcttlre tfr a:D was characterized by TEM and electron diffraction. TEM showed no Figure 2. A molecular dynamics simulation of 20 eV carbon (880 atoms) impinging on a silicon surface. Substantial evidence of any ordered structure clown to II)A, indicating its ,amorpht_us nature. Unlike natural dinmond or I)I.C, n:D has a flat transmission spectrum frtma 0.8 to > 5()).tm, which is due to its amorphtn.ts nature and the lack of hydrt_gen. The transmission of a free-standing film w,ls mt.asured using a I:I'IR spectrophotometer, l:r_)m the interference between the front ,rod back surf,ices and range2.47t()2.57.Thisisch)seto2.42, tht, rt,fractive index of natural diamond. Using Ml) simulations, we have modeled the condensation of carbon atr)his onto n silicon substratt, to see the effects of deposition t,nergy (,1 coating strucltlre ,llld stress. Figure 2 shines cnrb(m deposited on n silicon surf,ace, l!ven ,at the di, position energy (_1 2()t'V, thr'rr, is substanti,ll -1 _!i. :i" !. -_:i. 0 _ _ ,_, I( ii.i ii_.,_,,_.'_I( i._ I 1 X(nm) 2 mixing occurs at the Interface. The carbon atoms are shown asdarkgraycircles;thesiliconatoms are Iight gray. The view Is parallel to the original silicon surface. tlae measured thickness of the films, we determined the index of refraction ofoura:l)tobe in the Technology FabrloationTechnology• Fabrication of AmorphousDian}ondCoatings mixing at the interface. We are now using tile ctx:le results to interpret the electron diffraction measurements. By Fourier transforrning the atom posifions in the simulation, we were able to clo._ly match the ob_,rved positions of diffraction rings. _1_ Wock We have de_ribed only a few wf the possible applications of a:D, with others to be realized as the material L_.,comt_better ella racterizc_.t.The combinafionofextremehardness, lowfricfion, sm(x_thness, and low deposition temperature make amorphous diamond a unique and very promising material, The next step in the development of this material would be tw test our amorphous diamond films in practical applications. However, we have not yet obtained continued funding for this project. Acknowk_ellNNl_ We wish to thank R. Musket for providing the RBS and FRS measurements; R. Chow and G. [._)nlis for the optical measurements; M. Wall for the TEM and electron diffraction work; J. Ferriera for the hardness tests; J.H dePruneda for insight into medical applications; and the Vacuum Protests Dlboratory staff for their technical :,upport. 1. 2. 3. S. Falabella and D.M. Sanders, l. Vac. Sci. and Teclmol.A 10 (2), 394 (19_2). C. Feldman, E Ordway, and J. [k,rnstein, I. Vac.Sci. andTeclm,,I.A 8 (I), 117(lq_)0). P.J.Martin, S.W. Filipczuk, I,Ll). Netterfield, J.S. Field, D.E Whitnall, D.R. McKenzie, ]. Mat,'r.Sci. h,tt. 7,410 (1988). L_ Laser Assisted SelfSputtering *.'. Fabrication Technology Lamr-Asted SeSmmedng Peter J. BlltoR, Steven Falabella, Steven R. Bryan,Jr.,and RalphF. Pombo Barry L. Olsen MaterialsDivishm ChemistrttroutMaterials ScielweDepartnzent Materials FabricationDivision Mechanical Engineering Our goal for FY-92was to demonstrate lair-assisted _lf-sputtering as a methocl for sputter deposition of thin film coatings in a high vacuum environment. II II1_ ()ttr experirne|atal investigate merging program was dt_ignet'! to the technology of magnetron sputteringl and la._r ablation _ to create a weilcontrolkxl deposition proccss fret, of the net_J for a pr(x:t_,_ gas. _qf-sputtering of copper, using a conventionai magnetTon sputter gun, has _'en reported.3 in this proct.,ss, a glow di_harge plasma was initiated bv ot.x'rating a magnetron in the conventional manner, with argon as the prtx:L_s gas at a pressure in the range of from 5 to 2() rnTorr. After : __::_: .......... - :, . :, (:; the plasma was well establisheci, the process gas prt_sure was slowly reduced. As this was done, sputtering was maintained by ionization of sputtered copl._,r atoms in clo,_ proximity of the cathode. We hope to demonstrate self-sputtering initiated by a lair-induced plasma in the ab_,nce of any proct.,ss gas. Our first goal was to design ture that would accommodate and build installation .... ..... (: . " _ : a fixof a F/l_m 1. Initial (left) and final (right) conngumtionof tlm sputtering appara- Sputter - L--I .... I Coolm8 ";:i"_; :: , [ power supply ..1.. .,,,,m, I Fabrication Tochnolo_ • L,tset-Ass1_h?d Svll&_uHomq_ conventional magnetron sputter gun into an existing vacuum vessel designed for thin til|l| growth by laser ablation. Wt, selected a small, commercial, spt|tter-dep_sition source (2-in. US gun) for our first evaltnltioll. A schematic of the experimental apparatt|s in presented in Fig. 1 (left). Initial deposition runs were conducted at pressures below 5 x lOs Torr, as measut'ed using a hot cathode ionization gauge on the vacuum vessel. We used a pulsed-output i-ICI laser operating at a wavelength of 308 l'ml to initiate the plasma. Typical operating parameters fin. the laser were I- to IO-ilz repetition rate and 160-to 320-mi pulse power. The laser beam was de-magnified using a 500-mm focal length, plano-convex lens external to the vacuutn vessel, Power density at the sputte," source cathode was between 21 and 42 J/cre 2. A high-output power supply designed fiw |uagnetron sputtering was used to bias the cathode to -5000 V. While we were able to briefly maintai|l a plasma at the sputter source, we discm'ered that the laser damaged turning optic 2 rapidly, redt|cing the power density we were able to deliver to the cathode. To rectify this problem, we reconfigured the apparatus as sl'|owr| in Fig,.1 (right). in the second configuration, we were able to initiate and mair|tain indefinitely a toroidal plasma at the sputter target. The color of the plasma ft," the copper target was bright green, indicating the presence of high ctmcentrations of copper speties in the plasma. 4Using this setup, we deposited severalthin filmsofcopper, l)uring I()-minute deposition runs, the magnetron power supply outpt, ts indicated that the peak voltage was 5(1{1{1 V, ,lilt] average current was 1).I A. _'6 Thtu|t Area Report FY92 ":" I I)l,tttlpl't;t)l._ f¢(,',t,,l/('ll I){'vt, l(JlJtll1_ttl Using ,i storage oscilloscope, we observed that the voltage output of the Illilglletr()ll power supply was reduced allnosI to zero tolh_wing every laser pulse. In an effort to deliver higher Cllrrel'ltto the sputter source, wt' installed a (1.I I.II: capacitorcapableofoperatingat > 5 kV, between the magnetron SF,Utter supply and the sputter source. No appreciable benefit was realized througl'_this modification. Results We have deposited thin films of copper, ah|miau|n, and tantalum by laser-assisted self-sputterir|g in a high vacuum enviro|mwnt. IX,position rates for the copper fihns were observed to ht, greater than O.I nm/s. This represents an increase in deposition rate of greater than a factor of 50 compared to pulsed-laser deposition of copper under identical circttmstances. Ac_knowl_elnen_ We would like to tl'|ank Nell l,tmd, who designed and built the hardware used in this work, and Bob Teach for his assistance with the HCI la_,r. I. 2. I.i,. Vossenand W. Kern,"l'hinl'ilm I'roasstw, Atadernic I'rt,ss, li'lc.(New York, New York), I_J78. I).B.Chrisey and A. Inam, Mahs. Res. lhd/., 37 (Febrt|,lry 1992). 3. R. Kukla, T. Krug, IA;c,.m R.41 (7-t)), 4, CRC I hmdl_oohoftVr'ntislry mtd Physit'.,.;, CRL" I'mss (lloca I,lalon, Florida), It,)g(). ,JHtl lecl tlt)log; R. I,udwig, ItJhS(19t)()). and K. Wilmes, Simulationof DiamondTurningof Copperand SiliconSurfaces4* FabricationTechnology Simulation of Diamond Tuming of Copper and Silkm Surfaces David B, Boercker and James Belak CondensedMatter PhysicsDivision Phfiics Department Irving F, Stowers PrecisionEngineeringProgram EngineeringDirectorate We have applied molecular dynamics modeling to the diamond turning of a ductile metal (copper) and a covalent material (silicon). On the nanometer-length scale, both materials show ductile behavior, but the atomistic mechanisms that allow the behavior are significantly different in the two cases. In addition, we studied the wear of small diamond asperities while they machined a silicon surface. i the atoms in the diamond tool are assumed to interact with the metal atoms through a LennardJones potential. For the silicon simulations, we have implemented interatomic potentials for silicon and carbon,3 which include angular-dependent forces that are very hnportant in covalent materials with low coordination. Interactions between like and unlike atoms are included in this model. |_ Diamond turning is, by now, a well established technique for machirting high-quality surfaces with dimensional tolerances of a few tens of nanometers.This technique isparficularlysuccessful when applied to non-reactive, ductile metals such as copper, lt is less useful when applied to carbideformers, like iron, or to brittle materials. Tribochemical reactions can cause excessive tool wear, while brittle fracture produces surface damage. Recently, there has been interest in diamond turning silicon to obtain precisely shaped optical substrates. In this case, both problems cK:cur.Silicon is a strong carbide former, and it is a covalently bonded, hard material that is prone to fracture, To gain insight into the atomistic mechanisms of importance to diamond turning and to diamond tool wear, we have performed molecular dynamics (MD) sinmlations of the machilting of both copper and silicon surfaces with diamond tools. The basic MD method is the same as that used previously I to simulate orthogonal cutting and nano-indentation. The simulations are performeKt in the rest frame of the cutting tool and follow the detailed, microscopic motions of the atoms, both in the tool and in the work piece, as it moves under the tool. Such simulations give good qualitative descriptions of chip formation and dislocation propagation, Thecentral input to the simulations isan appropriate interaton'fic force law. In the copper simulations, we use the embedded atom potential 2 for the interaction between two copper atoms, while Engineering We have performed two types of sinmlations, each designed co look at a different aspect of the problem. Chle class is designed to sin'mlateorthogonal cutting and to f(xms on chip fomlation and mechanisms of plastic flow. The other looks in detail at possible wear mechanisms, suchasgraphitization and carbide formation, for the tool. In both types of simulation, the work piece is a large slab contailfing terks of thousands of atoms oriented with a specific crystal direction face up. Most of the atoms in the work piece move freely according to Newton's laws. Relatively few atoms near the upstream boundary and the lower boundary have additional constraint forces that maintain their temperature at a constant value,4 allowing heat generated at the tool tip to flow out of the system. Finally, a constant velocity boundary condition is imposed on the lowest atoms in the slab. Atoms leaving the simulation cell at the 'downstream' end are destroyed, and new ones are periodically produced at the 'upstream' boundary. Performing tile calculation in the rest frame of the Research DeveloOmont ,1hd T_'cht_olOlly _ "_ Thrust Area Report FY92 5.7 Fl_._d_ Tl_-.Im_logy i F/_re ./.. Contrasting _ ofcop p_ andsak'._ under _c,-utUng(al _cl_prema_ _I_ .,I. Smmlatlon of Dlanlond (al Si) 6J) and Sihcon " sm_e e, e.|," tt'_'f,'_ . • .o ,. ,';J;_ ,,, _f,#Og,'ese_IbW-LQ,@_@OOO_6°@ _ , . o • ,; • | ._i '" t • • gll _:::.'::::::: ...... .... (b) "." ..• .... , "...." "...." '...." "., . ._ eO ' :': ..... ",:':::'_".'_/ " ": •::::";:,:.. ..,..,,..,...;,. • ._.._:. _,, _,.MI_, .,.,,. ,, •_,,,,,,,,,,,. M_i'_,_._,_:.,:;_. --._i_,_,.,,.,.,,-,. S.O 'snapshot' of this simula- silicon clinging quite tightly to bott" the rake and clearancefacesof the t_x_l. face and observing their interaction with the sillcon work piece. The asperities differed in size, but were 1._th shal:_:! as square pyramids with the four triangumr faces being (111) surfaces. The square base of the larger pvramid contained "#... .. 64( = 8x8) ato'-_s,whi le the base of the smaller one contained 36(= 6x6) atone. Ali of the atoms in both u_ .............,. • • •. • e •• •q_...... e $ o e_ 4 $ _... m_'emee1_ee_eeeseo_eeeo° 0 Q_ • • • • • •::_-:::- .... . ...-.-....-.-.: ............... ,. o _ K0 "-.°.-'i:"-:!':':':'.':':':':".':':':_:':':':'::.t::.'.:: I asperities were free to move as Newton's equations dictate. The bases of the pyramids were (001) plan___attached to the bottom (001) plane of rec- ' 6.0 X (nra) We simulated diamond turning in theorthogonal cutting g(._}met_' by creating a wedge-shaped hn}! with a close-packc_ (l 1l) cutting face, and impc_sing l.x_ri¢Kticboundary conditions in the direction parallel to the surface and normal to the cutting dirt_'tion. In the ca_' of copper, the diarnond t_x_lcompri._'d a rigid array of atoms with about a 2 nm radius of curvature. The work piece contain_M 36,{XX) copl.x,r atoms with the (111 ) face up, and moved, ,rider the t_n_lat a st._&'dof about I(X)m/,_ from left to right. A cro.ss-_ctional 'snapshot' of the simulation is shown in Fig. la. From thi_ picture, we nohce that the chip has n nained crystalline, but it ha_ ['_._.,nn._riented to form a (111) slip plane in the primao shear zone in front of the t_l. tangular diamond slab, four atomic layers thick. The atoms hl the bottom two layers of the slab also moved according to Newton's eqt|ations, but their temperature was controlled. The atoms in the top two layers were kept in a rigid lattice that initially moved downward at a constant velocity, but stoptxKt after the desired penetration was obtained. After that time, these atoms were held fixed in space. S(×m after the asperities made contact with the silicon, the atoms in their tips began to break away, and some were replaced by silicon} Later in the simulation, a graphitic cluster of six carbon atoms appeared at the surface on the downstream side of each asperity. No other damage to the asperities, except for a build-up of silicon on the pyramid faces, was visible during the simulation time of at.x_ut 10 ps. The central result of this work is the contrasting behavior of our prototype materials, copper and silicon, under orthogonal cutting. Copper forms a face-centered-cubic (fcc) cr),stal with a single-atom basis. As a result, slip along the close-packed (111) planes is analogous to sliding stacks of marbles over each other, and as ,_n in Fig. la, the copper chip remains co, stalline, but reorients and slips along the easy plane. In contrast, silicon forms a diamond lattice that is aLs()fcc, but contains a _,o- In contrast t_ the cop_x,r simulation, the silicon calculation allow_ the lower atom_,, h3 fl_e t(n_! to move according to their force laws, and only the uppermost atom_ are held rigid. Atoms just below the rigid ],:tr°rs are maintaint_.i at consta _t tern_x'ratun,.. The work pi(:ce consi_tt_t of 20,16(Ia_ms with _,..(_wujpI ta,,,. _,, "'_"" ..... ;:'¢,',,," '_'_ _'1-' ,'_,,,'i,,oalaN_t ....... _ ....... v44_ m/,..loft ' atom basis. Consequently, sliding along the (111) plane is hindered by the str_)ng angular forces, and Fig. lb shows thai silicon amorphizes and then 'flows.' This suggests that the surface selects the state that minimizes the work done by the hx)l. Our simulation (ff the wear of small diamond asoeritic_ t while cuttin_ silicon showed evidence =0 4.o Sl) tt×_i allows the simulation of cutting over lengths thatare manv times the computational cell dim°nsion, without having to folk_w the motion of a prohibitively large numt'ver of atoms. Orthogonal Cutting : Area T_x_lwear was simulated bv suspending hvo small carbon asperities from a flat diamond sur- 6.0 "_'¢ '°'_"">-, •, • .-.,i,__.,_,_._',,_"%_I_:; _,$•".',,'.. ......... •"'"",'.'-'.'.'. _ _,_ ee ee_ee • Thrust to right. A cn_,-_,ctional ......... . •.: • ; ,.... ..... .•, ...... Tool Wear ===================================== _; (blsl.co. _a_,_,, 5"S Su#ac es tion is shown in Fig. lb. The first thing to notice is that both the chip and the cut surface are amorphous. In addition, there appears to be a boundary -_ laver of - TM . .,;,-:.;;,_.;.... -, ,,,'_-o*_,' _: _I,.;,_t_.' r4e4141Q • II O i,_,,_ll_,ll . ,.,, .... • _ • iii " %,j/,L,.':_, z !:._ ,, = ,,_ ._'__ ,,;,,_, aw_-e_w41 • ,; .,t.,',_-,',t .. "41' _!1 __" ql i) • s ; . es reorients to slip Mong the e_sy (111) of Copper li "" but Turning Report FY92 ":" __'_ "r,: _ _;,_*st._" _: L;_.,_.. -;2",,_: _,_ "_.._."'_,_,,#_, 1. Simulation of Diamond Turning of Copper and Silicon Surfaces of both 'graphitization' and carbide formation. Six carbon atoms broke off the asperities and formed hexagonal rings, while silicon atoms filled the resuiting vacancies by bonding strongl3 to the diamond. Futw_ 1. J. Belak and I.E Stowers, "Mok'cular Dynamics Modeling of Surface Indentation and Metal Cutring," En_ineerin_Research,Dez,elopment,and Technolo,knj, Lawrence [,ivermore National Laboratory, Livermore, California, UCRL-53868-91,4-3(1992). 2. D.J. Oh for andClose-Packed R.A. Johnson, "Embedded Method Metals," Atomistic Atom Simulathm of Materhfls: Beyond Pair Potentials, V.Vitek and D.J.Srolovitz (Eds.), Plenum Press (New York), 233 (1989). 3. J. Tersoff, Phys. Rez_.B39, 5566 (1989). 4. W.G. Hoover, Phys. RL_,.A 31,1695 (1985). 5. D.B. Boercker,J. Belak,I.E Stowers, R.R.Donaldson, and W.J.Siekhaus, "Simulation of Diamond Turning of Silicon Surfaces," Proc.ASPE 1992 Ammal Meetiny (Grenelefe, Florida), 45 (October 18-23, 1992). LI tile-brittle transition in glass is critical to improving the economic viability of the state-of-the-art machining capabilities being developed at Lawrence Livem_ore National Laboratory (LLNL). Our next objective is to define the mechanisms of microplasticity and damage initiation in fused silica by using MD techniques, to follow changes in the stnJctural properties and the dynamic interactions of the atomistic glass network. We hope that an explicit demonstration of the ability to m_Ktel these processes will greatly enhance the competitive- Enl_lr_e_'rln_, Technology ness of LLNL's materials fabrication efforts within the Department of Energy and elsewhere. Work The ability to Lmderstand and control the duc- 4° Fabrication R_:se_trct) De_,lol) m(,t;t _tnd Technology 4. Thrust Area Report FY92 _*_ Materials Science and Engineering The objective of tile Materials Science and Engiheeling thrust area is to enhance our understanding of the physical and mechanical behavior and the procl.,ssing/struc._lre/propel_correlationsforstnJcrural materials that are of interu.'stto Lawrence Livermore National Lat'n_ratory (LLNL) programs and U.S. industry. We aL'_ .,_'ek to enhance our abili_ to m¢_.telthe pr_K'_._ing of th_._e materials using LLN L's finite element ccKIc_. (_Jr activitil__art, cun'ently focused on coml.x_sitematerials, sul._rplasticity, ro'ldprocc._ss mtx.teling, to monitor in situ the state of cure in polymer matrix composites. We also work on metal matrix composites (MMC's), which are materials of choice hl applications requiring high specific strength and stiffill._,_. Thc._ materials can have excellent thermal and electrical conductivity and, depending on the alloy matrix, excellent high-temperature behavior. During FY-92, we studied the procc_.,,_,_ing/structure/property correlations in a unique fom_ of MMC, called a laminatt_i metal ¢.x_mp(_ite,in which alternating metallic layers are prt,,ss-tx_ndc_.ttogether. Composite Materials Our work in composite materials is directed toward polymer matrix composites and metal matrix composites. LLNL has a long history of achievements in the investigation of polymer matrix composites. The_ materials have received considerable re,arch attention Superplastic Materials Superplastic materials are crystalline._iids that can be deformed in tension to such an extent that large strains will be attained at very low flow stres_s. The_ materials, which deform like hot glass, permit components to be formed into shap_, the dimensions of which are very clo_ to tho_ and pnKtuct application at Li_NL and in industry becau.,_' of their unique properties, including high sp_,cific strength, high specific stiffness, composition of low Z atoms, corrosion resistance, and the desirtK! in the final pr(Kluct ('net shape processing'). Thus, machining and machining-related operations can be reduced or eliminatcKi. Our work in this technok)gy has b(:_n stimulated by U.S. possibility for a low coefficient of thermal expansion. These properties can also be tailored to specific applications. During FY-92, we have focused on studying the three-dimensional mechanical response of continuous fiber, poly,naer matrix composites. These studies have significantly enhanced our understanding of the respon_ of the_ materials and our ability to test and m_.iel this behavior using finite element codes. I)uring FY-92 we have also studied the use of laser Raman spectroKopy industry, which has demonstrated a strong interest in superplasticity for net shape processing. Currently, LLNL is engaged in two collaborative research and development projects with industry in the area of superplasticity. One project, with three parhlers, is developing the technology for commercial pr_Ktuction ofsuperplastic, ultra-highcarbon st¢._ls. Another project is developing a superplastic aluminum alloy with a faster forming rate and the capability for diffusion bonding. Su- Section 6 perplastic forming can also reduce environmental, safety, and health problems in tile Department of Energy nuclear weapons complex through the reduction of toxic and radioactive scrap produced during the fabrication of components. This year the thrust area has been studying the microstructural changes that take place during superplastic defomlation. A model is being developed for use in LLNL's finite element codes that will account for the influence of material microstructure and its evolution on the stress-strain-strain rate behavior of superplastic materials. Process Modeling Our work in process modeling is inspired by the enorrnotts impact of this technology on economic manufacturing competitiveness and by the unique opportunities for LLNL to assist industry, given its extensive experience with modeling problems and its extensive computational resources and codes. Researchers within this thrust area are enhancing the capability of LLNL codes to model the casting process. Casting is a common industrial manufacturing process that is also very complex and hxfluenced by many process and component variables. For these reasons, finite element modeling is a very powerful tool for tmderstanding and predicting the success or failure of industrial casting operations. Work is continuing on a unique fluid-thermal-stress finite element code that will predict the final shape and stress state of precision cast parts. Donald R. Lesuer Thrust Area Leader ,, 6. Materials Science and Engineering Overview Donald R. la'suet, Thrust Area Leader Processing and Characterization of Laminated Metal Composites Chol K. Syn, Donald R. Lesuer, and O.D. Sherby ....................................................................... s.1 Casting Process Modeling Arthur B. Shapiro ....................................................................................................................... e.7 Characterizing the Failure of Composite Materials Scott E. Groves, Roberto ]. Sanchez, William W. Feng, Albert E. Brown, Sh_en J. DeTeresa, and Richard E. Ly_m ....................................................... Fiber-Optic Raman Spectroscopy Polymer Composites e.11 for Cure Monitoring of Advanced Richard E. Lyon, Thomas M. Vess, S. Michael Angel, and M.L. Myrick ............................................................................................................................. e.17 Modeling Superplastic Materials Donald R. Lesuer, Chol K. Syn, Charh's S. Preuss, and Peter 1. Raboin .......................................................................................................................... s.23 Processing and Characterization o:. Materials of Laminated Metal Composites Science and Engineering Processing and Characterization of Laminated Metal Composites Chol K. Syn and Donald R. Lesuer Engil_eeringSciences Mechanical El_gineering O.D. Sherby DepartmeJztof Materials ScieJlce and EngiJleeriJlg Stm!fi_rdLhtiversity PaloAlto, Cal!forJfia We have made laminated metal composites of (1) ultrahigh carbon steel (1.8% C) and brass (70% Cu-30% Zn), and (2) Al 5182 mad Al 6061-25 vol % SiCl_ The laminates were prepared by hot pressing alternating and fracture toughness layers of the component materials in an argon gas atmosphere. Tensile were measured for different processing conditions of surface oxide descaling, layer thickness, mad heat treatment. Descaling of the surhce oxide prior to the pressbonding was found to eliminate premature delamination along interfaces, resulting in an increased yield strength and tensile ductility. Reduction in the layer thickness brought a large increase in tensile ductility, and a small decrease in yield strength and fracture toughness. T6 heat treatanent on the Al laminates induced a substantial increase ha the yield a_ld tensile strength, but a decrease in tensile ductility. Fracture toughness measured both in the crackarrester and crack-divider orientations showed a large enhancement over that of the component materials. Damping capacity measurements also showed rather remarkable increases over that of the component materials. |_ction The idea of laminating different metals and alloys to form a composite material that exploits the gt×_d properties of the constituent materials has been known from antiquity: The llliad of Homer, e.g., describes Achilles' shield, made of two outer layers each of bronze and tin and one middle layer of gold.1 The idea has also been used in many industrial applications. 2However, most of the current hadustrial metal-based laminates contain only two or three layers, and are used to save material cost while maintaining required wear or corrosion resistance. Recent studies 3,4,,_ show that multilayer laminated metal composites (LMC's) can have superior damage-critical properties such as fracture toughness and fatigue resistance, over that of the component materials. Damage crack propagation in a laminate of dissimilar materials is inherently difficult, sinceaninterfacecanactasabarriertothe crack propagation, especially when such an inter- Er_glr_e('rlt)g face delaminates at the crack tip and blunts the crack." Studies 3,4,-_ also show that it is possible to design a LMC with given performance character- _,- v _' F/g, urez. ,_ examlJ_oC_ R_-s_,dr(h Devt.'ll)l)lSl('ot nod AI/A_iCp laminateaftert_ edg_ _ l_.'clI11ololt ) o;, Thrust Area Report FY92 t_mm_. 6-1 MaterialsScienceandEngineering.._ ProcessingimdChiTractenzation of LimmT_ited MetalComposites li ii i Table1. Tensile propertiesofAI 5182/AL6061-25vel%SiCp. [ • " r , Uy_ : " ,"k'ale Not I#,enl_ wed 1)e_'a led l)esca k'd, T6 IX'scaled,Re-pres,_,d, T6 pm ivl_pa_l) MPa_i) 750 750 7511 100 138120.0) 162(23.5) 232(33.6) 201(29.2) 262(38.1)) 206(38.5) 333(48.2) 324(47.0) istics, through the choice of component materials, number of layers, thickness of the layers, and interfacial bond strength. A g¢×w.texample is the LMC formed by press-bonding altemak, layers of ultrahigh carbon steel (UHCS) and mild steel. In this LMC, the dynamic fracture toughness is far higher .... _. , ..... .i.'_ " ' " " _' ,_ . "" o., " '__'_=" ..... ,'_ " • " • _-_.'f_'.:g:g... • . _o. ?_': ._-'7_'*'v_ ;_'; :.,: i."_ " . ...... + ;". : ,; '- ." . . " _ " " "' ,I " ,',:,,,,4 ''_ .... ,a. ,:,, .... " . _ .- "" "": ,' :" , " _ ' :. , . . -_. :: : ,, .. , . • •" " " '' } "" ' _ I().() 163) 7.2 12.1! than that of either of the component materials. LMC's can also have damping capacity superior to that of the component materials, which can be very t|_,ft|l in structt, res wquiring high acoustic damping. We initiated the pw_nt w._arch in FY-917 to investigate the influence of pr¢wcessing and structural variables on the mtvhanical properties of multilayer I.MC's made of two constituent materials, one ductile but tough and the other brittle but strong. We cho._ in I'T-91 to study two LMC systems, UHCS/brass and Ai/AI-SiCp, and continued this study in FY-92. The._ two systems were cho._,n to show that the toughness at ambi- ,_..., . • :' ......, *" _'", ,.. ,. .... ,,,:_ "'_:'_'4J _"b('a'_rV • ." " " ," -.'.• ""''" '*"" % ent temperature of hard and brittle UI4CS and Al-SiCp can be enhanced substantially by lamirlation with ductile but tough countelparts. The main thrust for FY-92 was to study the influence of the surface preparation comfx_nent materials layer li of _jara-,t.,' " .... the and the thickness; of the iaminatts on their interfacial micl'(_structureand mechanical proF__Ttic.'s. I Experimental Procedure Materials and Processing. UHCS of a nominal composition of Fe-l.8% C-1.65% AI-1.5% Cr- ] i 0.5% Mn was preproces_,d _to have a fine-grained ferrite matrix of about 0.5-Hre grain size and spheroidized iron carbides on grain boundaries. Brass (70%Cu-30'_,Zn), Al 5182 (AI-4.5','4,Mg0.35% Mn), and AI-SiCr [AI 6061 (AM.0% Mg0.6% Si-0.28%Cu-0.2% Cr) matrix with 25 vol.% SiC particulate] were obtained from commercial SOD rces. Ali materials Figure2. (a) Opticaland(b) scanningelectronmicroscope microstructure in thevicinityof an interface in AI/AI-SICp laminate. S-2 Thrust Area Report FY92 _ Engineering Resei_rch Development were sliced to 50 mm-x-50 mm squares. AI 5182 and AI (-_)61-SiCpsquares were descaled using an acid solution. UHCS and brass were surface-machined and degreased. A lami- i_d rechn(_logv Processing arid Characterization nate containing an equal volume fraction of the nents. Eachstack was pres_d to one third or one fourth of its original height. Such a large reduction ensured gtx_clboncling at ink, rfaces. UHCS laminates were press-bonded at 750°C, and AI lanaiwere sliced into _:-:.:,,_::,+._3-:ea: ,,)_ _ ',_:.,','_:_ _.>-!_? .:_:!::_17_!1 3: __E!._7; i_ _,! ._! if _i_ ,'_ ...... __ [/' .., " _ to obtain laminates with redticed layer thickness. four eqt.al-sized pi_-ces,re-stacked, and re-pres_d Average hayer thickness was about 7_)lam for :, i.:,<:-:.,___3,_ _,,, ___ for UHCS and 100 Bm for Al laminates after reboth laminates initial pressing; pressing. _m_eafter Al laminates were about given 200 the lain T6 _'_ :_,_ _,.. _g_ heat treatment for the Al 6061 matrix of the AI-SiCI, __"_ Testing. Tensile tests were performed with flat specimens cut with the tensile axis parallel to the layers. Fracture totighness was measurecl with • chevron-rlotched short bar or three-point bend bar specimens in which the notch was cut either in the crack arrester or crack divider orientation. In the crack arrester orientation, the crack front propagates in the thickness direction, cutting the layers _,quentially. In the crack divider orientation, the crack front propagates through the laminate, cutting ali the layers simultanc:_,msly. Damping capaci .tyalong the thicMacss direction of the laminates was evaluated by a pul_-echo method for the ultrasonic frequency range, and by a torsion bar technique for the 0.1 to 100 Hz range, Experimental Results Interfacial Bonding and Microstructure. The Ai laminates that were chemically descaled and the UHCS laminates whose layers were surfacemachined prior to the press-bonding were well bonded and did not show any sign of interfacial delamination during machining of test specimens. A typical well-bonded as-pressed AI laminate, alter its edges were trimmed, is shown in Fig. 1. Figure 2 shows an interface in the AI laminate shown in Fig. 1, both in (a) optical and (b) scanning electron microscope photomicrographs. No interfacial pores or unbonded areas, and no secondary phases are visible, indicating that no reaction between the component materials occurred. Tensile Properties. Tensile properties of UHCS laminates wereincluded in our FY-91 report.7Sum marized in Table I and Fig. 3 are the tensile properties for the Al laminates in the as-pressed, and T6 heat-treated conditions. For the T6 heat-treated condition, laminates with two different average layer thicknesses (750 _Jm and 100 IJm) are com- Engineering .l, Materials Science and Engineering r_+!:'<+i.l',_i.._+,_+,,+.+_:+t+m)+_'_7+Z;D++m++<__=:.'_,_<_s_ two conlponent materials was prepared bv " hotpressing a stack of alternate layers of the cornpo- nates at 450"C. Some laminates of Laminated Metal Composites , • D escaled, p Re-pressed lOOBm . . . uesca,ea, . T, '7.n,,m _ 1 X ,x........ , .... x / As-pressed 7501am I --_ Scale not removed, As-pressed 750_tm _.___1__ ......... pared: the 750-1Jm-layer thickness material was obtainecl from the initial pressings, andthel00-lamlayer thickness material was obtained from repressings as de_ribed earlier. Table 1 clearly shows the effect of surface oxide removal for two 750-1am-layer laminates. Descaling of the constituent materials led to a noticeable increase in the yield strength, from138 MPa (20 ksi) to 162 MPa (23.5 ksi), and to a very substantial increase in ductility (by almost 7%), from 10% to 16.9%. No significant change in the ultimate tensile strength was observed. Figure 3 shows that the descaling treatment increases the flow stress over the entire strain range, most likely as a result of good bonding between the constituent layers, which prevents premature delamination. The importance of preventing delamination can probably be traced to the fact that in these materials, flow kx:alizafion precedes fracture. Gtx_ bonding inhibits flow kxzalization in the less ductile layers, which in turn results in greater elongation (and higher strength) before fracture. Heat treatment considerably influences the mechanical properties, as shown by the results in Table 1 for 750 lain-layer laminates. The T6 treatment increased the yield and ultimate tensile strength by about 70 MPa (10 ksi), but reduced the total elongation drastically, from about 17% to 7%. Figure 3 shows that the flow stress was also increased. Reduction of the layer thickness affects the tensile properties significantly. When the layer thickness was reduced from 750 I.tm to about 100 Dm trader the T6 heat-tceated condition, the yield strength was decreased slightly, but the total elongation was increased rather remarkably, from 7.2% to 12%. No significant change in the ultimate tensile strength was observed. A similar strong corre- Research Development mi and Technology ,l, Thrust Area i_'_ = __L_ i/ _ 3. ren_l_ atnn_4tn_tn _v. _ro¢lo/,_teplnr Inate. Results shows the Inffuenoe ofilur. _e a_a#n_, heat tn,am_nt, _¢tlynr th_kmn_. Raport FY92 6._ MaterialsScienceand Engineering.:. Processingand Characterization of LaminatedMetalComposites lminamJ I (al oHC_ru, .... _ I I 1 i.... tion tendency decrea_,_s with decre,'_qing layer thickne_s.'_Thus, it is likely that the higher toughness in [ UHCS 200_m, C.A. 750pm, c.A. the thick-layer laminates could be due to the blunting of an advancing crack by delamination, lt is interesting to note, however, that delamination redtlces the tensile ductility and strength, as ob_rved for the tensile properties. Interfacial delamination was observed also in ] ] ] 2o0pm, C.D. 750pm, C.D. i0 0 ........... I " ] 20 i r 60' " ........ .... _ _ ;. _ _ the crack divider orientation), as shown in Fig. 4, while the T6 treatment led to a reduced toughness (as measured both in the crack arrester and divid- _ ':_' I I 6061-SICp. the Al laminates regardless of the descaling or T6 treatment. The descaling treatment, however, led to an increased fracture toughness (measured in " ......I .... I ...... _ : ] Descaled, T6/C.D. er orientations). The beneficial effect of the descaling treatment restdts from the controlled and timely delamination of an interface as a crack approaches the interface. In the laminates made without the descaling treatment, delamination ] ] was extensive .... Figure4. Fracturetoughness measured(a) forthedifferentlayerthicknesses in and occurred rather prematurely. The increased yield strength and reduced tensile ductility upon T6 treatment, as shown in Fig. 3, were reflected in the reduced fracture toughness, a trend observed similarly in most monolithic materials. Damping Capacity. Damping capacity was measured only in the as-pressed condition, where the layer thickness was 750 pm for both UHCS/ brass ca.[d Al laminates. At low frequencies, damping in the UHCS/brass laminate was two to three times the damping typically observed in brass or steel, and was lowest at 2 Hz. Ultrasonic attenuation measurements of longitudinal waves showed that at 2.25 MHz, the UHCS/brass laminate had an attenuation coefficient of 160 dB/m, over 12 times the attenuation coefficient for the steel com- UHCS/brass laminatesand(b) fordifferentprocessing conditionsin AI/AI-SICp laminates.TheInsetdrawings(c)definethecrackdivider(C.D.)andcrackarrester (C.A.)orientationsusedin thefracturetoughnesstests, ponent and over four times the attenuation coefficient of the brass component, i0 The ultrasonic attenuation coefficient for the AI/AI-SiCI, lami- lation between the layer thickness and ductility has been observed in the UHCS laminates, as reported in FY-91.7 Fracture Toughness. Results of fracture toughness tests are summarized in Fig. 4 for both UHCS and Al laminates. For laminates of both systems, it is clearly demonstrated in Fig. 4 that the lamination of a hard material (UHCS or Al fl)61-SiCp) with a ductile material (brass or Al 5182) results in substantial enhancernent of toughness. For UHCS/brass, the laminates with thin (200 pm) layers show slightly lower toughness than the laminate; with thick (7_) pm) layers regardless of the specimen orientation, i.e., crack arrester or crack dMder, relative to the layers. This trend could be due to the influence of the interfacial delamination on crack growth. Studies have shown that the delamina- nate (266 dB/m) was greater than that for the UHCS/brass laminate. These results clearly show that LMC's can be more effective damping materials than their components. Descaled/C.D. ] Un-scaled/C.D. Descaled, o T61C.A. ] Descaled/C.A. ] I........ lo 2o [ 3o lo ...... (c) Crick divider (C,Di) orientation 6-4 Thrust Area Report FY92 _ Engineering Research Development I=UIii¢O Wock We are continuing to characterize the UHCS/ brass and AI/AI-SiC laminates regarding their (1) damping capacity in the audible frequency range, (2) fatigue behavior, (3) response toballistic impact, and (4) deformation behavior at elevated temperature. We are planning to make LMC's of other light materials such as Mg alloys, (a) containing a high damping capacity material as a component and (b) containing an intermetallic or superalloy as a component. These new lami- and Technology Processing and Characterizationof LaminatedMetal Composites _o Materials Science and Engineering hates will be tested for their strength, ductility, toughness, and other characteristics reported here for the UHCS/brass and A1 laminates. 5. O.D. Sherby, S. l,ee, R. Koch, l'. Sumi, and J. Wolfenstine, M,lterhllsan,tM,tm!thctlmn,_ Processes, 5, 363 (1990). 6. J. Cook and J.E. Gordon, Proc. Rollal Soc. Ix,ld(,1, 282, 508 (1964). We sincerely appreciate assistance provided by Chris Steffani for descaling Al alloys; Ralph Otto and Bill Stutler for pressing laminates; Dick Sites 7. C.K. Syn, D.R. Lesuer, K.L. Cadweli, K.R. Brown, and O.D Sherb_; "Prix:essing and Testing of Metal Composites of l[Jltrahigh Carbon Steel/Brass Lamihates Aluminum and Laminates," En,yine('ring Research,and Development, Technology, Lawrence for preparing test samples; Al Shields for conducting mechanical property tests; and Jim Ferreira for Livermore National Laboratory, fomia, UCRL-53868-91 (1992). metallography. 1. The llhid qfHomet, translatect by R. G]ttimore, University of Chicago Press (Chicago, Illinois), 411 (lines270-272), 1951. 2. E.S. Wright and A.P. Levitt, "Laminated Metal Composites," Metallic Matrix Composites, K.G. Kreider (Ed.), Academic Press (New York, New York), 37,1974. 3. C.K. Syn, D.R. Lesuer, K.L. Cadwell, O.D. Sherby and K. Brown, "Laminated Metal Composites of Ultrahigh Carbon Steel/Brass and AI/Al-SiC: Processing and Properties," Proc. Col{f[ D,'vehv,nents in Ceramicand Metal-Matrix Conlposites, K. Upadhya (Ed.), TMS, 311,1o91. 4. D.W. Kum, T. Ovama, J. Wadsworth, and O.D. Sherby, ]. Mech. Pilys. Solids, 31, 173 (1983). Englr_eerlng Livermore, Call- 8. O.D. Sherby, T. Oyama, D.W. Kum, B. Walser, and J. Wadsworth, ]. Metals, 37, 50 (1985). 9. C.K. Syn, D.R. Lesuer, J. Wolfenstine, and O.D. Sherby, "lalyer Thickness E_'ct Oll Dtlctih' Tensile Fnlctutv of Ultrahigh Carlnm Steel-Brass Mmillates," Livermore National Laboratory, Livermore, Califomia, UCRL-JC-110413 (1992), accepted for publication in Metall. Trans., TMS. 10. B.P. Bonner, D.R. Lesuer, C.K. Syn, and O.D. Sherby, "Damping Measurements for Ultrahigh Carbon Steel/Brass Laminates," Pivc. Syrup. Damping of Multiphase htorganic Materials (Chicago, Illinois), R. Bhagat (Ed.) (November 1-5, 1992); to be pubLI lished by ASM International. Research Development atld Technolot_Y .',, Thrust Area Report FY92 6-5 Casting Process Modeling 4. Materials Science and Engineering CarolingProcessModeling I Arthur B. Shapiro Nllch'arTestEllgineeri_g MechatticalEngineering In predicting the quality of a cast part, two important factors are (1) correct m(Kteling of the fluid flow and heat transfer during the filling of a mold with a molten metal, and (2) the thermalmechanical physics of solidification and cool-down. Determining the dynamics of the flow and the free surface shape during filling are essential in establishing the temperature gradients in the melt and in the mold. Correctly modeling the physics of volume change ota solidification, shrinkage on cooling, and contact resistance across the part-mold interface directly affects the cooling rate and, ultimately, the final cast shape and stress state of the cast part. This year our efforts were fcK'usedon modeling fluid fill and on the physics of solidification. i I_ Casting manufacturing covers a broad range, from the large tormage of continuously cast steel products, through the intermediate-weight output of superalloy precision die castings, to the relatively small quantity of high-purity crystals, Although this project benefits modeling efforts in each of these three casting areas, we have focused on modeling precision die castings of superalloy parts, Our approach to casting process modeling is to tt_ the computational fluid dynamics code PrcKSASTIto model elements of_themold-filling process, including tracking of (1) the free surface of the molten metal as it rapidly fills the mold; (2) solidification on the walls of the mold; (3) temperature transients in the mold; and (4) temperature transients in the liquid and solidifying metal. When the mold is completely filled with liquid metal, the existing temperature field at that instant in time is re-mapped (using REMAP 2)onto a new mesh for a CAST2D a ,analysis to predict the final cast shape, stress state, and defects. • ii i' _ . Figure 1. Exped. mental (a, b, c) and numerical (d, e, f) resuits for the filling of a spherical annulus mold, with a liquid metal at 0.6, 0.9, _: , and 1.5 s, respec. tively. i ii Engineering Researctl Development and Technology .',. Thrust Area Report FY92 6-7 MaterialsScienceandEngineering_ CastingProcessModehng ........... II III[I II . ;.; ;., , . .,,, J',.r/, . .... - .... "." "...... " •. ,_._ . , ' , , " ; ,_4,,/ ,.j _, ' I , ';*/':, , "" ", '#.' . _ I ____ ' .... '.'7.,,',.:, . , .... .Bj , .., .e ° '_.. "...._" ..... .