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LS-TaSC™

1. Note that the word case is a reserved word in the C programming language 5 3 7 Ist Constraint The structural constraints for a discipline are specified in the following data structure struct lst Constraint char Name Float UpperBound Float LowerBound Char Command struct lst Constraint Next j Name The name of each constraint is a unique character identifier UpperBound LowerBound The upper and lower bounds on a constraint are specified using these variables If there is no upper bound a value of 1 0e 30 must be specified for UpperBound Similarly a value of 1 0e 30 should be used for LowerBound when there is no lower bound Command The definition of each constraint provides interface to LS DYNA databases The data extraction from both binout and d3plot databases are supported 5 3 8 Ist Joblnfo This data structure contains the LS DYNA job distribution information Create and set this data structure to change the default of running LS DYNA locally as a single process struct lst JobInfo Int NumProc Int Queuer Char EnvVarList NumProc This parameter indicates the number of processes to be run simultaneously A value of zero indicates all processes would be run simultaneously Queuer This parameter is used to indicate the queuing system Different options are tabulated below Q system Option Q system Option Q system Option QUEUE NIL 0 NOS 4 BLACKBOX 8 LSF 1 USER 5 MSCCP 9 LOAD
2. lst Root root lst RootReadDb print Existing number of iterations root Method NumIter 5 6 2 Restart for an additional iteration Requiring four lines of code this is slightly more complex than the previous example lst Root root lst RootReadDb root Method NumIter root Method NumIter 1 lst RootWriteDb root lst CreateTopology root 54 5 6 3 Creating a topology database An example script is shown here The example performs topology optimization of a single load case problem using extrusion mode lst Root root lst RootGet lst Case cse lst ProblemAddCase root Problem TOPLOAD datal tushar submit pbs small example k 2 1 lst JobInfo ji 1st JobInfoNew ji NumProc 0 ji gt Queuer 3 lst CaseSetJobInfo cse ji lst Part prt lst ProblemAddPart root Problem 103 0 3 lst PartAddGeometryExtrusionConn prt Extr 1 lst RootWriteDb root 5 6 4 Printing the content of the project database The following script prints the content of a project XML database define int Print JobInfo lst JobInfo jInfo char whitespace int i print whitespace JobInfo n print whitespace tNumProc t t jInfo NumProc Mn print whitespace tQueuer t t jInfo Queuer Mn if jInfo gt EnvVarList i 0 while jInfo gt EnvVarList i print whitespace tEnvVar t t jInfo gt EnvVarList i
3. 0 ji gt Queuer 3 lst_JobInfoAddEnvVar ji LS NUM ABC 5 lst CaseSetJobInfo left load case ji 2 Adding JobInfo to the case RIGHT LOAD that does not use any queuing system Tstidobinto Ji lgt JoBLIartoNewi ji gt NumProc 1 ji gt Queuer 0 lst_CaseSetJobInfo right_load_case ji h Specifying Optimization Method Parameters Once the root data structure is obtained the data in Method data structure can be directly manipulated 1 Specify the maximum number of iterations root Method NumIter Int 2 Provide convergence tolerance root Method ConvTol Float 3 To specify proximity tolerance use root gt Method gt ProxTol Float 5 4 3 Execution Functions a Saving the Project Data The program save the project input data in form of a XML database lst RootWriteDb root A default filename of Ist_project Istasc is used but you may specify the filename lst RootWriteDb root filename xml b Reading the Project Data The project input data can be read from disk as lst Root root lst RootReadDb A default filename of Ist project Istasc is used but you may also specify the filename lst Root root lst RootReadDb filename xml 52 c Create Topology Following command computes the topology lst CreateTopology root The status of each simulation can optionally be reported every Interval seconds as shown in the following command lst Crea