-....., :,(-5 - . ,,' .... • .,_ .... ,.._i_. ::'-/. -;,.;.. _,_ .,-. Figure2. (a) CAST2D calculations at anearlytimeduringcool_lown, showingtheheatflowpathetobe radiallyoutward. (b) At latertimes: gapsbetweenthecastingandmoldappeardueto the-6.6%volumechangeofthealuminumcastingon solidificationandshrinkageoncool-down. (c) Thedirectionof theheat-fluxvectors,changeddueto thepartshrinkingaway fromthemoldonsolidification.Theheat.fluxvectorsareseekingthepathofleastresistanceto heatflow. CAST2D models the thermal-mechanical response during c_×_ling to r(×ml tempera_:re including volume change on pha,_ transformation, CAST2D also calculates thermal contact resis- heat, and viscosity, were allowed tobe functions of temperature. Results of the analvsis, are presented in Figs. ld, le, and If. These three figures show the free surface and level of fill at the same tance across the part / mold interface, times a s the ex peri men ta I res ults. The nu merical analysis does not show the wave motion and non-symmetry at early times as observed in the experiment. However, it does show the wall jet effect as the melt enters the annulus (Fig. ld) and a fill level that is near the average level of the experiment (Fig. le). At later times, when the flow is more even and syrnmetric, the analysis compares favorably with experiment (Fig. lf). We performed a fluid-thermal-mechanical analysis of the casting of a three-spoke, 38-credia aluminum wheel. The liquid aluminum at 780°C was injected into the steel mold, which is heated to 730°C, at a rate that fills the mold in two seconds. By forced convection, the outer surface of the mold lost heat to the environment. ProCAST was used to model the fluid-filling process. When the mold was completely filled with liquid metal, the existing temperature field at that instant in time was re-mapped onto a new mesh for a CAST2D analysis. CAST2D was used to nlodel the thermal-mechanical response during cooling to room temperature. Thealuminum undergoes phase change at 660°C with a volume change of-6.6%. The aluminum part is in good contact with the mold at early time. The heat flux vectors are seen to go radially outward (Fig. 2a) through the alun_inum part and mold to the environment. At a later time, the alumiili.1111has shrunk away from the mold due to volume shrinkage on solidification, and gaps have opened up (Fig. 2b). The heat-flux paths ,., An experimental and numerical analysis was performed to investigate the filling of a spherical mold witll a liquid metal. The experiment provided visual data of the filling of the shell for comparison with the numerical calculations. The die-casting process consisted of pressurizing a pool of molten metal in a crucible and forcing the melt tlp a small tube to be injected into the bottom of a spherical annulus-shaped cavity. The experiment was conducted in a vacuum, The experimental data consists of a 16-mn1 motion picture (24 frames per second) of radiographs of the filling of the spherical amlulus. The spherical annulus filled in approximately four seconds. Figure I shows radiographs at three different times during the filling process, The radiographs sllow that initially the melt splashes fairly high up the annulus (Fig. la) in a nonsymmetric fashion. Although still showing considerable wave motion at later times (Fig. lh), the melt is seen to be filling the annulus in a more symmetric fashion. At still later times, the fill level advances evenly and ';'ymmetrically tlp the annulus (Fig. lc). ProCAST was used to n.m_eric;:lllv model the mold filling process. The spherical anrlultls was modeled a:, a two-dimensional, axisymmetric problem. Fluid properties, i.e., density, specific _'0 Thrust Area Report FY92 "¢ Engineering Resuo_(:t) D(.'vOlOlJtnt;nt _*t)(/ f(_Chnolog_ CastingProcessModeht_g.:oMaterialsScienceandEngineering shown ill Fig. 2c are seen to be considerably changed from the pattern of Fig, 2a. The direction of the heat-flux vectors has changed while seeking the path of least resistance to heat flow. also plan to conduct dation. experiments for code vali- i. I¥oCAST '_' Us,'r_ Mare,al ¼'rshm 2.0, UI';S, Inc., 4401 Dayton-Xenia Road, Dayton, Ohio 45432- 2. A.B. Shapiro, REMAP--A Conlput('r Co,h' Thai l)',mqi'rs Nod(' h{li)rnlationBetweenDissintihlrGri,ts, l.awrt,nce l,ivenno_, National LaboratoD; l.ivermore, California, UCRHD- 1{_190(l_-_-J0). 3. A.B.Shapiro, CAS12D--A Finitet:.h'mentCompuh'r Codetbr Casting l_roc('ssModeliny,,l.awrence Livermort, National laboratory, l_.ivemlore,California, UCRL-MA-108598(1991). L] !_,4. Future Work In the future, we plan to develop a closely coupled fluid-thermal-mechanical code to be used for analysis of casting problems. Numerical modeling in the areas of fluid fill, solidification physics, and material constitutive development must be refined for stich a code to be useful in casting process modeling. We Et_lglrteerlt_[g Resu,_rch Dt3v(,lol) m(,n! ;a¢761 Tt,_hl_(_/o/_ ,:, Thrust Area Report FY92 6-9 Characterizing tl_e t;_flu_e oi Composfle Match, Hs ._. Materials Science and Engineering Characterizingthe Failure of CompositeMaterials Scott E. Groves, Roberto J.Sanchez, William W. Feng,and Albert E. Brow_ El_k, illeerilzy, Sciellces MechmficalE_tyiJteerilzg Steven J. DeTeresa Richard E. Lyon MaterialsDivisioll Cla'mistrymat MaterialsSciellceOepartme_lt Our goal for this project has been to characterize the three-dimensional (3-D) performance of continuous-fiber polymer composite materials, by developing new experimental and theoretical methtKts. This report highlights our major accomplishments: (1) mulfiaxial testing of composites; (2) the development of a new composite-failure criterion; (3) the development of ORTHO3D, a 3-D orthotTopic finite element c(_:le; (4) the dwlamic testing of composites; and (5) a helical comp_'ssion studv of filament-wound composite tubes. iii introdud_lOlll This project has helped to develop carbon-fiber composite materials for use in penetrating warhead ca_,s, gull barrels, advanced munition components, projectiles, nuclear weapons, SDI, and high-energy-density flvwh_._qs. We have had the opportunity to jointly pursue some of this work with various re._arch and development centers of the U.S. Army and Navv, as well as with various contractors in private industry. the primary reason for selecting carbon-fiber " composite materials is their high specific strength opment of ORTHO3D, a 3-D, orthotropic finite element code; (4) the dynamic testing of comp(,sites; and (5) a helical compression study of iliament-wound composite tubes. Multiaxial Testing of Composites Our m(_st iml.x_rtant accomplishment has tx__'n flaedevelopment of a unique multiaxial tt.,stsystem Wedge _ torquingbolts clude low 'Z'Other material composition, c(_-ffiand stiffness, factors influencing low design incient of thermal expansion, impact rcsistance, and _ Load r]_,_._L These materials are generally limited not by fire sa fetv. their performance capabilities but by our lack of understanding and ability to model their c(maplex 3-1_)response. Our research effort has made great end conesfor 15° flared gripping _-'-]11-- Our major accomplishments have been (I) muf tiaxial testing (_fcomp(Mtes; (2)the devel(_pmel'_t of a new ccmaposite-failure criterion; (3) the devel- _ .... _: h e_, _ attachment Figure1. Multlaxlal base _ .,,_ I / ! C _*"*_" _ strides in providing the necessary tools and infor- Grip test system forcom- Ix)site tubes. _ ,---, 2' washer Thrust " collar transfer _ Composite test specimen ma ti( _n t(_(}ptim ize these dt_,signs, f rr_, L ;, wedges 15° split Wedge securing cap compression plug _ I I! Internal O-ring seals i [_ Internal pressure _, t ()_'_,t'"_ _',! _ _"" "K, ":" Thrust Area Report FY92 6-11 Materials F/_m 2. kience and Engineering ..'. Characterizing tlm Failure of Composite Matenals Load deformultiaxi- -' load Axial T403 epoxy having a tensile strength of 10 ksi. This material system has been u.'_'d in tile majority of tile composite structures we have designed and fabricate_J. scrl_ at te_t_i_, Torque Laminate staT'_king sequence , The multiaxial gripping concept has lead to the development of an efficient high-strength shear joint for split composite pressure vessels and for modular 90* -45" \ o ............... 1/_ composite gun barrels. We have also Stackedlaminate Axialstr_s successfully .,_aled up the gripph'_g system to test 9-in.-dia composite tubes under axial load. The Hoop Shear stress cu._d on the optimization of the compression performanceu_ ofoffilament-wound tubular has structures, biggest this system, however, been losuch as those used for composite penetrators, projectiles, and support structures. _ epoxy cone for gripping New Composite-Failure Criterion ' Fig_Jre Multlaxlal _ilum 3. surface for a -|000 -500 Axial O stress(MPa) 500 1000 1500 1400 1200 fll_t-w_.,t_ ToraylO00/ ""' D£R332-T403/_+l.s, , /" +_4s.*_S91_rbon/ _ 1000 800 epoxyl_inaRe. ! 400 2.00 ¢,_ 150 / 2504_100_; / ," _ _.,,_ _ ///zi 6OO _. 2000 / , _1_2 _234 ; strains and the deformatkm gradients. Among the,'_' strain invariants, two are ffmctions of the fiber orientation, and three are not. Therefore, the 3 {' _ I failure criterion can be further dMded into two modes, the fiber-dominat¢__i failure and conthe matrix-dominated hilum m(gie. Themtxle criterion tains five hilum material constants for infinitesi- In the there are three quantitiesthe goveming theoiterion, failure surface in composites: disreal, general, 3-D strain states. torfional energy, the dilational energy, and the difference between compressive and tensile strengths. The minimum number of constants refor l:_lymer c(mlposite materials. I This technique quired is three for each failure mcx.le. Therefore, allows te_ting of 2-in.-dia coml:_rsite tu_ under a this failure criterion repre_nts the minimum numcombination of axial, torsit_n,and internal prc_surizaber of constants required for determining the failfion. The unique advancement with this system is the ure surface of composites for the ._,cond-order simple but efftvtive gripping mechanism that incorstrain-failure criterion. l.x)rat_ a 15_-I__ttt_i el_x_xycone h)r providing a We have previously obtained the unidirectionsmtx,th trartsition in load [x,two.,n tJaegrip and the :,1iamina failure surface for Toray 10{X)/DEIL332tc.st sF_<qmen. The tc.st swdmen itself is a straightT403 carbon/epoxy fiber composites) In this walk_.i coml_x_sitetun e. Diagrarns of the muifiaxial projevt, we have obtained experimentally the fungrip and test sl2<vimen are shown in Figs. 1 and 2. damental material properties for this t|nidirectionThis k,'st system has provide_.t Lawrence Livemlore al composite, both elastic constants and strength. National l_a[-_mt¢_n'(IA.NL) with an unrivak_,i capaThe corresponding strengths obtained by the Feng bilitx' to generate mulfiaxial failure data for t._}l,vmer failure criterion for s.vmmetrically balanced anglecoml:_site materials, pl}, laminates, is sh¢_wn in Fig. 4. The results show The most extensive multia×ial failure surface that the Feng criterion predicts the fiber- and mathat was generated with this system is shown in trix-dominated failure modes. Furthermore, for Fig. 3. The material system used in this study ct)n- Tr)ray 100(}/19E17,332svnm_etricallv balanced an,.i_!,- ,_f ria,, l-(mw. I(I_K; carbon fiber having a g,le-plv k .ninates subjected to uniaxial load, the 9_-k,4 tensile strength, in3preb,mated with DEIO32initial failure consistently initiates in the matrix. | '_ _- : 8-12 r.,ust Area Report FY92 , -- '¢:_(_ 5/,," ;_ F.xperimentaldata" --- Convexity boundary In this project, we have devek)ped a new failure criterion for composite materials, the 'Feng failure criterion. '2 The failure criterion is written in temas of the strain invariants in finite elasticity. The_ invariants are written as functions of the Cauchy _ f _'!_''_',''."2Ig ;¢t's_',_,,_ / ---/ _ D*';_',Ol_,,;_"; _ I ,_,,_; r_., _i_,(_oi, _, Characterizing theFailureof CompositeMaterialso:.MaterialsScienceand Engineering Development of ORTHO3D 40oo During the _,cond year of this program, we began an effort to devdol:_ a simple, 3-D, orthotropic finite element program for the evaluation of composite failure criteria. This algorithm has be- I , 3000 - _ ---_ iqgure4. Failure II I bytheflnite-strain-invariantfailurecriteristrengthspredicted onforToraylO00/ Matrix-dominatedmode I Fiber-dominated mode --] callybalanced angl_ OER332symmetr_ _:_ oped come under kdlOWn a university as ORTHO3D contract and with has Texas been deve[A&M Universiby. 4 in all, five failure criteria have bt_n i 2000 T_i-Wu, Hashin, and the Feng failure criterion. To perform accurate_al,uremodelingofa _ '_ laminated composite structure, ORTHO3D was writ- plylaminates. _ analysis of generic structures such as cylinders ten to permit detailed sub-lamina (single-ply) characteristic and cubes. These kx:al two volumes genericof shapes larger structures reprt_._nt such as penetrator missile ca_s or thick laminated ] 0 _ -_""-'"'""_m : plates. Performing this level of analysis explicitly with NIKE3D or DYNA3D is k×} cumbersome to becost effective. Furdlermore, largestructural anal- : "'_ [i* i "ii,'ii,i'I . [/ el the global behavior of a structure and mcKlel the IR / perform accurate local-failure analysis (locai/global mt_.ieling). ORTHO3D, k_cal which is written in Fortran,detail is opercharacteristic volume in st,fficient to " .Is0 ing Macintosh, Vax, and platforms, IBM. The includsize of ational on a,'arietvSON, ofcomputer ed only by computer memory. Even small local problems (i_Kalvolume) thai o.le can solve is limitvolumc.'s require an astonishingly large amount of memory. Typically, a single ply is 0.005 in. thick, and thelocalvolumeiscompo._dofmanyrdthese layers. Generally, we recommend a minin um of three elements (8-noded brick elements) through the thickness of each pl}, to capture representative kx:alstress/strainbehavior. Maintaininga respecfive aspect ratio (< 10) for each element, the number of elements required to model a k)cal volume can be reD, large. At 8 nodes per element and 3 degrees of freedom per node, the memory requirements can quickly exceed most small computers. Typical local volumes that we have solved require ~ 20 Mb of ram. Efforts ore1 the last year have focused on minimization of memory requirements via more efficient equations _flvers, nodal humber schemes, and array sharing, To facilitate the 34) modeling of composite structures, ORTHO3D was adapted to generate the effective, 3-D, homogenized pn_perties for the characteristic local volumes required by NIKF, for analysis of large (global) cornposite structures. The homogenized 3-D properties are considered more ......... representative of tl_c.,tctual .-,t. LILtLII ,li __L_l_d_.Át}[ I...... :" " of Er_g*r_eer,r_M _ ('_, :,_,:ii I",, |I _gure s. Hi_ strein_rate-t_arlng compr_sionof ril Withoutfixture I 0.25" x 0.25" "_i i;i:iii:i[: I taperedcubas. cubes _ _;-) ] BIO0 _-- _. iso_ " ,"-4 [,_, - 93 + 2.q 10g/* 0.238i' flog)2i - 0.074i'(Iog/'1 / el, , ,,,,,,I , ,, ....,I , , ,,,,,,1 , , ,,,,,,I. 0JI00_ o.o01 _ 0.1 :10. " Sbmln_(btdl_t) the local volume than those properties predicted by available, 3-D, micromechanical constitutive _lutions. Once NIKE mix,es the structural problem, the kx:ai traction set can be passed to ORTHO for detailed failure analysis. Dynamic Testing of Composites To provide design support of the composite penetrators, gun barrels, and projectiles being developed at LLNL, we have evaluated and developed a variety of new high-strain-rate testing techniques for polymer composite materials. _ Prior to this investigation, an extremely limited data set was available on the high-strain-rate response of polymer composites. We have successfuily generated strain rate data from O/s to 300()/s in compressi_m and 0/s to l(}()/s in tenNIOI'I, tlSil'Ig a "" ",,h, ,_,, machines. " ,,n,_,_ of t"_'t Ot, r el- Rt.s¢',_r¢ h Dt'_,'lopme.t ;trot! le_t}t_olt)#;_ + Thrust Area Report FY92 6-13 MaterialsScienceandEngineering4. Characterizing theFailureof CompositeMaterials .g._ 6. St_in rate sensitivity 'i:i!_i oft_ I'"'i';_' """i" il_i[-- | averagem_dulusfor Average modulus values __ oxy.DERX32"TZ_3 ep. """I' ' """1" '""_" '"'"f"' ""'1 _1] li between5 and 10ksi stress - - Tensile,nodulus - - Compression modulus - ]._.[ ] that were co,web,cd with the quartz load cell data. _CJecond,a high-speed data-acquisition system was developed that significantly automated data gath- eringfi×tuwand reduction. Third, a precisiOnwith alignment was developed ah,ng precision-machined test specimens, whicll resulted in a signifiof the composite materials as well as minimized I Thn._.' interesting results from our efforts are presented. Aliofourexperimental results indicate an increa.'_, in bothstrength and modulus with _=,.,._.__,_;_;=a_ 400 - _ 2_1c"""'J ,,,,,I .... •0.m_ .... 0,0el''"'''_e.01' 0.1, ,,,,,,,I 1 , ,,,,,I 10 , iJ,,,,J 100, ,,1000 Strainrate (l/s) ......... _ ..... compressive flow stress forthree ._an-i w epoxyresins. | ' 'I I -" Anhydride95°Cl'pnxy / -- -- DER332/'I" 403/ _ -- _._. _i I _ i _/i Compression _ -I i00 1000 forts have yielded some very interesting and encouraging material responses, M(_st of our efforts f(_:tl_,d on devehlping an acoustically damped, high-energy drop tower for evaluating the high-str,fin-rate compressive performance of composite materials. Three maj(lr advances occurred to the drop tower system thai creatc,d a highly capabh., material-evaluation system. First, an acoustically damped ba_' system was installed that eliminated spurious shtvk waves . TaMe1. Basicepoxyproperties, Gm Iii s¢,flow Iksi) ty ( Viscosity Iii) T(_ ) of Filament- wrapped carbon/epoxy tribes I'was perfornled tlSing the th ro., d itferc,nt epl)xy resins sl'uiwn in Fig. 6. tion (,f the compressive perforn,arlce of Iu.,lically The objective (if this study was tl) optimize the conlprt_sion 0 --j 1 I I I 0.00010,OOl O.Ol o.1 l lO Stralnrale (InJlnJs) Study Wound Composite Tubes l)uring the lasl year of this progrnnl, art evalua- , Epoxylysteln Finally, Fig. 6 shows strain-rate _,nsitivity effects Oil the compressive flow stress of three different epoxy resin systems being evahlated at lJ.Nl_. Helical / i ao -- terial is pre_,nted in Fig.(x:curring 4. This result reveals significant st|'e|lgtheni|_g at strain ratesa above I()/s. An examination of neat resin behavior revealed similar trends. Figure 5 shows the change in neat resin nli)dulus as a function of strain/'atc. ..... _ :i' "' ...."1 I I ' l - -- MY0510/HY350 Rgum 7. Strain ratesensitivity effects on the increasing the bea|'ing compression strengthstrain of a rate. [(I,90]First, laminated composite ma- perfol'llla11ce of fi lalllellt-WoUlld CO111- posite structures. Table I lists the basic properties of the_, systems that influence, the compression strength of composites. The last two cilltlnlns in Table I ii re prilcessing pa ra meters. The compressive strength ota unidirectional composite material is controlled by the properties of the matrix surrounding the fibers. Ii has been argued that compression of unidirectional compigsties is a micro-buckling t'()nh'olit'd event ill the fibers, and thus dependcull i)ll factors such ns the hvcal shear modulus (_fthe matrix. What we were hoping to find was an inlprovement in comprc, ssion strength of helical composite tubes fabricated with the MY(1510-1tY35()epoxy system. Figure 8 shows the vari,ltion in axial conlpl'essiiin strength for T()ray 7IX)[gg,-t_(),,--Hg]helically wrapped con'iposih.,stribes ,Isii function (If helical angle, 0. l'hese tests were cllriduc'ted using the multiaxial gripping system. The MYI)51(i system I)ER332-T4(13 16() 12 (_.5 till 7.8 rnigllt be ciulsidered lo be' Sll'iillgt'l', but the evil.lt'lice iS l]lil t'iint'lusi\'e, a pl'iiblt'lll with pi)lylller Anhvd ride 18() 1H g,7 14() 3.4 MYI)SlI)-iIY35(} 2()q 21.1 1().7 18() I.l c'(mlp()site m,iterials is that ii is impt)ssible t(_is().................................................................................................................................... late singh' variables. 'l'lle viscilsilv (if lhc epilxy 6-14 Thrust Area Report FY92 s_ t _t_tll_,_,l_l,p, Ht.,,p.lr_ h l;_'_'lOl_m,'t_ ,_.<1 I_,_ t_tlo/.if_ Characterizing theFailureof CompositeMztterials*:* MaterialsScienceand Engineering -120000 I Y ' : F' "Characterizing tilt, Failure of Coral: osttcs will bt' to modify ORTHO31_) to model Iong-ternl ther- I mal-viscoelastic efft'cts for the_, materials. The multiaxial test specimen developed in this pro- "_"_ilm "11_1000 _ for long-term fatigue testing becaum, of the lack of a free edge associated with the cylindrical test gram has been .,a?lected as a prime test specimen LLNL weapons-related specimen" Finally' we willactivities c°rltinue int° composites, SUl:)p°rt the "1_ _ l -.40000 - - anhydri that will make significant use of the multiaxial test I-2_ _j_l( ::_H_i_I J lO 20 30 40 $0 Helical ansle Rgure8. Normalized axialcorn#'essionstrengthforT700 189,±0,--89]helically wrapped carbon/epoxy tubeswith threedifferentmatrices, 0 turned out to be a major factor as weil. The MY0510 system has a mucla higher viscosity than either the Anhydride or DER332 epoxies, which makes it very difficult to p rtx:ess. This resulted in a composlte material with higher void contents and resinrich areas, in contrast, the Anhydride epoxysystem produces very high quality composite materials, specimen. i. S.E. Groves, R.Sanchez, and W.W. Feng, "Multiaxial Failure Characterization of Composites," especially in the area °f c°n_pressi°n °F)timizati°n' Comp(,sites: Design, Mmn(/hchtre,and Applicaliiut, S.W. Tsai and G.S. Springer (Eds.), l'ro('. Sth IIII. Ciu{/iC(mtt;osih'Mah'rhlls (published by SAMPF,), (July 1991). 2. W.W. Feng and S.E.Groves, On the Finite Strain hn,arhutlFaihm'Crih'ritm.lbrComp(_sih,s,Lawrence Livermore National l,aboratory, l,ivermore, Callfornia, UCRL-JC-104825(1991.)); accepted for publication in ]. Comp(_s.Mahv: 3. 4. M.A. Zocher, D.H. Allen, and S.E. Groves, "Predicted StiffnessComposite Loss Due to Delamination in Filament Wound Cylinders," C(mtposih's: t)t,s_,,,,Mam(fiwture,andAlv;lication,S.W.l_ai and G.S. Springer (Ed,;.), Prec. 8rh Int. Con[ C(nnpos. Mater (published by SAMPE), (July 1991). 5. S.F.. (axwes, R.J. Sanchez, R.E. Lyon, and A.E. Brown, "H_kqtSlrainRah'l_ff{'clsforC(_mp(_sih'Materhils," l,awrence IAvernaore National I.aboratory, I,ivermore, Ca lifornia, UCRL-JC-107836(I 992);accepted for publication in ASTM C()mt_osih'Mah'ri- A somewhat surprising result was the small variation in compression strength at helical angle between 0° and 10°. Again, pr(vcessing influences these results; it is very difficult to achieve until)rra part quality for helical winding angles less than 10':'.Furthermore, helical angles greater tl|an 1()° a re much faster (chea pet') to hbrica tc. _I_I'Q Work We have ._cured 6. a long-term Cooperative Re- .,a_,archand l_)evelopment Agreement with Btwing Commercial AirpianeGroup tostudy the"Strength and l)urability of CtiiatiiaLious Fiber PolynlerComposites." Natural extensions of our past efforts iri [ngttlc,_,,tiHg W.W.Feng and S.E. Groves, 1.AdvancedGmtt;osit,'s Letters I (l), 6 (1992). Rest,;it(;h als: "[i'slin,_,, and l)es_k,lt (I 992). S.E.Groves, R.J.Sanchez, and S.J.DeTeresa," Evaluation of theCarbon/F_poxy Ct)repressive I)erformance (If Helically Wrapped Tubes with Three Different Epoxy Matrices," presented at the ASTM Sympr)slum: Compression Response of Composite Structures, Miami, Florida (November 16-17, Itit)2)' L_ Dttvolopnl(tnt iind l(_chnolo_,V ,',, Thrust Area Report FY92 6-15 Fiber, Optic Ratnat7 Spectroscopy for Cure, Monitoring oi Advanced Polynter Composit_.'s o:oMaterials Science and Engineering Fiber4)ptic Raman Specb'oscopy for Cure Monitodng of Advanced PolymerComposites Richard E. Lyon Mclterh#sDivish,z ClmmistryroutMaterials ScieJtceDepartmeltt Thomas M. Vess and S. Michael Angel EJivirolunel#alScie,,s.cesDivisiolt M.L. Mydck Department_Chemistry Uitiversity((South Carolilm Cohmtbia,SouthCarolilm The curing reaction of an epoxy resin matrix that is used h)l"wet-filament-wound composites was monitored using Raman spectroscopy measured over fiber optics. The resin system consists of the diglycidyl ether of bisphenoI-A in combination with a polyethertriamine hardener in a 1:1 stoichiometric ratio. The extent of chemical reaction of the epoxy as a function of time was measurable through changes in peak heights of _'veral vibrational modes. A Raman peak associated with a phenyl ring vibration in the epoxide component was used as an internal reference to correct for density changes and instrumental variations. The feasibility of simultaneous temperature measurements was successfully demol:strated with the same fiber optics u,_d to obtain the cure chemistry data, by measuring the intensity of anti-Stokes Raman ._attering from the epoxy, i ii introduction sensors for automated control are currently limited to dielectric 1,2,3or ultrasonic 4 measurements, Although significant improvements in the performance of fiber reinfl}rcements and polymer naatrix materials have been achieved in the past decade, composite processing technoiogy hasnot kept pace with tl-le_, advances, ConseqLlent/y, high-perfof mance material properties are not realized in composite parts fabricated using ctlrrerlt processing meth(_Js, and manufacturingcostsarelfigll.'Smart' processing of thermoset matrix composik,s could dramatically reduce manufacturing costs by reducing the rejection rate and improving part quality, through cLire cycle (_ptimization and '()n the fly' process adjustments to account for variations in the chemical composition of the starting maleriills. Unforttlnately, commercially available cure which sense only mechanical property changes in the resin and cannot provide a direct measure of the cure chemistry in the composite. Furthemlore, recently proposed fiber-ol:_tic spectroscopic sensots using mid-infrared , , or ultra_ lokt-_ isiblt; , wavelengtlls areeitller prollibitively expensiveand yield littleor n()additional inf(wmati(,1 when compared with c(mlmercially available cure sensors, or contain a large number _)fspectral interferences that make data interpretation difficult, if nc_t impossible, li) 14amanspectro_'opy isanestablished technique ft," the analysis of polymers, 11,12,13chenlical reactions, 14and thermil_,iting plllynler conlposite t'tll'e I'eactitil_S.I_,1_'Ii has nlally advantages over mM- ,rtlgtnr>utltl[.J fTese,lt_h I)¢,vr, l_ll_m_tlt ,It_U ll,( llr_,Jllll{V oi• Thrlist Aren Report FY92 6-17 Materials Science and Engineering .:- FiberOptlc Raman Spectroscol)_hm Ctne Monitor, lg of A(lwu_codPol},nlel Composites li nii n in Figure1. Experifordual-fiberprobe geometry. Inset emphasizessample I(_ mental arrangement cation. M: spectr_ graph, D: detector, L: lens, S: laser source,FO: fiber o1> tic, F: filter. S [_ _ _l i F M I .... stlurces for cure n-|oriitoriilg was dt'rnorlstraled iii comparison studies with a conventional Ti-sapph(re laser operating at 81CJ-nm wavelength. We also demonstrated for the first time the proportionality between Ramarl peak ratios and t'poxide group concentration in full density epoxide resins, validating the Raman scattering technique for thermoset resin cure monitor(Jig. and economical, di(_.te la_,r-excitation _lurcescoinmonly used in commuilications and electronic Experimental equipment. 17 Subsequent to monit(irirlg the cure reaction of the composite matrix, the quartz optical fibers could be used as embedded strain or damage sei-ls(li's, or used for monitoring chenlical degradatioil or moisture absorptioil of the resin, t:Y-c)2, the firsl year iii the project, Ra- l'he epoxy system studied was a i:1 stoichiometric ratio of diglycidyl ether of bisphenoI-A resin(Dl!R332,1)owChemical)andapolyoxypropylene tr(amine hardener (It, ffanline T-4()3; l'exaco Chemical) in a weight ralio iii 1()()/45 reshl/ hardellt, r. A detailed characterization (if this epoxy has been repolied elsewhere. I,l,21) The dual-fiber pilib(, expt,rinlt,nl is sllliwn in Fig. I and hasbeen described in detail elsewhere. Ix man-active vibrational bands in epiixy resins were identified, and tentative band assigllmellts were made for tilt' epoxide ftlncliiil]al gr(itlp al'ld the phenyl ring backbone, from model conlpotind st(idles. Cure nlonitoring of standard epoxy resins was denlon._trah.,d using several meter lengths iii 2()()i.im-dia quartzoptical fibc,rusiilgeithersinglefiber iii" dual-fiber probes.lV_ l'he single-fiber probe experiniellt._ were di._t'(ii'itillued due t(I prtlblc, il'is l)tlai-fiber Raman probe._ consist of two fibers, side-by-side, cemerlted in piace between two micriist'(ipeslidess(iasttlnleetatanangletlfapproximately 15", with the polMwd probe eilds iii" the fibers extended several millillleters bevond the lep slide, as shown in the in,_et uf Fig. 1. (.)he fiberoptic wa._ tl._t'd to transmit the laser Iii the epoxy sample, while the olht, r was used Iii collect the Ral-nail ._cattelil'ig tronl lhe sample and tl'allsmit ii with high fiber background and the inability io accurately olrrect the data.The utility iffeconilmi(al near-hlfrared (NIR) dkltte lasers as excitation i_lhedelecii_iilsvstem, l)ual-fiberprobecurenlc,asuienlents were ill<ltir' bv Ihlu'litlgllly mixing (he liquid epllxy cllmt_ilni,l_ls, and lht'n adding a drilp l)uring Thrust Area .......... infrared absorption and UV-visible flut_rescence spectroscopies for polymer composite cure monitoring, includingbroaderapplicability, potentially higher sensitivity and selectivity, as well as the freedom from large background corrections cau.'.__'d bv fiber absorption. More(iver, I,_aman spectroscopic measurements can be conducted remotely and in situ using rugged, inexpensive, fused silica optical fibers (availabk, from domestic suppliers) Progiess 6-'JLS ... Report FY92 _,. ! ng_l_,et_llt tre_;_'arcn L)ul¢'_l._m¢.,_l .,,_i ;"' l'"*';,'r;_ Fiber-Optic RamanSpectroscopy for CureMonitoringofAdvancedPolymerComposites..'. MaterialsScienceandEngineering of the epoxy mixture to tile probe tip so as to cornpletely cover tile sensor. No effort was made to de-gas tile epoxy before injection. Some air bubbles a ppeared d uNlg processing, but these did not appear to affect the signal quality. A cover slide was then placed over the probe area, using spacers to provide a 2-mm gap filled with epoxy, and the entire assembly was placed in a temperature-controlled oven. F/gure 3: Isothermal • eli"._ _'_e_ tln_. Solid and open • circlesaredatafrom diode-laser and Tl:Sapphlreqaser Ra. manexperiments, respectively. • : • ."• _,_.. 0_0:iI ' • _L"'r:_'_:': '_':'_:'ff_ '. Results and Discussion Separate Raman measurements of the DER 332 resin and Jeffamine T-403 hardener components revealed that the resin component scattering was approximately three to five times as intense as that of the hardener, so that in the 100/45 w/w ratio used for the epoxy cure studies, the resin scattering is dominant. Figure 2 shows a series of in situ spectra obtained during a typical epoxy curing, These spectra are averages of spectra accumulated over several minute intervals. Measurements at one-second interx,als yielded comparable results and confirm the potential of this technique for realtime cure monitoring. One major peak near 1112 cm -1 remains relatively constant during the curing process and can be used as an internal standard to correct for fluctuations in the sample density, clariO,, refractive index, and instrumental factors during measurement. This peak has been associated with an asymmetric breathing vibration of the aroma tic rings in the diglycidyl ether of bisphenol-A epoxide resin. Several peaks disappear or shift during the curing process, while sereral new peaks appear. The most obvious change is in the peak located near 12'40cm -1. This peak loses much of its intensity during the cure and can be assigned to astretchingvibrationoftheepoxide ring. Although all of the peaks appeared to change ReferanCeband _ _ a_ ofcure(_) forepoxyat 90_Cvs . " in absolute intensity, probably in response to the changing density of the epoxy as it cures, the ratios of the 1240 cm -1 peak to the 1112 cm -1 peak decrease smoothly as a function of time. Figure 3 is a plot of two sets of Raman data for degree of cure, R(t), vs time for an isothermal cure at 90°C. Both experiments used the 2-mm sample thickness, dual-fiber probe arrangement; however, one experiment used a TJ:sapphire laser while the other used a diode laser. The agreement between the duplicate cure experiments is seen to be excellent, indicating a high degree of reliability for the technique. Moreover, the trend of R vs time closely approximates previously published degreeof-cure data for this same DER 332/T-403 epoxy, 19 using NIR absorption spectroscopy 1° at slightly different stoichiometry, temperature, and sample thickness. In addition to the peak height changes, the peaks were seen to shift to lower energy as the cure progressed. The total shift was small (approximately 5 to 20 cm -1), but was reproducible. A study performed on a previously cured sample showed no change in vibrational frequency with temperature. Consequently, the peak slrift to lower energy during cure is not simply a thermal phenomenon, but may be caused by a change in _ i _I , ,, /. b.andEp°xlde i_ " _'::'" 12 •- 8 _ -° l.o_,,_ 80O 1000 1200 1400 Raman shift (cre-1) 0 1600 Figure2. Seriesof corrected,dual.fiber probe,Raman spectrafortheepoxy,takenimmediately aftermixing (black),1.2 h at 75_(gray),and2.2h at 75_Cfollowedbya 1-hpost-cureat 9(TC(white). Engineer,rig Figure4: Anti-StokesRamanspectrumof thecuredepoxy, superimposed onStokesRamanspectrumfora temper& tureofIO(Y_C. Research Development and Technology .'.. Thrust Area Report FY92 _.1S MaterialsScienceandEngineering.:oFiber.Optic RamanSpectroscopy for CureMonitoringof AdvancedPolymerComposites tile kx:ai environment as the curing prtx'ess occtu.'s. For example, the increase in viscosity during the curing process may stiffen the local environmerit and mix the vibrations of the individual monomers more strongly with low frequency bulk vibrations. If this is the case, it is conceivable that this phenomenon could be used as a measure of kx:ai viscosity, but this possibility has not yet been tested, The measurement of sample temperature by comparison of Stokes and anti-Stokes Raman _attering (see Fig. 4) is straightforwaM and readily accomplished. The theoretical ratio of the intensities of the anti-Stokes (IAs) and Stokes (ls) scattering is IAS Is = exp IV(0) v(i)] 4 {-hcv(i)} v(O) + v(i) kT (1) ' Area Wink Future work will focus on (1) refining and rainiaturizing the sensor; (2) evaluating the Raman fiber-optic technique for monitoring other thermoset polymer cure ci|emistries; (3)performing measureme|_ts in thermo._t matrix fiber composires; and (4) developing simultaneous, multi-point sampling capability. Ba_d on the preliminary resuits presented ieathis paper, we feel that in combination with compact new instrumentation and economical diode-laser excitation sources, fiberoptic l'laman spectroscopy can be used to configsystem for an automated, polymercompositeproure a rugged process monitoring and control duction environment. Ackm_wledgements The authors would like to express thanks to Gerald Goldstein of the Office of Health and Environmental Research (RPIS No. (D3906) for supporting a part of this research, and to Katherine Chike of the University of _uth Carolina for experimental work in validating this application of Raman spectroscopy. the iu situ temperature of the resin system at any given time during a cure cycle. The precision of temperature |neasurenlents is limited by the sig- 2. scribed here, by using high-perfornaance optical filters and also by using longer integration times. In summary, fiber-optic Raman spectroscopy can be used for remote, in situ monitoring of the reaction chemistry and temperature of epoxies used as matrix materials in fiber composites during the cure cycle. While single-fiber probes were found to suffer from fiber-background effects, dualfiber probes having dimensions on the order of 2001.tru have been demonstrated successfully, Moreover, the quality of the spectra obtained fl_r the epoxy is sufficient to warrant use of the dual- Thrust Future where v(0) is the laser frequency; v(i) is the vibrational energy of the i-th mode; and h, c, and k are Planck's constant, the speed of light, and Boltzmann's constant, respectively. For the epoxy system studies here, a plot of the natural logarithm of IAS/I s (using the 829+_3cm -I vibrational mode) against the inverse temperature, 1/T, for temperatures ranging from T = 294 to 455 K yielded a straight line with a slope of 1200 K, an intercept of 0.517, and a correlation ct_2fficient of 0.997. This calibration curve can now be u_d to determine nai-to-noise ratio of the much weaker anti-Stokes peak (S/N = 20 ieaFig. 4). An uncertainty in temperature, AT -- +5 K, at 373 K is estimated from the relationship, AT = T2/[ B(S/N)], obtained by differentiation of Eq. 1, where 13is the slope of the line. However, the accuracy of temperatu|'e measurements can be improved over the results de- _'20 fiber Raman probe as all in situ quality control technique prior to cure mo|fitoring. Report FY92 .:" Etlgtnot.,tln,q Rc'search I)t_v¢_lopmot_t 1. P.R.Ciriscioli and (,.S. Springer, SAMPE/. 25 (3), 35 (/989). W.Sichina and D. Shepard, Malel. Eng., 40 (July 1989). 3. 4. 5. 6. 7. anH I).R. Day, D.D. Shepard, and A.S. Wall, "Thermoset Process Control Utilizing Microdielectric _nsors," Proc.ASME Co_¢fAdvanced Compositesand ProcessingTechnology(Chicago, Illinois), 1(November 27-December 2,1988). S.S.Saliba, T.E.Saliba,andJ.E I.anzafame,"Acoustic Monitoring of Composite Materials During the Cure Cycle," Pr0c.34lh Int. SAMPE Symposium 34 (1),3,7 (1989). R.E._hirmerand A.G.Gargus, Am. l_tborah,?137, (November 1988). I_.R.Young,M.A.I)ruy, W.A.Stevenson, and D.A.C. Compton, SAMPE ].25 (2),(1989). M.A. Druy, I.. Elandjian, W.A. Stevenson, R.D. Driver, GM. i.eskowitz, and L.t!. Curtiss, "Fourier-Transfl_rm Infrared (Iq'lR) Fiber Optic Monitoring t}t: Compt_sites I)uring Cure in an Autoclave," SPIE Proc. Vol.I 170,Fiber()ptic Smart Slrt,'hm's and Skins II (B¢_ston,Massachusetts), 150 (_,ptember 5-8, It_89). let:hnology Fib_-:r (.)plJcRiemann Spectroscopy k:JpCurt, Momtom_t4_t Adv,mced Pol)/m_,lCompos/tes o_oMaterials Science and Engineering 8. R.I.. l.evv ,rod S.I)..%'hwab, l'0/j/m. C,_mt_os.12 (2), t)(.,(1_.)_.)15. _-J. N.H. Sung, V. i_)nng, and 1I.I. I'nik, "h+ siltl Mtmitoting of Epoxy Cutv by l:iber-(._ptic Molecul,u" ._.,l"lsors,"l>roc..3(_1/I Int. SAMI>I7 5Rmposimn36 (2), 14(,I (It)_l). i7. S.M. Angel, M.I .. Mvrick, ,rod 'i.M. Vt,ss, "l¢,emt_tt, R,ml,m ."4pectrt_sct+pyUsinlg I)it_de I,,lSel'S dlld I:iber-t.)ptic I'robes,'l_rt_ . Sl'Ill '5_1,( )l_lit+flA+l+'th<_+ts /irr I.IIh'ast'nsiti_,e 1)ch'cti_,J,,mM/Xn+&lsis: "li'thniql,'s mM ,'Xt_plic_llit_ns (I ,t_sAngeles, L'aliiort_in), 143£ 72 (it)91). 18. M.I.. Mvrick, SM. Angel, R.I.I.i .y_,l,,md 'I:M. Vess, .c'AMIq_ I. 28 (4), 37 (It,_t._2). 10. H. i)annenberg, SPE "l)'mts.3 (I), 78 (1%3). 1I. !).1.. (_,errard and W.I'. Maddams,/ll_pI. 5t_cctrosc. It). '1'.'i'.(.'hiao,md R.I,. Moore, "A I_,(_om-'lbmper,_ture Rez,.22, 251 (It)8(_). Curnbh., l:.poxy for Advnnced (._'_m_pt_sites," Prec. 12. W.F. Maddarns, Amerh',,,_,.l.,,'tl_or.,'flor)l (Mmvh It._14(_). 291h /'_mm_fl"li'chnicolC'_,_t/:Rcin/i_rc_'dI_laslic.,.;/C_m p_sitcs Inst., .":,PI,.%,orion lt'-,-B,I (It)74). 13. C.E. Mille_, [).1). Atvhibald, M.I_..Myrick, and S.M. Angel, AppI. Spcclrosc. 44, 12_-.17 (19_-)()). 2(). F.M. Kong, C.M. Walkup, and R.J. Morg,u't, "Structure-Property i,_elationships of l'olw.,tl'_erlinmir,.,14. W. Doyle and N.A. Jermings, St_cch'(_SCOl_._l Inl. J. 5 Cured l_isphenoI-A-diglycidyl l{ther I_poxies," (1),34 (It)t)()). I'.t_o. W Resin Chemish',qII, R.5. I_,mer (Ed.), ACS 15. C. Johnson and S.l.. Wunder, S/1MI-'I_ I. 26 (2), I_-_ (I_()). Syrnposiun_ .%.,ties221, 21 I, 1_-._83. 18. J.C. Jolmsor_, l:T-Rmnm_ Ini,est_wth_n olO,'i,,_; Reactions in PoOliHtid_%I'h.D l)isst, rtati_,n, "IL'mple University, Philadelphi,_, Pennsvh'ania (It_t)()). l n_l_'e_t_l' ti'(',i(.n_ h I.)ev_'l,,l_n_'_t ,_nO I_._ h_,,l(_t'_ .'." Thrust Area Report FY92 6-21 Modeling Superplasttc Materials o:o Materials Science and Engineering Modeling Supeq)lastic Materials Donald R. Lesuer, Chol K. Syn, and CharlesS. Preuss EllgineeringSciences MechanicalEngineeriJ_e, Peter J. Raboin NuclearE._#osives EJtgillwriny, MedtmticalEltgipweriJtg We have developed a model that accounts for grain growth during superplastic flow, and its subsequent hffluence on stress/strain/strain rate behavior. Our studies are experimentally based and have hwolved two different types of superplastic materials: a quasi-single phase metal, Coronze 638, mad a microduplex metal, ultrahigh-carbon steel. We have studied the kinetics of straha-enhanced grain growth in both materials as a function of strain, strain rate, and temperature. An equation for the rate of grain growth has been developed that incorporates the influence of temperature. Our model integrates grain growth laws derived from these studies, with two mechanism-based, rate-dependent constitutive laws to predict the stress/strain/ strain rate behavior of materials during superplastic deformation. The material model has been added to the NIKE2D code through an enhancement of the Deformation Mechanism Model. The predictions of the model have been compared with data from several experiments. I_d_Olll Superplastici_, is the capability to deform crystalline solids in tension to unusually large plastic strains, often well in excess of 1000%. This phenomenon results from the ability of the material to resist localized defomlation much the same as hot glass. The material also deforms with very low flow stress. Thus, materials with superplastic properties provide the opportunity to form complex components into shapes very near final dimension. This greatly reduces machining and material costs and minimizes the amount of scrap produced, Superplastic materials exhibit high elongations, because adeformationmechanismknownasgrain boundary sliding (GBS) is active. This defomlation behavior occurs within a relatively narrow range of temperature and strain rate. If the strain rate is too high, then a different mechanism called diffusion-controlled dislocation creep (slip creep) is activated, and ductilities are substantially reduced. On the other hand, if the strain rate is too low, then a deformation mechanism known as diffusional flow prevails, and the ductilih, is also reduced relative toGBS. From a commercial standpoint, forming components at high strain rates is attractive, because operations can be done with Engtr_¢'er,ng less time and cost. Often this means superplastically forming at strain rates close to the slip creep regime. Thus, our work is concentrating on the two higher strain rate regimes, GBSand slip creep. The active deformation mechanisms also depend strongly ota the microstructure of the naaterial, such as an ultra-fine grain structure. Unfortunately, tllese ultra-fhae grains can grow during deformation, resulting in the loss of superplasticity. Thus, it is important to gain a quantitative understanding of this process and its influence on material forming. For these reasons, material models for the constitutive behavior of materials during superplastic flow should account for microstructure, its evolution, and changes in deformation meclaanism throughout the deformation history. The objective of this project is to develop a model of these structural changes and their influence on stress/strain/ strain rate behavior, using mechanism-based constitutive laws. in our work during FY-91,we (a) established the kinetics of strain-enhanced grain growth for isothermal conditions and (b) developed a model that integratesthesegrain growth laws with mech- Resoa_cl_ De_elol) nlont at_ci Technolog), .:. Thrust Area Report FY92 6-23 Materials Science and Engineering _. Mc)dl,ll_Jl.,, _(lll_,ll_/,l_fl("M,Ili'lhl/._ I __ IJ li ........ I , II ...... till . . III __ III (al 6-24 Thrust Arell Roport I_I I lbl FY92 .:. t _ll:_,_,.,'_/'. h*_,',l',ltl n Ill, il, f,;_il_ll, ll! ,lllll _., tplil,/_,llt li .... IIUl I ModehngSt:iJetp/ast_c Malenals o:oMaterialsScienceandEngineering iu o. f .yl 0.7 ( (;i (;BS/Slil) , 0.6 __ annealing limit - / .,'_'_-d OA .............. .001s-' -- 0.3 _ -- .01s-t __ ..........! _-' -- .......................... Slip -- 0.1 01 / 0.5 1.0 limiting . rate _ / ""0.2 t///ll region I 1.5 I 2.0 u/do _ _lildo cia/de.'" Lo_ (i') 10-2 ] I _ • Cu-Al-Si-Co (this study) - 550 C l Cu-AI-Si-Co(this study) - Oil0C 2.5 _" 10-3 -- 0_ Cu-AI-Si-Co_ Cu-AI-Si-Co(this study)" Strain Figure2. Normalized strain-enhanced graingrowthvs strainforCoronze superplastically deformed at fourtrue [] _ " 650 C / After Caceres . Sn-B, strain rates. Oon,lnant deformation m_hanlsm is noted for each straln rate. - _,, •ss/ [3 ""_ _s J ,,."_']t .- 0 Z -Al I a.dWilki.so,_,::i ......... A TI-AI-V I /'_-'"' _ C.-P ! .d-'. i_'f " II S.' ing. Tilts suggests that the kinetics ofgrain growth are detem'iined by the kinetics of carbide coarsen- ' 1o-4 _ ,_ _, ....................../_,s' irnportance of this grain growth on the deformaing. The stress/strain curve in Fig. ld shows the tion behavior of UHCS: increasing the grain size 1 ;_ from its(1.48btrn) initial sizehas (0.74lanl) to tl-,.,size at a strain of 1.42 raised the flow stress from 5 ksi to over 9 ksi. Thus, grain grow'th has pro- ./_....:_.-/s.... ,'"" " , " " 10_s D .................... / " O'S` o's _] l 10-3 Strain rate(s-1) l 10-s 10-_10-7 Slip creep_ dominated GBS dominated 10-t fluced significant hardening, and the grain size is an irnportant parameter for characterizing the current mechanical state ¢_fthe material. Figure3. Normalized graingrowthratevsstraMratefora numberof quasi-single [tl the_, studies, static armealing grain growth (normal grain growth) and strain-enhanced grain growth are assLimed to be additive, Thtls, the kinetics of grain growth can be expressed as phase andmicroduplex superplastic materials. Plotisfromthe work of Caceres and Wilkinson. 2 Datafromourstudyof Comnze at 550 C, 600 C, and650C havebeen addedto theplot. Thestrainratesoverwhichthereis a transitionin deformation mechanism fromGBStoslipcreep,areindicated.Theinsetshowsthethreedifferent regions for thecurve. ti dr) - ,'t,,. +--=-, 't_1 'tl_ tia (1) where ei is the total rate of grain growth; !ia is the grain growth rate due to static annea!ing; d,,, is the grain growth rate dtle to strain; and dr, is the initial grain size prk_r to deformation or exposure to elevated temperature, The grain structure in the gage section of sampies is the result of both static and strain-enhanced grain growth. Ota the other hand, the grain strutture in the grip is the result of static grain growth only. The strain-enhanced grain growth was calculated as the difference in mean-linear-intercept grain size between naeasurements taken in the gage and grip sections of the sample. We used this procedure to determine the normalized strain-enhanced graingr_wth response forCoronze. Wilkinson and Caceres2 have obtained data for this Fnt4_t, vortt)ld material, l'he present studies have obtained data at higher strain rates. The strain-enhanced grain growth for Coronze is plotted as a function of true strain in Fig. 2, for tests conducted at 55(YC and four strain rates, l?,esults have been nonualized by the initial grain size. The tests at the three slowest strain rates were in the region in which (,BS is the dominant deformation rnechanism. The test at the highest strain rate was in tlw region where the dominant deformation mechanisna was slip creep. For the three slowest strain rates, the normalized strain-enhanced grain growth was found to have a linear dependence on strain and a power-law dependence on strain rate. These results are consistentwiththeobservationsofCaceresand Wilkinson on the Cortmze alloy. 2 For the highest strain rate, the grain growth data in Fig. 2 had a much smalh_'r slope. The reason f_r this will be discussed in thL' following paragraphs. R¢,svarc_l l) f _,lop._l :_, ,_1 ;_ _ n,_,_! ,F_ ":" Thrust Area Report FY92 6-25 Matelrlals Ik:lence end Engineering ":' Modeling Superplastic Matonals Figure 6. Grain growth rates for UHCS at 750C, predicted by Eq. 5. Calculations are based on the parameters in Table 1. Experimental data Is provided. realized grain growth rate is alpower law function of strain rate; at higher or lower strain rates, the normalized grain growth rate reaches a limiting Figuro4. Normallzed graingrowthrate vsstrainratefora value that is independent of strain rate. Tlle_, numbarofquasl-singlephaseandmicroduploxsuperplastlc regions are shown schematically in tile inset for materials. Plot is from the work of Caceres and WilMnson. 2 Data fromourstudy ofthe superplasticdeformationof UHCS at 750'C has beenaddedto the plot. Strain rate b_ low which GBS is the primary deformation mechanism, is i_ dlcated, Tile normalized, strain-enhanced grain growth rate (with respect to time) can be calculated from the data in Fig. 2, by multiplying the slopes of individual lines by the strain rate for that test. The_ grain growth rates have been calculated and added to a figure previously reported by Wilkinson and Caceres, 2 which shows a log-log plot of normalized grain growth rate vs strain rate. The results are shown in Fig. 3. The plot is quite signifi- Fig. 3. The region at tile lowest strain rate is tile result of static grain growth, whereas the regions at tile intermediate and high strain rates represent tile result of strain-enhanced grain growth, lt is reasonable toassurne that the highest grain growth rate represents a limiting rate determined by tile kinetics of grain boundary migration. The curve shown in Fig. 3can bede_ribed by ,i = _,ia + .... 1 / 'ii'i'' / di) ,tl) di) ( _ii + _i,, )' cant, sinceitshowsdata forbothquasi-singlepha._' and microduplex materials, for different homologous ternperatures and for a range of starting grain sizes, lt is clear that a common equation can de_ribe the grain growth behavior of a number of where _ti is tile grain growth rate at intermediate strain rates, and d. is tile upper limiting grain growth rate. Tile intermediate region has a powerlaw dependence on strain rate, which produces different materials, includingCoronze. Thecurve has three distinct regions. In one region, tile nor- " i . F/gumS. (;rain 0 predtctedbyEq.5. 0 Data - 650"C "_ ._5()'_" 0 an, aters given In Ta- o .................... 450'C , t -"<>'- 6st)c 55o'c -_-' "'," 2,0 e =o 1,S 10"_ I• 650'C are given. ..... 0'.... 450C I 10 .4 I .....I 10"2 1 I 100 I 10: Strain rate (s-1) • ..... Thrust , '0....__"_,, bio 1. Experimental data at 550_C and _'_ ...., 7 0 ........... t '_ '_ -. 3,'_ Data-550"C based on the param- , 1.o t410 Coronz.at450_C, 550'C, and 650'C, II ' , S,S 4'S growth rates for caloulat, (2) Area Report _ FY92 .:. -_ _,/:: .... • 101 • " • ..... £ngJneetlng R(_seatch L)L'vC ,,l) m_,nt Figure 7. Calculated grain sizes for Coronze after constant strain rate testing to a true strain of 1 at the Indicated strain rates. anu It_chnol()gi ModelingSuperplasticMatermls 4, MaterialsScienceand Engineering the following empirical expression for the nonnalized rate of grain growth: 3S - ........ I Calculation Strain Strain,ale! i5 .03 .03 .03 aO_ .03 .03 11 s .o3 .03 .o3 .o3 .03 .o3 I0 .o3 .03 .o3 .03 .03 .04 .03 .04 -- do - do + .......[ do Atli"+_i. j' (3) where _)and n are constants. _ The strain rates at which there is a shift in the operating deformation mechanisms (from GBS to slip cre_ep)are also shown in Fig. 3. lt is important to note that the grain growth rates for the three slowest strain rates appear to laave a power-law dependence on strain rate. The grain growth rate for the highest strain rate, however, shows a substantiallv smaller increa_ with increasing strain ]7 S rate than the grain growth rates at the lower strain i rates. -Dais transition occurs at about the same strain rate as the transition to slip-creep-dominated defomaation. The obvious implication is that the loss of GBS as a deformation mechanism has reduced the contributiolzs of strain-enhanced ..... ," ii :,::: : _: gTain determinedstrain ratestrain history. growth to the total grain growth rate. Several mechanisms have been proposed to explain strain-enhancedgrain growth. 3-"Ali of these mechanisms result from grain boundary sliding or grain switch- (-Qi] t'ti = ;til b" exp _)/-_ . ifstraining enhanced events, grain lt is reasonable growth will to assume exist only that these mechanisms provide significant contributions to the total strain. Thus, contributions from strain- ,i,, : (d,,)o exp ( -Qt, RT ])' shown In the Inset. strain rates studied. Temperature Dependence of Strain-Enhanced are al modeldescribedin this report.thematerk basedon (4b) where Qi and Qu are activation energies for tile intermediate, and upper regions, respectively; K0 and(du),areconstants;Risthegasconstant, andT is the absolute temperature. Combining these expressions yieldsa general equation for the temperaturedeFn_,ndenceofstrain-enhanced grain growth: 75ffC. Results are presented in Fig. 4 and fall within the range of grain growth rates for other materiS als represented on the plot. For UHC_, no upper limit is reached on grain growth rate over the , , 104 ........J "'""_ ........i ......_ ......_. _ _ ,;.., ' '_ Rgun_9. stress/ strainrateresponse forOHCSdeformed at 750C. ,/ _, Grain Growth. A general extension of Eq. 3 that accounts for the temperature dependence of grain growth can be developed assuming different temperature dependencies for the three proces_,s in Eq. 2. The temperature dependence of normal grain growth kinetics has been studied and equations developed (see,for example, Ref. 7). The primary interest in this study is strain-enhanced grain growth, and thus the intermediate and upper rate eer_ng Thestrainrate/ stralnhistory is (4a) The calculations enhanced grain growth can be limited by a loss of superplastic flow or by the limiting grain growth rates defined by the rates of grain boundary naigration, Identical procedures were used to detennine the normalized strain-enhanced grain growth rate for UHCS during superplastic deformation at Er_glt) RgumS. Stroll strainr_pon_ for ones de_,m_at 750_C througha pre- pr(x:esses repre_nted in Eq. 2. The temperaturL, dependence of the_ proces_s can be represented as Res(tatch t" ,," 103 - / / ,/ / 102 _,,u,,,.l,, ..... , 10-5 10_ 10"_ 10-2 10"1 10° Stralnrateis'_) De.,_e/opm¢,nt at;d _.( h_oJ,,g_ o:. 1LO1 10= Thrust Area Report FY92 6-27 Materials Science and Engineering .:. ;do_leh,t_ Sup,,rplast_c fvl<lte_tals i o plasticstrain UHCS at1023 K, Low strain rate = 0.01 UHCS at1023 K, High strain rate dsf time==1.00000 1.00000+oo -02 dsf +°° time==1.00000 1.00000 +m Minval = 7.40-o7 Maxval= 8.67-.o7 (a)/ t (b) fringe levels 7.49 -07 7.82_07 7.57.07 8. 03-07 7.65 ..o7 8.24-07 1 8,45 -07 1 7.74.-07 1 7.82 -07 1 1023K, UHCS at 1023 High strain rate K, Low strain rate = 0.01 time : 1.00000 -02 dsf = z.O0000+°° tc) Minval = 5.15-o4 Maxval= 1.02 +02 time = 1.00000 +01 dsf = 1.00OO0 ``00 td) Minval = 2.25 -o5 Maxval = 3.75.-o2 fringe levels fringe levels 1.69+ol 6.26-.o3 r-----m 3"39*°1 1"25-02 5.00 +01 1.87 .-02 6.77 +°zl_ 2.50 "°21 1 3"12-02 ! 1 8"46+°1 I Figure 10. Hourglass-shaped sample of UHCS deformed at 750 C for two different extension rates: one in which aBS is the dominant deformation mechanism, and one in which slip creep is the dominant deformation mechanism. The figure shows contours of constant grain size and strain rate for the sample. Table 1. Parameters used in Eq. 5 for temperature dependence of strain_enhanced graingro_h. _ (de) 0 [(lam/s)snl (lam/s) do (btm) ( ,H'i,ll/t' I. c .17'S \, tl'_,Hi,,llt'Iwr_,, t_,r ar,lll_i,,,uit, + \<ll,,,;ti,,ll,'i 6-28 Thrust Qi Qu (kJ/mole) .,Slit_ li 104" .Tct c_ li 17(it n 7".cJ,_.,lit I t. IK'-, .74 l-q_ I.cl2.............................................. ill 7 t<,r,,,tiil,i-u,i_ Report FY92 ":" _ ; RT ii I (5) RT The temperaturedc'pendence of strain-enhancefl grain growth for the Coronze alloy was experimentally evaluated at 6t}0°Cand 650°C. The restllting grain growth rates have been added to the ph,t in Fig. 3, and appear to fall within the rarlge of strain-enhanced grain growth rates for other materials. These results suggest that strainenhanced grain growth for the Coronze alloy is independent of temperature and that Qi for this material is zero. As mentioned in the previous ,,a_'ction,the limiting grain growth rate at high strain rate is probabl,v controlled by the rate of grain boundarw migration. We therefore assume that a reasonable \'altle for Qt, is the activation energy for grain boundary diffusion. The calculated grain growth rates that are predicted by Eq. 5 are plotted as a function, ' strain rate in Fig. 5 Calculations =, c . ' '"_'cau.,<.the strain-enlaanced grain growth is independent of ternperature ill the intermediate region, at very !ligh temperatures (higher than the temperature stud ied here), the contribution of static annealing to the total grain growth rate could be significantly higher than the contribution from strain-enlaanced grain growth. In Table 1, the parameters for UHCS are also given. Both Coronze anti U HCS ha\'e \'erv similar strain rate exponents (ll) and values for the constant X. The calculated strain-efdlanced grain growth rates for UHCS deformed at 75()C are shown in Fig. 6. Good agreemeat was obtained with experimental data. [lae final grain sizes that would be obtained for Coroi-lze after tensile testing (to a true ,train equal to 1) at a constant strain rate are shown in Fig. 7. Calculations, which were done for thrc,e temperatures (45() 'C, 55(Y (.7,and 65() C), are based on Eq. 5, tlsillg the parameters given in 'Fable 1, and, tllus, t.ltl not incluch.,the effects of static-annealing. Restilts in Fig. 7 sh(Iw a dt'creasil-ig final grain size with increasing straiil rate anti \'er\' little /grain growth abtlvt2 .l/s fill ali testing tt_'nlperattlres. (;rail'l gn_wth decreaseswittl illcrt.,asillg strain rate (Pig. 7) de.spite the il-lcrc,asing grain grllwth rate ir,,l{' < ;...... q c, ,are shown for three temperatures, 4. I)'C, 5.0"C, and 650':'C; the parameters are given in Table 1. lqae calculated grain growth rates show gcxx.lagreetaunt with rates derived from experirnental data. ii_ t,¢lrt.<,,ptwr 's l;-t t, ,r :e,r<ill_b, ,t!ild,tr_ <tlilu,,i,,llil_f_li,t. Area 'iii Ali t;''_exp dll RT Minval =7.40-o7 Maxval=7.91-.07 fringe levels 7.61-o7 UHCS at _tl_.n(ii,,)exp Ii ,i ,, 1 -'--- : -- :',, ,,- :_,, ,', .... ,,,,s t,. '," "F, ModelingSuperplasticMatenals.:. MaterialsScienceand Engineering mi with increasing strain rate (Fig. 5). This occurs because tile strain rate exponent (n) irt Eq. 5 is less than one. to The amount _nsitive thetotal value of n. of grain growth is ve D, Two ratc_tependent constittltive equafiolL_;have been used for GBS and slip creep, \.../ d-t',,,,, Parameters used in Eqs. (6) i ngb, PSI_ [s-l(psi)-'a(pm)PI _.s4x 10-3 (kJ/mole) 177 2.27 3.0 "_llp QI_ nsup Palp Is-I(psi)-'(IJm)_l (kJ/mok,) 7.14 3.0 1.41x 252 lO -2l i 6and7forUHCS. Osb* Asbs Mechanical Response = A x,l,s expf_/a",.,,, i Table2 o in psi d and _.in _.tm [',lip = Aslii, exp ( -_/ -QI / cr'.t,,/lt'._,_,, (7) _'.,lip+ _;e,l,s" deternlined experinlentally f obtainedfrom Ref.9 speed performance of the DMM is within a factor of three of NIKE2D model 19, a rate-dependent, power-law plasticity model. We have evaluated the performance of the material model, using a _,ries of experinaents of increasing complexity. The first experiments were simpletensiletestsconducted atconstanttruestrain rates, and excellent agreement was obtained between model predictions and experimental data. llae results were reported in our FY-91lj report. The second set of experiments inw)lved deforming tensile samples through a predetermined strain rate/strain history. This applied strain/strain rate where _'_b_and /_'._lip are the strain rates for grain boundary sliding anrMd slip creep, respectively; _ is the stress; Agbs, A_lip, ilgb_, ll_,lip, pgbs, and pslip are constants; _. is the nainimum barrier spacing governing slip creep (typically, the interparticle spacing or the grain size); d is the grain size; Qgb is the activation energy for grain boundary diffusion; and QI is the activation energy for lattice diffusion, Since the deformation mechanisms represented by theseequations areadditive, the total strain rate can be represented by ['h,hfl = _t (8) The mean, linear, intercept grain size is typically used for the grain size term in Eqs. 6 and 7. For fine grain materials deforming in or near the region of GBS, the minimum barrier spacing is the grain size, and thus for the_,studies, we have assumed history and the resultingstress/strain response for UHCS deformed at 750°C is shown in Fig. 8. The parameters used in Eqs. 6 and 7 are shown in Table 2. in Fig. 9, we show the stress/strain rate behavior of UHCS. In both cases, excellent agreement was obtained between model predictions and experimental data. A third set of calculations was done to evaluate the material model on a that Kequals d. The grain size was obtained from a time integration of Eq. 1. sample containing a non-uniform stress state. The sample had an hourglass shape and was deformed at two different constant extension rates. At one Model Implementation rate, GBS was the dominant deformation mechanism, and at the other rate, slip creep was the dominant deformation mechanism. The extension rates are indicated in Fig. 10, which shows contoursofconstantgrainsize(Figs. 10a and l0b) and constant strain rate (Figs. 10c and 10d) after an extension of x in. The sample deformed in the slip creep region Ims started to neck, and the contours of strain rate arc highly localized. The sample deformed in the region of GBS has avoided necking (exhibited characteristics leading to superplastic behavior) by distributing the strain rates throughout the hourglass region. and Evaluation The grain growth kinetics, expressed by Eqs. 1 and 5, and the constitutive laws, expressed by Eqs. 6, 7, and 8, were integrated into an existing material model in the NIKE2D code, called the l_)efomlatit)n Mechanism Model (DMM).I_) This nlaterial model solves the constitutive equations, withan implicit solution pr,_cedure.Theevolution of grain size is als() solved with an implicit procedure. The numerical nacthods used in this model emphasize accuracy, but ali of the alKorithms are vectorized for the Cray computer. Generally, the = - Englnc'orlng Roseat(.h Devel_Jpn_unt _ltlcd rechnol()l_y ": Thrust Area Report FY92 6.29 Matorlals Sclonco and En_nooring .._ Modeling Superplastic Materials AcknowledgmnmltS Conclusions 1. We draw four conclusions from our work: The dependence of grain growth rate on strain rate for superplastic UHCSand coronze falls on a master curve, as originally proposed by Wilkinson and Caceres.2 In the copper alloy, the transition in grain growth rate from a power-law dependence on strain rate to an upper limiting rate occurs at the transition from GBS-dominated behavior to slip-creep-dominated behav- We are indebted to Oleg Sherby (Stanford University) and Amiya Mukherjee (University of California Davis) for helpful discussions oll superplasticity. We are also indebted to Jack Crane (Olin Corporation) for providing the Coronze 638 and to Oleg Sherby for providing the superplastic ultrahigh-carbon steel. 1. D.R. Lesuer, C.K. Syn, K.L. Cadwell, and S.C. Mance, "Microstruch|ral ChangeandItsInfluenceonStr_sStrain Behaviorof SuperplasticMaterials,"SuperplasticityinAdvancedMaterials, S.HoG M.Tokizane, and N. Furushiro(Eds.),(Osaka,Japan),139,1991. ior. The transition to an upper limiting rate (d _,in Fig. 3) can occur because of a loss of superplastic 2. 3. flow or a limiting grain growth rate defined by grain boundary migration. For UHCS, within the strain rates studied, no upper limit was found to the grain growth rate. An equation describing the temperature dependence of the strain-enhanced grain growth rate has been developed. The equation predicts grain growth rates that agree well with experimental data. For Coronze, strain-enhanced grain _rowth appears to 2. D.S. Wilkinson and C.H. Caceres, 1. Mater. Sci. l.x'tt. 3,395(1984). 3. M.A.Clark and T.H. Alden, Acta Metall.21, 1195 (1973). D.S. Wilkinsonand C.H. Caceres,Acta Metall.32 (9),1335(19_,). 4. 5. K. Holm, J.D. Embury, and G.R. PuMy, Acta Melall. 6. 25,1191(1977). D.J.Sherw¢_)dand C.H. Hamilton, ScriplaMetall. 25,2873(199l). be independent of temperature in the intermediate region. In the high strain rate region, the strain-enhanced grain growth rate 7. 13. Cotterilland I3.1,1. Mould,Recrystallization andGrain Growthin Metals,John Wileyand Sxms(NewYork, New York),279,1976. appears to have an activation energy equal to the activation energy for grain boundary diffusion. A material model has been developed that 8. M.EAshby, ActaMetall.20, 887 9. B.Walserand O.D.Sherby,Met.Trans.A 10A,1461 (1979). combines 10. the temperature-dependent grain P. Raboin, A Dq,fbrmation-Mechanism Material Model growth law described above and mechanism-based 4. constitutive forNIKE2D,LawrenceLivermoreNationalLabora- equations, This model was incorporated into the NIKE2D code, and validation experiments 11. Thrust Area Report FY92 4, Engineering Research Development tory, Livermore, California, UCRL-ID-] 12906 (1__N3). D.R. Lesuer, D.K.Syn, K.L.Cadweli, andC.S. Preuss, "ModelingSuperplasticMaterials,"En,s;ineerin,_ Research,Development,and 7_'chnolo,_y, Lawrence LivermoreNationalLaboratoryLivermore, California, UCRL-53868-91 (1992). LI show excellent agreement between model calculations and experimental data. 6-30 (1972). and Techllology Microwave and Pulsed Power ThegoalsoftheMicrowaveandPulsedPower thrust area are to identify realizable research and development efforts and toconduct high-quality research in those pulse power and microwave technologies that support existing and emerging programmatic requirements at Lawrence Livermore National Laboratory (LLNL). Our main objective is to work on nationally important problems while enhancing our basic understanding of enabling technologies such as component design and testing, compact systems packaging, exploratory physics experiments, and advanced systems integration and performance. Durhlg FY-92, we concentrated our research effortson thesix projectareas described in this report, 2. We are studying the feasibility of using advanced Ground Penetrating Imaging Radar technology for reliable non-destructive evaluation of bridges and other high-value concrete structures. These studies include conceptual designs, modeling, experimental verifications, and image reconstruction of .simulated radar data. 3. We are exploring the efficiency of pulsed plasma processing techniques used for the removal of NOx from various effluent sources. 4. We have finished the investigation of the properties of a magnetically delayed low-pressure gas switch, which was designed here at LLNL. 5. We are applying statistical electromagnetic theory techniques to help assess microwave effects on electronic subsystems, by using a mode stirred chamber as our measurement tool. 1. We are investigating the superior electronic and thermal properties of diamond that may make it an ideal material for a high-power, solidstate switch, 6. We are investigating the generation of perfluoroisobutylene(PF1B) in proposed CFC replacement fluids when they are subjected to high electrical stresses and breakdown environments. E. Karl Freytag 77u'ust Area Leader Section -w_ m m m _:._ j_------,_.__ ........ 7 7. Microwave and Pulsed Power Overview E. Karl Freytag, Thrust Area Leader Pulsed Plasma Processing of Effluent Pollutants and Toxic Chemicals George E. Vogtlin ....................................................................................................................... 7.1 Ground Penetrating Imaging Radar for Bridge Inspection John P. Warhus, Scott D. Nelson, Jose M. Hernandez, Erik M. Johansson, Hua Lee, and Brett Douglass ........................................................................ High-Average-Power, Electron Beam-Controlled Switching in Diamond W. Wayne Hofer, Don R. Kania, Karl H. Schoenbach, Ravindra Joshi, and Ralf P. Brinkmann ..................................................................................... Testing of CFC Replacement By-Products 7-13 Fluids for Arc-Induced Toxic W. Ray Cravey, Wayne R. Luedtka, Ruth A. Hawley-Fedder, and Linda Foiles .............................................................................................................................. Applying Statistical Electromagnetic Chamber Measurements Delayed Low-Pressure 7.19 Theory to Mode Stirred Richard A. Zacharias and Carlos A. Avalle ............................................................................... Magnetically 7os 7.23 Gas Discharge Switching Stephen E. Sampayan, Hugh C. Kirbie, Anthony N. Payne, Eugene Lauer, and Donald Prosnitz .......................................................................................... 7.27 PulsedPlasmaProcessingof EffluentPollutantsand ToxicChemicals0:oMicrowaveandPulsedPower Pulsed Plasma Processing of Effluent Pollutants and ToxicChemicals George E. Vogtlin D_;fi'tlse SciellcesEngineeri11,_ Divisiott Eh'ctroJHcs EJl_qJleeriJz X We air exploring the efficiency of pulsed plasma processing in the removal of NO× and other pollutants. Our ultimate goal is a flow-througl-i system where gases would be treated during a single pass. We are currently using a closed-loop system with mixtures of bottled gas. The closed-loop system permits testing of processes, without a requirement for file development of complex and expensive power supplies for the one-pass treatment. We have constructed a new processor this year that can accommodate many electrode shapes at temperatures up to 400°E Introduction The efficient removal of NO, ft'ore effluent sources is essential to meet the requirements of the Clean Air Act. NO, is a mixture of nitric oxide, NO, and nitrogen dioxide, NO2. We are exploring the efficiency of pulsed plasma processing in the removal of NO_ and other pollutants. Pulsed plasma appropriate for processing is generated by a short high-voltage pulse between two electrodes, The electr()ns fr()m this discharge create radicals from the air molecules. These radicals can then react with the pollutants to give hamlless or Analysis can be conducted during or after these tests. We have constructed a new processor this year that can accommodate many electrode shapes at temperatures up to 400°F. This processor is shown in Fig. 1. Electrode geometries can have a crucial role in the efficiency of this process, lt is essential to efficiently couple the energy uniformly into the gas. The geometry can affect the power supply coupiing efficiency, the discharge uniformity, and the pressure losses due to turbulence. re- Figure1. movable substances, Our ultimate goal is a flow-through system where gases would be treated during a single pass. We are currently tlshlg a closed-loop system with mixtures of bottled gas. The closed-loop system pollutants. |ligh-voltage permits testing of processes, without a requiremerit for the development of complex and expensive power supplies for the one-pass treatment. We also believe that flow through the reactor should feed ) Gas flow Rogowski be in tL!rbLllent flow. "I-LI rbLilent flow mea ns that a li the gases in the processor flow through at the same velocity, including that at the wall. The dosedIo(_psystem pemlits these high flow rates without an extensi\'e gas-mixing and heating system. Processor forremovingeffluent 2-inch outer _-- Resistive monitor tube Gas flow -_ ) Progress Experimental System anode The experimental svstem permits the introduction of \'ari()us gas combinatit)ns prior to testing. El_gln(tetrng Re.s_?arch De_,t_lopmg'nt i_n(; [¢:r.l)nology o:. Thrust Area Report FY92 _'_1. Microwaveand PulsedPower .:. PulsedPlasmaProcessingof Effluent#'ollutantsand ToxicChemicals i _ 0.040" Electrode geometry forprocessor. 5 5" Titanium dioxide3 = 100 O M_/ Stainlesselectrodes Platinumelectrodes Brassdiscs0.005"thick 0,25"separation Tile processing chamber has been designed with an outer pipe two filches in diameter. Tills tube cml be used as an electrode; other geometries of smaller dimensions can be placed fllside. The reaction chamber can be increased in length as needed to match the impedance of the high voltage feed to that of the processor, for maximum energy transfer. Configurations tested for NO removal are shown ha Fig. 2. Nitric Oxide Removal We measure the efficiency of rernoval in eV/ molecule. The performance of the removal in ev/ NO molecule is a function of the NO concentration. We are presently charging the system to approximately 600 ppmv (parts per million by volume). NO reacts with itself in the presence of air, and the change hl concentration is proportional to the square of the concentration. This means that the natural rate of NO reduction at 500 ppmv is 25 times that at 100 ppmv. This effect must be subtracted from the reduction due to pulse plasma processing. Tile natural reduction of NO has a Figure3. Nitric ox.. ' 200 I show data from NO ide removal. Plots and NOx processing, ' I Platinumwire 0.040" Titanium oxideplates Stainlessoutertube negative temperature coefficient, which means the reduction is less at higher temperatures. At room temperature, the natural decay at 500 ppmv is approximately equivalent to20-pulses-per-second pulse plasma processhlg. We feel the present system gives good data to the 500 ppmv level and can go to higher ppmv at higher temperatures. The efficiency of NO removal has shown to be sensifive to concentration. Figure 3 shows this effect, lt appears that the removal of NO2 increases once the NO Ims been removed. Initial measurements will be made with the closed-loop system; however, we intend to convert this system to a flow-through system, which will permit steady-state mixhlg. Additives: N-octane and Water The addition of n-octane has improved the efficiency of NO removal. Figure 4 shows efficiency improvements with 0, 1850 ppmv of n-octane. N-octane is similar to gasoline and has a flammability limit of 8000 ppmv at room temperature. The addition of n-octane, suggested by R. Atkinson, I uses a process that effectively burns organics by recycling the OH radical. This process should be likely that the work by Fujii,2 using an oil that is possible with many organic compounds, seems vaporized in the processing chamber, is altsimilar [ _100 ' ' NOx ppm • -. m _ _Z Tests to date have been with dry air and with process. approximately one percent water. The tests with dry air have an efficiency similar to wet air. We plan tests in the near future with water up to eight _ percent by volume at 200°F. Diagnostics J 0 0 "li-2 Thrust Area Report _'Vg,_ 100 Time (s) .:. r,,o,..,._.,,n,_ Ros_afc:h 200 Develoonlerlt Diagnostic systems have been used to analyze the light emissions of the discharge. These include a monochrometer and an open shutter camera. Devices to measure the results of chemical reac- ._tlltl Ic'chI]oIogF PulsedPlasmaProcessingof EffluentPollutantsand ToxicChemicalso:*Microwaveand PulsedPower 800 I ,[ I I I .... 600 I_ackgrotmd 400 _' -- V/N(_ _ i-_/ III -- I,abair \ that the electrical energy that can use be generated thermal-electric generators the engineL_y waste "N ._ " l __ • °0 2 I 4 J I 6 8 Time (rain) ] 10 meet these requirenlents if the efficiency of NO, removal is sufficiently, improved. Our goal would be to remove the required NOx with lessthan two percent of the engine power output. This would require 8 hp or 6 kW for a 400 hp engine. The efficiency of the overall processis the key to diesel applications. The higher the efficiency, the more likely this process will be practical, lt may be 12 Figure4. Resultsfromn-octaneadditioninNOremoval, tions include a chemical NO, meter, a chemiluminescenceNO_meter, andan lRand FTIRanalyzer. The measurernent of energy is essential to determine the efficiency. We measure the energy by recording the voltage and current asa function of time, and then integrate the product. This gives us the joules per pulse. The pulse rate is measured by a counter. The total energy in any time period is then the product of the time pulse rate and joules per pulse. To prevent reflections, a load resistor is included at the end of a short transmission line, where the voltage is measured with a voltage dMder. The current is measured with a 0.1-(2 resistor in the return path. Applications Diesel Application. The application of thistechnology to diesel exhaust cleanup poses many challenges due to weight, size, life, cost, and efficiency requirements. We are developing power supplies with similar requirements as part of the Laser Isotope ,_'paration Program at Lawrence IJ\'ermore National Laboratory. lt ma t, be possible to Other pollutants may be removed or destroyed gine power to clean the exhaust. bv this plasma process, lt is likely that fuel droplets, carbon monoxide, and volatile organic hydrocarbons may be oxidized to harmless compounds, lt may also be possible to remove particulates using this pr(x:essin the presenceof liquid droplets. Coal-Fired Power Plants. This technology can be applied to coal-fired power plants, lt may be possible tosimultarleotMy remove NOx, SO\, mercury, and particulates ft'ore the effluent. The remoral of both NO, and SO_ would be accomplished by their reaction with ammonia. This reaction gives ammonium sulhte and nitrate, which can be sold as fertilizer. The critical issue in this application is cost. lt must be competitive with other processes, lmprovement of efficiency results in reduced capital costs and operating costs. Our primary goal is improvement of the efficiency of simLfltaneous removal of NO_ and SO_. Other Applications. There are many applications for pulsed plasma processing. These include destruction of vola tile organ ic hyd roca rbons, el iraination of hydrogen sulfide from fuel gases, and others where plasmas can induce or accelerate a chemical reacti(,n. 1. I,_ogerAtkins(_n,Chcm.I,M..85,69(1985). 2. K. Fujii, I_)th Int. C_nf. I'henomena in Ionized (;ases(llCi(,cco, Ital\'), I¢-;_;]. L._ GroundPenetratingImagingRadarfor BridgeInspection.', MicrowaveandPulsedPower Ground Penetrating Imaging Radar for BridgeInspection John P. Warhus, Scott D. Nelson, and Jose M. Hemandez D_ft'llseScieltces EJz,e, iJzeeriJlg DivisioJz Hua Lee and Brett Douglass Eh,ctroJfic mufComplaer EllgilleeriJzg DepartlneJzt Electrolfics Lhfiversity EJlgilzeeri_lg qf Cal!fi_rltia Smlh7 Barbara Erik M. Johansson laTser EJ_gilu'eHitg DivisioJl Electrolfics Ellgilteeri_g We have developed conceptual designs, completed requirements analyses, and performed experiments, modeling, and image reconstructions to study the feasibility of improving groundpenetrating imaging radar technology for efficient mid reliable nondestructive evaluation of bridges and other high-value concrete structures. In our feasibility study, we made experimental measurements of frequency-dependent electTical properties of cement, ft'ore which we derived an electromagnetic (EM) model for concrete, to use in system-level simulations. We performed parameter studies to evaluate key system design issues, using two- and threedimensional, finite-difference, time-domain EM analysis codes to simulate an ultra-wideband synthetic aperture radar and produce simulated radar data for a variety of concrete structures. Images produced from simulated radar data were analyzed to evaluate important radar system performance parameters and characterize imaging algorithms we are developing. Introduction (h'ound-[x, netrating; imaging radar ((;I'IR) radiatl.,s velw-short-ba._'band (i.e., without a high fr_quency carrier) eh_vtromagnetic (EM) pul._'s into ground m_._Jiasuch a.s._il and concrete to prowl_x, for featurt_s of intert.'st, without disturbing the mt_tia, This tt_.:lmt_log 3, is attractive for u_, as a bridge insb_vtion t(×d bc_:au_, ii is non-contacting and can pr(__iucehigh-rc._luti_n I't__'OllStFtlCtt_.'_ imagcsofimt-_.tdc_.istructural teaturt_ using a vehicle moving at highway sbxx,ds. However, the full capability of the teclm(_log3'has not t-__,nexploited at a commercial h_,ve].Limitations preventing ctm'ent gr_und-pent_trating radar K;I'R) systems ftore Lx,ing more widely u._'d forbfidgeinsp_vtion includedifficultdata interpretation (no image revonstruction); inaccurate depth and position measurement; _vlati\'ely p_×, spatial rt_lution; and limited area c_werage, which limits (_perating efficienc.v, _rl_;r_f,t_!t_ , ,e .......................................................................................... n n _ ' , I I lp . ............. In an improved bridge inspection GI_R system, a mobile u ltra-wideband (UWB) radar gathers data for high-res(dution image reconstruction of features and defects embedded within tile structure. Performance enhancements are achieved by increasing transmitted pulse bandwidth and power, using recei\'ingantenna arrays and synthetic aperture radar processing techniques, and adding highresolution imaging. An advanced (;I'IR and imaging system has the near-term (2- to 4-year) potential of addressing critical national and international needs for reliable, cost-effective nondestructive e\'aluatiol_ of bridges and other reinforced c(,_crete structures. There are more than 578,()(1()highway bridges in the U.S., and more than 4()",, _t; them are either structurally deficient or functionally obsolete. I These conditi(,_s limit usefuhlt,ss and can pose a safety threat t_) the bridge users if the bridges are not properly monitored and maintained. f4#,_.t,,tr( ..,,.,,.--,,,..,,,,,,..,,.,,.,._,,,, t_ ' [J_'_t !i,l_#.tit . ,,,,m--.n,,,.nnn.u.nm ' _ ,_t_l l_,t ttt_lt_l_ mmnuln I ,,,mmimnumnnlllmmnim alp ' o:. Thrust Area ,annum nmnmilg_ntlnl_lltlllNInl _ Report nN! i n, FY92 I! , 'H_fll_ I Hl| 7-5 lH! I_11 I _1111 nnpan I Microwave and Pulsed Power .:. Groum/Penetrating imaging Radar tor Budge Inspection til _ ii t _ t! Figure1. GPIR bridgeInspection concept, Single transmitting antenna Mass data Image processing and display Multichannel receiver Ultrawideband transmitter Linear receiving array (1-by-n elements) The bridge deck and its wearing surface are the most vulnerable parts of any bridge, undergoing piing) and targets (structural features like reinforcing bars, or flaws like voids or delaminations). damage from routine sel_'ice. They are particularly well suited for inspection using a vehicle-mounted inspection system. The deck has a shorter average service lift' (35 years) than the bridge itself (68 years). The wearing surface, which provides the drMng surface and protects the deck beneath it, is usually designed to be replaced many times Using analytical capabilities that were improved during FY-92, we also conducted parametric studiestoevalttateimagingresolutionandperfonnance issues, especially with respect to dispersion effects. Our FY-92 work showed that current technologies can provide the performance required to iraplement an improved GPIR with some limited over the life of the bridge. Concrete slabs with concrete or asphalt cover are the most widely used decks and wearing surfaces in ali types of bridge corlstruction. 2 Our approach in this study has been to use system-level design, supported by experiments and analytical modeling, to evaluate key system performance parameters and requirements an,.I to needs for technology development. Additional development work is required in image reconstruction and enhancement, UWB antennas and arrays, and low-power, high-repetition-rate UWB transmitters. Our assessment of these developmental needs indicates a high probability of success in achieving project goals. determine System-Level feasibility. Prog_re_ Requirements Analysis During FY-92, our efforts were aimed at defining requirements for improvingGPIR performance and evaluatin G the capability of available technologles to satisfy those requirements. We developed an overall system design concept lk_ran improved inspection sy,stem and analyzed its requirements, We investigated the electrical properties of cement To establish a design baseline for our feasibility study, we formed a basic system-operational concept from which a system conceptual design was de\'eloped and performance requirements were defined. Basic operational concept guidelines included: (1) the inspection vehicle moves over the bridge deck at a speed of at least 30 mph; (2) data is acquired for one traffic lane-width of bridge deck with each pass of the vehicle; (3) bridge deck struc- (a kev constituent (}f concrete) to develop a model for concrete and to Gain insight into imaging enhancement and correction issues. We modeled radar systems and concrete target structures to simulate and evaluate interactions of UWB pulses with clutter sources (aggreGate in the concrete, concrete surface reflections, antenna cr(_ss-cou- tures are inspected to a depth of 0.5 m; (4) images are reconstructed in three dimensions, with resoluti(_n ()n theorder(ffS0 mm;and (5) image reconstruction is done off-line, at rates permitting l() to 2() bridges to be covered per day. As shown in Fig. 1, a transmitting antenna and a linear array of receivers travel over the bridge GroLmd Pe/_etrotmg InlGgltl _ RztOor for Br/dg(, I/Lsp(,ctior; o:oMicrowave 200pm I_H_I FWHM = 250 ps .... P°u' = 432 W' peak tr = 100 ps I Transmitter I N = 4 dB /_ Transmitting antenna , .