4. lsda_open lst binout lsda cd handle sprintf dirName design d iter while lsda cd handle dirName 1 wmEID lsda getR8data handle Total IED amp numV aveChng lsda getR8data handle Density Redistribution amp numV print iter wmEID O aveChng 0 n iter iter 1 sprintf dirName design d iter free wmEID free aveChng lsda_close handle 6 APPENDIX B THEORY I must say it looks a bit like science fiction to many people Ofir Shor June 2009 while evaluating the alpha version 6 1 Background The traditional approach for solving topology optimization problems is based on sensitivity analysis that is inexpensive to obtain for linear static problems However deriving analytical sensitivities for dynamic analysis is very difficult due to the complex interactions among material nonlinearities geometry and mesh and transient nature of load and boundary conditions Numerical computation of sensitivities is also not practical due to the high computational expense Hence the conventional sensitivity based approach of topology optimization is not practical for crashworthiness problems To overcome the aforementioned difficulties in topology optimization an optimality criteria approach was proposed This approach does not require gradients and hence there is no need to compute the sensitivities In previous versions the approach was refer to a
5. the extrusion direction must be on the symmetry planes the casting direction must be on the symmetry planes and the extrusion directions must be orthogonal to casting directions Only one casting definition may be defined per part The symmetry and extrusion definitions are implemented by assigning multiple elements to a variable while the casting definitions are implemented as inequality constraints requiring certain variables to be larger than others according to the cast direction 15 For a casting definition the free faces are selected as shown in Figure 2 2 It can be seen that the algorithm will select faces inside a hole All of the material shown can be considered to be defined using a single PART definition from which it can be noted that the object to the right is considered for design even though it is in the shadow of the object to the left These extra faces will cause the algorithm to fail An analyst can enforce a desired behavior by breaking the part up in smaller parts and applying the casting definition only where desired B Material removal direction Faces selected for material removal Figure 2 2 The faces selected for design in a casting definition are all the faces facing the material removal direction The extra faces will cause the algorithm to fail 2 6 Design Variables 2 6 1 Mapping Elements to the Design Variables A design variable is assigned to every finite element in the design parts For
6. wrapper in the submit script is given in another example log file as follows STARTING command home jim bin runqueuer PORT 56984 JOB LoadLeveler llsubmit The job 1 1 1 has been submitted home jim LSOPT EXE Xrapper Command not found Finished with directory home jim LSOPT 4 1 0ptQA QUEUE EX4a remote remote 1 1 1 5 The wrapper will also extract the data immediately upon completion on the remote node A log of the database extraction is provided in the logxxxx file 7 7 Environment variables These variables are set on the local side by the runqueuer program and their values must be carried to the remote side by the queuing software The examples above illustrate two methods by which this can be accomplished LSOPT HOST the machine where LS TaSC and therefore the runqueuer is running LSOPT PORT TCP IP port runqueuer listens on for remote connections 7 8 l Troubleshooting Diagnostics for a failed run usually appear in the logxxxx file in the run directory If there is almost no information in this file the wrapper path may be wrong or the submission script may have the wrong path or permission For any job this file can be viewed from the progress dialog on the Run page Please attach the log file Isopt output when emailing support a stc com Make sure that the permissions are set for the executables and submission script Check all paths to executables e g wrapper etc No diagnostic can de
7. 2 3 Problem Definition Sese ese Ee sn edo esee O 13 24 The Design Pintar ld is 13 2 4 1 Elementwise Material Density and Element Deletion for Solids 14 RAZ Desi idas 14 DAS A al ad e 14 2 4 4 Material data iesu eot deed dos dde tete date Neds ate es 14 2 5 Geometry and manufacturing definitions sse 15 2 6 Degem Variables oos O E 16 2 6 Mapping Elements to the Design Variables eee 16 DG Piltetinp of Results ou eaae A bo oe duobus 16 2 6 3 Initialization of the Design Variables ooooononnninccnincnnncoconnconcnonnnconccconocnnos 17 Duc ES D YNAC SPOS A e e ea LN EE 17 2 sd The Contact Def nito e p Qi e cedes PO ERE 17 24 2 Disallowed keywotdsu iii tette titre eet tt oer iter aei dites 17 273 ESDENAS lis 17 228 Global Constraints sesuai e aul a iu nans is meist ate 18 209 gt Setting Up the Problemy 2 aches wien i iodo 18 2 9 1 TheTnformation Panel erasini do 18 2 9 2 The Cases Panels na E ev en E DR eau 19 2 9 3 The Constraints Panels uoo tete ea De MV OOo m din Loi we da RON E 20 2 9 4 The Parts Panel laa ola a E lassus dile IE 22 2 9 5 Part Geonmlebry ede Idea te viden e e Oe ee Ra ee ERR YR DE UN Pe RR 24 2 9 6 The Completion Pane lorisan ei od ae E atu LIIS HIC HIR RERUMS 24 2 9 7 A i Lan aR ir E E aac 25 2 9 8 Phe View o A e C RN 26 2 10 Databases and Plena ir is 28 2 11 Opening and Saving Projects A at doeet ade eas iain 28