__ I_._. _ I 1000pulses, ./,-" 5 Mpulses/s . .I" Figure 2. Improved GPIR block diagram. PRF triter ir s_"i_ 3.73 m subsystem Trigger , Delayed PRF trigger 270 pps BWr= 5 GHz G = 16 dB 0 Mass storage subsystem (removable Ch I OO_ processor (100 MFi.OPS, typical) Image laser disks, streaming tape, and/or solid state memory) antenna linear array Ch 41 Sampler SNR = 20 dB 5 M-samples/s MDS = 1 nW BW = 5 GHz Noise floor = lmV deck surface, sweeping out a traffic lane-wide sw> thetic aperture. Data recorded from the receivers is transferred via multiple data streams to a mass data storage subsystem, from which it can be accessed for image reconstruction. Image processors in the vehicle or at centrally located processing centers, reconstruct three-dimensional (3-D)images of tlae bridge deck structure for evaluation bv a bridge inspector. Images for a bridge 100 m long and four lanes wide are reconstructed in less than an hour. Mobile data acquisition, at speeds approaching highway speed limits, will permit efficient and cost-effective ex'aluati(_n of large areas of bridge decks in very short times. Evaluation of reconstructed images produced from the radardata will allow bridge inspectors to determine bridge conditi_ns, and prioritize maintenance and repair activities and expenditures_n the basis of high-qualitv inspection data. A more detailed system-level concept is illustrated in bh_ck diagram form in Fig. 2. Kev system requirements that we identified and defined for this design include: receiver dynamic range and minimum discernible signal; the ntlmber of receiving channels (and array elements) required t(_ achie\'e the desired traffic lane-width ctwerage and image res(_lution; peak and a\'erage transmitter power; transmitted wa\'eform characteristics; transmitting antenna characteristics and ptllse repetition frequency; data accluisition and transfer Display subsystem Sampler memory/ control and Pulsed Power buss 566 K-bytes/s peak, per array element rates; and conaputational power required to provide efficient image reconstruction tun>around. Material Characterization ro better understand the problem of collecting radar data and producing images of features erabedded in a lossv heterogeneous material like concrete, we performed broadband (0.1 to 4 (,t]z) S-parameter measurements (_f transmission (attentlation) and reflecti\'ity of cement samples. The,_' measurements were made with a netwCn'k analvzer and a coaxial line in which the dielectric material surrounding the center conductor was frHreed from cement, i:nml the S-parameter data, we calculated thecomplex dielectricconstant. Many measurements were made over a periled of about nine months to observe variations of these properties as the cement ctlred. Figure 3 shows typical results of nleasurenlents and calculatil_ns f(,'a cement sample at eight and 204 days after it was poured. The decreases in relati\'ediek,ctricconstant(l:,)and attenuati_,lover time reflect the reductk,1 ()f the amount of free water within thecuring cement. Important c_,lsequences of the frequency dependence _f t" ancl attenuati(,a are that c¢.lcrete is dispersive and acts as a bandpass filter, l,)ispersi_,l distt,'ts the pn_pa-gating and scattered IqM waves in the media by reducing risetime and increasing pulse width, and attenuati(,1 redtlc('stl',.'effecti\'eb, lndwi_ltl_¢_ltl'w Figure& La)Measuredtransmi.ion (S21) and ............. O 1 l '"1 I '1 [ l tel'_ of concrete required for accurate n'_odeiin_ using analytical cocles like AM(.]S or 'I'%\R. In " _(_ reflection (S:L1),and addition, _ -5 --_-- tive dielectric con- i -10 __'V_ slant {cr) for cement sample, t i 15 _x _ " X_x "_ _. "" _ /" ..... "'", 20 --25- I 30 I lbl I l ' I I " I l!) v%% _ " I I I '1 _ Day 8 .... Day 204 ,,, -., .....,. "" feasibilitystudy,including: developingand validating ali EM nlock, I for cono'ote; nlodeihlg providing a llleans to evaluate algorithm perfof mance; and performing trade studies that exam- - perforrnance parameters. inedTo radar configuration we options satisfy system our requirements, used twoandfi- - which were developed and are rnaintair_ed by Lawrence l_,ivermore National l,aboratory. Those _ _ codes, AM(_-_ and TSAR, permitted tlS to evahlate a wide rarlge of technical issLles, without rc,quiring the invesmwnt of limited project pronite-differerlce tirne-dtmlain EM resources analysis to codes, - duce physical hardware or t'xt'ctite Iltinlerous t'Xperiments. In support of (ltir no,cd tri model a .......... / 0 I I I I I I I 0.05 0.55 1.05 1.55 2.05'2.55 3.05 3.55 4.05 lilqueney (GHz) - -' ' dispersive nlateria[, both codes were tlpgradt,d to permit modeling EM wave propagation and scattering in a mediunl whose dielectric properties are l:requency dependent. By combinhlg results '"......... 0 ' Rgure4. Resu/ts from (a) 1-Dexperimental data and (b) 1-Dcementmo_L el. 1 I I acterization - dimensitulal - stlrelllL'lltS. -15 7-8 Thrust Area experiments from early material with analvtical charmodel- ingtools, we dt,veloped all EM nlodt,l for COllCrt'tt'. lk'rmittMty data derived fronl material charactt, rization rllt2aStll't2illt'lltS %%'tW12 Lisud in a o11u- -5 -10 COlll- ph.,x brMge-Iike strtlcttlres to ._tlppoi't otlr image' reconstrtlction algorithm developnlent effort by -- 10 _/ 5 l-- system _ I and Image Reconstruction Ctllllp(,illUlltS and targets. (_)ilr modelillg reqtlirenlents incltlc|ed net,ds f(u" Olle- , two- , and three-dimensional simulations. Those requiremellts CtlVt'l'od a variety of isstleS important to Iltll" ". _ [ _ gainc,d from these nwasure- insights into ways in which cor- illallct, I't'qUil't'lllt, lltS was FM nlodeling iii radar A kev elenlent in otlr sttlclies of svstt, m perfor- __ 15 i achieved. m.,. _',_ . [ . 25 -- _ Modeling s .... sll d.ay204 --s21day8 .... s21day 204 -30 tilL'tits provided " __N d knowledge -- _'-"N -20 _ental-- resultsModel" results" -25 O I 0.5 s2, - model Lo simLilate those mea4 is a plot of nlc, aStll'ed data overlaid with results from the |-I) model, ing good agreement between measurements the mi}del "'_ 1"0 extend I I . 1.0 1.5 Frequency (Ghz) (l-D) Figure these rr:stills to two dimensions, add ilk mifi experi nlt, n t was pt, rft)Mled. 2.0 showand an LiW B puis- eS were latuwhefl thixlugh a concrete bh_ck, using a broadband alltOlllla, alld detecled and I't,Ciil't_lod EM energy. These effects dograde the l't'soltltilln of images rt'c(instrtlcted from the UWB radar data tin lhc, other side of lhc' block with a UWB St,llsor alld rc'cording systein. A two-diinensiiulal (2-1)) and catlst, erl'llrs in depth 111t'astlrelllent. Data obtained from tlle_l., nlL,asurL,illents wt, rr; useful in defining the dominailt electrical paramt,- naodi.,I of theexperinlent was COllslruclc'd and rtlll using AMt)S. The model used the comple× permittiviiv data from the I-!) case, and incluclvd Report FY92 .> Lnt{llii;,l'lJll_>' [T(,Sc'<ilch Dt''_i'/o,,iml, lll ,lrtd lt'( hr) ol()p', GtounH Pol,_.tti_tul#'_It_hll_mt'_R._(/.U rot Ht,l_:_' I,._p_'('t,.I ,'o Microwave and Pulsed Power ii sucil details as tile antenna beamwMtll, radiated electric field w,weform, dimenshms _f the bhwk, ...................................................................................................................... dispersivt, effectsof the cement, and clutter effects prt_cluced b\' the aggregate within it. Figure5 shows plots of both the experimental rneastu'ements and simulated results° Again, fairly good agreement between experiment and simulation provMed valictation of the concrete EM model. After cord:h'rrlhlg the validity of otlr 2-1) EM Model for concrete, this analytical teel was tlsed extensively to evaluate radar system design pararneters and image rectwlstruction algorithm performarlce. Parametric studies we conducted using this model are summarized in Table 1. Image rcconstructitms were made frtml the sinmlated radar data for retest of the cases listed in the table, Tiae illhlges aided assessments of the impacts t)f design parameter charlg,es on overall system perforrnance and cornplexitv, and in evaluating irnage quality for specific imaging teclmiques. In addition to the studies listed in the table, 2-I) simuhatitms permitting ex'aluatit,'l of air/concrete bt_undarv and antenna cross-coupling effects, and of the impactof using multiple transnaittersas well ,as multiple receivers were,llso run. These studies helped to confirm conceptual design ctnach.tsions and permitted us to consider othe," rnore cornpk, x system configttratitwls, .,Ntaexample of results frona one important study is shown in Fig. 6. A series of simulatitms was run in which a single target of fixed size was embedded ,at increasing depths within the c(mcrete. The purpost, of this series was to evaluate imaged rangeandcross-rangeres(_lutior_ofthereconstructed target and to assess the accurac\' tri:the position h_cati(_n of the target after corrections for dispersion effects had bec?r_made. The image sequence was recor_structed using a multi-frequenc.v Ilolograplaic rnetht_d, which include,', a correction for the effects tridispersion, ] I [ _-_- 0.4 0.2 Block No block -__ _ -__ --_ i 1 2 I I 3 I()()t_ I00(1ps Array elementspacing, _patial',amplerate _ to-l_ mm larger cro._s-sectionsi/t, :, tl,_7_ IDIll larget depth Irlto I'_()mm Clutter source (aggregate) density I(1to _0",, lblget density/type No targets, I x'¢_id,2 reinforcing 4 Figure 5. I I I 0.6 0.8 --0.4-- [ _ _ I No block Block / Results from (a) 2-D experi- -_1 (b) 2-0 concrete mental data and model. -0.2-- -0.4 i Radiatt'dpulsewidth (b) ... 1.0 _ I -- 1 Variations The degrading effects oi dispersion and fl'equency-selective filtering on resolution areclearly shown in these images. As predicted from materi,al characterizatitwl measurenaents and analysis, while the target's dimensions rernain fixed, its image increases in size in both dt_wn-range and cross-range directions,as its depth increases. However, careful analysis of the images shows that the target depth, ,as intiicated by the peak of the image intensity, is located quite accurately when dispersion corrections are applied. The only exception is the case very close (!() mm) to the transmitter and receivingarray.Tlaemostlikeh,,causefortlleerror, in that case, was EM wave interference that occurred because the reflected pulse fron_ the target was incident on the receiving antennas, while the tail of the transmitted pulse was still propagatir_g past the receivers. The three-dirnensit_nal (3-I)) EM modeling elfort was started late in the year, to support testing -0.2 -0.6 Parameter bars (rebars), 2 rr,bars plus I void, a reb,u"grate, and rt,bar shaded fl'onl I.ikl radiation by otlwr rebars (a) 0.6 i,i Table1. Model.basedparametricstudles. I "--0.,, ...... 5 -0,6 -0,8 z -1.0 ..... ........ 0 I 1 i 2 Time (ns) t I 3 4 5 6 Time (ns) [ '_! ,,,' .... ,i_ ,q',",,',i', " [;,., '.,i';",";' .,,_t I_., ,.,,,,_, ::, ,:, Thrust Area Report FY92 7-9 and Pulsed Power Microwave .:o Ground Penetrat'mg Imaging Radar for Bridge Inspection iiiiii ii iili ii i i iii ,[Transmitter Figure 6. 2-D image sequence of rebar target at increasing depths. A array AReceiver " ........ Simulated Reconstructed depth (mm) image depth ........ o (mm) 10 16 20 21 30 31 4,0 41 50 50 60 60 70 69 80 8O 90 89 100 100 110 120 111 120 1 iiiii iii ilia Iqgure 7. iii li Cross range ;,_ _ ."', four rebars space and in free (b) volumetric rendedng of 3-D image _'_/_! " .Jt_",.[ t i _,:', _"_ _j'!E reconstruction. !t., t 7-10 _- Thrust Area Report FY92 ,:, [:-_lg,t_(_(:_rl_._ R(,so;tr(;k: Dov(.'lODtll(,li¢ or]rJ • ' l(.(llflr_/:),u,_ i _'_ I_i_ ' 'V I|l _ ' II q ' , Ill _1 ' ' rl , , , ,r r at II1 ' ' , GroundPenetratingImagingRadarforBridgeInspection,',, MicrowaveandPulsedPower of 3-Dimage reconstruction software. Very simple physical models were used in the early tests. An example of a test case is shown in Fig. 7. in which four rebars, three of which have gaps, are assembled in free space. This simple model permitted evaluation of the imaging sof_,are without hlcluding the complicating effects of clutter, dispersion, and filtering. After the image was reconstructed, it was pr(x:essed and enhanced with some rudimentary techniques to provide a means for viewing the 3-D rendering as shown in the figure, Images of time rebars are clearly visible in the rendering; however, the gaps in timebars are not. The gaps are not _en in the rendering because they did not produce any reflection of the EM energy launched in the simulation, and the energy scattered from the rebars tends to fill in timevoids. In the case where air-filled gaps in rebars are etabedded in concrete, we do expect to detect and image the gaps because the air/concrete interface at time gap will produce a significant phase reversed reflection, to simulate bridge construction features, and ill wtmichwe embedded several flaw simulants. UWB antenna and transmitter developme|mt will be pursued, and image reconstruction algorithm development, testing, and refinenment will continue with timegoal of having optimized radar hardware and imaging code available late in the year to support the demonstration. A low-cost prototype system will be designed to permit demonstration of base data acquisition and image reconstruction perforrnance. The objective of the demonstration will be to show improved performance in resolution, and accurate reconstruction of embedded structure. AdcJIowl_:l__ We wish to thank Jim Brase, Remote Sensing, Imaging, and Signal Engineering Thrust Area Leader, and John DeFord, Computational Electronics and Electromab,metics Thrust Area Leader, for their support in supplying the resources needed to develop and evaluate imaging techniques, to perform EM modeling, and to enhance the capabilities of EM modeling codes for this project. Future Work 1. Our continuing efforts are aimed toward a field demonstration of a limited-capability prototype s),stem late in timenext fiscal year. To support that effort, we will complete a series of experiments to 2. confirm key modeling results and verify system desigll parameters. Tho_ experiments will be conducted using a concrete test slab that was designed Our Nation_ H_,hways: SelectedFactsand Figures, U.S. Department of Transportation, Federal Highway Administration, Publ. No. FHWA'PL-90-024. N.P. Jon¢__and B.R.Ellingw(x_d,"NDE of Concrete Bridges: Opportunities and Research Needs," Federal Highway Administration Conf. on NDE for Bridges (Arlington, Virginia), (August 25-27,1992). = _- E_g_r) eer_ng Researctl Development and rect_nology o;* Thrust Area Report FY92 7.11 High-Average-Power, Electron Beam-Controlled Switching in Diamond o:° Microwave and Pulsed Power High-Average-Power,Electron olled Switching in Diamond W. Wayne Hofer Defense ScieJlces EngiileeriJlg Division ElectrolficsEngilleering Karl H. Schoenbach, RavindraJoshi,and Ralf P. Bdnkmann Old DominionUniversity NoJ_blk,ViGqnia Don R. Kania InertialCol!fiJlenleniFltsionProgram LaserPrq_rams The superior electronic and thermal properties of diamond make it an ideal material for a high power solid-state switch. Our FY-92 goals were to identify and address technical issues that could potentially limit the anticipated performance of electron beam-triggered, high power switching in diamond, hl particular, we concentrated on the role of contacts and non-lhlear effects at high electric fields, electron beam range in diamond, and carrier trallsport modelhlg. lm Introduction The superior electronic and thermal properties of diamond make it an ideal material for a high power solid-state switch. We predict that an electron beam-controlled diamond device could switch well over 100 kW average power, at megahertz repetition rates, with greater than 95% efficiency and voltages greater than 5 kV. High power diamond switches could significantly increase the performance of high power ..... switched power supplies, modulators, and power converters. Commercial applications include high power radar, contr()l for electric vehicles, high power hldustl'ial controJlers, and 2000 cm2/Vs. At room temperature, diamond has the highest thermal conductivity of any solid, 20 W/K cre, about five times that of copper. The electronic properties of chemical vapor desposition(CVD) diamond now exceed those of the best natural diamond (Table 1). CVDdiamond substrates can be cooled using microchannel cooling, a highly effective thermal management technology developed at Gawrence Livermore National Laboratory (LLNL). When the electronic proper- possibly solid-state Figure 1. Electron beam-controlled -e-beam switching at utility substations. The crystal structure of diamond is relatively " Research -.- switch. 100 switch, In our keV electrons are al_ "- sorbedin a thindla_ I_ mondfllm, andby ionization, generate ] Load well characterized, lt is a semiconductor with a band-gap of 5..5eV at 300K. By comparison, the band-gap of GaAs is 1.4 eK/.The high band-gap of diamond results in a small clark current compared tc)Si or GaAs. As a result, the breakdown field or holding voltage is very high, i.e., 1-10 MV/cm. The electron and hole mobility are approximately Engtneerlng E Diamondewitch a highconcentration j of electric carrlers in the diamond. M.J Pulsebias Development and Technology + Thrust Area Report FY92 7-13 Mlcrrweve and PulsedPower .:. High-Average-Power, ElectronBeam-Controlled Switchingin Diamond II II II Table1. Electronicpropertiesofdiamonds. , _,-i_ ,"Sinsl_stal ' Homoepi_ film Thickness 25-500 pm 1x 1x 3 mm 3 120pm Grain size 10-100's pm single.-crystal single-crystal Electrical 105-1011 > 10:I > 101l 1.00-800 100-1000 150 500-4000 2800 3000 1330-1334 FWHM 4-9/cm 1332.4peak (FWHM 2.4/cm) 1332/cm peak (FWHM 2.9/cm) resistivity (P-cm) Lifetime (ps) Mobility (cm2/ Vs) Raman ties of diamond and its superior thermal properties are combined with microchannel cooling and the rapid advance in CVD technology, diamond becomes an excellent solid-state material for advanced, high performance powerelectronics, electron beam is absorbed in the diamond film. The controlling electron beam can be generated and modulated at megahertz frequencies by compact, long-life, commercially available grid-controlled thermionic cathodes. As an alternate to thermionic cathodes, recent research and development of new high-current-density electron sources, such as ferroelectric cathodes, micro-field In our switch (Fig. 1), a high concentration of carriers (corresponding to kA's/cm 2) are created by ionization when a high voltage, low current emission cathodes, and even diamond field emission cathodes, could potentially be combined with a thin film diamond to create a very compact, robust, high power solid-state diamond switch. Our FY-92 goals were to identify and address technical issues that could potentially limit the _ ...... 1 I A ,.,_::,. _._103 101 102 l_V3 _,_ !10100 7 1,7/ --- nonlinear at high electric fields, transport electron beam rangeeffects in diamond, and carrier _ / 10" Voltage (V) ..i_ ,- /35 / _ _ .... •" ", -_ / __: 1[_i; •../ mm thick natural II-A --- diamond _ I 102 Voltage (V) .5_:' : i_i_"" -- ] 103 Dark current vs applled voltage for 35gm natural lI-A dlamond film. The currentincreasesrapidlyoncethetrap.filledlimit is reached(~200kV/cm).Similar resultswereobtainedfor50_n_thickdiamond, butthedarkcurrentIncreased rapidly at about ..,_v"'_ kV/cm. Figure2. _ 7-14 Thrust Are,* Report anticipated performance of electron beam-trigticular, we concentrated on the role of contacts and gered, high power switching in diamond. In par- FY92 4" Engineering Research Devolopment modeling. Our work is a combined effort with researchers at Old Dominion University at Norfolk, Virginia, and at LLNL. Contacts Diamond and is normally Nonlinear thought Effects to be an excellent high voltage insulator. However, we have shown that for both natural and CVD diamond on silicon, the dark current (no electron beam-generated carriers) increases by 10-11 orders of magnitude at high electric fields. For natural II-A diamond, the strcmg nonlinear increase starts at 200-kV/cm for 35 pm-thick diamond (Fig. 2) and at 400-kM / cm for 50 pm-thick diamond. We believe that this threshold corre- and Technology Switching in Diamond .:. Microwave High-Average-Power, Electron Beam-Controlled and Pulsed Power |11 u I 10"2 V2 Isr = _ ro r,. V d:--iV_ 1_1m tI1ick /lr : ll,_/tj, c 0 v, r d-T Doubl Oa i charge 10 -3 I " / -- Single charge -- CVD diamond ,_--- on silicon _ 10 "4 -- ,, -10 "s -- '_ 101 ,m 10-8 I _, ,, s / i -- _ 10 .6 -- ,_ /_ / / " curve-Lower curve + 10 ° -- Voltage (V) 101 102 /JJ V T-F Li,nii 10"1° _ lO1 J .. 102 103 mend on n-silicon. The onset of rapidly Increasing dark cur. n5. Dark I Figure vsI voltage lsLnvthick dla_is rent 10 depends oncurrent the polarity of the for bias. When theCVD silicon _ 104 biased negative, the hold-off voltage is highest. Volta Figure 3. Drift-diffusion modeling results. A model based on charge Injection qualitatively predicts the rapid increase in current at high electric fields. spends to the trap-filled limit. The thickness dependence correlates well with photoelectronic theory where the trap-filled-limit electric field is proportional tc) the square of the material thickhess. As the field is further increased, dark current is dominated by charge injection at the contacts. Bothourqualitafiveand morecomprehensivedriftdiffusion modeling results (Figs. 3 and 4) predict these results. At even higher fields, a negative differential resistivity phase quickly leacts to de- _2 "" struction of the switch, most likely due twcurrent filaments. Similar tw natural diamond, the dark current in CVD diamond on a heavily doped (_10 l_ cm '_) n-silicon increases rapidly at high fields (Fig. 5). However, the electric field threshold was in excess of 0.9 MV/cm, much higher than that for natural diamond, and it depends strongly on the bias polarity. Apparently silicon is a very 1] ,) I i I I 7' Beam off 600 _ ] Beam on _ Figure 6. Voltage vs time for electron _, Switch- 106 I ] Diamond dark current _ 300 '_ 102 -- •• 100 _tm thick Natural ll-A oI_ m 15001 Swi lO"2- (b) 1040 100 [ 103 10 z Voltage (V) '_ Figure 4. Drift-diffusion modeling results. Data from our drift-diffusion model with injecting contact and deep trap centers agree wifh the behavior observed qualitatively and At the lower field (a), the conductivity lows the electron fob I I I natural dlfforentblaslevels. beam, thethe higher but fleldat(b), current continues after the beam is tumed off, due to _ voltage Beam off " tch g --- S.0 -- '_ 2.5 _ _-- 0 10 20 30 40 charge inJection. 10 7.5 ent 180 0 35_rn-thick, I _ 540 _ 360 104 3.0 _: I 'N...._._.__._._._._ 1.5 0 ..._ 720 P-"'___l 101 II-Adlamondat two I Switch 10"a -- 4.5 i:" 1.1 ! .o 8.0 - 450 0 50 Time (gs) experimentally. Engineering Rosvarch Do_e/opnic, nt _nd rc'chnc_loljy ":" Thrust Area Report FY92 7-15 Microwave and Pulsed Power *'o High-Average-Power, Electron Beam-Controlled i - i :1.8i l 16 _- i I (a) Silicon ....I l negative Voltage 12 Switching in Diamond Silicon (-) . ii --- 200 175 -- 150 (a) Monte-Carlo 14I f" _ "i Currentdensity 25 o4_ _6 I 14 -- (b) Silicon I. I I I / 10 Voltage -- -- Current 8 -- _'_ density :_ ,200 -- -- 125_ _ -- 100 ,50 25 0 0 10 20 30 Time (ps) 40 _ I I I I 180 I I I I results ll-A diamond -- ./'--+ ,150 200 _"--_ Diamond / -- 4. Engineering J" i V" '+> I ,050 .ooo 130 140 150 E-Beam ' --"" l U _'_"--_. /E-Beam 35_tm I l 160 diode 25_tm TI l 170 180 voltage (kV) ] cup [ l_araaay---_ I _I 190 200 50 Figure 8. (a) Monte-Carlo calculations of ISO-keV electron beam penetration in 35Ttm diamond. Scattering effects in a Conductivity When the natural diamond switch is irradiated with an et_'ctronbeam, the switch conductivity foilows the beam profile at lower electricfields;but at higher fields the switdl remahls conducting when the beam is turned off(Fig.6).At even higher fields, the switch hilure islikelydue to filamentarycurrent. We believe this corresponds to operation in the negativedifferentialresistMty mode. When irradiated with an electron beam, the conductivity of the CVD diamond follows the beam profile (Fig. 7) up to 1.8MV/cm when the silicon is biased negative. However, when the silicon is biased positive, the CVD diamond remains FY92 I 160 Energy (keV) 35 J.tm natural --150 24 Electron Beam-Induced Report /f .250 -- (b) Experimental good blocking contact. Dark current in diamond is highly dependent on carrier recombination and trapping at deep energy levels in the diamond and whether contacts are blocking or injecting, Area 140 t _ 175 Figure 7. Electron beam-induced conductivity in l_m-thick CVD diamond on n-silicon for opposite polarities. When the n.silicon is negative (a), the switch conductivity follows the beam current. However, when the n-silicon is positive (b), the switch conductivity persists after the beam is turned off. Thrust -- Silicon (+) . 0 + ' 200 -- positive 12-- 120 0so I" /. -- _' " 0 2 modeling f 0.4 -- i i mo0.8 125 _ - I __ '_ 10 7-16 _ I 225 Research Dev(_lopmenl 25_m Ti anode foil are Included. (b) Transmission of the electron beam in a 35-_tm-thick natural diamond film. The electrons are completely absorbed at about 130 keV. conducting even when the beam is turned off. Based on these data, it appears that CVD diamond on silicon may limit carrier injection, thus enabling us to switch higher voltages. Ba_d on our current data, we should be able to switch voltages ranging ft'ore 4(X)to 4(X)0V. If the kxzk-onfieldcan be extend¢__-! 5-10 times by tailoring the diamond growth and conikTcts, we maybe ableto pr(Kiucean on-offswitch operating at20to 40 kV. To hold-off and switch higher voltages, we must extend the onset voltage threshold of the rapidly increasing dark current by using better blocking contacts. Electron Penetration Depth Electronpenetration depth determines the maximum diamond thickalessfora given electron beam energy.Thediamond thickness in turn determirles the maximum h(_ld-offvoltage. Modeling results show that the penetration depth for 150kV electrons in diamond is about and Tech_olo_{v High.Average-Power, ElectronBeam.Controlled Switchingin Diamondo:oMicrowaveandPulsedPower 35 Mm (Fig. 8a). These results are confirmed by our experimental data (Fig. 8b). F/lltUl_ W_ To switch the highest possible voltage and power, we must extend the electric field threshold of the nonlinear increase iii dark current. This will be accomplished with non-injecting contacts t_blocking contacts) and by understanding and controlling deep-trap center impurities hl the diamond switch. We will concentrate our efforts on CVD We will obtain data on deep-center impurities and defects in diamond by using Electron BeamInduced Current Transient Spectroscopy (EBICTS). EBICTS spatially resolves the activation energy and density of deep-level traps. These data will be used in our drift-diffusion models that calculate carrier transport in diamond at l'figh electric fields. Finally, we will construct a prototype switch to demonstrate kilovolts switching in diamond and a range of hundreds of amperes. 1. diaxnond grown on highly doped silicon and determine how voltage hold-off scales with diamond thicl_less. Engineering R.H. Bube, PhotoelectricProperties_" Semiconductors,Cambridge University Press (Cambridge, England), 1992. Research Develol]ment _lnd lechnology o:. Thrust Area Report FY92 7-17 Testingof CFCReplacement F/urdsfor Atc lnduced To_'/cBy-Products o:oMicrowave and Pulsed Power Testing of CFCReplacement Fluids for Arc-induced ToxicBy-Products W. Ray Cravey Dq_,lrSe Sciellces Ellgi_weril_g Divisioll Eh'ctrollicsEJlgi_weriltg Ruth A. Hawley-Fedderand Unda Foiles Coluh'JlsedMatteralut AJuflytical Scie_zces Divisiolz ChemishyalutMaterhTlsSch'lweDtt_artnletlt Wayne R. Luedtka ComplttermufCollmuuzicatioll EJzgilweriJtg DivisioJl Electronics Ellgilweriplg We have developed a unique test-stand for quantifying the generation of perfltloroisobutylene (PFIB) in chlorofluorocarbon (CFC) replacement fluids when they are subjected to high electrical stress/breakdown environments. PFIB is an extremely toxic gas with a threshold limit value of 10 ppbv as set by the American Conference of Governmental lndush'ial Hygienists. We have tested several new fluids from various manufacturers for their potential to generate PFIB. Our goal is to determine breakdown characterist-ics and quantify toxic by-proclucts of these replacement fluids to determine a safe, usable alternative for present CFC's. We are currently working with 3M, DuPont, and Ausimont, key manufacturers of these replacement fluids, to test them for potential PFIB generation. u Introduction Restrictions on the use of chlorofluorocarbons (CFC's) worldwide, nationally, and at Lawrence Liverm(_re National Laboratory (LLNL) will have an enormous impact on industry and go\'emment laboratories.On September16,1987, several CFC-producing nations including the United States signed the Montreal Prot(wol, which called for the phase-out of production of CFC .; no later than the \,ear 1997. President Bush, reacting to scientific data showing the m Northern Hemisphere, ordered the phase-out of CFC's by the year 19_;5,two years early than the /Vlontreal protoc(fl. I Worldwide usage of CFC is estimated at 750,',J00metric tons- (see Fig. 1). Almost half o_ this amount is used either as cleaMng agents in electr(_nic PC board manufac.... j. ,." in the fl_am blowing industry (an_ther v-,,. _-. ,,_. The majority of the remaining CFC use is in refrigeration and aerosol sprays. CFC's are used extensively in the automobile l, industry, as weil, as a refrigerant for vehicle air conditioners. Although several replacements for existing CFC's do exist, many of these replace....... Worldwide useofCFC.To*al useis 750,000 met- Worldwide CFC usage Figure1. 750,00n metrictons ric tons. L / 15% " \ \ _N. Clea agents 2,1,, 20'!,,/,, ,, Ii ] 7 VehicleA/C ;, / MicrowaveandPulsedPower + Testingof CFCReplacement RuidsforArc-Induced ToxicByProducts i lU i analysis on GC/ECDor GC/MS ['r-_[gepera,!or_C ......--_-] ...... I'Maichi_g Liquidsamples I ..J II removedfor Dielectric [ ...... I network _1 [_.._'_l li Ti.,er/Icounter I ,generator DC _ I generator I test To computer for post processing _ I k_ - I network I testcup I t %,,-I digitizer I Figure2. Blockdiagramof CFCreplacement fluidtest.stand.Theusersetsthe timeornumberofpulsesforthedesired test: AC,DC,orpulse.Theoutputofthecorresponding generatorisfedthrougha matchingnetworkintothedielectrictest cup.Thetest cuphousesthegapelectrodesandcontainsthefluidundertest. Samplesareremovedfromthetestcupand analyzedonagaschromatograph (GC)or GCmassspectrometer, to quantifytheamountof PFIBthat wasproduced,if any. Thevoltageacrossthegapandthecoincidingcurrentaredigitizedandrecordedona computer.Theretheyareanalyzed, andthepowerandenergyaredetermined. whirl1 was our foremost goal.Work isp rocc_,ding on the compressive data collection and analysis that is neces._ary to quantify the toxic by-pr(x-luct pr(x:luction for given breakdown conditions. Initial results from tc_ts conductecl with the test-stand show a linear trend with respect to arc enerb,y. We have receivc_:!ffmding from the Superconducting Su]._,r Collider (_SC) for analysis and testing of file c(×_ling fluid u_:t in flleir low-energy bcx_ster(LEB)cavities. A room de_'scriptivesurnmary of our progress is giverl in the sub_]uent _'_fior_,_. Replacement Fluid Test-Stand We have identified fl-m.,eelech'ical breakdown/ Figure3. Photoof test.stand, merits are toxic,,_flammable, or highly expensive. In addition, two replacements, although not toxic, have Lx_n identified as ozone depletion agent, and flleir u._ will L-_pha_:t out in the near future.t We are shMying several new replacement fluids fl_rCFC's fl-_atwould have similar electrical and therreal characteristics. CFC's am currently u_'d as high voltage elech'ical insulators and dielectric o×Mnts for the high-a\'erage--power rncx-lulatol_ u_4 to drive the copper vapor la_21sat the Atomic Vapor La,_r lsotOl__Separation (AVLIS) facility at LLNL. Several substitutes have been suggestc_:l to replace thc_;e fillids. But a stumbling block associatecl with thc_9.:,replacemenL,_ is the p(_tential to generate toxic gal.'s, such as PFIB, when the fluids are stibjc_ztc_'l to high ek_:trical strc_ and/or breakdowns, (X'er the last year, we designed, fabricated, and tt__teclthe new CFC replacement fluid tcst-stand, 7-20 Thrust Area Report FV92 • L_l_l_l(,(,_I_g R(,_i,<srctl Dc'_¢,topme_t sU'c_senvironn_ents that may contribute to PFIB producfion in CFC replacement candidates: AC breakdoyen; high DC field stress; and pul_.-] breakdown. Our test-stand was designed to simulate all Lhreeof the:_2environments. A block diagram and dc:'scription of the operation of the test-stand are _ven in Fig. 2; Fig. 3 is a photograph of the test-stand. An impofl:ant test that has application in the refrigeration industry is breakdown due to high AC voltages. We have the capability of pr(Mucing (_)-Hz AC, high voltage breakdown conditions with voltages ranging from 0 to 40 kV, and any dcsirc_i gap spacing acr(_ss fl_e test cell electr(×tes. CMr capabilities allow tlSto simulate the inside environment(ff theoMinary refrigeration compres_)r/motoras_mbly. High DC field sh'css tK'CLU.'S: in many situations where there are high \'oltagc_ present. Elcx:tricalarcing is not associated with thc._ conditions; however, there can be extremely high fields and corona (_n._t. With CILIF system, we air able to gerlerate thesehigh pre-breakdown fields in the fluid-under-test for any prc,_,.,ttime limit. After thegiven time lirnit, thefluid is analyzed fl_rl'Fli_Jformation. atr,/ le_lt_ir_lot'_ Tc,sting oi CFC Rc_p/oc'_,_L;ntf-h,(Js tor &c hUJLJc_,O To_JcB>P_oducts • I'ui_.{ breakdown environments are pr(w.tuced with nannyhigh voltage nlodtllators. T_l_icall\,,th(._, " " 2.o IlltK'ltllatcIl_ 1.6 -- accelel'atof ill'e Ll_d for driving cells, live )lave i'adal's, la_,l_, a wide i t (a) and i'ai_lge of i_-)tll_.t li, i I _ N such as voltage, current, pul.,K'-widtla,pu 1.,_'repetition fl'equenc3, (pTf),and energa'. PFIB prt_Juced with tile pertinent conh'ol variablc_, _. _ila 3.0 4.0 - F.ne,'gv 2.0 -- ./" ..... from tlaedielLvtrictcstcupbeforeexcitingthefluid, at 20kV,-II) kV, and 1(X) kV pul.,_.'s',lk,tween each sampie inteFval, the voltage and current wa\'efonaas were recorded, and the instantantx_us power and energ3, were calculated for the arc. A _Tfical data _'t is illustrated in Fig. 4. There are two loss naechanisms ,lS_w_qatL_.t with the a rc di._ha rge: re._isti\'e / ind ucti \'e phai*, Ios._s and ct)ndLIction loss. The resisti\'e/inducti\'e phase d urillg .-4-10 0 -10 5.0 -I tile time tilt, voltagecol- /. Arc voltage / d Top -- I -._'l J. 30 50 70 Time (IUS) I I I I (bl ! 90 110 "! N,,___ _ electr(x.k_confornling to ASTM standards_ was u_.t for testing. Tile dielt_vtric tt._t cup was filled with 85 ml of the fluid under test. _amples were taken los.'.;t.Sare prl_.iuced voltage 0.4 _ __,,. /,Conduction _ 1.0- j,_-,__ 0-10-10 30 -- current __ 50 70 90 I .....1 110 Time (ius) ......... "_ _ _ a= 100 .... 75 -- I F--II--1 I I =_.___.IL___ -+5",, of value 0 -- 0.010 gap spacing 50 _ _ 0.8 & _ 0.4 -_, 0 ' 0 -- • • I 80 I 160 ] 240 320 Energy (J) Figure5. Typical data set for pulse breakdown-induced PFIBgeneration. Typical data for (a) voltage and (b) current Breakdown _ to1.-;.The fluicl was subjectecl to ta _}-kV pul_ _at a pul_ repetition rate of 75 Hz, with a frill-width halfmaxinmm of 1rX)_.ts.A 10-nailgap spacing with brass I waveforms. _ 1.2 _ ,._ 0.8 ;> Measui'emeilts ha\'e been made on a ca,ld\late replacement fluid for the copper vapor ia._'r nat_.lula- i Figure 4. - >" and Pulsed Power - I conditions that can be pr(Kiuced with our pre_,nt \st-stand. in addition to Lx,ing able to pr(Ktuce tile pul,_d conditions mentionc_t, we have implemented a complete ekvtrical diagnostic system for naeastll'in#, tile breakdown \'oitage, di_harge cun'ent, arc pox\,er, and energy that are as_ciattxi with each puM,. Through tile u._' of tile data that is rtx:orded by tile diagnostics, we are able to correlate the quantity" of Experimental Results ";. Microwave The fluid sample was pulsed with a 30-kV, lap.,a.,s acrosstile gell.-> and tile CLIITellt begins to rise. < During this phai', then.' is a powerand energa'loss associated with the instantantx_us current ri_' and l-_ts pulse at a prf of 75 Hz. This data was generated with brass electrodes and a lO-mil gap spacing in the dielectric test cup. The energy per pulse is 4 mJ. voltage collap._,. The faster the voltage collap.,a_,s,the less apprt_viable the_, Ios_'s are. lhc .,vecond loss mt_vlaanism,\\'hich appeai.'s to be the most dominant in this experiment, is tilt, loss ass(K'iated with the \'oltagedropacrossthearc it_,lf.Fhe forward di'opel tilt' spark gap \,,'as ob_,rved to jump betwc_.,n-l()and fR)volts. The iaaaxinlulal (lutput ctu'i'ellt is 1allap f(ll tile pre.,<,ntcolafigtiration, limited bv tlleotitput trans- ing. the calculated field for tilt' breakdown \'oltage is much lower than what was exported ba._d on tile publishtm_ fluid characteristics. [:urther investigation slao\\,ed that tile breakdown level is much I_igher at lower ptf dtle to fluid I'ecovelT. Although this is no surpri_', it is a kev variable in the pul_'d breakd(_wn t)f the.<<'fluids. fo,'mer Superconducting Super Collider Tests flit' sam pies were a na Ivzed (_lla d ua Ic(_lunto gas claromatograph equipped with an eltvtlt}n capture detL_:tor.l,k'stfltsfrl_mtheanal\'sisaresh(_wninFig. 5. The reduced data shows a clear trend with respect t_ energy. Wewt_tfldlikett_predicttheamt_unttffl'FIB til<lt is formed t:(ll laigherenergies, b\' usiilg the data wecolh._:tol_thetc!st-stancl.Initial data l(nlkspromis- Wt, ha\'e been funded by tilt, SSC to test f_r the amount ,_t l>l:ll] that is potentially pr(_duced in their 1.15.Bcavities. We hak'e set tip a w(irking agl'eellqOllt with SSC tt_ establish I'l:iB gellL'l'atj(in data t_r 1.1{I$ca\'ities, exists,we art, prtl\it:tn,e, i11L, iaStli't_,nlt,ntcapabilities f(_i"qu,_r_lif)'ing Microwave and Pulsed Power .:. Testing of CFC Replacement Fluids for Arc-Induced Toxic By-Products PF1B in samples they provide. Tile first sample generated by SSC was subjected to 60 kV for 20 hours of operation. An electrostatic model of the LEB cavity was generated using Ansoft's Maxwell 2D 7, and the maximum electric field in the fluid was calculated to be 83 kV/cm. They reported that during the operation, there were no detectable breakdowns. The samples were analyzed, and no PFIB was measured above the 60 ppbv detection limit. (3) Future Work Our plans for the next fiscal year are focused on three key areas, (1) We are currently working to generate a comprehensive and complete data set for various arc-induced breakdown conditions for (2) various fluids. The last year was dedicated to developing the needed test-stand and diagnostics as well as chemical and analytical techniques. Now that the testing facility is in piace, we will fill in our data set and analyze the results for PF1B generation trends, with respect to parameters Stlch as energy, power, and prr. In addition to the continued testing of the replacement fluids, we propose to test, in cooperation with 3M, a fluid contarninatiorl detection system. The system uses a UV source (not specified) and detector to measure the transparency of the fluid. Initial tests have been conducted bv 3M, which show that the fluid's transmission changes b\, as nltlch FY92 .:. as _u ,'(_ 9n,,J when the fluid is subjected to high thermal stress. We will test various detector configuration and breakdown parameters to decide if the detector can be 7-22 Thrust Area Report ................................ Ett[J, ttt(,t,f(qg --.,..,., ...,-,.m..m t?_:'_(',trch ,,,,m..,,..n. D('t_,lo/)nl_'ttt 1. 2. 3. 4. 5. 6. 7. 8. ,_/_(1 used as a reliable means to signal {he possibility of PFIB contamination in hostile working environments. The third area that has been identified is the refrigeration industry, in the majority of industrial refrigeration systems, the refrigerant is circulated through the compressor motor, for cooling and lubrication. 8 In large systems, the voltage level can exceed 1000w_lts, leading to the occasional and often catastrophic electrical breakdown of the fluid. Our test-stand is capable of reproducing these breakdown conditions in the laboratory where a comprehensive analysis can be performed. Statement by Presidential Press_,cretary Fitzveater on the Phaseout of Ozone Depleting Substances, February 1/, 1992. I: Elrner-Dewitt,"How DoYoul'atcha Holeinthe Sky That Could Be as Bigas Alaska?," Time139 (7), (February 17,1992). A.K. Naj, "CFC Substitutes Might Be Toxic, Rat Study Finds," Wall Street]()urn,ft,July 2,1991. M.Weisskopf,"Study FindsCFCAitematives More Damaging Than Believed," The WashinNtonl)ost, February 23,lqC)2. ASTMStandard D877-87,DMectricBreakd0wnVolta,,C('(!flusulaliu,%, Liquids llsi,,k,Disk Electrodes(1989). J.C. Martin, Na;t(_secoudPulse 7i'ch;;iqu('s,Atomic Weapons Research Establishment, United Kingdam Note4, t970. A.iax_(,('// 2li) I'Md Simulator, Version 4.33, Ansoft C_rporation. Althou._,,Turnqtfisl, and Bracciano, Mo_h'ntRcfi'i,_erali(,;mat Air C(,;dilh,fiH.k,, The C;(x_.thearl-Willcox Company lhc.,(_uth Holland, Illinois)1988. L._ l(,(hn()JoH_ m,,,,,m,mmm,. ,,..,,.mumro,mw n_m mmmu mmmnn ulmIIInun IInlll m mnml nunmmmmmlm limBlm iiirillmpl lbliRiiimlnnllll iiIllmIIn_l ii| IfMIMI IIINIIIBI InlNIIIIIIIMIIm11IIIIIII INIIIIIIIIII_NIIBI, U lIlllplllr,I '1I1[11 II[11 AIoDl_mgSt_ptlstlcal Efectrom_gt_etic TtTeot_;to Mo(le Street/Chamber M(.'_su/ement.s .:. Microwave and Pulsed Power Applying Statistical Electromagnetic Theory to Mode Stirred Chamber Measurements Richard A. Zachadas and Carlos A. Avalle D_:ti,Jlse Scie_tces Eite,i_leerilze, Diz,ish_Jz ElectroJ&'sEIts_i_leeriJ_ S We are developing measurement and analysis tools to assess microwave effects on electronic subsystems that operate in large metal cavities, such as avionics boxes in aircraft. The measuremerit tool is the mode stirred chamber (MSC), which is a metal-walled chambeb large relative to a wavelength, into which electromagnetic energy is injected, lt usually contains a stirrer paddle to randomly change resonant mode patterns as aftmction of time. The analysis tools are based on statistical elech'omagnetics. This theory predicts that the microwave power measured at an arbitrary point (not near the walls) within an ovemloded, randomly complex cavity is a Chisquared dish'ibution with _,o degrees of freedom. This is a single-parameter distribution. Therefore, the mean power densit T measured at an arbitrary point in the cavity is sufficient to develop a complete statistical model of the power at any arbitrary interior point. By showing that a randomized aircraft equipment bay has sufficient Q and ensemble variations to behave as such a random complex cavity, we have determined that the mean coupling measured at a point in the cavih,, would be sufficient to predict the microwave stress (statistical dish'ibution of fields) to which an avionics box would be exposed over an ensemble of like aircraft (the fleet). A M_ could be used to generate the same distribution for testing avionics boxes uninstalled. This method could provide tremendotLs cost savings in testing. In FY-O2, we developed a small, lowpower MSC and verified that its interior power distribution is indeed predicted by the theory. We also made measurements in two equipment bays of a Boeirlg 707 aircraft and verified that the power measured at various points in these cavities has the same distribution. The aircraft tests were funded by the NASA Langley Research Center and were conducted in collaboration with the U.S. Naval Surface Warfare Center, Dahlgren. m, i in i i n Introduction need to ensure tile survivability Modern transportation systems and rnilitarv svstenls are increasingly dependent on sophisticared electronic controls. At the same tinle, tilt, potential for electromagnetic tEM) susceptibility oi electronic s\'stems is increasing tor several reasons: modem integrated circuits with higher densities and speed art' often more sensitive to EM transients; modern composite material structures nlav provide pc}orer F.Mshielding; tilt, EM power ill ihe enviror'Ullent is increasing as more users share the airwaves. Because (_fthese fact(_rs, tl_c telns that nlav be exposed to high-power EM sigrials has become of great interest. Ad\'isorv regulatit_n has recently been drafted for aircraft that would require testing and/or analysis to assure tile EM hardnessof installed flightcritical and flight essential equipment. Similar safer\, assurante certification pn'c_cedures nlav be imposed on other electronicall\' controlk,d transportation svstenls of tile t:uttlre. The l)epartment of l)efense (I)OD) is pal'ticularly interested in dex'eh_ping methods for assessing potential I{Meffectson nlilitarv svstems, SillCetilt' II(H'lllal ell\'il'(Hllllellt these of electronic svs- ,i Microwave t iii and Pulsed Power t ii .:. ,41._pl_,m_ Stot/sticol . Eh_ctrom,_gnet_c"r/Teor_ to Mo(le .%tHtt,OChot)_t_('r M(,,_(/r(.,/i,,/_ts _ t i i Mode stirred chamber Figure 1. Block diagram of Mode Stirrer _ Diffuser Stirred Chamber t ) Instrumentation. Cou ,az" rf source unit systems operate in is often quite severe (e.g., ata aircraft carrier ch.,ck),nncl since these systems may be e×posed to high-power signnis intentionally tr,msmitted by an adversary. The IX)D niso neecls similarmethodstoassessthelethalitytffproposed EM wenponsagninstcandidatetargets. I While full-system, full-threat testine, may be the most thorough manner to determine susceptibility, it is often too expensive to be prnctical for inrge systems. Conaputer models alone have been unsuccessful ill,lccurately predicting EM susceptibiliW, especially ,at high frequencies. At Lnwrence Livernaore National l.aboratorv (LI..NI_j, we have developed econonaical assessment techniques based on measuring and comparing EM stress and strength.-' The power to a device or circuit (stress) is extrapolated from a low-power EM coupiing meas'.lrement and is compared against the up,;et threshold (strength) of the device or circuit, A system model is used to relate de\'ice or circuit effects to system effects. This teclmique works well for small systems such as missiles and land mines, but for large systems, the number of measurements and analyses becomes large. In addition, as the system size becomes many wavek, ngths, the coupling as a function of frequency and angle also becomes extremely ctmlplex to the point that deterministic descriptions cannot be made. In this regime, new methods of testing and modelirlg must be de\'eh_ped. We believe that the mode stirred chanaber (MS(?) and statistical electronaagnetics will pnwide a new method to make vinble stress-vs-stre|lgth c(mlp,_rist,'lS forsubsvstt'ms. 3,l,q 7-24 Thrust Area Report FY92 .:. _rl_)t,(,_,l_ l?e*,_ o,vh Dt'_t,/o' _'_,t Progl'e_ C)ur first major accomplishment was to develop a small, low-power M.LT)(_ _r 1 ill chamber was equipped with o prover level:., i, _.lrcuit nnd with automated control nnd data ncquisition instrumentation. Chamber performance was characterized. C)ur second naajor accomplishment was to measure nnd anal\'ze the statistical distribution of microwave pmvt'r in equipmept ba\,s of a fullsized transport ,aircraft. 'llle me,sured distribution m,atched that measured in the M.qC and that predicted b\' theor\,. MSCDevelopment Our MSC was built from nn existing tr,ms\'erse electromagnetic (TEM) celI. A TliM cell is designed tooperatesinglemodeand producesa well-known field pattern usually used to calibt'ate senscws. Above its cutoff freqtlellcy, the TIqM ct,li bet'ollles increasilagly t_\'ernlt_dt.,d. To pl'tmlote mtwt, effectix'e twermoding, we removed a sectit_n of the septum (center conductt_r), and added large rcflecti\'e diffusers, to scatter the energy in random directions within the cell. A mt_tor-sptm stirrer paddle, large compared tt_ thr' w,l\'elength, r,mdomizes the field pattern as a tunction of time. At fretltlencies greater than st'\'er,ll times the cutofi (J> 400 MHz), the mode densit\' is large, ,rod the stirring produces t'andom field patterns. Figure 1 shows ,1 bh)ck tti,lgr, lm t)t: thf N,1S(" instrument,ltion. A Iow-pt_wer micrt_wa\'t, st)urt't' ,_ 0 t_,_ !_, _,i,_:_ 4lJpl_,n_gSt,ltJst_c,ll Elect/(nn,tl_r_t,t/c Tl_t_ot_to Moll(, .%ht/(,(/Ch,m_D(v /Vh_,_._uron_t,r_t_*:* Microwave - i and Pulsed Power ii dclivcr_ tlwF.M cncrg.v intotllc cllambcr. llw rf signal can bc fcd into Lilt.,chaniLwr lhrougll tlu., usual TEM ccll input port or bv d scparatc h_wn t'ockpil cabin antenna placed inside thf chan_bcr. A power h.'vcling unit was dt,vch_pt'd h) dvnanlicallv adjust thc power to compensate for power reflcctcd at the tlansnlit illltClllla due to changc.'-; iii thc voltage standing wave ratk_ (VSWR) as the stirrcr turns. Wc used a varictv Si:_cctrtlnl of SCllSt)i'_ and antcnnas, allaiv/cr to illcastlrC point._ in the chanlL_er. Fully pt)wt'r and Wire txt antenna _ I Ho,'n txi Wire rc,,, antenna anlenlhl. I a /-// l bay autonlatic control arid _ C',_rgo bay i - Landing gear well i Stirrer Avionics instrumentation lnsh'unleniation _.\'erc Colldtlctcd ,it Davis Moritllarl consisted transmit of a long antennas wire were and driven .'-;OLli'CCSinstalled ill an illicrow,lVC mcntation van, and wcre o1: tilt, receiving illtln_tnation allah'zcl'_ oriciltt_,d a horn van q_ [ _ 1/ equipment ha\, under study was ,.intcnnas. instrumented with two tr,msnlit arid two i'ccciv¢ Each pair rack Air Force I]asc in Tucsorl, Arizona, l'hc cxperirrlcrltal setup is shown il_Fig. 2. The interior of the aircraft Tllc box .--" Avionics 707 Tests Tests Insh'umenled electronics lhlm roy anlenna at vari()LiS data acquisition wcrc inlph:nlCntt,d with a personal conlptitcr, Boeing l',i,i,,,enger rf sources rf amps GI'I B Sp_,_tru,_ bus antcnl'la. by low-power adiaccnt illslru- to avoid alltcnl'las. clircct Spcctl'tlm Figure 2. V_'CI'L'Ll_cd to l'llLk-I._LlrC]90_VCI" at varioLIS Block diagram of instrumentation for microwave power statistical distribu- tion measurements made at Davis Monthan Airbase on a Boeing 707. points within the ba\,s, while a nlotorized stirrcr paddle randomly changed tilt' mt_de pattcrn <l._a t:unctit_n of tin'lc. Thc stirrer lll(_tion sinlulatcd tilt, ....... \'ariations in tile po._ition ofcquipnlent in tilt' I__a\sthrt_ught_ut the fleet t_f aircraft, lkwtilble conll._utcr.<; wcrc usc,d for data acqtiisitiorl and "_ 0.14 = measured power in (a) the mode stirred ,_ 0,12 chamber and (b) the analy sis, I 'i_wt, r wa._ nlcastlrcd _0.10 equipmentBoeing 707.bay°fa ralldom tics for l't.'ct'i\'t' each of alltt'lllla tilt' four at discrete frcqucn- I:>Os.'.;iblc transmit COlllbii_dtiOllS. Tilt 0,18 Figure 3. 0.16 -- la) 4.0 (_;tlz Probabllitydensltyof and _ 0.08 IllCa.'-;LlrCillClltS i_ 0.06 were rcpcatcd for scvcr,.il antenna locations within the a ircra ft ba\'s. 0.04 0.02 0 Analysis lllt' timu and Results (or ,;tirrcr -rs pt_.,;ition) wavcl:orna.s for 0.20 botl.i tilt, MSt and aircrat:t data l(_okcd similar in that tilt' rcceivccl amplitude varied rapidly with - was (ii: 2()dB or nlt_l't'. Thf timc data '_ 0.15 stati.stic,.illv anal\'/t,d ,_ c'Xctlrsion5 sit\' histt_gram.s shown to gr!ni'raft, probability den- of the I__owcr (in di;lm). Thr, st arc, in Fig, 3 (a and hl, for tilt, aircraft and ,k:l$(_", -70 L lbl 4.0Gttz I i _ 0.05 was dcrivud l:l'(im a ta,vtl-dcgrot,-tll:-trc,t_'dol)% (..iii_;c/tlarcd dc'ilSi,v rising a v<.irial_lt, trail._t;ornaatit_ia to 0.00 -35 - I,.l/,-- -70 -60 c( iii \'OFt til d []. ['llt' d ircrd t:t a lid ,l_/1 _(.) da la t'( )Ill ['iii rc well to each tlthc, r dnci to tilt'tW,. Jl','%I'<.ll -40 l Iit [ _ 0.10 ]-- respcctivel.\', along with tilt, thtioretical probability dcnsitv (dashc,cl oArvt.'s), lhc predicted dcnsitv i,')L_':;l;£'/'ll..t_ -45 -65 Power -60 -55 -50 (dBm) -50 -40 -30 Power (dBm) }J It)¢'i l''r(I/It,i11''!' t #'J!t rf'( "_:'_:t'ii_ "1" Throst Are;! R{_port FY92 7-25 MicrowaveandPulsedPower o:.ApplyingStatisticalElectromagnetic Theoryto ModeStirredChamberMeasurements I_m Work Four issues must be resolved before certified, quantitative subsystem assessments can be made in MSC's: 1. MSC tests must be shown to be repeatable, predictable, and rigorous. This is necessary for the technique to be accepted by government regulators and industry, 2. The power distribution in the MSC must match that fotuld in the system cavity. This ensures that the subsystem sees the same EM power environment as if it were installed, 3. Coherence length must be understood and the effects of structures near the subsystem taken into account. A structure installed in the cavity will interact with a subsystem if their separation is witl_n a coherence length, Therefore, structures within this length will need to be simulated in the MSC for accurate results. predictable. Since tile prediction will be based on the correlation of file field components picked up by wire segments of the antenna, this will also serve to validate our understanding of coherence length. Separability will be demonstrated experimentally in our anechoic chamber and MSC using simple metal boxes representing an airframe and an avionics box. Once shown for a simple case, the measurements willbe repeated with various cable and transrnission line comlections to the avionics box to establish the cases where separability does and does not hold. The end product of this study will be a set of theoreticany and experimentally validated EM susceptibility assessment tools that would allow accurate EM effects testhlg of subsystems at high frequency, while avoiding expensive high-power full-system tests. 4. 1. A. Pesta and N. Chesser, Department of D_fense Methodolo,k;yGuidelinesfi_r High PowerMicrowave (HPM) SusceptibilityAssessments, Office of the Secretary of Defense, HPM Methodology Panel Report, Draft (1989). 2. R.Menshlg, R.J.Khag,and H.S. Cabayan, A Method fi_rEstimatin._the Susceptibility_"Eh'ctnmicSystems to HPM, Lawrence Livermore National Laboratory, Livermore, California, UCID-21430 (1988). 3. M. Crawford and G. Koepke, Desex,m,Evaluation, and Use of a Reverberathm Chamber._r Pe_rming Eh'ctromagneticSusceptibility/VulnerabilityMeasun'merits,NBSTechnical Note 1092(1986). R. Price, H. T. Davis, R. H. Bonn, E. P. Wenaas, R. Achenbach, V. Gieri, R. Thomas, j. Alcala, J. Hanson, W. Ha_aes, C. McCrea, C. Montano, The transfer function describing coupling to devices in the subsystem must be shown to be separable into a product of coupling from outside the system cavity to its interior, and coupling from the cavity interior to the devices within the subsystem. An example of a non-separable case is when the major coupling into the subsystem is through a waveguide that exits the cavity. In this case, the random field environment in the cavity is immaterial, and MSC tests would not provide accurate results, In FY-92, we developed a small MSC facility and instrumentation. We made measurements in the MSC and in a commercial aircraft that showed that the power distributions Thrust Area i_pot| FY_2 ": Ellgil, eeling 4. matched each other and the theory. In FY-93, we are planning experiments to resolve the remaining issues. We will use statistical EM theory to make predictions of the coupling as a function of frequency, onto simple 7"_ wire antennas in the MSC, and compare those predictions against nleasurements. This will help to demonstrate that MSC tests can be rigorous and Re_u,*lt.h D_vvlupi. e,_i R.Peterson, B.Trautlein, and R. Umber, Determination qf the Statis_.icalDistribution of Electromagm'tic FieldAmplitudes in Complex Cavities,Jaycor Report No. 88JAL129(1988). 5. a_;d T.Lehman, StatisticsqfEh'ctromagm'ticl-iehlsin Cavities withThe Comph'x Shapes, Phillips Laboratory Interaction Note (1993). Tt..t. lint) log._ Magnetically Delayed Low-Pressure Gas Discharge Switching .:, Microwave and Pulsed Power Magnetically Delayed Low-Pressure Gas DischargeSwitching Stephen E. Sampayan, Hugh C. Kirbie, and Anthony N, Payne LaserEllgilweringDivish,l ElectmJficsEllgineerillg We have investigated Eugene Lauer and Donald Prosnitz AdvmlcedApplicationsProgrant LaserPrograms the properties of a magnetically delayed, low-pressure gas discharge switch. We performed measunaments of the closure and recovery properties of the switch; performed quantitative erosion measurements; mid observed the onset of x ray production in order to compare switch properties with and without delay. Further, we performed qualitative optical measurements of transition line spectra to correlate our electrical recovery measuremerits with plasma deionization. lUln ii iu Introduction Progress Fast-closure-rate, high-voltage (> 1(X) kV), highcurrent (> 10 kA), high-repetition-rate (> 1 kHz) switching has remained a major area of research in the pulsed power field.l.2,,__lid-state switching has generally been limited to several tens of kilovoits;high-pressuregasdischargeswitchingislimited to repetition rates below 1 khz; vacuum switching is generally a slow closure process; and magnetic switching requires exh'emely precis" voltage and reset state control to minimize jitter. Our magnetically delayed low-pressure switch (MDLlX3) test-stand was built primarily tosupport the long-pulse, relativistic klystron (RK) and fl'ee electron laser (FEL) work at Lawrence Livermow National Laboratol_y (LLNL)._' In this application, a closing switch initiates a pulse, which is delivered to an induction accelerator cell.7 The induetion cell accelerates an injected electron beam to a sufficient energy suitable for the RK or FEL. Low-pressure gas discharge switches have shown promi_, as a hst-closing, high-repetitionrate device such that if sufficiently fast closure times can be achieved, single-stage power conditioning chains would become feasible.4, 5 The primary difficulty with this switch, however, is anode electrode damage during closure initiation, resulting in short lifetimes. Once triggered, electrons emitted ft'ore the cathode plasma can form a pinched beam and deposit significant enough localized energy to vaporize anode material. Inserting a series delay element, which inhibits the application of full voltage and current until such time that the discharge plasma has filled the gap, minimizes this effect, lt is this version of the low-pressure switch that we are presently studying, Apparatus Engln(,_rlng The MDLI_ test-stand (Fig. 1) consists of a single water-filled, 1242, 70-ns Blumlein from the advanced test accelerator at LLNL. The Biumlein is attached to a liquid load and charged from a single dual-resonant transfl_rmer. The transformer is powered by two charged capacitor banks discharged through separate thyratrons, diode isoiated and fired sequentially to produce two charging pulses. A trigger pulser initiatesa singleclosure event at the peak of the first charging pulse; the second, variable timing, charging pulse is allowed to ring to zero and is used as a test pulse to verify gap recovery. The low-pressure gas gap consists of an anodecathode electrode pair separated a sufficient dis- R_,sealch Devei(;pnl_,nt ,:_n(I T('_:hnol(_t;) ,:. Thrust Area Report FY92 7-27 Microwave and Pulsed Power .:. M,L_tr>trv,_lll D_,/<_,(,(JI_o_v/_r(','_su/_'G,_ D,_ci_,u_o ,'-;_wtclnn_ Figure1. Switch /" _ test-stand used to _ ATA Blumlein _ study magnetically delayedswitchprop- ertles, Magnetic delay |'_drt__'] the _,rfornlance with and without the _ltttrahk' ind uct_w. A c_m F,afm,1 of b'F,iCaIck_survpn _tx'rth.'s is showll iri Fig. 2, and of t\,pical reco\'erv Low- _....._. Liquid I II12_> "_0kV,70,,_II.... ..... Iliilp ressurewas ['Wt)_.%'l'tit_ in Fig. 3.J:lw thtr' d,'lta, the_apsp,win_ load switch I cre, the gas was nitrogen, and the antxk_'ath_]J .... IL__ pulse 2SkV>_ _le\'olta_ewasl_t) kV, (.'l_sure time, defined as the Ii) to L_},,,,transition Reson sllowed a factor-of-byu irnpro\'t,t_wrlt at lower pr,,,,stimeofthe,'oltageacro._thelow-pr_st,,'ega,_gap, stu_ with the magnetic delay, i.e.,with the,_tu rable inductor. Al higher pr_,'s,.;ures,above appr_ximately 7 m I',the _turabh., inductor had littk, eft_vt. Reco\'erv lime with tile _'l'k_ _lurable inductor ant_ charge Switch chassis Solid-dielectric cable larlct' to prevent _'lf breakdown (at aPProxin_ately IIX) to I._.)kV/cm). A surface flashover tril._et'ing device, eml×'dded within the cath_xle, initiak.,s the ionization pr_x.'t,_,._,'s that render the gas highly conduct|re. A s_turabk,inductor plact_] in _,rit_ with the switch, d(?i0\:s the on,,_,toI:full current, allowing the ionization pi'_x.'t_,._lo spread throughout the gap volume prior to full closure.'ITw_turabh: inductor is dt_igned to limit current flow Ix,low thethrc,'sholdfor constrictc_!di_'hargts, and hold off the full anbn:lecath_x.h., voltage until the di.,,_'harge has l:illt_l the gap volume, l)iagnostic_ for the tuft-stand consisted of current and voltage ,_'n,_,_ for the switch and l]lumlein, Other diagnostics consistedof a fast x ray detector, a fast gakvl camera,and a ().2,_mmon_x:hromat_,'.Al prt,'_,t,we u_'d an image-intensified _atedcamera to t}b,_,rvt, the n_on_×'hn_mahwi_lltpul. We are installil_ga gak'clphotomultiplier systen_for ftlturt, work. F,xperil_lerl_ improved significantly and was exh'emelv reliable: _)",, recovery probability was _slimated. At k_wer pre,_tu_, extremely g_x_| rt_'o\'erv tirn_ (approximatt>lr 5()I.tsor 2()kl Iz-cqtdvah.,ni pul_, n.,tx,tition l:r_luency) were ob,_,rve,l, whi h.,at higher prr,'ssurt,,s, tWoverv time was ob_,rved h_Ix, 51.is.By contrast, reco\'c,rv Pr_bability without the ,_,,l'k__turabk, iridueler was not reliable and was meastu'ed to Ix, Lx,tween_) and _()".,. Although at lower prt,'ssur_ and this recovery probability, l:astt'rrtvovt,l'v timt_ were ob_'r\'ed, rtvover\' did n_t _x'ctu" above 7 mT. Wemadequalilati\'esl×vtro,'_'opicmeaslu'emenls of late-time line emi_,_ionfrom the gap in order to vet|l\, our recovery measurementsix,rlormt_l ek_'tritally. S|xvtro_'opic ob_,r\'ations of the di_'harge showed thal line radiation from thenitrogen &,caved within l()_.is al:Irr currt,nl c,t.'s_'_li_n.I.ine radiation characteristic of the anex.lematerial, however, requir_l greater than 5()rasto tltvav. 'l'his rt,,sultwas consistentwith ot,rele,,'tricalmeast.'ements. lines|on rah_ with the ._'rk_ _lt,'abk' inductor were a factorof (_)It,,_sthan tho_, of a similar liMime ttstwithotiltlw_,ritss_turableindtlcttw.l'hoto_raphic coinpari_ll_s all, showi_ in Fig. 4. l'ht_, tt.'_ls\vr,re ctlnducittt di q()kV, with I_ih'ogt,I1al 8 nll' t_rtssurc, and using alul_lil_un_<u_l_.k ._.In the fii._iic._i(Fig. 4a), .'gt'\'tWt' <'lilt Kit' d0nldgt' Wt, _,,rfol'n/ttt ,_ldi_dill'd magnetically delavctt i sttlc|it._ tit the Iow-prt._,_urt,._\vitch and o_m- .., _ 400 .... 300 lay ......... 200.... the tl'i_tT Measured --_ ' ._ ",,, tl\'tw thf ,ll_ct pdrlit'tllal'lv t'ntirt' dcTO._,_fi'_lnl el_vtl'_tk'.'l'he total i_tlll/i_,,r tit sh_is was 5 Pressure 10 / 10 ..... 1 15 0 Area Report FY92 *:. Irt, ll_,_>#_# , t_'<,_',t_, 1, Without ll_'_'l_,p_i,'slt ,l_i,t l_,_l_,/,,llt (Ni) I'I'CAiVI'FV) del ..... _ With delay _1 .,/" 5 Pressure N 2 gas, (mT) Figure 3. Thrust .... > oo.l loo 14'iii,delay _"-----i...._e"l"-_'_i_N'_ll l_oui de II I I 500 o 0 ?-28 \vds tli_,t'\'t_.t stii'tdt,t ' of the t'ltt'h'lttt' illl closure results with and without delay. Figure 2. pal'ai_c,hic" 11 . 10 N 2 gas, (mT) Electrically measured recovery results. . 15 MagneticallyDelayedLow-Pressure GasDischargeSwitchingo:..Microwaveand PulsedPower appro,ximately 16,0(_).In the second test (Fig. 4b), a less pronotuaced hadentation rt__ulted ft'ore the test, with minimal damage having occun'_i throughout the anode surface. The total ntmat'_r of shots dttring figs latter test was approximately 400,000. We l._rform_xi x ray measurements (Fig. 5) to understand the thne evolution of electron emL,_ion ft'ore the cathcnie of the low-pre,xsLweswitch. Our relative me_stu'ements of the integrated x ray output durhag switda closure showed an order-of-magnitude deca'easewith the series saturable hlductor. Further, we ob_r_.'ed the most hltense x ray output from the lowpressure switch during the irfitiation or 'trigger delay' I_-_'ri(Kiwithout the series _lturable inductor, mad after the closure process had begtua with the series in'tplementation pemlits the construction of a detail_i system simulation model of the test-stand that Figure4. Compar#son ofetectroae erosion (a) without _turable inductor, We aL_ meK_uredthe variation of the x ray output from thegap at various gaspl_ssures. From this measLLrement, we ob_r_,o.i the x rayoutput deo_ease by about ._<'/,.when the gaspressure vv&,_ increaso.i from I to9 naT. includes the dlarghlg drcuit, Bkunleh'l, magnetic switch, and load. We tksea magnetic switG_,model that indudes rateKlependent k×_p-widening of the hysteresis kx_p, hysteretic losses,minor kx_ps, and hysteresis effects.SPresently,we are validating the low-pr¢_ure switch mid ma_letic switch m(×iels agah_stexI._rhnental data. Once validated, the com- and (b) with Modeling plete system m(_.iel should pemait LLS to study the sensitivity of switch closureperformance to magnetic coreparametersand to low-pressure switda parame_ ters suda as elec_'tKiespacing and initial electron density, and thereby provide LLS With a tool for making switda design Lradeoffs. We develol_-_da one-dimel_sionalmt_.iel for the clostu:eregime of Lhc low-presstu'e switch. In this m(_.iel,the motions of ions and electronsarem(_.ieled by cold fluid equations that include collision ionizalion mad space charge eff_xts. The m(×iel equations are p_ameterized in terms of gas t_l._e(iol_zafion coeffident) and pressure; svvitdagap lenb_.hand crosssectional area; and the initial electron density pr(}duced by the trigger puPse. This m(_.iel I._nnits LLS to follow the space-time ev(_lufion of the ek_tric field and the ion and elech'on current densities in the gap, as well as the total switch cu_ent and tem_tinal voltage during switd_ clostwe, We have implemented the m_Klel in a generalpuq.x)se network and system simulation code. This i magnet. ic delay. FILItUl_ Work We have demonstrated that the use of a series saturable inductor placed in series with a lowpressure gas spark gap greatly enhances performance. From our measurements, we understand this improved performance to be primarily due to minimizing anode material vaporization during the initial closure of the gap. Without the series saturable inductor, x ray etnissiola occurs i Figure5. Measured x raypulse(top curve)andclosure (bottomcurve)of the low-pressure switch(a) without magneticdelay(0.5 V/div.)and(b) with magneticdelay(0.1 V/div.).Horizontal scaleis100 ns/div. Engineering Researcli Development and Technology .:, Thrust Area Report FY92 7-29 Microwaveand PulsedPower .:. MagneticallyDelayedLow-Pressure GasDischargeSwitching from the point of triggering until the initial collapse of the gap impedance. The energy deposition into the anode is large as determined by the integrated x ray intensity. With the series saturable inductor, energy deposition into the anode is initiated at the instant the collapse of the gap impedance occurs. The net effect is lower energy deposition into the anode. From our data, we conclude that with our present triggering method, this switch is capable of operating as either a low-repetition-rate final output switch or, because of the slower closure times at low pressure, as a high-repetition-rate initial commutation switch, i.e., in the initial stages of the power conditioning chain. Although the present triggering device appears adequate, it is difficult to couple a significant portion of the trigger electrical energy into the low-pressure gas. In future work, we will install newly developed, simple, ferroelectric electron emitters as a triggering device. '_Current densities from 0.1 to 1 kA/cm 2 have been extracted from such an emitter for several hundred nanoseconds. Such a device should allow better coupiing of the trigger electrical energy low-pressure gas. We would therefore much faster closure times sures, Our spectral observatioi_s ery is primarily h_ibited by ing iorfized in the gap. lt is to the expect even at lower presindicate that recovanode vapor remainwell established that anode materials with low heat of vaporization, in order to rninimize the accumulation of anode material vapor in the gap. 1. G. Schaefer; M. Kristiansen, and A. Guenthel; Gas DischmRe Closing Switches, Plenum Pwss (New York, New York), 19_)0. 2. H.C. Kirbie, G.J. Caporaso, M.A. Newton, and S. Yu,"Evolution of High-Repetiti,,_n-i_,atelnduction Accelerators Through Advancements in Switching," 1992 Line,r Acceh'rah,"Col{fiProc.,595 (1992). 3. R.A. Dougal, G.D. Volakakis, and M.D. Abdalla, "Magnetically Delayed Vacuun'lSwitching," Ih'0c. 6th IEEEPulsedPowerCol!fi,21 (1987). 4. E.J. Lauer and Int. D.L. Birx, "Low Pressure(1981). Spark Gap," Proc.3td PulsedPowerCoq]i,38{.) 5. E.J.Lauer and D.I_,.Birx,"l_,sts of a Low Pressun? Switch Protected by a Saturable Inductor," IEEE Coqt: Record 1982 15th Power Modulator Symposlum, 47 (1982). 6. T.L. Houck and G.A. Westenskow, "Status of the Choppertron Expenments, " • " 1992 Linear Acceh'mtor ConfiProc.,498 (1¢_-)2). 7. S. Humphries, Principlesof ChmRed Partich'Acceleration,John Wiley and Sons, Inc. (New York, New York),283ff(1986). 8. A.N. Payne,"ModelingMagneticPulseCompmssors," Confi Record 1991 Partich'Acceh'ratorCot!ft, 3091 (1991). 9. H. Riege, N_t, Ways oi Electron Emisshm.tbrPower Switching and ElectronBeam Generation,European Organization for Nuclear Research, Report CERN-PS 89/42(AR)(1989). [_ recombination fimesformetalvaporexceed those of gasses by at least an order of magnitude. Thus, to enhance recovery, we will investigate the use of 7-30 Thrust Area Report FY92 _ EnE, tnt_erlnl_ Re, search Developmel) t Jnd Techn()loi;y Nondestructive Evaluation The Nondestructive Evaluation (NDE) thrust area supports initiatives that advance inspection _ience,'md technology. Tile goal of the NDE thrust area is to provide cutting-edge technologies that have prornise of inspection tools three to five years hl the future. In selecting projects, the thrust area anticipates the needs of existing and future Lawrence Livermore National Laboratol 3, (LLNL) programs, NDE provides materials characterization inspections, finished parts, and complex objects to find flaws and fabrication "'_: ::_ defects and to determine their physical and chemical characteristics. NDE also encorepasses process monitoring and control sensors and the monitoring of in-service damage. For concurrentenginee_lg, NDE becomes a frontlinetecl'mology and strongly impacts issues of certification _d of life prediction and extension, In FY-92, in addition to suppo_@_g LLNL programs and the activities of nuclear weapons contractors, NDE has irfitiated several projects with government agencies and private industries to study aging infrastructures and to advance manufacturing proces_s. Examples of these projects are (1) the Aging Airplanes h'_pection Program for the Federal Aviation Administration; (2) Signal Processing of Acoustic Signatures of Heart Valves for Shiley, Inc.; and (3)Turbine Blade hzspection for the Air Force, jointly with Southwest Research Institute and Garrett. In FY-92, the primary contributions of the NDE thrust area, described in the reports that follow, were in fieldable chemical sensor systems, computed tomography, and laser generation tection of ultrasorfic energy. and de- Fieldable Chemical Sensor Systems Our objective for this project is to develop diagnostic instruments for quantitative measurements of the levels of chemical contaminants and concentrations in the field or on-line in operating processes. We believe that the integration of Raman spectroscopy ,'rod fiber-optic selzsors will allow a revolution in chemical analysis by developing the capability for field analysis rather than the more conventional methods requiring extraction of stunpies for later evaluation in a laboratory environment. We are in the second phase of a two-phase project. In the initial phase, we detern@led the widespread needs for chemical sensors to measure contaminant levels in liquids and gases and on solid surfaces. We selected Raman spectroscopy as the first system to develop because of its wide applicability as a chemical monitoring technique. During the second phai, we have devel°pedastate-°f-the'artmicr°-Ramanspectr°meter' designed two unique fiber-optic-based sensors for remote coupling of the spectrometer to either liqujd/gas phase samplesorsolid surfaces, and purchased a new imaging spectrometer and low-light-level detector. Computed Tomography We continue to develop computed tomography (CT) scanners coverhlg a broad range of object sizes. An integral part of this work is to derive the Section 8 ,. reconstruction and display algorithi_s. The overall goal of tl'fiswork is to improve the three performance parameters (spatial and contrast resolutions and system speed) that characterize CT imaging systems. In addition, we have addressed related topics such as elemental or eff_tive-Z imaghlg, model-based imaging using a priori infomlation, parallel prtx:essor architectures for image reconsh'uction, and ,scientific visualization of r_x:onstructed data. In FY-92, we cornpleted the California Competitive Technology Cone-Beam CT Project with Advanced Re_,arch and Analysis Corporation as our industrial pm_ler. We continued to work on two other projects: the active/passive CT of radioactive drums and characterization of high explosives for the Pantex plant; and high-purity shlgle-crystal germanium detectors in collaboration with the University of California, San Francisco. _'-- ".C _!;_4_ _,__ Laser Generation and Detection of Ultrasonic Energy Finally, we have de'¢doped a facility to generate and detect ultrasonic energy with lasers. Lasergenerated ultrasonics is ata attractive alternative to traditional ultrasonic NDE, because it allows remote, noncontacting, ultrasonic NDE. We are de'veloping NDE applications for use on contamination-sensitive components and in hostile environments. Lair ulh'asonics has several _> other advantages, such as broadband excitation, multimode acoustic energy generation, and adaptabilitv to scanning complex shapes, i_,......... __ Satish V. Kulkami _" -- ZZ ..... II!_D|li_-,=_=-- .... "'iii.= 'iilll .-"--=--= _-._ lillllliillIllllii___G# ,iii IhH' i,ii iiiii .......... I r' .......ii ''-_- =-- i liil,i__i",e __-___= = i illl,, 8. Nondestructive Evaluation Overview Satish V. Kulkarni, Thrust Area Leader Fieldable Chemical Sensor Systems Billy J. McKinley and Fred P. Milanovich ................................................................................... s.1 Computed Tomography Harry E. Martz, Stephen G. Azevedo, Daniel J. Schneberk, and George P. Roberson ..................................................................................................................... Laser Generation 84 and Detection of Ultrasonic Energy Graham H. Thomas .................................................................................................................. s.23 FieldableChemical Sensor Systems o:oNondestructive Evaluation Fieldable Chemical Sensor Systems Billy J. McKinley EngineeringSciences MechanicalEngineering Fred P. Milanovich EnvironmentalSciencesDivision Biomedicaland Environmental ResearchProgram In the initial phase of this project, we determined the widespread needs for chemical sensors to measure contaminant levels in liquids and gases and on solid surfaces. We selected Raman spectroscopy as the first system to develop because of its wide applicability as a chemical measuring technique. During FY-91, we developed a state-of-the-art micro-Raman spectrometer capability, designed two unique fiber-optic-based sensors for remote coupling of the spectrometer to either liquid/gas phase samples or solid surfaces, and purchased a new imaging spectrometer and low-light-level detector. During FY-92, we developed two complete systems around these two new sensors and demonstrated the application of the solid surface sensor in the analysis of diamond coatings. Introduction Our objective is to develop diagnostic instruments for quantitative measurements of the levels of chemical contaminants and concentrations in the field or on-line. We believe fiber-optic coupled Raman spectroscopy will make a significant lmpact in chemical analysis by developing the capability for field analysis, as opposed to the more conventional methods requiring extraction ofsampies for later evaluation in a laboratory environment. We are in the second phase of a two-phase project, In the initial phase of this work, we surveyed the needs for sensors, particularly with respect to environmental restoration and waste management concerns.1The most obvious needs were for chemical sensors that can be used in the field, thus eliminating the costly, time-consuming, and often impossible process of bringing samples to the laboratory for analysis. From our involvement with Nuclear Weapons Complex reconfiguration planning, we also obser_,ed a need for on-line or nearline chemical analysis in chemical processing. The combined set of needs ranges from in-situ analysis of contaminants in grotmdwater to on-line monitoring and feedback control at multiple locations along the process linefor chemical-processing operations. We are addressing these needs by developing diagnostic instruments and sensor systems Engineering thatare simple,robust, portable,,andsensitiveenough forfieldoperation and decisionmaking. We have chosen Raman spectroscopy for development for a number of reasons,l primarily because of its wide applicability as a chemical sensor. The majorproblem in the application of Raman spectroscopy is in the signal-to-noiseratio, which is related to theextremely low scatteringcrosssection(10-2'_ cm2/ mol-sr). In a typical measurement, coherent scarer from the laser is 10_times greater than the Raman shifted incoherent scatter. The major thrust of our project,therefore, is to createsensors that maximize the Raman scatter and the acceptance angle of the opticalsystem, which collects the scattered light for thespectrometer. Miclzi-Raman Spectroscopy Capability DuringFY-91,we establisheda micro-Rarruanspectroscopycapability.2Althoughthemicro-I_arnanspectrometer developed representsmajor progress in our facilitiesmadcapability, it is limited in various ways: (1)it can only accept 0.5-cm-dia _amples; (2)it requires considerable alignrnent of the optical componentson a regtfl_ basis; and (3)the old spectrometer has considerable scattering noise, ,and the detector system's sensitivityand noise figure are not as g;n_d as thatof more mtKlern detectors. Researclt Development and Technology ,I, Thrust Area Report FY92 8-1 Nondestructive Evaluation .:. Fleldable Chem/cal Sensor Systems detector. The combination of these new insh'u111ents is a significant advancement in our capabili- Rgure 1. Miniaturized fiber-optic coupled sensor. The sen- sorreplacesali ty other optical apparEP tus shown in tograph. to adLt ress thepho- Fiber-Optic [, h igh-sjgect ra i-resol t ltiOll, Remote Coupling Devices As l:weviotlsly stated, the core objective of this research is to develop the instrumentation necessary to perform field analysis. This includes two fiber-optic-based devices for remote coupling of the spectrometer to the sample. The first, to be used in analysis of solid surfaces, is referred to as the one-sided sensor; the second, for analysis of Figure2. Illustration of the principle of operation of the one-sided Raman " sensorforsolidsurfaces, Sphericalmirror 0.6mm radius Planerirror Center sphe.rical mirror "/ "_ •' _ Laser input fiber Scatter output fiber _ nunlert_us interactive, optical-alignment adjustmeats; to accommodate large solid-surface evaluation; and to allow more practical, robust, quantitative field applications of spectroscopy. The fiber-optic-coupled sensor shown !taFig. 1 replaces ali the other optical apparatus ,,:hown in the photograph, reducing the system size by tatleast a factor of 100.The fiber-optic sensor :_eeds no adjustnaents; only" its photons move. Figure 2 shows the principle,, of the sensor operation: light f|'ona the laser is foctlsed onto the Sample plane *----_-. I 23 Compari- I and micrc_Raman ,.. 18 -- system. _o I I J I I _l Raman 2-32731 N lC normal ized _ son of data for onesided (Nta) sensor ._ •_ 13 -- __ _ 8 -- > .= ell "d 3 -- _,_.,.___j <4. -2 [ 0 I 50 trace concentrations in solutions, is a iiquM-core optical waveguide. The liquid core serves as the sample cell and as a Iow-k)ss light transmission line. The waveguide not only retains the laser excitation light, but is an efficient concentrator of the Raman scatter. Both of these designs are disCtlssed ftlrther below. One-Sided Sensor. Ottr goals with the onesided sensor are to achieve a major advance il'l mirfiaturization of instrumentation; to eliminate ./ _ .......... Figure3. 111I.II tipoi11 broad-bandwidth spech'al analysis and the very deIll011d ing low-light-level record ing issues associa ted with Ra ma n spectroscopy. the k.._.,_,_.-------= k,_ t I I .... l I 1 100 150 2oo 250 300 35o 400 Pixel number surface of the object of interest throtlgh an aperture (2()-t_tm-dia) in a plane mirror. The mirror is a thin (2-_tm)aluminum-coated polvmer membrane. The plane mirror is off-set from the center of the spherical nairror ,at the appropriate distance for maximum light-gathering efficiency. Ijght scattered back throt|gh the aperture is collected directly by to thethefiber tlp to ,111incident angleof the rouglaly egr|al nt|merical ape|'ture (N.A.) fiber (the acceptance angle of the fiber is proportional to theN.A.)._'atte|'ed light incident at greater angles is reflected by the two mirrors back to the fibt'r at a 'shallower' angle within the N.A. tri;the fiber. The prototype for this sensor has been evalu:ated, and a comparist,a is made with the microl{ama|l system (Fig. 3). Allhough preliminary results are very good, furtlaer imprtwements are p_ssiblt' by appropriate tttttical filtering to elimi' I '1_ correct the deficiencies of this system and to m_ditv it to serve ,as the testbed for more advanced svstems, wel:_t|rchased animagingspectnulleter and a Iow-light-le\'el, liquid-nitrogencooled, two-dimensional charge-couple-device _'2 Thrust Area Report FY92 4. t i,i:pr_f,_,tJrl F t?c,,,_,,it_ h I)e_,!(_l_m_'nt ,_nU I_,, Ill_(_lllt{_ FieldableChemicalSensorSystems+ NondestructiveEvaluation hate the Raman scatter behlg produced ill the Figure4. Testbed forevaluatingnew waveguides. couplhlg fibers, Liquid-Core Optical Waveguide Design. Our goal with tile liquid-core optical waveguide is to make a major breakthrough hl lowering the threshold achievable in on-line analysis for trace concentrations in aqueous solutions. As mentioned earlier, the major limitation Hf ushlg Raman spectro_opy for chemical analvsis is the very low molecular Raman scattering cross section. For analysis of low (ppm) concentrations h'l solutions, the problem is orders of magnitude more severe tl_ml for concentrated solutions. To overcome this limitation, we have desibmed the optical system to maximize the samplhlg interaction path length in the solution mad the acceptmlce angle Hf tl_e scattered light returned to the detector. The test bed for evaluating these new waveguides is shown in Fig. 4. _1_ (3) W¢I_ Our plans for future work hlclude three areas: (1) Optimization of optical system throughput, Greater efficiency can be achieved by optimizing the h'ansfer of light from the sensors to the spectrometer. The spectrometer has a numerical aperture qf .24 and a minimum slit width of 10 _m, which set the bounda D, conditions for tlle entire optical system. We have begtm the optimization desigj1 for the one-sided sensor. Many of the limitations and the optimization methods apply directIv to the liquid-core waveguide as weil. (2) Testing the liquid-core optical waveguide (cell). We intend to test the system on two Acknowledgements lt_e authors would like to acknowledge John Lutz and Sang Sheem for their contributions to this project. 1. B.J. McKinley, F.P. Milanovich, M.S. Angel, and H.K. McCue, "Fieidable _,nsor Systems for Envirt_nmentalCon tarain ants," Enk,ila'¢'j'ilI_¢Res,'archan,t De-eelopna'ut,Lawrence l.ivermore National Laboratory Livermore, California, UC1_1,,-538(_8-_)0, 7-_) (1991). 2. B.J. McKinley and F.P. Milanovich, "Fieldable Chemical _'t:_sorSvstems," EuRiueerin,\,I@sem'ch, L)eveh,pmeut,and Teclmolo\,y,Lawrence [.ivcmxn'e National Laboratory, Livermore,California, UCI_,I..53868-91,7-1(19u2). LI categories of probh'ms: (1) analysis of trace contamh-lant concer, trations in groundwater, and(2) chemical process monitoring and feedback control. In the latter case, we will choose a chemical from the uranium-processing lhle identified in the Nuclear Weapons Complex Reconfiguration Study, as the model for the analytical system in the de- Eng_neerlni sibylof the cell. We will al_ develop the sF_'ctral mlalysis algorithms that will be nec__,_kl D, in a feedback conh'ol k×)p. Sl.x'ctroscopy. To complete this phase of the project, creating a capability for l_'mlan analysis, we must develop more tmde_tandhlg and have more experience in slx?ctro.'Kopic analysis. The first steps have _,en taken in the ptu'dlase of new sFectral-analysis _ftwam and a Raman Sl__vtra-comparative database. We are working with sF_vificexamples, such as the diamond coating evaluation. Rese;stch De_'l_l_met_t ono I ,(h_ol_g_ .:. Thrust Area Report FY92 8-3 Computed Tomography o:o Nondestructive Evaluation Computed Tomogray Harry E. Martz EngineeringSciences MechanicalEngineering Daniel J.Schneberk ApplicationsSystems Division ComputationDirectorate Stephen G. Azevedo EngineeringResearcllDivision ElectronicsEngineering George P. Roberson DefenseSciencesEngineeringDivision ElectronicsEngineering We are developing several data-acquisition with associated computational techniques for report describes recent progress in active and specialized applications research. We have scanners for computed tomography (CT), along image reconstruction, analysis, and display. This passive CT, cone-beam CT, high-energy CT, and sought to advance the state of the art in CT technology, while at the same time actively supporting programs at Lawrence Livermore National Laboratory and new business initiatives. Our goal is to provide reliable and efficient nondestructive evaluation techniques for use in probing the internal structure of fabricated objects and materials associated with a broad spectrum of applications. IntroductJofl Nondestructive evaluation (NDE) is being u_d in an ever broadening array of industrial and military applications. One area in recent years where growth is evident is computed tomography (CT). First used in the 1970's as a medical diagnostic tool, CT was adapted to industrial and other nonmedical purposes in the mid-1980's. Standard radiographic techniques, such as single projection radiography, hide crucial information: the overlapping of features obscures parts of these features, and the depth of the features is unknown. CT was developed to retrieve three-dimensional (3-D) information. For CT, several radiographic images of the object are acquired at different angles, and the intensiW information collected by one or many detectors is processed in a computer. The final 3-D image, generated by mathematically combining these iraages, gives the exact locations and dimensions of internal features within the object, as well as external details. Over the past six years, we have worked on research and development (R&D) of many CT topics, concentrating on three main areas: (1) scannets, (2)software tools, and (3)applications.l -_ Engineering 4 Two years ago, we began R&D on a combined active and passive computed tomography (A&PCT) system.l,2 In this report, we describe our major progress in A&PCT, cone-beam CT and high-energy CT. We also present advances in the application of these and other capabilities for both Lawrence Livermore National Laboratory, (LLNL) programs and bushless. Lastly, we outline our fllture plans. Plrogress A&PCT Research Characterization of mixed (radioactive and hazardous) wastes requires that the identity and strengths of intrinsic radioactive sources be determined accurately. In collaboration with LLNL's Nuclear Chemistry Division, we have developed a three-phased plan to address the nondestructive assay (NDA) of 208-L (i.e.,55-gallon) drums. These phases are (1) experimental A&PCT research and development, (2) simulated A&PCT research and development, and (3) determination of minimumdetectable limits vs waste-matrix attenuation. We report here on the experimental and simulated Research Development and Technology o:o Thrust Area Report FY92 8-5 Nondestructive Evaluation.:- ComputedTomography A&PCT efforts. The determination of mhlimumdetectable liwtits vs waste-matrix attenuation ef- file identity of any radioisotopic sources present; and (3) ACT data, to correct the PCT data so that fort was funded by the Office of Safeguards and Security and is described elsewhere, m A&PCT Scanner. Experimental data were acquired on a small-scale canister containing mock wastes and two passive sources, 95-pCi 133Baand 74-pCi _sTh, using a medium-energy CT scanner (MECAT) built at LLNL.II,12 These data were used to investigate (1) ACT, to obtain inlages that represent cross-sectional attenuation maps of a wastecanister's contents; (2) PCT, to locate and determine accurate source strengths can be determined. Our experimental results reveal that ACT scans properly map the canister's attenuating matrix and, when coupled with PCT scans, yield quantitative source strengths.m Preliminary results suggest that heavy-metal content, which is larger than the volume-element size imaged, may be identifled. These encouraging results have led us to design and construct a full-scale, 208-L prototype A&PCT drum scarmer. The full-scale, 208-L prototype A&PCT drum Dark shaded areais middle 1/3ofdrum ,,and light shaded areais the scanregion _a) Top of barrel athighest elevation Leadwall collimator Top of barrel Detectorcollimator atlowest elevation "N _ Radioisotopic HpGe _ source "_3200__ _ I °°O n __ Ooo_om °o '0 .......... 