8. Assuming ERROR termination for LSDYNA job 8 HONDA STATUSFILE variable not set HONDA Error SHONDA STATUSFILE not set 9 Could not open SHONDA STATUSFILE HONDA Error Failed to open HONDA STATUSFILE pbsq status 10 LsoptJobCheck script not found for non LSDYNA job HONDA Error LsoptJobCheck cannot be found HONDA Assuming error termination for non LSDYNA job 11 LsoptJobCheck script did not print either a FINISHED or b FAILED 73 HONDA Error LsoptJobCheck did not return a valid status HONDA Assuming error termination for non LSDYNA job If SHONDA STATUSFILE is not updated in a timely fashion then the scheduler can hang forever never moving forward A message is passed to lsopt through the communication socket if this happens Warning HONDA STATUSFILE out of date by more than 5 minutes Job progress monitoring suspended until next update Even though the status file is checked before starting the scheduler it is still possible for file errors to occur These are also sent directly to LS TASC Error SHONDA STATUSFILE not set Error Failed to open SHONDA STATUSFILE pbsq status 7 12 Microsoft Windows Compute Cluster server LS TASC supports submission of jobs to the Microsoft Compute Cluster Pack Scheduler Two scripts called submit cmd and submit vbs that work together are available to interface LS TASC with CCP The script can be downloaded from ftp ftp l
9. 06 1 3E 06 44 20 20 Iteration Iteration o N S MassFraction Part 101 Mass Redistribution 10 2b 30 40 10 20 30 40 Iteration Iteration Figure 3 12 Convergence history for the example with multiple constraints The convergence history for the multiple constraints example is shown in Figure 3 12 There were minimal changes in the geometry after 25 iterations and the simulation converged after 40 iterations While there was largely monotonic reduction in the density redistribution the constraints and IED were oscillatory in the behavior The oscillatory behavior of the constraints was due to their conflicting nature where an increase in displacement required an increase in the mass fraction which resulted in higher forces At optimum a balance between the two quantities was obtained It is important to note that the mass fraction for this example was not held constant Instead it was automatically adjusted to satisfy the force and displacement constraints though the final mass fraction was fairly close to the desired value 36 b Density Contours The evolution of the topology of the clamped beam with multiple constraints is shown in Figure 3 13 The final structure had many cavities and resembled an optimized truss like structure The main cavities in the structure were formulated by the 15
10. 2 12 SSG ri Command A UI aioe te Abe aang Ma a ato 28 3 Example Problems it Ad re adea Yeu cut A re ieri 29 3 1 Fixed Beam with Central Load e e e due vtae tee oe ym ta 29 S L Problem Description a need ra dried Sept Ha baiuli ida ids 29 3 1 2 lc H 29 She SUOUEDUE t oe A d an 30 d Convergence History Gusta deest en Ue ba treten ate 30 by Density Contours A t ue d tet een eae da 30 2 Beam using geometry definitions us eoa td erai quete quida 31 3 251 li eoue ees 32 3 2 2 O et che tion vno toa amu du Pr ea Moe 32 d Extrusion and Castings sesini gaben A A 32 b Extrusion and two sided casting esses 32 3 Multiple Load Cases A A 33 33 1 Problem DePmitiofcz cs vasco ea diee a rM a e et udd 33 3 3 2 O 33 Sede COMPU as 34 Convergence History ice AA tere due A Al 34 Dy Density Contours Ges pU eee A desi a a 34 3 4 Force Displacement Constraints iii 35 341 Problem Definition cese nei tbe tin oseauicasbivaeateatectee 35 3 4 2 Tapte O RNA 35 p MES oo TH ES 36 2 Convergence History co ovo ee pe em db eu eo E PET 36 By Density Contours cid 37 3 5 Eimear Statio Eoadmgi esp E 37 Sod Problem De fMn A a eae 37 3 5 2 O A 38 3 5 3 udi A AA AA A A A A 38 a Convergence AS bra mod si mei atas Vista Re ese en 38 b Density Contour s steam o D etie tor dena eiue Lee 38 3 6 Shell EXample eue te go eene oec ca