5'x12" °° ' and 5 1 oo o oo o°0oO oo o o° ................ scanner design and progress to date are shown in Fig. 1. This scm'mer will be used to better explore and understand the relationships among the four most important CT performance or resolution parameters---spatial, contrast, (or speed)---from the point energy, of viewandof temporal assaying nuclear waste drums for radioactive content. The definition of contrast resolution differs for the • °°v oO oo oo =o o oooo "° o OOO " it_. _l -_ -__ -- _-_"_ collimator 0 di detector scanner uses a single, high-purity germanium (HPGe) detector of the type used in nuclear spectroscopy measurements. This scam_er's construction is scheduled for completion early in 1993. The A&PCT measurements, o ° oo ° " ) Oo °° o o O o ooO Oo C_°° O _." o deep pit o o o ..... °. Oon°O o. o ° o%00 0%o Oon°O o _o o _° o°O° o°Oo o . hl the former, it is a mea- sure of attenuation differences that can be observed; in the latter, it is a measure of radioactive strength differences. Speed includes data-acquisition and analysis time. Limits to improving the PCT activity results include geometrical uncertainties caused by the collimator's angular cone of acceptance, photon scattering, lack of sufficient counts, the randomness inherent in photon counting, poor detection efficiency, the energy resolution required, system noise, data-acquisition, and times required for data analysis. Quantitative assays using PCT are further complicated by the need for attenuation corrections, which are obtained from the ACT data. Unfortunately, these data are limited by many of the same performance parameters. Reconstruction Technologies. We have developed A&PCT image-reconstruction and simulation algorithms to better characterize mixed-waste drums, in collaboration with Laboratoire d'Ek_roniq ue de Tech nologie et d'hlstm men tation (LETI) in Grenoble, France, and the University of California at San Francisco (UCSF). The A&PCT :. Figure1. (a)to ACTandPCr prototypescannerdesign:(b) scannerphoto,showing construction date. _'_ Thr.st Area Report FY92 0 EnE_l;_._e,,ng Resea,ct_ Dc*velopmur_! image reconstruction and analysis process consists of mapping the actMty of intrinsic radioactire sources, using PCT data, and correcting this and Tectlr;ologv ComputedTomography.:o Nondestructive Evaluation data for attenuation, by usirtg an attenuatiop, matrix obtahled from an ACT scan. Simulated data are necessary to better understand A&PCT reconstruction algorithms and measure their performance, and to better interpret experimental data. The simulation program is based on a forwardprojection algoritban 14 that discretely computes the projections; i.e., h_tegrated counts per unit time per malt volume, of an emitting object attenuated by a user-specified matrix. We use two algebraic, iterative, A&PCT reconstruction codes: a weighted-least-squares, steepest-descent (WLS-SD) algorithm_ad a maxhnum-likeliht×_d exp_tationmaxhnizafion (MLEM) algorithm.W4 We studied three simulated phmatoms: (1) a large homogeneous source included in a large homogeneous attenuator; (2) a mock-waste drum involvhag small sources; and (3) a spatial-resolution phantom, l_ All three examples hwolve attendata, and the last example includes For tile attenuated PCT scan, a combination of three hctors yielded noisy net passive projection data: (1) 3-x-3-mm aperture, (2) the short dataacquisition time (150 s), and (3) the attenuation of the passive sources by the copper cylinder (_ i0.1 cm o.d. and _ 8.9 cm i.d.). The passive sources' energy peaks were within the Compton and background distributions, lt is important to point out that the method of extracthlg the net-passive projection data (gross counts minus spectral background) fl'om the gross projection data is not adequate forlow-count-rate PCTdata, and resulted in naeaningless net-peak intensities for the passive projection data sets. Figure 3 shows a representatire comparison between the gross and net projection data for the 228Thsource at 238/240 keV, and for the 13_Basource at 384 keV. Neither the =,sTh nor the 133Ba net projection data reveal any noise. The 0.25 0.20 O.lS 0.1o 0,05 0'30f_ 0'00 0 noise is generated to match experimental Lancertainties. Results showed that both reconstruction algorithms recover the actMty values to within uation but are uncertainty not strong erlough cause missing experimental (countingto statistics). The WLS-SD algorithm produces more spreading of the activiW over multiple pixels, but also performs slightly better than MLEM (i.e, it gives more accurate activi_ values) in the case of noise. We are working on a number of improvements in these a lgori thms; e.g., incorporation of col lima tor geometD,, addition of the effects of very strotlg atterluation, and optimization qf the code for speed and activi b, accuracy. We are also investigating other algorithms. A&PCT Applications. In addition to continuing experimen ts on the small-sca lecanister of muck waste, we studied the attenuation of both passive sources by a uniformly attenuating Cu cylinder. A representative ACT image of the Cu cylinder with both passive sources is shown in Fig. 2. Note that the locations of the cylinder and both passive sources are easily visible, lt is also interesting to point out the 30% difference in the Cu cylinder wall attenuation value. We fourld that this difference 0.00 0.03 2 d'k _ 4 6 8 Distance (cre) ] I ] [ 0.06 0.09 0.12 0.15 0_18 0,21 0.24 Linearattenuationcoefficient (cre-1) AI 10 I 0.27 12 I 0.31 Figure2. Representative ACTImageofa Cucylinderwithpassivesources.A 1-D profileof thisdatais ontheright. _th 2381240kev Gross data Net data lSSBa384keV Gross data Net data may be due to a wall thickness variation of- 1 mm from one side of the cylinder to the other, and porosi_,. A portion of the resultant change in the wall attenuation value can be attributed to partial \'olunle effects (due to the crude 3-mm spatial sampling) instead of a noticeable change in wall thickness. £nglt_t,erlng o_ ............ I..... I I I 5.06 10.11 15.17 20.23CountWunit 25.28 30.34 35.40 40.45 45.51 50.57 56.00 time Figure3. Representative grossandnetpassivesinogramdataat 238/240 keVfor the228Th source,andat 384 keVforthe133Bapassivesource. Rese,lrci_ Dt,_elopm_,llt ,_'pd lt,ct_r_nlot_ ,{. Thrust Area Report FY92 _'7 Nondestructive Evaluation.'. ComputedTomography internal source distribution nor did the finalattenuation corrected PCT images (see Fig. 4). The resultant, noisy, passive sinogram data are due to a low count rate. Since the net projection data did not result ill passive source identification or localization of actMty, we analyzed the gross projection data. As expected, these data are distorted. For example, the gross 133Baprojection A&PCT WLS-SD-reconshl.icted PCT-image data (Fig. 4) appear to have three internal source distributions: (1) a 133Bapassire source at the location, as expected from the ACT image in Fig. 2; (2) an appm'ent 133Basource at the location of the 22sTh sou:'ce, and (3) an apparent 133Baring source. Only the first distribution is real; the latter two are artifacts and are very misleading when these data are analyzed for the 133Basource actMty. For comparison, the results of PCT scan data without attenuation (i.e., r|o Cu , _'Sth238/240keV 133Ba384 kev GmssPCT _ 0_0 Rgure4. o.79 _s9 i I 3.17 3._ 4.76 5_s Count/unitI_me _ I I I I 6.34 7.14 7.93 8,80 Corrected PCT images obtained by reconstructing the net and gress sino- gramdata,usingtheWLS/SDalgorithm. ,.. " .... : .... _ " • . i __ .i __[__';lli::: I I 0 Counts/unittime 59 118 -0.98 6.08 13.13 Counts/unittime/unit Voxel ,_:_::'_,i ¢" " I 20.18 Figure5. Representative unattenuatedpassivesinogramandPCTimagedatafor the 133Ba source at 384 keV. _'_ Thrust Area Report FY92 _.. En_tt_,(,rlng R_sc, alch D<,vvlol)nltJt)t cylinder or 228Th passive source) are shown in Fig. 5. We are investigating tile use of other gamma-ray spechxlm processing methods that will improve the extraction of the net-peak data from noisy gamma-ray spectra. Using a better method is important, since we expect low-count-rate data to be the norm in mixed-waste drum assay scans containing LLW amotmtsofactMty. Cone-Beam CT Research We are expanding our research in cone-beam CT imaging methods. We begin this _ction with an introduction to cone-beam CT imaging, and follow with our progress during FY-92. Computed tomography of the 1970's and early 1980's has been an inherently two-dimensional (2-D) process. Typically, a single detector or linear tone-dimensional (l-D)] array of detectors is used to gather x ray-attenuation transmission gauge measurements through the object under inspection. One gauge measurement is called a ray sum; multiple ray sum measurements along a single line are called a projection. Many projections are acquired at various angles about the object, but always through the same cross-sectional plane (see Fig. 6a), creating a 2-D data set called a sinogram. Image reconstruction of such 2-D sinograms usually involves filtering and backprojection operations that are well characterized and underst_×xt, and results in 2-D, cross-sectional images. With the ready access of microfocus (spot sizes of about 1 to 50 pm) x ray machines, good 2-D (planar) x ray detectors and improved video technology in the last decade, CT research has concentTated on direct 2-D projection (or radiographic) measurements and one-step, 3-D, volumetric image-reconstruction methods. This speeds up the data-acquisition process (since multiple slices are acquired simultaneously) and results in a more efficient use of the x ray source. Until recently, 2-D projection measurements were acquired with the x ray source far from the detector, so the radiation penetrates the object with parallel-beam rays and standard 2-D image-recor|struction methods could be used (Fig. 6b). Currently, the more interesting case is to acquire projection data with the source close in cone-beam to the object x rayar|d imaging detector.(Fig. This 6c).mode Cone-beam results CT allows the use of geometric magnificatior| to improve spatial resolution, and it makes the most efficient use of the source radiation. Problems to be solved with cone-bearn CT include scanner alibpamellt and the need for more complex image-re- and fecllnoltJId) Computed Tomography o:. Nondos'_ructive construction algorithms. We have addressed these problems m_d will show some results throughout the following sections, Cone-Beam CT Scanners. Several of our CT _anners are inherently cone-beam systems.2, -_Our recent collaborative work on cone-beam imagereconstruction methods (discussed below) has enabled us to use these scarmers in a variety of new applications, and to take fill advantage of lmprovements in source and detector technology, This has resulted in a better tmderstanding of the components involved in cone-beam scanners, A crucial component of rnany cone-beam scanners is the scintillator, the mechanism for convertbig the x ray photons into visible light. Recent developments hl glass scintillator fabrication and manufacture provide the potential for increased performmlce of our lens-coupled, camera-based scanners such as the Micrc_K:AT and the highenergy CT scarmer (HECAT). To examine the possibility of increased scanner perfomlance, we have applied our lens-coupled scamlers to evaluate this new type of scintillator glass, called Lockheed high density (LHD) glass. In general, we seek to establish the spatial resolution, speed, energy response, and contrast limits of this glass for the wide variety of different digital radiography a_mdCT applications we usually encore-iter within the Nondestructive Evaluation section, The promise of this new glass is high brighb-iess and high spati_ resolution, a combination which ks not readily available without subst,_fial costs. High brighbless can be obtained with off-the-shelf image intensifiers, or in-|age-intensified d_lrged couple devices (CCD's). Often these imagers include spatial distortions due to their physical shal__, and image intensification coml.x)nents. Distortiol_s must be accounted for before meaningfi.d CT imagc_ can be obtk3ined.2 Furthem_ore, intelzsifier-based CT scan- Initial measurenlents by other researchers have shown that the LHD glass composes a fiat-field, distortion-free projection image with at least - 25to 35-!urn (or 20- to 14-1p/mrn) inherent spatial resolution, and is bright enough for standard, nonintensified, visible-light CCD cameras."' We are currently evaluating a Cohu 4910 camera, operated in two nxx:ies, variable integration mode and RS-170 mode. We have also used the EI_10 Image-lntensifiedSilicon-lntensified Target(SIT)camera and a Photometrics CH200 CCD-based camera to further explore the properties of the LHD glass at high energies (4 and 9 MEV). If the reported properties can be realized routinely on general purpose, le|is-coupled, x-ray imaging systems, with a variety of cameras, then a relatively inexpensive and high-perfomlance, x-ray imaging alternative has been established. To evaluate the new scintillator glass over a broad range of energies, we ran three separate series of experiments at the following energies: (1) at 90 to 130 kVp, using the MicroCAT scanner; (2) at 200 to 320 kVp, using a PHILLIPS 320-kVp medium energy source; and (3) at 4 and 9 MeV using two VARIAN Linatrons and the HECAT scanner detector. In ali three experiments, we used the scanners in a similar fashion to that with their original scintillating glass materials. The only difference was that the original scintillators were replaced with the new, clear, LHD glass scintillators. Our low-energy studies have produced data with spatial resolutions (_ 14 to 20 lp/nim) consistent with earlier results, 17but with a slight variation in technique. Scintillating glass can be fabricated as a clear sheet, or drawn into fiberoptic bundles. We are interested in detectors that can support cone-beam imaging modes, and consequently restricted our evaluations to the clear, LHD scintillator material, lt is known that cone- ners can have other limitations due to the ac__lal spatial resolutions that can beobtained, l beams of x rays impinging on a fiber-optic scintillator will induce cross-talk in the fibers, and result (a) (b) 2-D Detector (c) Evaluation 2-D Detector _ __ _ _ _ __ detector Source Source Figure 6. Methods of acquMng 3-D CT data: (a) multi-slice CT by acquiring each 2-D cress-sectional slice independently, (bl 3-D parallel CT with a 2-D detector and source at infinity (one rotation and standard reconstruction codes are used); (c) cone-beam CT by moving the source close to the object. New reconstruction algorithms are needed to process this data. Er_t_sr, ec,_ ng Rc's('_r(t, I),'_'J,,l_m_',,r ,_n !_'< t_r;,','_'t_ ':" Thrust Area Report FY92 m-_ Nondestructive Evaluation .:. Computed Tomota, ral.)h.v Figure 7. Digitalr_ di_nlph ofhollow thenn_oupieplug, ill a Iossofspati,_l t's.is in ,ldditilln, viewed directly, .... i't'stlltiiitlll as c'tlllt, all l41t,illc'rc,astilt' tlllprtlt't'Sst'd imagt' cnn be' without any ._tlbtractitln tit the cross-hatch in tilt, fiber-bundle usuall\' prr, st,ni in tinprocc'ssc'd illldgt's ft'llnl fibcr-tlptic scintillators. Figure 7 is a digital radiograph til a hollow fllc, i'- taken with MicroCATsystem. nltll.'tltiplc, pltlg ctl\'t,r, taken on our Micro('A'l' s\.'stem. (.)ne surprising result til tills in\'c'stigatitln is the increased spatial pcTftwnlant't' obtained when the t:t_.'al plane of the c'allit, l'a is positioned inside the scintillator glass, as opposed lo li'lc, back face plarle of the glass. The advantages til this tccllnique are visible iri file imag,., iii Fig. 7. ! tmvever, this added clarity is ai the' cost of some brightness, since some of the scintillah)r malerial is not in t"OCLIS for thec'drllcT,l. 9; 0,00 0.36 I 1.09 0.73 I 1.45 The M icroCAl' sc,lnner's spatial rc,sillulion performance using the I.! II) glass scintillator was furtller stcldied by analysis otn line-pair gauge Figure8. Thespar tlalresolutionperformance ofMicroCAT studied by analysis ofaline-pa#gauge, (Fig. 8), There was alnlost IlO magnil:icatit)n in\'ol\'L'd in this t,,_postlrt, ([VI = l, l), alld with Otil" Micro-Focal s\'stc, nl( I()-t.im spot sixes), blur due to finite spot size is effecti\'elv eliminated from the systc,nl. i" As ilhistratc, d in this t:igure, the hiss in spatial nltldulatitln is less thall 5()',,, from 12 to 14 lp/nim, alld thr, re is significant nlodtliatit)n iii 16 lp/ni)Ii. With the nlicTo-foc'al Stltil't_'t', nldgnifications of 2 to 3 can be achic'vc,d with a minimtlnl ot sOtil'c'c' blur, which can easil\' extend the spatial 700.00 I i 1137.79 lpi 918.90 rc,solutitln tit this stallllt, r initl file lH- to 2li-lr/real I i I 1356.69 1584.00 _/t' ha\'t' scanilc,d ditto, rr,ni objects, and tltll" restllts ha\'t, shown JlIc'rt,iIst,d pt, rforlllilllCt, t'OD1pared to scans with the fiber-optic scintillator Hsed railer!. 1250 I prc,\'i_lusl>,, i\ COlllpai'istln o1:tilt, c'llhanct'nlt'nt, 1200 o'swith the older fiber-optic scintillating glass pinch-weld C'I' stud\' are shown iii Fig. 9. 1150 1050 :'-_ has bt't,ll substantiated b\' sllnat, tit t)tll prt, liillinar.v ,_tudies using tilt, I,I II) glass scintillaltir at nat,ditlnl dnd high c,nt,rgit,s <is weil. For example, n repi'c,st,nt,lti\'t' digital raditlgraph tlta -3-cre lurbinc blade ,lcquiit'ct with a It,ns-ctluplc, d, leO0 271)-k\/p x ra.v sl_t'clruln 950 0.0 Thrust Area for a l'ht' spatial restllutitln pc,l'lt wllaanct, by the,new 1.1ii) glass scintillator and titherreptll'tt,d di ffCTt'nc'- _1_ I ._l 1100 8-10 in Report FY92 othc'rs 1 lp l_m i J 0.5 Distance 1.0 1.5 2.0 (mm) .:" t !l i: i t} {' i' i i II _[ li) ii ii f'lt _ f I 2.5 t! I)ti_l>,' mt,diulll- c'nt'rgv Ill,lc'hint, stltll't't, (sD_l sil,' -0.4 mill) is shtiwn in Fig. 10. We t,slinlalt, the sp,lt)al rt,slllutilln t/t: tills digital r,lttiilgr,lph til br, tin tilt, tu'dt,r tit "_to I{) lp/mill 3.0 +l)'t?t>'ll frtim ,1 l ihilirs rl I_ Iii !!J {l'''J!i Computed Tomography o:* Nondestructive Evaluation i (a) LHD glass (b) 2-year-old SDD glasa 0.30 | 0.25 _0,20 0.15 F 0.10 F 0.05 _-j .iolr 0 50 100 150 200 250 0.35 0.30 -- 0.25 0.20 0.15 0.10 0.05 0.OO -.0.05 0 Iqgure 9. Comparison of enhancement in (a) LHD glass scintillator and (b) SDD fiber_ptic ter of each image to the left are shown to the right. (a) 20 40 60 (b) 17.94 35.88 loo 120 140 160 180 scintillator for a pinch weld. 1-D profiles through the cen- (c) I 0.00 80 53.82 71.76 Turbine 89.70 blade I 107.64 I 125.58 I 143.52 163.00 Iqgure 10. Representative medium_gnergy radiographs of turbine blade at (a) O, (b) 45, and (c) 90. " ,: .... ;, ...... L:, ,,._,, ...... .,,_ ..... _ ;_'_ _..... _'N_ + Thrust Area Report FY92 8-i,_1, NondestructiveEvaluation,:, ComputedTomography The results of tile performance of tile LHD glass at higher energies is shown in a pair of digital radiograplls of a 5.0-cre doublet, single-cl3/stal turbirle blade acquired at both 4 arid _,tMeV, using two different Lirlatron sources arid a leris-coupled, Collu 4910, CCD camera-based detector system (Fig. 11). Tile pedestals arid features of the blade are on the order of I mm in spatial extent. More detailed explarlation of the turbine blade study is giverl below. We are atternpting to furtller quantify tile spatial resolutiorl lirnits of this new glass for both mediunl- and high-energy CT scanning applicatiorls. Our prelimirlary CT results for Ilighspatial-resolution, iligll-erlergy applications Ilave beeri erlcouragirlg. Figure 12 is a sample of irrlages ....... "" " from a 3-D cube of data acquired with a 9-MEV Linatron on HECAT; tile}, show tile doublet turbirle blade, measurirlg wall tllicknesses of 5(X)Iarn. In the next year, we will better quantify the spatial arid contrast resolutiorl performarlce of this new glass arid the irrlprovemelltS tills yields for lens-coupled, corle-bearrl C" scarulers. With this proof-of-prir|ciple work as a Dase, arid iri cooperatiorl with LLNL pllysicists workirlg iri astronorrly, we are assembling a Iligll-perfornlarlce CCD canlera with 14 to 16 bits arid 2048 x 2048 detector elements, which can further explore the properties of this glass, and provide a higher perfornlance, 2-D, cone-beam CT scaruler. We will also exarnine this glass iri slit-collimated corlfiguratiorls arid witll linear-array dekvtors as a mearls of obtairlirlg highcontrast, high-spatial-resohltion irnages that include less scatter. Cone-Beam CT Reconstruction Technologies. We have implemerlted corle-beam recorlstructiorl rrlethods of otllers 21-25arid developed our own, ali with good results. 1,2Last year, orle mernber of our re,_arch team (S. Azevedo) worked iri France at LETI on new cone-bearrl methods that benefited both CT projects. New reconstruction algorithnls arid scarulirlg rnethodologies were dm, eloped during the course of this collaboration, and a patent is perlding iii conjunction with tile French govem- 0.00 0118 0.37 I 0.55 0.73 0.92 Doublet blade I 1.10 i 1.28 I 1,47 Figuretl. Representative high-energy radiographs ofa doubletsingle.crystal turbine blade at (a) 4 MeVand (b) 9 MeV. !;<i i Ftglire12..RepmsenMflve 2_ imagesfroma volume f3OJCTdatasetofthedoubletsir_ g._crystalturbineblade,acquired ustngtheHECAT detectoranda 9MeVLINAC source. meat. 7_'This and other cone-beanl work are continuing in FY-93. lkqow, we de,_ribe some of tile pl'ogress during FY-92 iri irrlage-recoristruction technologies, h_duding region of-interest cone beam CT, axi-synmletfic C_, reverse COllc-bealll geometl.'y, and a fast image-n.vor_structiorl pix×-t,'s,,_r. Region-_?[inh'rest cone-beam CT. lt is often necessary to view a part of an object at higher magnificatiorl than is rleeded over tile rest of the object. Also, sometimes the object is too large for our corlebeam scanner. In these cases, the data we acquire will be 'limited'; i.e., there will be missing ray paths from our proitvtion measurements. This type of reconstruction problem is called 'region-of-interest' (ROI) CT and is a COmlYIOll problem in medical and industrial imaging. There have beerl solutions proposed for 2-I9 RO! imaging, but not for the 3-D cone-beam case. Our algorithm for reconstructing cone-beam R()i data, called l_,adon-ROI, uses matl'lenaaticai methods similar to tile (;rangeat method of conebeam irnage reconstructiorl. Irl Grarlgeat's method, tile 2-D radiograpllic projections are rrlathernatically corlverted (tlu'ough weighting, tiltel's, and re-binning steps) to ari interlned late,mathematical space kllOWla as the 34) Radon donlaill. Frtml this space, recollstructioll tri thf vohinat'tric Computed /omo,qtaphy .:, Nondestructive image is straightforward, requiring only hvo sets of backproiections. The Radon space is an ideal piace for combining data of different resolution, so it is ideal for ROI imaging. Two scans of the same object are acquired at different resolutions, a lowresolution scan covering the entire obiect and a high-reso:,,tion scan covering only the ROI. These two _ans are combined ta form a single Radon space,which is reconstruc _.edby the latter part wf Grangeat's algorithm to form a final volume that displays the ROI at higher resolution than the surrounding part, without significant artifacts. Ali example of the use of this method for RO1 scanning of an automotive prcxxmlbustion chainber is shown h_ Fig. 13. The image in Fig. 13a shows a single reconsh'ucted slice through the object taken at low resolution. The data were acquired ,_md reconstructed using cone-beam CT methods. The object has some shrinkage cracks just barely visible in the interior. A second scan of the precombustion chamber was acquired at a higher spatial resolution, but of the ROI only. The two scans were combined and reconstructed into a second image, as shown hl Fig. 13b. The ROI area of this second image reveals the much higher spatial resolution obtained by this novel method. 27 Axi-symmetric CT. We have applied the conebeam CT reconstruction methods to the problem of obtahling 3-D exterior and interior information from axi-symmetric objects with only one 2-D radiograph or projection. Tlais has application in several areas, such as manufacturing and high explosives testing. The problem is to perform conebeam CT reconstructk_n of an object that has quasi-axial symmeh3., from a single radiographic view. For example, a high explosive can be radiog-raphed during firing, with a flash x ray unit, but only one view is available. If we assume axial symmetry, greater information can be gathered from the single radiographic view. We have performed conebeam image reconstructions of such tests and of simulated data to better understand the combustion mechanisms. 200() per Figure23. ROI image showing(a)single reconstructed slice at low resolution and (b) combined low. and higi_resolution datareconstructed image.This is one slice out of a 3-D volumeacquiredby cone_beam methods. Notice the higher spatialresolutionin (b).(Datacourtesy ofLETI,Grenoble, France.) 0.00 206.78 413.57 I I 827.13 1040.1)0 620.35 .. 0.00 228.65 457.30 685.96 I t 914.62 1150.00 : ::,._- . .......:_,_-.:;, c::, "' ..:,;. Shllulations provide useful in- formation as to what kinds of artifacts to expect from any aswnmetries in the object. Another example is on-line monitoring of highvolume, axi-symmetric hldustrial parts. As an example, we applied this technique to a diesel engine piston. A single radiographic view of the piston was obtained (Fig. 14a) and reconstructed into a volume image. A representative 2-I) cross section of this resultant volunae is sllown ill Fig. 14b. With many such pistons being fabricated (as many as hour), complete impossibly time-constlnlil-lg. CT methods However, may tlSillg Er_p/n(,et,ng be the Evaluation i"- " ;, _ '".- ..... [ -200.00 _ I ,,i -128.18 ............. I ' I 0.01 0.01 i_,_,:_:_:.::::i I -56.35 15.74 Pss --- ...... _ _';%;:_"i 0.02 Plot I 0.03 I I 87.29 ' I 159.12 J i I 0.03 ' I 0.04 i Figure 14. Representative (a) 2-D projection radiograph and (b) 2.D CT images ota dleselenginepiston. The data are extracted from a volumetric image obtained from a single 2-D view. R(,s_,ar_h l)_._rt,,b,m<.,_' ._;;,: f_,_ I;r_,,_,,_:_ .:. Throst Area Report FY92 8-13 NondestructiveEvaluation.:. ComputedTomography abovecone-beam rLx:onstruction method, a single radiograph can display n,luch n,lore useful information about the part. For example, in Fig. 14b, small cracks within the interface between two different materials are much more visible than from the radiograph shown in Fig. 14a. Reverse c0ne-beamy,('(,,('try. A sn,fall company in San Ramon, CaliRmaia, called DigiRay, has develol.md a new radiographic n,lethod called "reverse geometu" cot|e-beam radiography. In this methlod, the source is a 2-D, raster-scanned flat panel, while the detector is a single elen'|ent. The source raster defir|es the acquisition geometry, whlichl is es,_ntiaily a cone (Fig. 15). This system is unique and provides some inherent advantages over conventional, cone-beam, x ray-imaging systems. The , Filmor.imageintesifer K Obrl'¢_> _.. are fron-| the CT since the_' have moir6 artifacts, due images, to the limited numbe|"data ttf angu- _ of results,that we mask still expect this Ira typespite of lar these projections, the scanthat results. " pQintXray.somce r _ with little to no scattering artifacts. Weare working with DigiRay to ,._t up an exl._,riment in whid,l we can obtain room angular projection data that shouM •• _: result in Cf-n.vonstru_o.t imagcs without moir6 artis)'stemWith could produce high quality 3-D imaging facts. the tLseof an enerb,y-di,'_'riminating detuvtor systen,l, further enhancements art, exl._Vkxt inK_ the n.-gime of materialscharacterb,.ation. Conventionalx ray •Scann_.g Leadshieldln s i Recollstruction hardware. Another detector x ray _s 4 ! _ _ To CPU _ Revemeseometry xray Rgurel5. Comparison between (a) conventionalcone-beam-projectionsdata-acqub sitionand(b) -_ - .... reverse geometry, cone_eam-projection data,acquisition .......... .... systems, ..... .,. -; ' _ ! Representative (a) projection data and (b) CT image of a MTF phantom usingreversegeometrydataacquisition.(ProjectiondatacourtesyofDigiray,San Ramon,California.) Thrust Area the image-reconstruction codes and architecture problem cone-beam CT imaging is the in spc_,d of u,_d. Weinhave addres,_d this problem a joint re, arch projc:vt with a private company, Adwmct_t COR) of Stmnyvale, California.Corporation Irathis prolect,-" _"ata l;',esearch and Applications (ARAadvanced computational engine, called the Konoscope reconstructor, was designed to reconstruct large cone-bean,l data sets in reasonable computation times (within 2 la of data-acquisition times) while being low iracost. This design was successfully completed in FY-91 and was realized as a and recast|re the performance of various algorithn,ls operating on the reconstructor. S__,veraIconebeam reconstruction algorithmas will be coded on the system for evaluation during FY-93. Also, the _ 8-14 important hybrid, parallel, multi-processing system. h,lthe last year, we have purchlased, assembled, and tested the basic building blocks of this system. This prototype was constructed to demonstnate .!_ Rgurela. use of a converging beam has tile potential to produce 2-D x ray transnlission images with little to no scattered photons. The DigiRay system also includes a NaI(TI) detector that could be configured to acquire energy-specific data. Until recently, this systen,l has been used exclusively ior industrial radiographic applications, not for CT. We have been evaluating the efficacy of usi|,lg their unique method es k_r industrial, cone-beam, CT imaging applications. DigiRay acquired 24 2-D, inverse-geometry, cone-beam projection images as a function of angle (eve U 15°) for a lexan modulation-transfer-function (MTF) pl|antom. Repm,_ntative 2-D proitvtions are shown in Fig. 16. These projection data were reconstructed using a parallel |'econstruction algorithm. A resultant CT image is shown in Fig. 16. lt is difficult to determine just how useful the inverse geometry scans Report FY92 .'_ Engineering Roseiltcll D(,v_lopment system will be used to evaluate other image-processil,lg algorithms that may benefit from this uniqtre design. iltld le(:hooIog; ComputedTomography .:. Nondostru©tive Ilvuluation High-Energy CT Research High-Energy CT Scanners. We completed the first version of the HECAT scanner in FY-92. This scanner incorporated the features and flexibility of the video-camera-based CT (VIDCT), area detector software, and built upon our past experience with film radiography using 4- and 9-MEV VARIAN Linatron sources. HECAT is currently an area detector-based scanner that can acquire data in either a variable integration (typically from 2 to 10sl, or ILS-170video-franle-rate, data-acquisition mode. Two different area detector systems have been used to acquire the CT projection data: (1) a VARIAN ER210, image-intensified SIT camera mad (2la COHU 4910 CCD camera. Both are lenscoupled to either a fiber-optic scintillator btmdle or to a piece of the LHD clear glass via a visiblelight 9(}° bending mirror. We have used the HECAT scanner to perform 3-D CT inspections of bridge members, engine pa rts, ceramic-metal castings, and single-crystal turbine blades, CT systen'k,;contain four COml.x_nents:(1) source, (2) detector, (3) object mmaipulator, and (4)data acquisition and image-reconstru_on and maalysiscomputer. (_le of the challenges for a high-et'|ergy CT system is to rt._iuce the efft_t of _ttr_._eblur (a blur from a fir|ite _urce-sl.x_t sizJe).High-energy _urces _l._ically involve relatively large source-spot sizes (2 mm in our ca_). Source blur, to first order, increases linearly with x ray ma_aification. A good rule of thumb is that the source blur, ;B, is equal to the spot size, A, times mabnaification, M, minus one, i.e., 6 = AtM-l). Consequently, the source blur due to finite spot size l_Jcan be quite large at moderate magnification (nominally 1 mm at a magnification of 1.5). Large objects are difficult to position very close to the detector, by their very size. Also, object manipulators that can support 300 to 1(_)0 lbs are not small, and it is difficult to minimize the source detector distance if the manipulator cannot De fixed below the source detector. lt is also useful to point out that to penetrate highly attenuating sections of an object, the source must be positioned close to the detector (to inc,'ea_, the effective flux per volume throughout the object), which increases the magnification for a fixed object to detector distance. Recently developed objects (e.g., single-crystal turbine blades) are small, but contain highly attenuating materials. Consequently, there is a need for H ECAT (Fig. 17) accomm(Ktates the_ demands in a number of ways. First we developed a highly flexible object manipulator (or stage) interhce, fixturing for two different object martipulators (1) a small, 15-cre o.d., rotation-translation stage that can hold up to 25-kg objects, and (2)a rotation, translation, elevation and tilt stage that can support up to - 350 kg and added fixturing that enabies the position of the stage and schltillator face front to be in a variety of positions. The small sta_ _ is approximately 7.6 cm from the _intillator face front, while the large stage, with a 46-cm o.d. rotational table, is a minimtml of 25.4 cna from the scintillator. The fixturing for the _intillator is adjustable for a travel of 30.5 cre. The camera is _atedonaNEWPORTopticalrail, and can be adjusted up to 20 cm inside the leaded enclosure to enable a variety of fields of view. Using these adjttstments and different lenses, wec,'m oblalin fields of view from 5 x 5 cna to 28 x 28 cna. This _anner has been built with the flexibility to,allow any object to be position_,xi as close to the detector Ks physically allowable. We have performed _ans with this system, for different sizcxt objects with cone angles up to 4.8°. : ::::::*' ' _ ,:' :_ -': * :_::_:_ _atz t_CAl'tCwot_. :_:: ii!il ,; L ;_ _i:'*_i '' ! high-energy, laigh-spatial-resolution CT scanners. This need will continue to increase as metal manufacturing achieves new levels of complexity precision. Engineering _ and 7 ::i Rese,'_rch DevelolJmenl aJnd Fechnolog}, 4. Thrust Area Report FYJP2 _'1_ Nondestructive Evaluation .'. Comput<>d/om(V_.q>h_ l'hi_ flexibility notwithstanding, one t'ontinuing, limitation of this system is the relatively small m,iximun_ fiehJ of view (2H × 2H cml of the svstt'm (rotation onk.')scannin_gt,omt, try and can bec_verc(mw by inlph.,menting and al_plyin _ _ec_nd-generation (translation-rotation) st'arming techniques. a_ a wholt,. ()he (_f the ,ldvanta_e_ of tile U Mt,V I.inatron i;; the ability to penetratt, t_biet't_ with dimen_i_ns much greater than 2Ht'm. The field-ofview limitation is only a rr,suit of third-gt, nt,r.ltion l'lwl,ltterlechniquee×tendsthefieldofview totlle total di_tanct' traveh.'d of the obiet't manipulator. Wt, are pursuing this enhancement to t,×tend the capability to IqI(CA'I" in the nt,xt fiscal vt,ar. We Ilavt' u_ed the Iii;CAT scannt, r to directly evaItlak' dil:ft'rent high-energy _-intillators and visil_le-light cameras. A COlllparison bt, twt_m thf two ...... radiographs iii: a Cak, rpillar portliner. Itoth radiographs were acquired at g MeV and are shown in . Fig. 18. Note thai the CCI) calllUl'a i%.'stllt_have dn incrt,a._.'d i.%,r|orlllailt_., (wt,r the SIT CallltTa rt_tllts. tligh-Energy CT Applications. Most of ilL!r CT , J rr Illeditlnlii 0.00 (2.q0tri i,3(Xi keV) energy ralige. VVe art, now ,'esearch studying has bo.,ntilewithin t,tfects theofI(iwhigh-energy (h til 25() keV) x ray to beams on tilt, available, dett_.'tors, and applications 0.16 0.33 0.50 0.67 i 1.00 0.84 I I I 1.1'7 1.34 1.52 Figure 18. Representativedigital radiographsof a prototype portlinerfromCaterpilltir, Inc. Theradiographswere obtainedusing a 9-MeVsourcewith (al the Vadan ER210 camera-baseddetector: and(bl the Cohucamerabased detector. Eachwas lens-coupledto the LHDglass. Imlll ..... LIIIII I I Jl I I. .............. thai req tj ire high energies for peneh'alion. t)ne application for high-energy C"l" is lilt, prtr:isitin tracking of tungsten proit_.'tilt,sin target materials "Pllree-dinwnsional CT meth(_.ts Call generale dimensit,lally accurate images tfr the path tlf a a target iii ali thre,.' dimensions, showing tilt, changes ill trajt_.'tory and iii tile character of tile proicctilt' <is it pas.,_,s through tile obic_'t,Figure 19 contains a _,t of 2-1) images I:ronl ii \'tliillllt, inlagt, ill Olle orientation, while Fig. 20 is proit_:tilethrough another .,_'t of 2-1) images for a difft, rent orient,Ili(In. I;i'onl tht,_, iinages, ii is parlicuhlrlv ink'resling tri study just how the proiLt'tile changed its dirt_.'tion by 181) `>til piiint iii tilt, direction of tilt' initial nlOllIentunl, This new capability t_rovides till tlnanlbiguotlS image of the path til the projt_:tilt, througla tile targvt nwdiuna. I ligh-enerh_, CF has [×_.'n applit_J tri varitlus die_'1 t'nghlt' conlF_iaents ,is a part of a C'txllxrrativt' 14t,st.arch and l)t, veltlpnlt,tlt Agreenlent between i.I.NI, and faterpillar, Inc. l'he goal tit this proit_'t is to ctlnlbine tilt' NII)I" and eonlputatitlnal reSlILII'Ct'S alld expel'tim, available ai IJ .NI., with tilt' d ie._'l-engine-design and manu factu ring e×perti._' tit; tilt' Caterpillar C?tlrptlration to de\,eltlp in-prt_ct'ss nltlnittiring and inspection tt_.'hniqtit,s for dit'_,l-t'ngillt, triitlli3tlstion challll_t,r C(llllp(llltilltS alltt malerials. I';arly devt, lt_pmeni til these techniques will assLirt' iht, ilpliilli/,ili()il iii thr, illalltltdt'ltlrin_ . I i I I I I 53.5(} 80.25 107.00 133.75 160,_o 187.26 214.01 211.00 t_l'tWt'ss bv tit,sign/insl_t'ctitln intt, rfaces, iiroit,ct gi)als inchidt, (I) til inl_l'ilvt, thf, t,fficiencv til dit,sel t,llgint,s; (2) tri lllt,t,i t)r t,xt't,t,tt ilt,%%, t,nviriillmt,ntaI lgure 19. Representative2-Oimagesalong the z axis froma volumeImageof the treck of a tungsten bullet. Thlsdata wasacquired with the ER210cameraand the 4 MeVsource. I't.t,tllatitlns; dntt (3) k) dr'vr'Ifip inspt'ctiiql and t_l'l)ct.s._t'(,ltrt_l tt.chnt_lt_gy I(_r the Fw(,.tuctit_n of adVdllt't'tt nlatt'rial._ ttlr inlt_rt_vt,d dit'._t,I t,ngiiat's. 0,00 _'1_ 26.'75 Thrugt Area Report FY92 .:" I '_K _",'_ "#_ //,,',_',l_, _ l'_'_,',',,t,m,',_t ,i#i,| li _, ll,/(,l,_ltl ' o:o Nondestructive Computed Tomography Evaluation Cornl.x_nentsunder study rangein sizefl't.n 2-mm o.d. fuel injector tips to _¼:m-x-_ cre-x-1.2 m cast iron exhaust manifolds. Most of tile effort to date has hwoivt_.i the interrogation of cast iron exhaust a_nlblit:_ and protota'l.x_ (l.x_rtline]_).Tile largt_t of tllt_ devict_ is complex and non-svnunetaicai, with nominal outside dimensions of X)cm x _ on × 1.2m. Our prelimina O, work has ftx:u_'d on a _ample stlb_tion of tile exhaust manifold assembly, a 12-cm-x-I 5-o33-×-1O-cnaLx_xwith an inner configuration of outlet hok_ and ceramic sleeving. Our research ha_ shown a substantial increase in spatial performance of tile COM U CCD camera as compared to tile Varian EIL210with both coupled to the LHD glass (Fig. 18). The port running down the height of tile object is lined with a ceramic material, which has nunaerous divots and cracks. A representative cross-sectional CT image of this 0.00 object is shown in Fig. 21. Fhe cross-sectional slice data reveal the ceramic-metal interface and fealures in the ceramic material. Figure20. Representative descdbedinRg.19. ' I 79.67 39.83 119.50 159.33 2-D Images along the y I ' 199.17' I 239.00 axis fromthesamevolumeImage charge. These plastic inserts were fixed to the explosive side of the copper wall, and the charge was filled with a mock plastic explosive. MECAT was used to acquire CT projection data of this shape charge at 7{)lmaa from the bottom of the charge. A summary of these results is shown in Fig. 22. The image on the left is the resultant inaage reconstructed from the projection data set. TIleCT image or tomogram represents a cross-_ctional view of the shape charge along its longitudinal axis, with 1-mm spatial resolution and a slice-plane thickness of 1 mm. Tile colorbar shown here in shades of gray relates colors in the image to tile linear attenuation coefficient in cm-I. Additional CT Applications In this section, we describe some additional NDE research problems in\'estigated during this fiscal year that are not published elsewhere, Shape Charge. We have perfomled proof-ofprinciple CT scans on a conventional munitions shape charge to show how revealing CT is in identifying inten_al flaws nondestructivelv. To rneet thisend, we fabricated a few plastic inserts to mock air voids (four sets of hollow cylinders 1-, 2-, 2-, and 4-mm diameter), and 1- and 2-mm mock separaKons of tile explosive from the copper shape iii ii for CT scan portliner 1-O profile 0.8 Figure 2.l. Representatlve 2-D Image from a volume-image pillar port liner. A 1-D profile shown by the black box is plotted 0.6 0.5 0.7 to the right. datasetoftheCater- __ j_ 0.3 0.4 0.1 0.0-- 0.00 0.12 0.23 0.35 ] 0.46 ] 0.58 I 0.70 L ,_',_'e',_t_g I 0.81 -0.1 0 Ruse iJ_.h ] I 2 4 D('_t,l(._pm_,rlt I 6 I I I ! 8 10 12 Distance (mm) a.'_(! Techr_(Jlut{_ 14 .:o I 16 Thrust 18 Area Report FY92 8-17 Nondestructive 8"18 rh_u_! Evaluation At(',l Ri#llO#f .:. ('lifT,iii/li,ii F'Y!I2 ":" ' I _ull )_:t.ll )l_; , ....... ' i' I .... ' " li C()ml_Ult'd ionT()l'U,Ufll_ ":. Nondestructive and elsewhere._ Representative results are shmvn in Fig. 24 for the/}'pe 2 blade using a mediument,rgy source, arm in Fig. 25 for the type 3 blade using a _)-MeV Linac. Bridge Cable CT Imaging. In cooperation with the California Department of Transportation and High Energy Services Corporation (I-II£5CO), Woodside,California, proof-of-principle experimerits were performed in an attempt to image internal features of bridge cables and bridge cable terrninu_,s. High-fidelity CT requiresa rather large nunlberofangularviews(tl'leASTM recornn'lends 1.5 times the size of the detector array in the horizontal direction). For a variety of reasons, most of which are related to functionality, components of civil bridges are highly attenuating with respect to x rays. Consequerltly, the internal inspection of these assemblies requires high energy (Mk,"range) sources, l'erforming the radiography is complicated b\' the logistical issues regarding shielding the on-conning traffic from the radiation, or bv developir_g reconstructit_ri sclaemes that cnn obtain useful informatitm from a limited nunaber of views, Using their in-depth knowledge of what can be doneon bridges, HE,q,_'Oacquired a lirnited-view cr projection (or radiographic) data set for application ofourCT image-reconstruction techniques. The data set consisted of 24 film radiographs e\'ery 6_'over 138_'.Wedeveh_ped inteJpolationschenles, Evaluation ill concurrence with other algorithm work, to e_Lendthis data to 30 vit, ws over 18(I._ (.)tht,r image-processing and image manipulation tools, developed for fi lm CL were then applied to obtain a reconstructed image of tht'cabh.,.Figure 26shows an examph., of the reconstructed images obtained using these methods. l'hese results are encournging enough to furtht, r pursue this method to inspect bridgecabh.,s. Ancient Artifacts from Iraq. We have used CT to investigate two, corroded, ancient artifacts that were excavated in Iraq by University of California Berkeh.'v arcllaeologists under the direction of Prolessor [)avid Stronach. These artifacts, along with others, were exported to the U.S. with permission frona the Iraqi archaeological autlatwities for scientific anah,'sis. The artifacts are believed to be objects used for personal adornment. l'hev were found oll an ancient roadway of the I l llzi (;ate at the sotltheast corner of the cii\' of Nineveh, the Inst capital of ancient Assyria. l'he artifacts were found anltlng skeletal remnants in the sack (destruction) level _f Nineveh dating back to (312I?,C,around the fall of the Assyrian Empire. lt is believed that the skeletal remnarlts are from an immense battle fougllt there. "flat' entrusted artifacts were nondestructi\'elv evaluated using a quantitative C-l"scanner to learn about their original ctmlposition and geometry. iiliB Figure 24. Representative CT images for the type 2 turbine blade, using a medF um-energy source at 2 70 k Vp and the Cohu camera coupled to the LHD glass. ! ii Figure 25. Representative CT results for the type 3 turbine blade, using a 9-MEV Linac source and the Cohu camera coupled to the LHD glass. Shown are 2-D 0.00 0.07 0.14 0.22 0.29 t _:,_a,.,.,,;,: I 0.43 0.36 tC,.,,,. ,.., ,. l', .. ,.'.,, ] 0.50 ....... ' ] 0.58 _ * ...... .' ] 0.65 ,.,:. ":" Throst images along the z, x, and y axes, respectively, of a volume data set. [ 0.72 Arei! R(:port FY92 8-3.9 NondestructiveEvaluation.:. ConTpuledTO,nOWaL)t,_, Figure, 26. Reacaseatae_e rad/o. ViewO:ecal157 grap_andrec_stnacted _ ot'a baagec,V_. meCT dataconsisted of24 vewsoverarangeof : :_ .(R_iographs courte_ t ofHESCO, tv_. Ca#fonWa.) View 1:line80 View 2:line82 View3:line 84 View 4:line 98 View 5:line 199 View 6:line 200 Extractedradiographshowing regions of CT reconstructions. CT reconstructionswere made from 24 views over a range of 138 degrees. 8"20 Thrust Area Report FY92 .:" ' ' ''" _ _r' _ ,'' _'r' .' . ' " B ' ' Comput(,d Tomogmoln .:. Nondestructive Evaluation _' .: ' , ' ".. ;.', .... ' ' : .... ', ' , • '. ":. Thrust Are;_ Report FY92 8-21 Nondestructive Evaluation .._ Computed Tomography 12. G.P. Roberson, H.E. Martz, D.J. Sctmeberk, and C.L. Logan, "Nuclear-Spectroscopy Colnpu terized Tomography Scamlers," Proc. 1991 ASNT Spring ConJl (Oakland, California), 107 (March 18-22,1991). 13. H.E. Martz, G.P Roberson, C. Robert-Coutant, and D.C. Camp, "Experimental A&PCT Research and Development Efforts ToCharacterize Mixed Waste Forms," Prnc. Transuranic Waste Characterization Co_, Idaho State University (Pocatello, Idaho), (August 10-12, 1992); also Lawrence Livermore National Laboratory, Livermore, California, UCRL- L.A. Feldkamp, L.C. Davis, and J.W. Kress, ]OSA A, 612(1984). P. Grangeat, Analyse d'un Systi'me d'lmagcrie 3D par Reconsh'uction i7Partir de RadhNraphies X en Gdom_;trie Conique, Ph.D. Thesis, l'Ecole Nationale Superieure des Telecommtmications, Grenoble, France (1987). 23. B.D. Smith, IEEE. Trans. Med. Ima,ging, Ml-4 (l), 14 (1985). 22. H. Kudo and T. Saito, JOSA A 7, 2169 (1990). 25. Ph. Rizo, P. Grangeat, P. Sire, P. LeMasson, E Melennec, ]OSA A 8 (10), 1639 (1991). tem," submitted to Med. Phys. (1992). 15. C. Robert-Coutant, H.E. Martz, and S.G.Azevedo, "Simulated A&PCT Data To Study the Mixed Waste Forms Characterization Problem," Pn_c.Transuranic Waste Characterization Conj', Idaho State University (Pocatello, Idaho), (August 10-12,1992); also Lawrence Livermore National Laboratory, Livermore, 26. S. Azevedo, P. Grangeat, and Ph. Rizo, "Procede de Reconstruction d'Images Tridirnensionelles d'une Region d'lnteret d'un Objet, Comprenant la Combinaison de Mesures sur i'Ensemble de i'Objet a des Mesures sur une Region d'Interet de l'Objet, et Installation Appropri6e," French Patent Application 92-11148, September 1992. California, UCRL-JC-110827 (1992). R.C. Placious, D. Polansky, H. Berger, C. Bueno, C.L. Vosberg, R.A. Betz, and D.J. Rogerson, Mats. 27. Eval., 1419 (November 1991). R.C. Placious, D. Polansky, E.S. Gaynor, H. Berger, C. Bueno, R.A. Buchanan, C.L. Vosberg, and R.A. Betz, "An Improved Glass X Ray Scintillator," Final Report submitted to Naval Weapons Center, China Lake, California (1990). 18. A.H. Rodgers, Private communication, Synergistic Dector Designs, Mountain View, California 28. (1992). A.A. Harms and A. Zeilinger, Phys. Med. Bio. 22 (1), 70 (1977). 30. 19. Area 21. 24. 17. ThruJt M. Barker, Privatecommunication, L(_ckheed Missile and Space, Palo AI to, Ca lifomia (1992). JC-110826 (1992). 14. J.K. Brown, S.M. Reilly, B.H. Hasegawa, E.L. Gingold, T.E Lang, and S.C. Lie_; "Computer Simulation of an Emission-Transmission CT Sys- 16. 11-22 20. Report FY92 4. Engineering Research Development and S. Azevedo, Ph. Rizo, and I! Grangeat, "Regionof-Interest Cone-beam Computed Tomography," submitted to JOSA A (1992). R. Albert, Private communication, Digiray, San Ramon, California (1992). 29. S.G. Azevedo, H.E. Martz, and G.P. Roberson, "Computerized Tomography Reconstruction Technoiogies," Energy and Teclmology Revh'w Lawrence Livermore National Laboratory, Livermore, Callfomia, UCRL-52000-90-11'12 (November/December 1990). anti D.J. Schneberk et al., Limited An gh' Radio%raphyBased Compuh'd Tom_Nraphyfi_r In-Situ Inspections of Brhtge Cabh's, to be published (1993). L_ fecl_nolog_ LaserGeneration and Detectionof UltrasomcEnergy,;* NondestructiveEvaluation LaserGeneraUonand DetecUon of Ulbasonk:Energy Graham H. Thomas E_lgilwerillgScieJlces MechmlicalE_lgilu'erillg We have developed a facility to generate and detect ultrasonic energy with lasers. Laser- generated ultrasonics is an ath'active alternative to traditional ultrasonic nondesh'uctive evaluation (NDE), becau_ it allows remote, noncontacting, ultrasonic NDE. We are developing NDE applications for use on contamination-sensitive components and in hostile environments. Laser ultrasonics has _veral other advantages, such as broadband excitation, multimode acoustic energ T generation, ,'rod adaptability to scanning complex shapes. |1 ul Introduction _rel. Ultrasonic nondestructive evaluation (NDE) is a valuable technology for material characterization and defect classification. I Laser-ba_d ultra- /a¢,_,__. sonics allows us to explore many new applications, For example, laser ultrasonics can be performed iri hostile erwirorurlents, such as in a furnace or a glove box. We are also pursuing laser ulh'asonic techniq ties for provid ing feedback control for pr_ces._s such as welding, composite curing, arid ultr_¢,o_ su_ wave islirstsensed by the_ _ as it_u_,ff_ beam. T_su#-,,_ wave_ _ o_' seln,l'le_ihe wekilerand_ _tll_ solid-state bond ing; _ /aseru/trason/c feedl_ksJ,_temfercor_ trolling welding CO2 __, r_ againbythedetection /aserontheretum. Progress i i _A/ehave acquired ultras()nic data oil a variety Figure2. Sample of specimens to test the svstern's capabilities. We have demonstrated the feasibility of laser tiltrasorfics to perform feedback control for directing a .4 -0 ,;,i'-_ -.4 ! fJ_ weldillg operat]oll. We perft)rrned an experimellt to show the ability of laser ultrasonics to measure the distance to a weld seam. The application we are considering is for laser welding, where the welding laser must precisely track the joint. Our approach is to rigidly fix the laser acoustic system totheweldingbeam.Thelaserac(_usticsvstemcan accurately measure the distance between the locatiol'l tfr acoustic generation and the weM seam. If the welding laser wanders off the seam, the ultrasonic path length will change (si-,eFig. 1). The path length change will bi., fed to the welding laser aligrlrnent controller t_ adjust the laser h}cation, We demonstrated theabilit\'(ff laser ultrasonics tr) i'ne_lsLirethe distance bc'twet'l_ thi-' tiltrasonic .__ ]_A.., ' _-_ resultsoflaserultraweld seam. Time sonlcslgnal from betweenpulses providesfeedbackto control weldinglaser _ vW_.y__ _ -.8 "6 ;> -1.2 --1.6 --2.0 --2 tracking. 0 I 2 I 4 l 1 [ I I I 6 8 10 12 14 16 18 Time (ps) surface-wave-generati()rl location arid the weld seam. Wi-' generated ultras¢)nic surface wa\'es in surn_gate specimens. Figure 2 displays an exampie _f the ultrasonic signals, where thi-' tirne bletwec,n the twit pulses is a function ill the distance to the seam. If these pl.llses n-ltwt' relati\'e to eact-i _ : Er_g_,_.i._,,,t_, , R_'_,e,t_c t! L),._uie,!.,m+..,,t <i,_,! !_., _"_"">tti ":" Thrust Area Report FY92 8-23 NondestructiveEvaluation.._ LaserGenerationandDetectionof UltrasonicEnergy other, the welding laser has moved off the seam. The timing between pulses should allow us to calculate position accuracy to .001 in. F/ldIure Work We are increasing our knowledge of laser generation and detection of acoustic energy, and improving our laser acoustic facility. We are investigating applications of laser acoustics to NDE problems simtfltaneously at Lawrence Livermore National Laboratory and within U.S. industry. Specifically, we will continue to explore applications for laser acoustics to control selected manufactur- ing processes, such as welder alignment, composite curing, and plutonium processing. Since each application of laser-generated ultrasonics entails a customized system, we need to have a thorough understanding of the fundamental capabilities and limitations of the technology to design the optimal inspection facility. 1. 2. J. KrautkramerandH. Krautkramer, LIItrasonicTesting of Materhfls,Springer-Verlag New York, lhc. (New York, New York),1977. N.M. Carlson and J.A.Johnson, "Laser Generation in a Weld Pool," Review(_ Progressin Quantitative Nondestructive Evaluation7B, Plenum Press (New York, New York),1485 (1988). L_ E 8-24 Thrust Area Report FY92 4. Engtneerlng Research Develol)ment and Tochnolog_ Remote Sensing, Imaging, and Signal Engineering Signal and image processing have always been important support for existing programs at Lawrence Livermore National Laboratory (LLNL),but now these technologies are becoming central to the formation of new programs. Exciting new applications such as high-resolution telescopes, radar remote sensing, and advanced medical imaging are allowing us to participate iv. the development of new programs, The Remote Sensing, Imaging, and Signal Engineeling (RISE)thrtkst area h_ been very a_ve in workhlg to define new directions, We aM) m,@ltain and continue to build for si_lal and image processing, These systems provide portability among tile many computer systems used at LLNL and give us a platform for transferring the results of specific research and development projects to application areas. Our major signal- and image-processingsystems, VIEW and VISION, are used by several major LLNL programs and have been distributed to many tuliversity, industry, and government sites. Work in RISE involves a diverse set of sciences and technologies ranging from optical physics to microbiology to advanced computer architectures. Collaboration with other thrust areas, such as Non- our technical base in signal and image processhlg in support of existing programs, through such applications as dia_ostic lmage processing and _ismic si_'ll processing, Over the past several years, RISE has developed a series of computer software systems destructive Evaluation and Computational Electronicsand Electroma_letics, and with other LLNL organizations, such as the Physics Department and the Biomedical Sciences DMsion, is central to our continuing work in innovative imaging and signal-processingapplications. James M. Brase Thrust A reaLeader Section 9 9. Remote Sensing, Imaging, and Signal Engineering Overview James M. Brase, Thrust Area Leader Vision-Based Grasping for Autonomous Sorting of Unknown Objects Shin-yee Lu, Robert K. Johnson, and Jose E. Hernandez .............................................................. Image-Restoration and Image-Recovery Algorithms Dennis M. Goodman .................................................................................................................. View: A Signal- and Image-Processing 9.7 System ]ames M. Brase, Scan K. Lehman, Melvin G. Wieting, Joseph P. Phillips, and Hmma Szoh'. ......................................................................................... VISION: An Object-Oriented Pattem Recognition 9.1 Environment sd.1 for Computer Vision and Jose E. Hernandez and Michael R. Buhl .................................................................................... _J.s Biomedical Image Processing Laura N. Masch_ ....................................................................................................................... Multisensor 9-21 Data Fusion Using Fuzzy Logic Donald T. Gavel ....................................................................................................................... 9-23 Adaptive Optics for Laser Guide Stars James M. Brase, Kenneth Avicola, Donald T. Gavel, Kenneth E. Walqen, and Horst D. Bissinger ............................................................................. 9.27 VlsionBasedG"aspmgfor Autonomous SorTtmg of UnknownObff;cts.:oRemoteSensing,Imaging,andSignalEngineering Vision-Based Grasping Autonmnous Sorting of UnknownObjects Shin-yee Iu, Robert K. Johnson,and Jose E. Hemandez Eib,fiJr'eriJt_ l_csearch DMsiolt Eh'ctrolfics EJlgilr'crill_,, The Department of Energy has a need for a method of treating existing nuclear waste. Hazarclous waste stored in drums and boxes in old warehou,_s needs to be sorted and treated by the new standards of environmental regulations. At Llwrence Livermore National Laboratory, we are developing a vision-based grasping capability that can be used to pick and place unknown objects autonomotisly. &_me preliminary results are described in this paper. i I_C_I_I_ in our experiment, we lav several obiects on a table at arbitrary k&'ations, simulating a conveyor belt. The objects are wrapped in plastic bags to simulate ,articles that are likely to be found in tl',.wastecontainers.Twocamerasarenaotuatedabcve the table to create a stereo view of the work c ql. Ihe cameras are mounted approximately 2 rn above the table, and have a field of view ofapproximately 2 m by 2 m. The images are captured and processed on a SUN Sl'ARCstation-2, with image rest_lution of 5 I(1x 480. l'he stereo images are registered pixel-by-pixel using an efficient stereo-vision algoritlam. A dense, tlaree-dimensit_nal (3-11))range map is generated by triangulating the registered pixels, l'otential grasp itx'ations for each ¢_bjectare generated bv analyzing the shape of a two-dimensional (2-I/)) projection of thc top view of the object, l,tx'ations around the handle or near the center of mass of the ¢>bjtx:t art' considert'd suitable for grasping, using a parallel gl'ipi_,r. Flat, rt_ult of this analysis is tl_:l to generate inft_rmation such as lx_sition, height, width, andorielatation forextwl.itingtllegraspingtask, l'he expeririaerltal re._ult shows high at't'tlracv in the I'dllgeestimatit_n. Wt, videotaped the experimt,iii arid studied the perftli'nlance. 'Fhe overall at.ctlracv iii] the plane perpt,ndit'tlldr t(i the calllel'- I fit.t,11_'l',sllll - as' lines of sight is within 2 Mi'n, and along the line of sight is 5 mm. The total CPU time required for generating the grasping information is approximately 70 s for four objects. The computation time is proportional to the number of objects to be handled. This experiment is an integration of camera calibration, stereo registration, slmpe analysis, and grasp planning. Algorithms used for camera taitbrat,on and image segnaentation follow existing rnetht_ds; however, our approacta to stereo registration is different from most of tbr, existing methods. lt is efficient and highly parallelizable. Grasp planning,at this point is a simple decision tree that matches the dwaamic range of grippers to the size of the objects, liach of the different tasks is explainedbehwvinnat_redetail, withanemplaasist_n the stereo registration algorithm. General Approach A set of transformatitln matrices for ep,pillar geometry correction are obtained thr_,ugh a camera calibration pr¢wedure. The images are segnlelited into regions, usirlg ii tlaresholding technique that separates the objectsfrom the backgi'tltllld. Sitice we assull'ie that the objects are not touching each other, each regioll segnlelll is assumed tri t'orl'eSpolld til art ob,ect iii the scelle. (_'orrespondel'ice tit regioils from the left image with thtlst' fl'Olll the righi im<lge is then esiablished, tlsiRg features such as lllcatitln dlltt size iii I?t'',l'<lt,h li_'_i'tI,I, tllt'llt ,lll_l II'(h_l(,li,lfl '_o Thrust Area Report FY92 9-1 Remote Sensing, Imaging, and Signal Engineering o:. VJ._()nB,ts(,(l G_,Ispm/_f_)t._h_tcm()m()l_.,_ S()rtlng(.)tUtll,J_()_tlOl_/_,ct_ iii i ii (a) 9-2 (Left) Thrust Area Report FY92 .:o / ,#_ ,,_._ ..... _: _.t_..,,. _: ,_ !', _, .':I,'_,+'_ ! .,. s _, _ ,,. ..... (Right) _;, VisionBasedGraspingforAutonomousSortingof UnknownObjects,_, RemoteSensing,Imaging,and signalEngineerin| ...... iii j i i i i (a) F/_re 4. 3-0roconstructlonelm LefteplpolarintemRtyeignal 0 o 30O 5o 1oo NSht ,plpolar..l.,tenlitysl_ 0 ...... . J o 5o I® ,,b) LeR¢orre,pond_n_ slpal I-_- / o0 311(I _'"_ _ _'_ lfJ_ tion, that pixels alongFhis epipolar have we the assume same left-right relation. relationlines can be represented mathematically by a linear order- _.y,. 1_ ing relation, t' The ordering constraint is generally IU_tt correspondence slS;nxl However, a strict linear ordering relation is obeyed by image pixels that pertain to the surface of an o i|\l _ ,_.,.....__.,.,... o 1_ Figure3. (a) IntensityprofilesofepipolarlinesfromFig.2; opaque object, true for stereo matching pair matching pair, that is, if pixels a and b are one registration, ,and pixels a' but andcanb' be are violated. another then if a is to the left of a' on one (a) (b) realignedcorrespondence profiles. '_; (b) age with the objects, and then thresholding the difference image. Size constraints are u._d to eliminate small, l'l(}isy, background-regiorl _gments. Regions in one image are matched with regions in the other image, using simple heuristics ba._d on the size and location of the ,_gmented regions, Two stereo images of the scene and resulting eorresponded regions are depicted in Fig. 1. Epipolar Figure5. (a) 2.0 depthmap;(b) 24) ii_ Euclidean distance :_i map;(c) 2.0sym. ::: metricskeleton. '! i._ " _:: (c) Line Registration Various dynamic programming techniques have previously been applied to matching edges in stereo images) ,4The result is a coar_, disparity ma p for which a com plex-su rface-reconstructi(m algorithm is required to generate the final range map. In our approach, pixel-to-pixei registration is done by matching the interlsitv profiles of two ctwresponding epipolar lines, using a special dynanlic prog_ramming technique called dynamic ct_rrelation. _ l)vnamic correlation is a method that " ¢! , ¢_ptimally aligns data points, based on a similarity measure, pre_,rving a defined ordering relation. When this technique is applied to stereo registra- En[glneerlng Research Development al, el fect) ncJloiqv ,l, Thrust Area Report FY92 O';_ RemoteSensing,Imaging,and SignalEngineering• Vision.Based Graspingfor Autonomous Sortingof Unkt)ownObjects Flgure 6...... Twopossibleparallel.graspor_ entatlons ' .......... COl,m) to C(O,O)on tile nlinimunl cost matrix, if C0,j) is derivect from C(i-I,j-I), then pixel a i matches bi; if C(i,j) is derived from C(i,j-1), then pixel b ion Lb does not have a match (a deletion); similarly, if C(i,j) is derived from C(i-l,j), then pixel a ion L,_does not have a match. Two corresponding epipolar lines are highlighted in Fig. 2 for the epipolar-aligned box object from Fig. la. The result of pixel-to-pixei registration of these lines is illustrated it| Fig. 3. The intensity profiles of the two epipolar lines are shown in Fig. 3a. These two intensity profiles are realigned after using tlae correlation algorithm. The realigned intensity profiles are shown in Fig. 3b. The matching pixels (substitutions) are aligned. When pixels on one intensity profile do not have a match (deletions), then a blank (shown as a zero value) is filled in on the ') / (Largegrasp) image, then it is ntn:es_ary forb tobe to the left of b' on the other inaage, Algorithms for pixel-to-pixel registration have to be effective in handling (1) difference in sealing, (2) occlusion, and (3) variation in light reflectance. The deletion (or insertion) operation in dynamic correlation is used to handle both opposite intensity profile. The occluded portions, i.e., the right-hand side of the box on the right inaage and the left-hand side of the box on the left image, are successfully deleted by the algorithm. The algorithm handles the slight difference in size (the box is at a harger skew angle to the left camera, therefore it is shown smaller scaling and occlusion. The substitution operation represents a match, but allows variation in brightness. Let La and Lbbe two corresponding epipolar lines, and let a i, i = 1,2.....n represent on the loft inaage than on the right image) by deleting four pixels from the right inaage at scattered locations. The 3-D reconstruction of ali four objects from Fig. 1 is shown in Fig. 4. pixels on La, and bi, j = 1,2.....na represent pixels on Lb. The dynamic correlation algorithm calculates the cost of matching a I, a2.....a i and b I, b2.....bi, denoted C(i,j): c(i, ii c(i-C(i, 1, ii - 11 _ (_ s(i, i) , 11 + :: min ! Cii- (2) ], i) + ,_ where s(i, i) ---1 1 2R,a,(i,i) } ', R,,,,_-_ _7(i) )" (3) • Here, R,_t_(i, j) is the windowed cross-correlation of L,_and i_bcentered about a i and bi respectivelv, Ra,a(i) IRt_t_(j)! is the windowed ,autocorrelatio|a of l.,_(1,b) centered about ai(b_), and (z is a fixed cost of deleting an element of t.,_ or Lb. The normalized substitutiim cost, %(i,j), varies between () and 1, and the deletion cost, (_, is fixed between 0 ,Ind I. We have achieved good results with (t between 0.2 and 0.5. The operatit}n in Eq. 2 defines a minimu|al cost na,ltrixfl}ri= 1,2.....nandj=l,2 .....m.C(O,j)andC(i,I)) ,1re given by i{i. ,lhd jet, respectively. The minimen1 cost ,alignment can De traced b,_ck from Grasp Analysis Since the objects in this experiment are small, not too tall, and the bag handles are always placed the table, shape can analvsis of paralh:l the 2-D to image t)f thea simple depth map be used to determine ata 'optinaum' grasp location with the gripper-oriented parallel table. First, we compute a Euclidean distance map from the 2-D projection of the depth map (see Fig. 5), using the fast raster scan algorithm. 7 A skeleton is theta generated by locating generalized local maxima in the distance rnap. s Associated with each skeleton point is a ,'ector pointing t_ the closest image point not contained in the object region. This orientation information is used to identify symmetric skeleton points (see Fig. 5) with respect to the object region boundary. Using information about the current available grippers, a grasp fe,ature vector is then computed for each symmetric skeleton point, ct)|asistingofpositic_nal i|aforna,lti(,1, ,1 gr,|sp size, a p,lr,lllelboundary deviation me,ast|renle|at, ,_nd the dist,lnce from the object region cent|'oid. Fin,lily, ,1 specified _ptim,ilitv criterion is used to Vision.Based GraspingforAutonomousSettingof Unl_nown ObJects.:oRemoteSensing,imaging,andSignalEngineering choose ali optimal grasp. Our current criterion consists of first only considering grasps within the range of the current grippers and with parallel deviations less than a specified maximum. Of those, the grasp that minimizes a weighted average of parallel deviation and distance from centroid is chosen as the optimal grasp. In practice, we often divide the current grippers into two groups, (1) small grippers and (2) large grippers. We then find a grasp for each group. For the current objects, tiffs often gives a large grasp about the center of mass and a small grasp about the bag handle, as shown in Fig. 6. Acknowledgements The authors would like to thank Maynard Holliday and the Advanct_'l l_rocc__sing]_'dlnoloKy Program of Lawrence, Livemlore National _l[x_ratory for their supl:_wt and for the use of the rol.x_ficfacilitit:s in the Interactive Controls Laboratooz. 1. 2. 3. I[_lllt_l_ Work 4. Prelirninarv results of applying stereo vision and shape analysis to robot autonomous grasping S.A. Lloyd, E.R. Haddow, and J.F.Boyce,Computer Vision,Graphics,and hnageProcessing39,202(1987). 5. S.Y.Lu,"AString-to-StringCorrelation for Image Skeletonization," Proc.6th Int.Algorithm JointC¢,lCtl PatternRcc_Rnithm(Munich, Germany), 178(October 1982). 6. A.V.Aho, and J.D. Ullman, The Theory o[Parsing, Translation, and Contpilin,g, Prenl_ice-Hall (Englewt_Kt Cliffs, New Jersey), 1972. 7. E l_,vmarie and M.D. Levine, CVGIP: Image/.Inderst'andin,_55,84 (1992). 8. U. Montanari, 1.Assoc. Computing Machinen! 15, (_oo (1%8). kl of unknown objects show that stereo vision can provide hst and reliable range infomlation. So br, we have u_'d a relatively simple approach for grasp planning. Weexpect todeal with morecomplex objects as the waste sorting project progresses. We are also interested in the proper mating of object geometr_' and manipulator geometry, and plan to use special hardware such as h'ansputers to speed up the process for real-time applications. i I D.H. Ballard and C.M. Brown, Comt,uh'r Vision, I'rentice-Hall,(Englew_x_dCliffs,NewJersey) 1982. R.Y.Tsai,IEEEI. RoboticsandAutomation RA-3,323 (1087). Y.Ohta and l: Kanade, IEEE "lhms. Pattern Anal. and Mach. h:tell.PAMI-7, 139(1_;85). l _,g,t;,.¢,_ t,g R_:,searct_ Dovelt_lJm_,nt ,,nU l_l:hclol_Ji;_. ,," Thrust Area Report i FY92 9-5 Image-Restoration and Image-Recovet_' AlgontlmTs.:. RemoteSensing,Imaging,and SignalEngineering Imags Restoration and Image-RecoveryAigorilhms DennisM. Goodman LaserEplgineerillg Diz,isioll Eh'ctrotfics El_gilleering We have written computer codes for soMng various image-restoration and image-recovery problems. The._ ctx.ies am,.,ba_d on a variant of the conjugate gradient algorithm that permits the imposition of constraints. Although the codes are essentially spatial-domain meth(_Js, most of the computation is done in the frequency domain. The result is that the flexibility of spatialdomain metht_.is is preserved, but computation time is clo_r to that of conventional frequencydomain methods. i Introducl:km A crucial tradeoff in applying image-prtx:essing algorithms to restoring a blurred image or recovering an image from data is accuracy vs time. Standard algorithms arenon-iterativeand operate in tiae frequency domain. Suppose tile image is an array of N-x-N pixels, llle number of floating point operations (FLOPS) required bv the.,<,algorithms is typically of order N21ogN, tile same order required for conlputing an N-x-N, two-dimensional, fast Fourier transform. Consequently, fl'equency-domain metllods are reasonably fast; unfortunately, they are not flexible enough to lmpose non-negativit3' constraints, to handle nonlinear problems, or to deal with 'ringing' effects that tKcur when the blurred image is not zero at its boundaries, llle._iution istou._,spatial_tomain metht_Js, but the price paid in computer time is \'el_' high. lkvau._, direct inversion metht_Js involve tile storage and inversion of nn N" x-N 2 matrix, fllese meth(x:ts are impractical for ali but ve_' small inlagt.,s. Instead, iterative metht_:ls art, u_.t. A typical iterative meth_.I c_mputt.,s one convolution and one correlation l.x'r iteration. If tht.'se are implenaent(__:lin tilt, spatial domain, each requirt.,s on the order of N4 Fl_Ol.xq,._ tilt, total nunaber of FLOIS ro.]uirt_Aby an iterative methtKt is on tilt, order of MN 4 where M is the nunal_x,rof iterations. For small M, iterative meth_Js are much faster than direct im'ersk_n meth(x_ts,btlt art, still much slower than frt_luency-domain meth(x.ts. In fact, they art, not practical f(}rimagt.,s larger than 128x 128pixels, We have developed a new method that is basically a spatial-domain ttvhnique, but implements tile iterations in tile frequency domain.lllis reduces tile cost per iteration to the order of MNqogN FLOPS. Our particular iterative technique is also new. lt is ba_,d on tile conjugate gradient algorithm and u.,a.,sa 'bending' line .,a.'arch strategy, a special implementation of the active m,t strategy and tile Hestenes-Stiefel formula. In IW-91, we applied this algorithm to the startdard, linear, least-squares image-restoration problem. We were able to demonstrate that tile imposition of positivity constraints and tile ability to properly handle boundary effects greatly enhanced in;age quality. This ,,'car, we performed Monte-Carloexperimentson small data problems, which dem(,nstrated that the estimates obtained with our technique I were at least as good as those obtained with m(,'e conventional methods, such as constrained regularization and maximum entropy. As noted above, the conventional spatialdomain metht}ds are too slow to apply to large data problems. Many image-restoration and image-rectwerv problems are inherently ntmlinear. For example, the algorithm we deveh_ped for the standard, linear, least-squares rest¢_ration problem is inappropriate when imaging at \err h}w light levels. This is because thf quantum natu re t_f light must be acc(_unted ft,, and the n¢fist, must be mt_deled aS l'oiss_la, rather than (;aussian. l'herc'suit Remote Sensing, Imaging, and Sipal Engineering "." ImageResto,,_tion and Image-Recoveo, Algo,_thms _ast.squares criteri- Figure 5. Reconstructed, three_imensional, cell for the protein thaumatin. Figure 3. unit crystal Estimate _,ai_bymaxlmlz. i,,_'_ _,f_r_ I_kel/._r ruination, is a highly nonlinear likelihood function that must be maximized. In FY-92, we extended our algoritlam to permit minimizing or maximizing general nonlinear functions. -_Figure 1 is a simulation of the result of imaging two closely spaced point sources througla a circular aperture at a low light level. The result of deblurring using the least-squares criterion is shown in Fig. 2; the result of deblurring bv naaximizing the likelihood function for Poisstul iloise is sllowrl in Fig. 3. The noise-ft'ce image is shown in Fig. 4. The estimate obtnined by using the proper noise model is clearl\' superior. We hax'e ,also applied oul"algorithm to ._,veral other n(_nlillear imagin,u, prt_blems. These includ_ speckle interfert)metrv, _ laolograplay, and cl'vstalh_graplav. A crvst,_llograplaic example is shown in Image-Restorationand Image,RecoveryAlgorithms .:. Remote Sensing, Imaging, and Signal Engineering Fig. 5. This inlage is a three-dinlensional rt.'o,)nstruction of the protein thaumatin. Tile reconstruction is obtained using the Eden algorithm, which u,_s our algorithm ,as an inner iteration to repeatedlv solve a non-negative least-squares problenl consistingof28,fX)Oequationsin36,000unknov,,ns, The solution shows excellent clustering sidual ._atterers, since the reconstructed tion occupied only 16% of the available grid W_Nck We plan to continue play problem in FT-93. I).M. Goodman, "l)econvolution for I'ositive Siglaals," I'undam,'nhfls ,q l)iscn'h'-Tim,' Sysh'ms, M. Jamshidi (l:.d.), lt_t)3. 2. ll.M. Goodnaan, EM..]olaans.,;on, and T.W.I.aw"On Applying tile Conjugate Gradient AIgorithm to Image I'rocessing I'roblems," Mullivariah' Analysis: Fuhtn' Directions, C.R. I#,ao (Ed.), North Holland, ItJCJ3. I'_'nct', of the reinforma- positions. Future I. work on tile crystallogra- 3. D.M. Goodman, T.W. Lawrence, E.M. Johansson, and .I.I! Fitch, "Bispectral Speckle Interferometry To Reconstruct Extended Objects from lhrbulence l)egraded lblescope Images," tlaudboi_k iii Sh#istics, Vol. III: S_k,nal Pr_ccssin,_ alld its Al_pJicalious, N.K. Bose and C.R. Rao (Eds.), North Holland, lt)t)3" L_ View:A SW7_# and Im_geProcessing Sistem .:. RemoteSensing,Imaging,andSignalEngineering View: A Signal- and Image-Processing System James M. Bmse, Sean K. Lehman, and Melvin G. Wieting LxTser Es_.%iJmerillg Divisiolt EhvtroiHcsEltgilmeriltg View is arl interactive signal- Joseph P. Phillips and Hanna Szoke Scieltt(ficSqtt_iare Di-oisioll ColupzttatiolzDirectorate and inlage-prtKessing erlvironnlerlt for UNIX workstations with the XI I window system. View provides tools for image enhancement and general signal analysis. The system is tl.,a__Jin programs at Lawrence Livermore National Laboratoly for exl.x.,rimental data analysis and has t___.,ndistributed tc)univei,_ity, government, and industrial tl._l_. In FY-92, we developed a capability to handle very large signal databases containing large numbers of signals or images with accompanying descriptive information; we continued to enhance the base View language, algorithms, and tools, and we demonstrated for distributed signal pr(Kessing on a workstation network. a prototype teel the principal system used for reconstruction tfr x ray h(_lograms and microscopy and as a diag- h11b'oduc_ion iX project tt_ develop \/iew, I an interactive signal- and ;mage-prtlcessing erwiroruneilt for UNIX wolkstati_,ls with the X II window system, was started at l.awrence IJvermore National I_aboratory (IJNI.)in 1q86 t_arlv work ftwused on tools for image enhalacenlent and analysis for nunde..... structive testing applications. View has been used extensiveh' for inldge analysis for radiograplay and ctmlputt,d tonlography as well as signal processillg for ultrasonic imaging. Our de\'t, lt_pnlent has continued with applications centt,red _._!1 radar imaging, rr'mote sensing applicatit,as, and highres{_1 utiiln astrononlical i magillg, iiicl Liding speckle interferon-lt.,trvailcl adapti\'e optics. \rlit'%%' pi'twidt's most (it" the tools Ct}lla111(lnlv ii required ltir signal and imat.r,eanalysis. Illleractive capabilities includl_,ciihlr nlap nlanipl.ll,liitln, lint.,llul iliad i'egiilil extractiiliL data \alut' displa.v, ,11_cl imatd, t, dnn(_tali(/ll. Vit,w's Cillllnldl-ld intt, rprt,ler pllwides a /.r,t'rlt,ralpurpilst, sigll,ll-Ill,illipulatitlll languagt, with hiilpill)4 aild c:(,lttitic,lal ctlil.MlUCtS. The sit.r, nal- dnd im<l/2,t'-t-u'tlc't,s,,,illg c<lpabililit,s include, spectral ai_al\'sis, _,mlllllhil_ and sharpt'i_in).r,t:ilters,ar_tta(tapti\'e n__i_.t,-it,ct ti¢lil ll_tt'chnicltir,s, Vit,w c(llltinut,s l_.,ht, tlSt,ctin thf, ,ipplic,_tii,as Figurel. Imageprocessing resultsfromournewtoolforinteractlvecolormapmadc'scribed abtwt' <>,wt,li a_,in _tlwr_,ai I I NI Ii is nipulatlon, allowing piecewise linear color maps. t,':,: ..... ,,,_' h',,,,,.,_,, , li,,;,,,,,l,,_,,,,_ ,-_t_,S /,,, '_',"_,>t!; ":" Thrust Are;I Report FY92 9-11 Remote Sensing, Imaging, and Signal Engineering .:. l Jt,n .I ,gtm_,J/,,n!/m,_/_,c,1't(_('(,_,1£,grub'/li 9-12 Thrust Area Repgirt FY92 ":" , .+, ,., , _ .... _, ,, , , I, , .... ,,, Wit,w: _ Sl_nal and hnageProc(;ssm_, Systenl in Fig.2.t)n the h.'l:tisthe original image.We,,_,parale it into low- and lli_h-frc_.iLtenc.vCOml_Onunts and applya nt+nlinearsharl,_,nin_ol__,ratitintoc,achcomI._llt.'ll[.2 The Ctillli._lllt'nt inlal2,t_ art' thr, li lCt'()lllbirled lo t4c'tthe It,_ulton Lhcril4ht.This all4orithm ha,_ rl't)VC'll Lib'fill ill t'nh<lncill_ Future (.')tlr third Network-based distribuled dt, vt, lornlt, s.vnthc'tic at'_'l'itll'L' rildar lli area in F'f-q2 o1 a pl'tilotvpe wa._ [tlundatit)ll xvorkstatitins will tor OLIr t'iftir|._ in hi_h-pc,rformancc' signal and imal4e pl'oce,_sin_. View will databa._es the work. teel {iii" di._tribuled bi., {tll'lht, r dt'vt, ioped and _llc ' ilrc, ctlrrt,nllv these capabilities. s),stc, ill tipnlt'n[ Io StlppOl't both thai span lhc nelredesi_nJn_ lhc' ._it4nal- C(_lllptliatitln,_; pri)ct, s._inl4 lalll4tlat4t' allows tiperations til he distributed livc'r a i-it,tWtll'k t){ UNIX workstafion._, t\n inleractive_raphical tl,_t_'rinterface(Fill. 3) allov,',_the user control over whk'h nlachinc,,_run each COllllllalld, ,_i_4nalCtilllnlLinic'atit)n is thi'iiut4h the nc,twtirk file svstenl. These capabilities will ._il4nal pl'tt'c'ssint4."l'llt.' {Ol'm thebase Work COIIIII1LIC' t(I [_t' ltlt' inla_ei._,', dt, nltln,_tration .:. Remote Sensing, Imaging, and Signal Engineering alld its inl:erpretc, We also (){ LlSt'r illli.'rtacc' plan r to ._UppOi'l contintled devel- c,nhLlnct, nlt, nts li) COll- t()rnl [o t'111i.'1"_i11_ slandal'd._ in _raphical tlser intci'faccs. AIl4orithm devclopmunt will c'()ntinLit, til [)t' d rivc,n bV onl2,oinl2 , applications. tor {LII-LII'L't.'IIII,II1Ct'IllL'IIISIi{VJL'w. I. 1. Iii'ase, V. Miller, N,I. Wit, tint4, II. Szoku, and I. I>hillips, 'I711'Vicrl, ,<4_\,n<fl _l/lit hllaTl' I>#'oil'$._ill7,ql/._h'lll, I .awit, nct, I .ivt,i'nltiit, N,ltJiinal ] ,ai_iiralor)', I.ivt,l'nltirt,, (.'alitilrnia, UL'II)-2 13(_ ( IqS_l). 2. _.K. Milra, II. 1i, I. I.in, and T. Yl.I, "t\ New L'la._._ifr N(inlint,ar hll. I:illur._ t()i" Inl,1)4t, I.]nhanct,mi,nl, ('_illf; .'li'iillslii'_, °' /_r0(". ._#i_'i'i'II,tlli<l ,q_,,_lltlll)l'(li'_'SS(ll_k ' L: (Ibi'i _nl(_, t',In,_da),( Iqq2). I i _ _'11 _'",': _*: H, ,,, <_,< t: li, _ ,,_,,,,,,, ! t,<s I,, !:_',_ _'/I_ ':° Thrust Area Report FY92 9-13 VISION:An ObjectOrientedEnvironment for ComputerVisiono:.RemoteSensing,Imaging,and SignalEngineering VISION: An Object-Oriented Environment for Computer Vision and Pattern Recognition Jose E. Hemandez and Michael R. Buhl EllgiJleerillgResearchDivisioli Eh'ctmJlicsEizgilleering VISION is a flexible and extensible object-ofienk_.t programmh-lg environment for prototyping solutions to problems requiring computer vision and pattern recob,mition techniques. VISION integrates si_lal/image pr(x:essing, statistical pattern rr'cognition, mid-level computer vision, and graphics into a cohesive framework applications at Lawrence Livermore National Laboratory. |llitco(_ction During tile past two years, we have been developing an object-oriented programming environnlent known as VISION, fl_r conlputer vision and pattern recognition. VISION is a hybrid svstenl consisting of C, Lisp/CLOS, I.2._and sonle FORTRAN code. CLOS, tile Comnlon Lisp Object Systenl, defines the new standard fl}r object-oriented progranlnling in tile ConlnlOn Lisp language. Tile VISION svstem was developed with several goals in nlind: (1) to provide a tedlnology base at Lawrence Livermore National Laboratory (LLNL) in computer vision and pattern recognition; (2) to provide support to programs at LLNL requiring this technology; and (3)to provide a software package capable of being extended and customized directly by tile end users. During FY-Ol, most of the object-oriented framework was developed, including basic classes of data structures for signal/inlage processing, nlidlevel b,vo-dinlensional (2-D) computer vision, and unsupervised and supervised learning algorithms including several neural netw,.,-ks.-bs _mle _f tile capabilities in VISi()N were applied to several projects sponsored by IJ.Nl_.'s Earth N'iences I)epartrnent. Aisle, \/ISION was used as a developnlent environment for the tenlperature-evaluated mine position sur\'ev ('I'I_MI_) project for locating buried mines._'Tllis prelimi_arv w_rk resulted in a 1.5-nlilli(,1-dol lar pn @ct curren tl v funded bv tile _ _*_:_l_,_,_r_g neural networks, low-and useful for a wide variety of Defen_ _AdvanctKt l;k_eardl Projects Agency, and a l.x_sible licensing agr,._enlentwith a private company. Dufirlg FY-92, VISION was u_'cl as tile development environment for a rt_arch project in stert_ vision and grasp planning for robotics. Tills effort r___ultedin a demonstratk_n system currently being u_Kt at LLNL's hlteractiveControls Lal_x)ratorymanagecl by the Advanct_:l Proct_,_ing Tt_dulology Program. _}nle of the capabilifit__in VISION have ai_} L__,llintegratc_t into LLNL's Seismic Exl._rt System, 7 Sl.X_n_r_xtby tile Treaty Verification Prob,n'am. In FY-93, VISION will Ix, u_i to prototyl.x, pattenl rt_zognition algorithms for LI_NL's INSENS proiect, Broken Heart Valve project, and wake detection project, and fordevelopingmoreadvancc_tcapabilitk_ in computer vision for rotx_tics. Overview of VISION VISlON consistsof_,onlajorparts: theprogranlnling environnlent, and the computer vision and pattern roco_lition capabilitk.'s. Tile progranlnling environment is primarily provided by the Conlmon IJspenvir_Jnmentitself.Sonleofitsfeatur_.._awlisted t_,low. (1) Interactive prograrnnling: elinlinat_._tilt, net_.| towriteaconlmand-driven u.,<,rinterfaceand encourag_._ increnlental development; (2) l_,un-tinle linking: C, I;:OI_,TRAN,and compiM.t I.isp c(_.tecan [x' I_ad_._.tand linked dvnarnical Iv at run-tinle; t?_'_,_,_rc/_ De_el(_/)m(:tlt and re(:/_nolo#,_ .:. Thrust Area Report FY92 9-15 Remote Sensing, Imaging, and Signal Engineering .:. VISION:An (_IvL'¢IOnt_nh,(!t_/m/()nm(,nt hu (_'(m_t)uh,/Viii(in |1 active class browsFigure1. Aninter- " -J C()pv obje_'l I Named l)bjecl I ,_ u_run. Vishm _ ,";tandard objed I)ublic plist standing the VISION class system. Attributed slot's (3) (4) (._) (f_) Autt_matic illt, nlol'V Ill<in<igt,lilt,lit: IL_p haildlt_thealllt'ationandde-alltt'ationlltlllenlo- set _,I data ._[rLicttll't'._ and algorilhnl._ within an llbiect-llric,nled il'alllt,W(il'k t/)l" (I) I't,t_rt,._eniing, rv, hence cltte can Ix, develotxtt faster; lx_'lv t)'tx_,t language: ._Jnct' there is no lltttt tri dtt'lare data t)'_x._, alg_,ithnl._ can ix, prtitll_+'t_.| ta.,4tel'; t:unctioilalprtlgranlnlJng: wellavelheabilitv to ct\'nanlicall\' define fl.inc'lJt)n._tri Jt' pas._t| a._argunlent._ to oilier functitlil._, which is L._._.'ntial to our traillt, wtwk tl_r patteill rct'_lgllJlion; p rt_ct,._Sillg, and ._egnlc'nlin g one-dinlt, nsional (I-I)), 2-1), i_l" three-dinlen._ional (7-1)) data; (2) calculating and evaluating ft,attlrt's for ._tatistical rilttern rectlgnilitln; and (])._t, vt, i'al paradigms [iii" _>biect i'ectigllititln and cla._._il:icatilln JilcludJng nt, tlr<ll ht, tWill'ks and ,iii Assulllptitln lruth Mainttulanct, .gVStt'lll. u In sunlnlar\I,, VISI()N is an exlen._illn Iii the (_'OnllllOn l.isp t,ll\'Jl'tilllllt, llt tri illakt, ii llltil't, useful tt)l" signal/ ()bjtt'i-(irk, l_ktt prognlillnlJng: ! .i._p._upt_iris the obict'i-orit'ntttt |_rtlgranlnling t_aradignl, which is t_._.,ntial for tit," exten._ible I:l'anlt'- Jnlilgt, t_rlict,ssing, t_atierl_ recl)gnitil)n, puter vision. work, thr<lugh C'l .( _; !!lilacs interface: t,xprt_itlilS, rt'git)n._, and bu//t,l._ within F_mac.,_ can Lt, subnlittctt it) tilt, (7) l.i._p interpreter dir_t'tl)', which inlprovc_ pi'oducU\'ik,; Altificial intelligence (AI)sifhval'e: l.isp _}ft- (8) wart, is available (tj) ill tilt' public dtlnlain In I'_'-cJ2,there were a substantial and el)Ill- IILIIllIXiF O{ illl- t_lt)\'t, lllt,ilL_ and c|t,\'t, lopnlt, lll._ ill tilt' al't'a._iii COlllptltt, l" \'ision and patterll rtt'(igniiiiin Ill,li.Jt, tri the I_'-CJl VISI()N i'elt,a_,. for stipt_lrting ill<lnv t)t [ht, t\1 pal'adignls for high-lt'velI't,a._.lning; and (.71,l_sL_row_,l': ali hlteracii\'e class [_l'liw._'i" ColledionObjeds ba_t on (]t\I_Nl71 is availablt, tlir brtlwsing the VI._I()N cla._<_ s\'stt,nl (._t' Fig. 1). ((;t\14N12I' is a I.i._p-ba_tt graphical Li_'r interface en\'ironnlent develoDtt at (_'arnegit' Mt'lion UnJvt'l.'sJ_'.,_) ftlndilnlt,nt,ll building bl_w.'k_in VISI()N. 'l'hN c'l<l._ unitit_ Illilnv tit the data strut'turts in VISI()N for storing colltt'til)ns of llther data sh'uctult._. I'erllat_s tilt, nlosi illlt_lrtant <lStXt't iii this cla._<_ is thai ii pl'lt \'idc.-_lll<.lllV i11t,lhi_ts t:()1ini|:_lt,nlentJng gt'nt, l'JChigh- l llt, c_lmputer vision and patit, rn i'ectlgnititln capabilities ill VI.gI()N con._isl ()t an integr,>.ied i'lle cla._s Colltt'tion-(_jt_:t is i>llt' of tilt, lilt)st er-order functions (ill i()!:). Iii l'hese are gt,nerit, {uncti(instilalacceptlltht,r ftlllCti_ln._a._argunlenL,-;lil i (ai (bi lc) Figure2. (a) 3-D data representinga cell, (b) thresholdeddata. Eachvoxel in the volumeis assigned to one of three Intensity bins representedby the three different gray levels. (c) Regionsidentified within the voxels In the third intensity bin. Threechromosomeswere found. 9-16 Thrust Area Report FY92 .:. / ,,_: .... , , ,,_i /,', ',, i_, 1, fJ_ i ..... _,_, , _ _ _,,,/ I,, ',,,,,I,,_I_ VISION:An Obiect Onuntvd Envlronnlt,nt tor Con4)uttv V_51un.:o Remote Sensing, Imaging, and Signal Engineering i ta) (b} Flgure 3. Example of the use of an automatic thresholding algorithm onthe gradient of an Image. Pictured are ta) a housescene and (b) edges of the Image. •. t'_,applio,i to the individual objectsin the collection. Generic functions-_,:_ are functionsfor which nletll(_:ls can t_,definc_tto provide theappropriate functionalitr for different cla_,._.'s _f obiecL'_. (;H()F provide a i:x_werfulmect-_anisrnfor _lving problems without tile explicitu._,of rt__.'tlrsit_n ¢_1" iteration.Furtlaernlore, they hide the internal reprt._ntatitwl of tile collL_:tion Volume Se_nentafion obiect, sirlce the iteratit_la prt_ct.,_,_is l-lidden. For exanl- done _ that it ct_tdd L_,extendt_t to any NMinlensit_nal pie, consider tile (,HOF gcount-if, which c()ullL,_tile nuna_'rofobit_:ts in the colk'ctitwl that _atisff, a predicate(tt_t). In thecontexttffct_naputer\isit_n, wect_tlld u.,,e this fi.llaction to count ali the rt_tm.d objt_,'ts in a _'gmentt_J inlage, space. Duett_ourlinlitt_J rt.'_urcc_, tllerearen(_plans at this point to develop .3.-!) grapilics capabilitit_ in VISION. However, an interface was develol._'d to write the different cl,l_-W<_of .3.-1)data objects in VI.qlON to disk in SUNVISION ft,'nl,lt for data visual- (gcount-if #'rt_undp _rgnaents) => 52 hl general, algt_ritllnlS can N' prt_to_'[_<i faster, An (_bit_:t-orie|ltedframework for .3-l) data .,_'gnlentation has t_._,ndevelol.×,cl.The newcapabilitic.'s are very ._imilarto the conlptiter-vision capabilitit.'s that were develo[x_Jlastyearf(w2-1_) data. Infact,the original, 2-D, c()nlputer-vision flUillewtwkwas re- iz,ation. 5UNVISION isa 3-l), interactive \'isuali/ation progranl available for tile SUN wtwk.,_tations. IJ_NII. currently Ila._ a site licen._, for SUNVISION. Ata ex- since we onl\' nt_.'d to develop prinlitivt._ that deal with the individual objects iii the collectitln. Wt, can then ti_' lambda exprt._sions to conlbint, tllt._, prinliti\t.'_ and ftll'lll naore conlplex expri.ssitlns thai can L_' applioJ io tilt, indiviclual <>bic_'ts ill Lilt' colltt'titln. l_,lmbda exprc._,_it)ns Iare antlnvnlt_US functit_n_ t3'picalh' defined to be p,lS._._.tas argUillents t(i tltiler function.,,, t:(li exanaple, we cl)ulcl ti_, a lanlbda exprc._sit_n to COtll'lt ali the signals {l'tllll a ct_llcctit>la (if anlple of a _'gmentt_.] vt_ltlnle showing tile nucleus lind chrolll().'_lllltS (ff<lcell is shown in Fig. 2. In _tllllnlarv, tilt, new .3-1_)capabilitit._illt:hide: (I) nltilti-level thrc_holding of_l)data, (2) rt'prt_._,t,ntatitin alia pl'tt't_Sillg cap,lbilitit.'s for ,inr arbih'al_, _,l (_f\'oxels in tilt, v¢)lunle (coniltwtt_;t (li" n(in-ct_nnt_:ted), (3) 3-1) gi'tluping algorithnl fill" identifying 3-1) 'l'e)2,itlllS'ill the vt>ltlnle, tinle _'rit .'.,that have a pi>siti\'e illean, (gctlulat-if #'(lambda (x) (plusp (llleall k)))si#,nals) (4) (5) 5)llle examplt.'s til _tl[tiasa._ tit tilt' class C_llo:tit,l-Obit_.'t arc': .qignaIs, t( li"_t(iri ng <lcl _11t_cti_ ,1 _f 1-1) AulomaticThresholding _l, lll(IChl'(llllt'-llllagt_, /iii" sttli'iilg a tilllectkln (lr 2-1) ii llagts; and .%.'Knlel_ted-lil_age, t_)r storinga ct)lit,tri(in (ifi't,,Ki(ln _,_lllt'lll$ in <ill linage, 5,\'t,ral alt4_,'ithnl.,, wt,rr, dt,\t,ltll_.,d tl_i <lilt(ilia,ltir" thrt._ll()lding lit: ct<ill, ii _lllt' _ll Ihep.' alg(withnl.,, <irt, u_'ftll {iii" _t'p<lralillg I_acku,rtltultt tl(llll i_l_n-l_,lt'k- => II wave/()rlll.q; t.,,,tf_,,,_,_l; _. fi'_,,>,..lt_ basic-shapt_analy.<_i_capabilitit.% and inteMact' it> SUNVISIC)N ttlr .%1)data \'isualizalilln. #, /._,,,.v/_,t,,.,,,', ! _.,_ I,., ,: .... _"_i, ":' Thrust Area Report FY92 9-17 Remote Sensing. Imaging. and Signal Engineering .:. VISION; 4n OtJ/_.c!Orlt.nn,c/Em',()nnr'nr f(. Comput_.rV,-;,.I _l i i Figure4. (a) An image froman infraredsensor showing severalobjects, (b) three sections in the image, classified as buriedmines using a neuralnetwork. i (a) An object-oriented framework for supervi_'d learning using statistical pattern rl_:ognition k_'hniqu_.,s and neural networks was f_,'mali/.c_.t this year. 1'he framework consists of two clas._..'s for manipulating databa.,-a._ ftw suD,r\'i_,d learn<rig; feature-.,a.,h.'ctit_nalgtwithnls I_f_,'e\aluatingand.,a.'ltvting u_,ful features for _lving cla_,_ification problems; and tw_l new class<field, a neart_t-neighbor classifier taken at aiq:>orts, for dr, retting expltMvts, and a pr_lbabilistic neural nehvtwk. I-1 M_st t)f the suD,rvi_'d It,aming ,llgtwithm.,, \"I51()N Ol.x'rate t_n a few data stl'ucturt_ referrc'd to a_ tr,fining and D_ttenls tablt_. A 'tluining table' is a Mare' algtlrithms were deveil_D_i bir extracting I;eatl.lrt% ftlr t>bicvii't't'tlgnitii)n..t'_'llllt' of tilt'Ill art, listed I._,h_w. (1) I listtlgram featurc.>s:al._lkrlown a._fii.'st-ordl.,r fc'dtl.ll't%,tl._t_.ttt_c'xtract t:t'dtl.ll'C._ fl'tlllltllt.'191"o['lab<lit\' dc,rMtv ftlllt_-titwitit thc, data; data structure thai as_wiatt_ a lai_x,I(ty,pically a symbt_l) I11Callt to It,pl't.,:-;t, llt the I1,1111t'ii[; a c'ategtll'y of Dattc,rlls, with a colh.'ctit,_ tfr obicvts (an instance of ,i Collcwtit,a-Obicvt class, in m_lst ca._). A 'pattt,rllS table' is a sDt'ial kind of tfdining table where the <>bicvt._ inthe colk_.'titlia arc' o_n.'-;trdint'd til L'_' fc'dltll't' (2) Central mt_ments: canN, u_'d toe×tract _hal._, inf_wn_atit,_ and are in\ariant tt_tran._latit_n; (3) I Iu laaonwnts: similar to tlwcentral nat,_ac,rlt_, but the\' are al_ in\ariarlt tt_ rotatitwl; arid (4) lc'\turc' ft_,aturc_:al._>kritIwn <ls._cond-twdc, r fedttiri_s, ti._l.,dlt>t'Xtl'dCt tc,xttirt, featUl'C.'st:1t)111 <111 in'lilge, Miln\' tither algtwithnl._ dlt' <llnl available i_," t'x- \'c'cttw.'.,,ali t_f thc, _amt, .,,i/t,..q.,\'eral (;tI()F are provided flll" i.-,t,rtt_rrnirlg trarIMtwlnations oll tllc_' data _tructtu'c_. l:l_l t'xalnpk,, in a typical applicatk,_, we might stal't by creating a training tabk' that keeps track of file ilanltts with the _wiginal nlt,ilStllt,nlt,nls <ls._lcidk'd with each catt'g(ir.v, _,,Vt, can ti.,,t,tht'_, i! i( )F maptable t(I err'atr' a p, lttt'rn_ table with the ,lctu,l] teaturt' \'c,c't(w_t(>bf, u_,tt b\' the It,,lriliilg algtwitllnl_. tiactingin ftwmatit in tllal cl _tltctI.t, used a.<_ ft,atu rt'_ ii, feahlrc_ can l_., u_,cl as Jllpl.lt til ,1 I'tllo-lM_'d ._\'_tt'lll til" til ,1 nt,tll,l] ilt,twtllk f<>r<>bi< vt rt_.l_gnil ii in. Ctln._idt'r the,il_lh iwing t,x,mapIt,, (_.,tcI tilc,_(inak.e-lraiiqng-t,d.qt' :lll,llt"("nl I.... 1112"...) :tt,ina lc,'(" t1.... f2" ...))) -::_".:trainin,z,-iablt, _. (st'tcIpa ttt'rn._(Inapial_lt' ft'caI<-lt,,l lt IIt'_ 1iIc_ :cl,_._'Pailt'l'l_<,-i,lblt')) ..... ;IM tiC'l'laMablt' • Thrust Alea in Feature-based Object Recognition <>bicvt i-<_:<_gllitk,_.lht_, 9-18 i Supervised Learning gr_,und pixels.The.vareal_,verv u_'ful for automatic thrtMl_,lding i_fgradit'nt imagt_ for edge deK_'tion (_'t' Fig. 3). A multi-thrcMl_lding algorithm was al._ de\'elOl.X_i,ba._,d on a K-means algorithm that cluste,.'s the data valuc.,s dirtvtlv from a histogram and therefore it i_ very fast. ll-le algorithm al.,.a_featurc_ tlle ability to find ti_etx_tnumtx, rofthrt_ht_ld \'alut_ba_,d on the ratio of the _;atter-matrict_. I-_llais algoritMn is cur-rentl\" Lx,irlg ex'aluatt_.i for .,_,grnenting x ra\'s of suitca_ i (b) Report FY92 "1. t .r .,, . ,_: #,',. _,._,, _ ii,._,.,:,; ..... .,s ,, _ r,.. t ...... ,2, VISION;An Object-Oriented Environment for ComputerVisiono;*RemoteSensing,imaging,and SignalEngineering Ill this example, we a_,_unle that the function calc-features has ah'eadv tx_.,n defined, such that nohNy, Iawtvnce I.ivermomNational I,Ibonltoo; I.iverm°re'Califlwnia'L/Cl_'l'5'_'qi'8"5(l_'_2)" given a file nanle, it reads the file, calculatt.'sfile appropriate featurt.'s,and returns a feature vtz'tor. "lhe function maplable takt_ care of appMng this " ftlllCtiOll to every,file name in tile original training table and pn_.lucing a new table with file actual feature vt_:tors. The lanl_ta exprt_,_ioslsare very u_,fui for proto_1.'fingfi.ulctions like calc-featuresin - 5. J.l-.Hemandez,S.l.u, l,I.J.Sherwt_A,t;.A.Ch_rk, and B.S.l,awver, A 5i_,,nal and ImagePa_ct_sin,,,, ()l,ieclBaa'd.qll,qh'lll [Isin_¢ CI.()S,lawrencel.ivennoreNational l.aboratory, Livermore, California, UCRI.-JC-1084(_-,_(I_,II). o. N.K.DelGrande,G.A. Clark,I:F.Durbin, l).J.Fields, J.E.t ten_mdez,and R.J.Sherw_xM, "Buried Objt_'t Remote l_.,tectionqbchnology forl_awEnforcement," Pn_'..qPlE (h'hmdo'91Sllml_siton(Orlando,Horida), (April I-5, I_Y41). order to try different kinds of feattm..'sfor the learning algorithms. AI.,_, filere is no nc_.i to store all of the irfifial raw dalal read fronl dL,_k(which could I._ a _'dOtL,_problem with large dala'lba_), since only file final IL_tllts(file feature vt_,_'tors) are kept in menlory. Once an initial _'t of featurt_ h&sbeen calculated, it 7. W.J.Maurer,EU.l.X_wla,andS.l:Jarlx',Seismicl:.wnt h#erpreh#ion [Isiny,Se!f-Ot_anizingNeuralNetTmrks, I,_wrt,nceI .ivennoreNational Latxwatot3:Livem_ore, California, UCRI.-JC-1086.R)(B192). is typically evaluatecl tL,_ingone of the _veral feature._h_'c'tionalgorithms in VISION, in order to find the t_'s't _'t of featurt_ that _,parate the N-dimensional 8. B. Myers, D. Giuse, R. Dannenberg, B. Zaden, D. Kosbie, E. Pervin, A. Mickish, and P.Marchal, "GARNF_," IEEEComputerA/h_ga:'ine 11,71(1_0). feature space. Th__._ featun._ art' then t_,a.'dto train one of tile _,veral clas,;ifiers in VISION, including a back-propagation neural network._Tht.'sek-'dmiquc_ have be,:n succts, ffully tkqt.Kt for dettvting and locating buric'd mint_ using dual-band, infrared _nsors (.,_'eFig. 4).l_,h q. R.J.John.,_n_,T.W.Canak.,s,D.L. Lager,C.I.. Ma_n_, and R.M _,arfus, "Interpreting Signals with an Assumption-Ba_'d Truth MaintenanceSystem," Pn_'. SPlE--The Inh'rnath,_alS{_'iety.[i:OpticalEngineeriny, 786,332(May 1987). 10. J.E. Hemandez, tt_h'r-()nh'r GenericFunctionsIi," CLC)S,LawrenceIdvem_oreNational l_aboratory,l_Jvennore, California, UCRL-JC-109776 (19'92). I1. R.Haralick and L.Shapiro, G,nputer and Roh_t Vi- WOiltk The main gtk31for FY-93 is to complete the dtx:umentation for VISION lato make its capabilitk_ more aco:._,_ibleto the LLNL commurfity. We art' also.,_'eking technology transfer opl_xwtunific_ that will allow us to further expand our technolob.w ba_' in computvr x%;ionand pattern recognition. Ch_eorganb,,ation from Padfic Gas and Ele_ric Conlpany is currently very intert_tt_J in ttsing VISION as its internal protot3.,pingenvironnlent fl_rapplicafiort,; in pattenl recognifion. We al_ exl_xX'tcun'ent projectstLsingVISION to contribute new algorithms and capabilities. 12. 13. 14. 15. sion,Volume1,Addi.,_m-WtMey(Reading,Ma.,_,_3chu_,tts), 1992. G. Coleman and H. Andrews, "Image Segmentation by Clustering," Pn_.'.IEEE67 (5),(May 1979). T.Young and K. Fu, bhmdh_k of l_atternR_n_gnith,_ and innatePn_cessing, Academic Prt,,ssInc.(_m Diego, California), 1986. D.F.Specht, "ProbabilisticNeural Networks," Neural N,'/_mrks 3,109(I¢,_)). E.M Johart_son,EU. Dowla, and [).M. (kx_hnan, Bm'kl,Ul_(_,,ation l_t'arning.]irrMulti-lJnlen'dFeed-For _turd Nem'alNehmrks Llsin_ the Gmjugate Gradh'nt Metla_t, Lawrence IJvennore National Laboratory, l,ivermore, Califl_mia,UCRL-JC-1048_)(1991). File authors want to acknowledge the contributions made to VISION during FY-92 by Robert K. Johnson, Sailes Sengupta, Robert J. Sherwood, Paul C. _haich, and William J. Maurer. 17. J.E. Hernandez, M.R. Buhl, and S. ,%.,ngupta,De- l. G.L. Steele,lr., Commonl.isp: The l.anguage,2hd cd., I)igital I_rt_s(Burlington, Mas_achu_,tts),lt_t_). 2. J.A.l.awlt_s and N.M Mille_,Lhnh'_.'standiny, CLC)S, 3. 4. 16. M.R. Buhi and J.E. Hemandez, Dual-Band,lnfi'an'd Burh'dMine Detecthmtlsiny,A StatisticalPath'rnJ,h'c_ Nnith,t Appn_wh,LawrenceLivermore National l.aboratory Livermore, California, in preparation. tectingand I.ocatinR BuriedMines from Dual-BandlR Data: A Pattern Recognition Approach, Lawrence IAvermore National Laboratory, Livermore, California, in preparation. The Common Lisp ()l,ject System, Digital Press 18. J.E.Hernandez, Usin,_Vision,l.awrence Livermore (Burlington,Mas._chu_,tts), 1t/t_1 • National l_aboratory I,ivermore, California, UCRI,S.A. Keene,( )bject-()rienh'dI_nNrammin,\ , in (_,mnon MA-112337-I)RAFI_(1992). List_,Add i_n-WtMey (Reading,Ma_achu_,tts), 1t189. I.E. Hemandez, (;.A. Clark, and S. l.u, "Computer Vision," f n,\,inecrin,\, R_'arch, l)eveh_lmtent,and /bcl/- En_¢neer_ne. Reseatc't_ Develuomt, r_t dncl _ecl_nolot!v .l, Throst Area ReDort FY92 9-19 BiomedicalImagePIocessing,:, RemoteSensing,Imaging,and SignalEngineering Biomedicalimage Processing Laura N. Mascio D¢_'nseSciences Engineering Divish_n ElectronicsEngineering We have developed a bio-imaging application for a genetics study and have made advances in projects related to automated fluorescence, microcopy, ,'rodmammography. I_ In FY-92, we used funds from a small grant to make contributions to_veral biomedical re,arch projects, including (1) colony filter analysis for genetic studies; (2) the human genome project; and (3) the detection of microcalcifications in digitizt_t mammography, Colony Filter Analysis for Genetic Studies We have made progress in the automation of quantitative colony filter analysis (CFA), an iraportant and versatile t(x_l u_d by biologists for a variety of r_arch goals. One application is to pinpoint interesting regions in human DNA so that more highly detailed analy_s, such as _quencing, can be applied directly to the_ regions, Another goal is to very preci_ly determine the expression patterns of a gene. Using the_' patterns for comparison can provide a measurement of the genetic differences between distinct groups, such as male vs female, di_a_,d persons vs non-disea_d persons, or young persons vs old persons, One of the many other designs for a CFA experiment can yield the location of a certain DNA _quence, or gene, along a chromosome, Because of its versatility, the CFA is a powerful t(nd in t¢Ktay's genetics studies. Also becau._ of its versatility, however, the analysis is highly complex, and automating this analysis is a technical challenge. One format for the data is an array of 18,0(X) radioactive data spots generated from a robotically prepared 20-cm-x-2()-cm filter paper, Each of the 18,0rX)spots contains a signal of importance, although many signals may not be visible when imaged, and some are even difficult to de- _.tlE, Itl(_(,'rlt)g tect computationally. When the filter paper has been imag_xt and digitized, it can fonn a data _t up to 23 Mb in size. To automate the quantitation and location of each of the 18,(X)0signals, we first develol._'d an image-processing algorithm that locates the spots that are detectable, and then predicts the location of tho_ that are not. This algorithm and its platform (SCIL-lmage) are capable of handling 23 Mb of original data plus 4 to5 times that for intermediate results. Morphological image processing is the prominent meth_KlolobD, u_d in the automated CFA tend. The maximum (gray-scale dilation) and minimum (gray-scale erosion) operatom are u_d in various combinations to provide background information, as well as texture or frequency information, for detecting the DNA colonies. These methCx.ts are documented thoroughly, I and outlined briefly in Fig. 1. Once the algorithm has detected ali spots, the image may be rotated _) the colony array is aligned with the image. Then, long, thin, maximum filters are u_d to 'smear' the dots, first horizontally, and then vertically. The intersection of the smearing lines predicts the location of undetected spots. The grid is then rotated to fit over the original data. The rotated data cannot be u_d, becau_ we are interested ill quantifying the colonies. The affine transform that performs the rotation u_s interpolation meth(Ms to assign each pixel a new value in the rotated image. Next, we u_' the smearing lines to fl_rm a dynamic grid (non-uniform) over the data set, so that each grid square contains only one DNA colony. This grid provides the framework by which each DNA colony can be assigned a coordinate position. That is, while it is trMal to know the pixel ccn)rdinates of a spot, it is much more useful and difficult to know its grid position. The assignment of coordinates to the grid squares is not as trMai as Rt:so_Jr(:h Dc, v(tl(Jpment _i)¢t l(,(:hr_olo_y _ Thrust Area Report FY92 9-21 Romote Sensing, hnaging, and Signal Engineering .:. tt....,,_.t1,,,_/Ip:,t**.,.J't,,,, ,,,,,rt/: 9-22 Thrust Area Rupo#t FY92 .:. # , ,, , ..... ,, ' ,,,, ,,,., ' , • ', , Mu/tlsensor [),_tafuslon L/sing/_u,','_'Iog.: 0:0Remote Sensing, Imaging, and Signal Engineering Multisensor Data Fusion Using Fuzzy Donald T. Gavel lals,'rEit_ineerissg, Di_,isioll F.h'ctrollics EIt,e, hwvrilt_ Wt' have develowd an expert system multiple _,nsors and make classification Fuzzy _,t theory has found successful applications train, and in recent that with years. proper Wt' ha\'e training, tests sorting radioactive test samples more conventional ._hemes. ba_,d on fuzzy logic theory to fuse the data derisions for ob|ix'ts in a waste reprocessing application in a number of decision and found that a fuzzy classification using logic system accuracy a gamma is quite spectrometer is rather high. easy to design Wt' perfomled to compare and ,_'veral fuzzy i I_ from stream. control logic i to i ['tit rlt'w ft,der,li guideIirlt.,s will rt_.lllJrt' Jt. The rtvycling of alloys U-T| and U-Nb will rtP,iLl|re _,gmenta- lhc lk,partment of Enerb,_, (IX)E)has an urgent i`1t_?dfor the developlllent of waste [,nx.'t,'ssirlg ,rod lion and tracking to prevent Cl'¢_,_-cont,lmillaticql. clt,allup tt,Chl`1(,lt_git.'s.()vt, r the post few yea_.'s, the Adval'lct_.| I'roct.'s,¢l'tvlmol(g,w I'rt_ram at l,awrt,nce l.ivermore N,ltionaI La[_ratt_rv has bt't,ll developing ro[_._ticsandautolnatit_lltechnol_g, ytosupl:_rtcleall- Robot Sorting System Wt, have a_senlbk'd ,1delllonstration n,[_tic waste _rting and cla_,_ificatk_n svstt, nl (Fig. l). l'his auto- tlp and reclaln,ltioll efforts. Irl our intt'ractive Controis 1,l[_.)ratol'V, wt, hove dt,vt'[o[._%| a _,n.,_r-ba_J i'o[_._tsvstt'll`1 [oi" nlatt, rial ,_rting tasks, Roi.a_tic ._rting of l_"1atelials in a waste stream has rnatcd workcel[ consists of a I'UMA ._'_)articulating i'oLx_t,11"111, ,1 rnachil`1t, vision system, a Ct)l"1Vt'vors\,stem, a suite t_f i't,n"1ott, St,l"1._l,'_,al"ld ,i hit, l'ard'l(C,l[ COlnputer control svstei"1"1tl"1,1tc¢,_rdil"1att.'s the act|vi- ix'en I,lrgel.v motivated by the IX)II. cit,al)up i_t't'ds. A large ft'act|oi`1of tl`1cburied radioactive waste must Ix' dug tip and rr,packaged [x'cau_,COl`1tal`1`1il`1ants art, leacl`1ing into undergn_Ul`1d water tablt.'s. ! ia/ardous waste stored ii`1barrels at I_'al sitt.,smust Ix, rt._l_ed, accord- tit.'s with|l`1 thf workcell. A nt,tWol'k of cornptltt,l,'s I{_t'attx| with|l`1 the I,iL_q'atorv allows mal-til`1`1econtl'ol ing to federal guidelint.'s, into categorits of high-level, low-level, transuranic, al`ld n`1i×edwaste, and dis[x_t,d of accordingly. (.'erlail`1inaterials, such as lead al`ld st,linlens stt_.,I,can Ix' rtvlaimt_:t after Ix,ing cleaned of radi_,activecontalnination, l,,w-level al`ld llliXt_,l r,ldi(uctive waste n`1tist Ix, ._rtt'd into c,ltt'gorits, such ,is bul'llablt, or vitrifiable, for later voltllllt, reductiol`1 ,lhd storage. Using l'O[x_tsii`|stead of radiation-suited workt, l.'sreducts the risk tohtimans, arid al_ il`1"1pl'O\'t.,s the reliability and s[_'txt of ol.x'r,lti_,l, Wea|-_ns d L_n"1antk'n"1ent is now az"1oti_eriii"lD)rtant i_sue. Ttvl"1z"1oh_git_need t¢_bf' developed t¢_ handk, the waste ro,itr'rials derived fron_ diSll`1,u`1tle- Flgure1. Interactive Controls Laboratoryat Lawrence LivermoreNationalLaboratory.Thescrap conveyoris shown in the foregroundalong with the sensors usedfor material characterization.ThePUMA robot arm with its wdst force/ l"1"1er_t I!"1particular, rtvyclil`1g of &,pit,ted uraniunl ,llhws has historically mit bt't,n cloilt,, torque sensor is ln the back_round. Notshown is a stereo camerapair mounted on the ceiling. Remote Sensing, Imaging, 9-24 Thrust Area Report and Signal Engineering FY92 ':" t _I" _" -:- [Vlultt._etl,_or[),lt, I tc,st(icl (/._ul£ I _,','_ l (_'j_' ' _! J,, <"_ ', I'_._, ,_',' ,'' ,, : I, , ,, MultisensorData FusionUsingFuzzyLoDc °:°RemoteSensing,Imaging,and Signa!Engineering i l llll Table1. Resultsfroma_ isotopeidentificationexperiment. fiand I Band 2 Band 3 Band 4 Am bg Cs bg Am 178'4 _0 15 15 171t9 -N) 24 5 -48 48 -43 I(X) 2020 33 20 4 2 23 -16 6 1pCi Nmlpk' bg Co bg Am 6 24 11 _0-t.', "_ " _ 112 _bl 28 23 3 3 -88 -21 -16 -1(_ -24 smoke detector bg H1 24 -243 - 1_ 12q8 11 -377 -2 -37 Coleman lantern mantels bg Fh -Fh bg Th 17 88 3113 -0 -52() 161 120 li 87 72 133(/,0 -59 -36,8 -lbq t) 2 -7058 7 40 -52 -'4 - 14(_ Th Co -Sql -16 3111 120 -1i)7"! -2e_ 86 953 1pCi sample I I.tCisample welding rods (under box) welding rods (on top of box) lens mantels IpCi sample ['hehighlightedart'aindicatt'_,wht,rt'tilL'thrt'sholdalgorithmwitha 10{I-count thresholdproducesa falsealarm: backgroundtbR)mi>identiliedas thorium232(Th).Thefuzzy logicsv.stem,relyingmoreon pattern recognition,correctly indicatt.sthi.'- ,I.', backgr_undradiatitm,i.t'., no sourcepresent.Nune 'counts' are negativebt,catlst., of data preconditioning ,lhd llorm,l]i/,llil)ll. t:x_ssibilit}'that infomaation concerning the prc._nce of thofiuna, for example, is prt._,nt in the ctsiurn band, and ._ on. rhert'fom, infomaation tt'.altfulin the catt_goriz,ltion of radioimtol.XS b; contained in the pi,ttem of the counts, not itkst in the COLII'II2";wr ind..ividual band. The mlc_ in the fuzzy rule ba_' were _,t accordingly. Forexample: (if band 4 k,;high or (band 4 is high and band 2 is high), then .,_urce is cobalt (-_)). Rc_ulbs from one test art' shown in Table 1. We tcstecl sample ._urct_ located from 80 to IN)mm from the dekx_'tor,and ai_ made an C_.lualnum[x,r of tests with no _urce prt._ent. The fuzzy kgic system Ct,Ttx'tlv identifit_.t the i_}tob_ with I(X)",,accuracy, while the thrt.'shold s\,stem had only 89", accurao,, (_ne miss and one incomx-t classification) with a 2(Xtcount thrcshoid, and _',,, accuracw (three incom.vt classifications and two faL,.a., alarms) with a l(lO-count thrtMlold. As the _urcc.'s arc, ._,paratt_.t from the dettx_'t(_r b\' larger d istanec.,,,the sigmal La.v(_mt.'s wea ker,:al the_,n_r aru:lfuzzy logic systemt.x,gin tl_fail to ch.,tt_'tthe radiation. However, e\en with weak sigrials, the i_tol.X' signature is often still prt_,nt. Wt' _,t up the fu/,zv logic system to gut>'i fiat' i._ti_l.X,,evell if the radiation count was low./kt ax'erage _,paration.s _,f r_,ughlv .RXlmm, the threshold sx'stem was failing nea fix' 1(Xr',, __fthe time, while the full\' classifier wa.,, FUtUI_ Wtltflk Sorting and classification of materials will be a crucial task in the weapons dismantlement process. Special nuclear materials resulting from dismantlement need to be identified and tracked by an automated system to prevent unauthorized diversion from the recycle stream. Depleted uranium alloys should be segmented from each other to prevent cross-contanaination. We _., this as a future growth area for multi_,nsor fusion and fuzzy classification systems such as the one we have de\'eloped. I. l).T.Gavel and S.-v.I.u,'"l'eleroboticsand Machine Viq,.:;;,"/;u,vine,'ri_}v I_,cq'arclll )(v,rlotmlcnt, and"Fwhnolo;qJl, [.,1wrt, nct' i.ivt,mlore National I_aboratorv, l.ivermore, California, UCRI.-538(_8-t_I,t)4_ (1992). "_ -' A. l)ougan, l).I. Gavel, 1). (;ustavesi_n, M. ! h_llMa\',R.! lurd, R.Iohnson, B.Kettering, and K. Wilhelmsen, "l)em,,nstrlltioll ,,1/11thunah',tI,h_N_ticW_ukcdlfiu t ta:m'd_u_s Wash'Charach'ri'.:ati_ul, "' ,_ubmittedto It,93 IEI'F.InternationalConf. I_,_l'u_tits and Autunaati_u_(Atlanta, ( ;e(,'gia),(Ma,,' 1t._t;3) 3. I_.A./.adeh, IIII[(_uth'_d8, 338 ( Itt(_'5), k._ ma king c(_rrtvt gtu_s_s with aN _ut .R)",,accu rac\'. t ,_< ",,'_ .... _: ¢.:,.,.,_.a,, _: I),,_c:_'_¢_,,,,.e;r ,_r,_i f"' t_¢'"".'F._ 4. Thrust Area Report FY92 9-25 Adaptive Optics for Laser GuideStars o:oRemote Sensing, Imaging, and Signal Engineering Adaptive Optics for Laser Guide Stars James M. Brase, HorstD. Bissinger Kenneth Avicola, E_ler&n/Systems EilgiJzeeHJlg Mechatfical Engineerilzg DonaldT. Gavel,and KennethE. Waltjen l__serEngilleering Divisioll Electm1'ics EngiJteeriilg We are investigating advanced concepts in adaptive optics (AO) systems and developing a comprehensive analysis and modeling capability to predict the performance of AO systems. In FY-92, we demonstrated the generation of a Na guide star and verified our models of its formation. We have made the first Hartmann-_r_sor wavefront measurement from a Na guide sta_, and evaluated its potential as a reference for a closed-loop AO system. hllb'Oi_ction Turbulence in theatmosphereblurs imagc_en in ground-ba_,d tele_opes and places a ,_vere limit on their angular resolution. Typical atmospheric blurring is so severe that even a 10-m telescope has no better resolution than a small 8-in. teleKope, despite the fact that the larger instrument gathers far more light, There are two methods for gaining drarnaticaiIv improved resolution. The first is to go above the atmosphere, as did the Hubble Space Tele._ope. This approach has the additional advantage that regions of the spectrum such as the ultraviolet, which cannot penetrate the atmosphere, are accessible. However, going into space isexpensive and inherently less flexible than ob._,rving from the _round. The ._'cond alternative is to u_, a tech- nique called 'adaptive optics' (AO) to irnprove resolutk_n for ground-ba,_d teleKopes. We are investigating advanced concepts in AO systems and developing a comprehensive analysis and modeling capability to predict the performance of AOsystems. AO systems have been demonstrated for astr_ nomical applications. 1The_ systems use a bright natural star as a reference to correct the dimmer astronomical object. One of the major problems with applying AO to astronomy is the scarci.tyof natural stars clo_ enough and bright enough to _rve as references. Our approach to soMng this problem is shown in Fig. 1. We will u,_ the copper-vapor pumped dye ia,_r system, developed for laser isotope _paration at Lawrence l,ivermore National Laboratory (LLNL,),to illuminate a small circular area of the atmospheric sodium lay- (,alaxv" f_:,; (b) (a) (,alaxv _!._ (c) l.aser guide star (;alaxv " !_i ' Laser guide star Co m p uter ad justs [,aser light causes sodium atoms tr) glow, creating api artificial star building lelesc_pe/_ I 1.a.'-:,e r " [ Under_round ' / / /_ / ,:omp,.'nsat,_' t.," / Image of atmospheric galaxy ix [ i% / j j tion and Improvethe resolution of ground- [ based telescopes. FlOWC d l.a,;er /j_:_ tL,l'bu k',lc_ _F be,,m lib iS created. (b)correctAdaptiVefor atmo-°ptics (a) Laserguidestar _/ / m lm using the reference. pipe to transport laser beam Fnlqlne(,rtng Useof the laserguide star system to remove atmospheric distor- a flexible mirror to _ / Rgurel. nomicalimage formed. is R_,',_';iIc:II Df,_,lrJpmt, r_t ,_l_¢J _'ctln_lt)l_; .:. Thrust Area Report FY92 9-27 Remote Sensing, Imaging, and Signal Engineering .:. Adaptwe Optics tor Laser Guide Stars er at a height of about I(X)km. When the lasT is tuned Figure 2. Na guide star. Thelaserguide starts the small to tile pl'O_T wavelength, the ._.tium will glow and prtw.tucea point-like reference ,_tirc(.'. Ali ob._,rvJllg telc.'_:ol.x,on the grollnd nleaslll'L,_ in detail the lightcoming ft'ore this'la._r guide star' and, with theaid of a computer, do.itlct.._what distortions have round spot on the right end. The long streakleadingto it is Rayleigh scatter from a point lower in the atmosphere, [%_'n placedon thewavefi'ont by atlnospheric ttlrbtllence. The conlptlter then calctllatL_ the corrccfioFt_; to L_'applit_.t to a deformable |nii'ror in the optical train of the tek._oF_' to correct for the turbulence. The light ft'ore a nearby astronomical object is al_ com.'ctc_.t bv the defomlable mirror _} that an improved image is foi'm¢_t. The basic technologies for la.,_,r-guide-star AO systems have been demonstrated over the past ten years. :,_,4 Success with Na guide stars has been limited by the lack of an appropriate laser. However, the LI.N Lcopper-vapor pumped dye laser is well-suited for the demonstration of astronomical Figure3. A Hart- laser guide stars, lt has more than ellOtlgh power star,in whicheach smallspot correspondsto apartof thetelescopeaper- at the Na wavelength ( 1.5kW at 589 nra), excellent reliability, and high beam qualiD,. We are performing a series of feasibility experiments on laser guide stars usillg this laser. Fl'om the data obtained in these experiments, we will be able to mann sensor image from the laserguide ture. By analyzing themotionofthe spots, we canrecon- design a smaller and more economical svstL'nl optimized for tlSeat an astronomical observatory. Otlr long-term goal is to establish a technology base in AO that will allow us to implement a system for a large astronomical insh'ument such as the l()-m Keck C)bservatorv telescope. The laser guide star experiments at LI.NL are being done in two phases. In the first, which began in July 1992, we have generated a Na guide star (Fig. 2) and have measured its intensity and motion. _ In the second phase, currently underway, we art' developing an AO system to demonstrate chased-loop correction of an astronomical object with a Na gtlidt' star." structtheatmo- sphericturbulence, Figure4. rhepredicted sodium emission intensity (solid 1 12 I l ] l E _- line) vs the expertmental measurements (squares) from the Na guide ._ powerlevels. ._ 6 ........ star at several laser 8 __, 4 Progress 10--8 ....... _ -- _ in t:Y-cJ2,we demonstrated the gc,neratitln of a titln. Wt, have made the first Hartmann sensor wavt'fi'illlt .... / '_ I!xperinlenlal / data nlt, aStllC, lllellt {r()lll a Na gtlide stag Na star and of its fornlaand guide evaluated itsverified potentialOtlrasmiidels a refi.,rence for a chlsed-hli_p i\() system. 2 ..... "_ illild / o 1 0 200 I 400 i i 600 800 Laser power 9-28 Thrust Area Report FY92 .:. [ , ,_ , ,, , ,, Wavefront prediclions t,] i 1000 1200 (W) _; .... ._, Sensing part of an A(I) svstc'm is the senthai ailalvzt's the laser guide star wavel:ront hl real time. (.)\'CTthe past year, wt' ha\'e devl.'hlped a new high-_pec,d t t,_,!'tl_l/tD, ll wAvt, t;l't)n{ SL'!]S()I "7CklAn imptwtant stir t_ !,+ ,_ J,,l,s,:,., i .,,_,s _,.. ,._,(),,,#; _ AdaptiveOpticsfor LaserGuideStars o:oRemoteSensing,Imaging,andSignalEngineering pable of measuring l(x:al wavefront slopes at one thousand frames per second. In a recent series of experiments, we made the first Hartnlan|l-senso|" wavefront measurements of a Na ia_,r guide star. A typical Hartmann image is shown in Fig. 3. Tile motion of individual spots in the_ images is analyzed to estinlate Itx_al wavefront slopes. The_, slopes are ultimately integrated into the waveh'ont pha_ distribution, which is u_d to control tile deformable mirror. We are in tile process of analyzing this preliminary data and performing more experiments to characterize the performance of this system. We have also performed a series of wavefront .'_nsing experiments using natural stars, to determine requirements for AO systems at LLNL.These experiments will be expanded to include tile University of California's Lick Observatory on Mt. Hamilton as the first step towards implemerltation of at| AO system there, dard astronomical measurements such as photometry and spectroscopy may become morecomplicated. Our sinlulation t(x_ls will allow us to explore the_ problems before large-Kale AO systerns are desib,med. (hie of our first tasks in model validation has been to conlpare the results of our initial laserguide-star experiments with the predictions of our simulations.Thecomparisonofpredicted Naemission intensity with the experimental measurements is shown in Fig. 4. Tile excellent agreement increa_,sour confidence in other simulation results. Analysis and Modeling tools. We are beginning to apply these tecilniques to a variety of new problems in highresolution imaging and beam control. Our long-term goal is to develop laser guide star systems for 10-m-class telescopes like that of the Keck Observatory. The iilitial development, llowever, will take place on smaller telescopes both at LLNL and at Lick Observatory. lt is vital that we use computer simulations to understand the ._aling of tile results from our denlorlstration experiments, to what we should expect from large astronomical tele._opes. The initial experiments will allow us to validate our simulations, so that [_ll_LlIJIl_ Work hl FY-93, we will demonstrate closed-loop AO correction of a small telescope at LLNL using a Na guide star. This demonstration experiment will require the wavefront sensing technology that we have developed, lt will also allow us to verify our analysis and simulation 1. 2. G. Rousset, J.C. Fontanella, P. Kern, D. Gigan, F.Rigaut, P.Lena,C. Boyer,P.Jagourel,J.l: Gaffard, and E Merkle, Astron. Astmphys. 230,L2_)(1990). R. Fugate, D. Fried,(;. Ameer, B. Boeke,S. Browne, I: Roberts, R. Ruane, G. Tyler, and L. Wopat, Nature353 (Septerr|ber12,19_)1). 3. C. Primmernlan, D. Murphy, D. Page, B.Zollars, and H. Barclay,Nature 353 (September 12, Iq_91). ill tile 4. C. Gardner and L.Thompson, Prvc.IEEI. 78 (11), 1721(1990), Some problems that will arise on large telescopes will not be evident in our smaller systerns. For example, as the telescope gets large, a single laser guide star ca n no longer be used to correct the entire aperture, because of tile finite height of the laser guide star. Multiple laser guide stars must be generated to accurately eorrect the images. A complete simulation will al- 5. K. Avicola, J.M. Brase, J.R. Morris, H.D. Bissingel; H.W. Friedman, I).'E Gavel, C.E. Max, S.S. Oliviel; R.W. Presta, D.A. Rapp, J.T. Salmon, and K.E. Waltjen, Svdium-l_}lerMser Guhh'Star Experimenhfl Resulls,l.awrence IJvermore National Lab()rah_rv, IJverrn¢_re,California, UCRI.-JC-I11896(19qJ2). 6. C.E. Max, tl.W. Friedman, J.M. Brase, K. Avicola, l t.D. Bissin_er,I).T.Gavel,J.A. t-h_rt()n,.l.l_1. Morris, S.S.Olivier, R.W. l'resta, D.A. Rapp,J.T.Salmon, and K.I:..Waltjen, l)esi%,n,l.ay_ml,and I.arly Rvsults qf a Irasibility Experiment.li_rSvdium-l.mler l_ser C,uhh. Star Adaptive ()plies, l.awrence IJvermore Nati_.lal l.,aboratc_ryIJvermore, Califl,'nia, UCRI.JC-I12162 (lt_92). ILK.Fys¢,I, I'rimitJh's_!fAdaplivr ()plies,Academic I'ress (B¢_st¢_n, Massachusetts), 1991. L,_ we can have a greater degree of confidence results for 10-rn tele_opes. low us to develop these tc-__hniques even before we have access to a large telescope, "[(_date, implementation of astronomical AO systems has been devoted mainly t(_system development. Very little actual astron(_nly with adaptivelv corrected telescopes llas vet been done anywhere in the world. Because of the change in quality of tile correcti()n acr(_ss the field (_f view and with changes in atm(_spheric c(,lditions, start- [ ni]lr_:errni; 7. R_:,,ear( h De_,l()l)mf, nt ,:_d l_.( Illl_l(,)_ .:o Thrust Area Report FY92 9.2_ Authors Alesso, H. P ................................................ 4-27 Angel, S.M ................................................. 6-17 Avalle, C.A ........................................ 1-21, 7-23 Avicola, K.................................................. 9-27 Azevedo, S.G ............................................... 8-5 Hemandez, J.E.................................... 9-1, Hemandez, J.M ........................................... Heuze, F.E.................................................. Hofer, W.W ............................................... l-k×wer, C.G ............................................... Hui, W.C .................................................... 9-15 7-5 2-27 7-13 2-11 3-19 Balch, J.W ................................................... 3-21 Belak, J......................................................... 5-7 Biltoft, p.J..................................................... 5-5 Bisshlger, H.D ............................................ 9-27 Boercker, D.B ........................................ 5-1, 5-7 Branscomb, E.W ........................................ 4-29 Brase, J.M ........................................... 9-11, 9-27 Brinkmarua, R.P ......................................... 7-13 Brown, A.E................................................ 6-11 Hutchings, L.J............................................ 2-27 Jarpe, S.P ............................................ 2-27, 4-17 Johansson, E.M ............................................ 7-5 Johnson, R.K ................................................ 9-1 Johnson, R.R................................................ 4-9 Joshi, R....................................................... 7-13 Judson, R.S................................................. 4-29 Bryan, Jr., S.R............................................... Buettner, H.M ............................................ 5-5 4-31 Kallman, J.S................................................. Kania, D.R .................................................. 1-7 7-13 Buhl, M.R ................................................... 9-15 Kay, G.J...................................................... Khanaka, G.H ............................................ 2-35 3-15 Caplan, M .................................................. 1-13 Chow, R....................................................... 3-1 Christon, M.A ............................................ 2-19 Ciarlo, D.R........................................... 3-1, 3-15 CoMn, M.E................................................ 4-29 Cooper, G.A ................................................ 3-1 Cravey, W.R .............................................. 7-19 Kirbie, H.C ................................................. 7-27 Koo, J.C ................................................ 3-1, 3-21 Landram, C.S ............................................. Lauer, E...................................................... Laursen, T.A ................................................ Lee, H ........................................................... Lehman, S.K.............................................. Daily, W.D ................................................. 4-31 Davidson, J.C............................................. 3-21 DeFord, J.F................................................. 1-13 De Groot, A.J.............................................. 2-11 DeMartini, D.C.......................................... 4-17 DeTeresa, S.J.............................................. 6-11 Dijaili, S.P.............................................. 3-1, 3-5 Donich, T.R................................................ 4-13 Douglass, B................................................... 7-5 4-13 7-27 2-7 7-5 9-11 Lesuer, D.R.......................................... 6-1, 6-23 Liliental-Weber, Z ....................................... 3-1 Lloyd, W.R................................................. 4-27 L)gan, R.W.................................................. 4-1 Lu, S ..................................................... 4-29, 9-1 Luedtka, W.R ............................................. 7-19 Lyon, R.E........................................... 6-11, 6-17 Falabella, S ............................................ 5-1, 5-5 Faux, D.R ................................................... 4-21 Mad_n, N.K ............................................... Maker, B.N .................................................. Maltby, J.D........................................ 2-11, Mariella, Jr., R.P........................................... Martz, H.E ................................................... Ma_io, UN ............................................... 1-1 2-7 2-23 3-1 8-5 9-21 Feng, W.W ................................................. Foiles, L...................................................... McAllister, S.W .......................................... McCallen, D.B............................................ 4-13 2-27 Engelmann, B.E........................................... 2-1 6-11 7-19 McConaghy, C.F......................................... 3-5 McKinley, B.J............................................... 8-1 Milanovich, F.P........................................... 8-1 Morse, J.D............................................. 3-5, 3-9 Myrick, M.L ............................................... 6-17 Gavel, D.T ......................................... 9-23, 9-27 Glass, R.S................................................... 3-13 Goodman, D.M ........................................... 9-7 Govindjee, S ............................................... 2-35 Grant, J.B.................................................... 1-25 Groves, S.E................................................. 6-11 Nelson, S.D .......................................... Harris, D.B................................................. 4-17 Hawkins, R.J................................................ 1-7 Hawley-Fedder, R.A ................................. 7-19 Englneer_ng 1-21, 7-5 Olsen, B.L.................................................... 5-5 Payne, A.N ................................................ Research Development and Technology o:. Thrust 7-27 Area Report FY92 Index-1 Authors :_ index-2 Thrust Pearson, J.S................................................ Phillips, J. P................................................. Pombo, R.F.................................................. Preuss, C.S ................................................. Prosnitz, D ................................................. 4..27 9-11 5-5 6-23 7-27 Raboin, P.J.................................................. Randich, E.................................................. Roberson, G.P .............................................. Rosinsky, R.W ........................................... 6-23 3-15 8-5 4.-21 Sampayan, S.E ........................................... Sanchez, R.J................................................ Sanders, D.M ............................................... Schneberk, D.J............................................. Schoenbach, K.H ....................................... Shang, C.C ................................................. Shapiro, A.B ................................................. Sherby, O.D ................................................. Sherw(×_d, R.J............................................ 7-27 6-11 _1 8--5 7-13 1-13 6-7 6-1 4-17 Area Report FY92 4. Engtlt_,(_tlt_g Re._eilrch Devc, Sinz, K.H.................................................... 4-23 Stowers, I.F.................................................. 5-7 Syn, C.K ............................................... 6-1, 6-23 Szoke, I-t..................................................... 9-11 Thomas, G. H ............................................. 8-23 Vess, T.M ................................................... Vogtlin, G.E ................................................. 6-17 7-1 Waltjen, Warhus, Whirley, Wieting, K.E............................................... 9-27 J.P .................................................. 7-5 R.G ....................................... 2-1, 2-11 M.G ............................................. 9-11 Yee, J.H ...................................................... Yu, C.M ...................................................... 3-15 3-13 Zacharias, R.A ........................................... 7-23 Ziolkowski, R.W .......................................... 1-7 Zywicz, E................................................... 2-15 lol)m('nt ,ltl¢l It/cltn(,l()/]_