11. 4 Edit Jcopy Delete 7 13 2 Editing an existing environment variable definition To edit an environment variable double click on the environment variable in the Environment variables list The display mode of the variables will change to make it editable 7 13 3 Set by browsing Select the Select by Browsing button In order for this option to work user supplied executables must be present in the directory HOME LSOPT SCRIPTS The directory LSOPT SCRIPTS must exist as a subdirectory of the user s home directory and it must contain executables If the directory LSOPT SCRIPTS does not exist or if there are no executables in this directory an error box will appear Setting the LSOPT SCRIPT Unix Linux Windows system environment variable may specify an alternative script directory After selecting the Set by browsing option a dialog of buttons will appear one for each executable in this directory For example suppose this is the directory listing for HOME LSOPT SCRIPTS rWXr xr x joe staff 13597 2009 12 01 18 09 Isdyna submit autounion rw r r 1 joe staff 13597 2009 12 01 17 46 stdin save rwxr xr x 1 joe staff 9 2009 08 10 14 23 test TWXI XI X 1 nielen staff 9 2009 08 10 14 26 testb Then when you select the Set by browsing option the following dialog appears 75 Ele View Plot Help Edit Case ethod Run View p General Scheduling Y Limit number of concurrent jobs Queu
12. Adding Case Data e A tene dae et paa eee vete dd 49 b Accessing a Specific Case Structure eese eee eee eee eene tentent et natnans 49 EJ Adding CONSTAR 50 dj Adding Patt Data wii cy idee a 50 El Accessing Para rel goi ette dos 5 f Adding Geometry Data s cusam venite b rua ila dives bd tiers 51 g Adding Job Distribution Data sss 51 h Specifying Optimization Method Parameters esee 32 543z e e osse meg etta caste aes B e Un ate QUE 52 a Saving the Project Data ddr 52 bj Reading the Project Dalai ina a i qai is 52 C Create Topolog ynei an A dee aan eases iet Ria OER 53 d Cleaning the III A a eter cad 23 Do Accessing Results gongi opo o Dep iP e aeo ed 33 5 0 Example SECpt e 54 5 6 1 Retrieving a value from the project database 54 5 6 2 Restart Tor an additional iteration ca 54 5 6 3 Creating a topology database sse 55 5 6 4 Printing the content of the project databas ooonoccnncninccnnncinococonnconcnonnnos 55 5 6 5 Printing the content of the results database oonnconncnncnnnncinncoconnnnnncnnnnos 57 Appendix B Ord reads da ia t dtu sr deu 58 Galles BACON E cr ti Sea eo a o fal 58 6 2 0 a A e EUN ed ded deti eder iode 58 621 Deli iii 58 6 2 2 Creating the Variables sta e t e eet ge das 59 62 3 Filtering OF results qu ceti Poe UM ne RISE ond caus exe dst E a 59 624 Material Parametros id isa 59 6 2 5 De
13. and rotation of plastic beam elements However the method ignored the contact between elements arising due to nonlinear behavior of the structures Soto 8 9 presented a heuristics based method using a prescribed plastic strain or stress criterion to vary the density to achieve the desired stress or strains with a constraint on mass However this method could not be generalized to solid structures Pedersen 10 used beam elements to handle topology in crashworthiness optimization Forsberg and Nilsson 11 proposed two algorithms to get a uniform distribution of the internal energy density in the structure In the first method they deleted inefficient elements and in the second method they updated the thicknesses of the shell elements This method also was limited to a small set of optimization problems Shin et al 12 proposed an equivalent static load method where they calculated an equivalent static load for the dynamic problem and then used the linear static topology optimization techniques to find the optimal topology The main difficulty in this method is the requirement to accurately compute the equivalent loads 1 3 Topology Optimization Method in LS TaSC A heuristic topology optimization method developed at the University of Notre Dame known as hybrid cellular automata 13 showed potential in handling topology optimization problem for crashworthiness problems This method updates the density of elements based on the information fro
14. be used to investigate the effects of filtering 20 info ses Constraints DISP 1 lt 30 HODOUT Last registered X Component of displacement of node with ID 7 ContactForce gt 15 RCFORC Last registered X master force of interface 987 15 NODOUTI 10 NODOUT Last registered X Component of displacement of node with ID 88 DYN LOAD DYN LOAD DYN LOAD Figure 2 5 The constraints overview panel r E Edit Constraint x Constraint type USERDEFINED IdentifierType ID RCFORC Displacement direction X Component O Y Component O Z Component Resultant Select Last value gt Filtering Case Name for constraint DYN LOAD 15 lt NODOUT1 lt 10 Figure 2 6 The constraints creation panel 21 2 9 4 The Parts Panel The part definition panel contains information about the parts to be designed such as the geometry and mass fraction See the following table Figure 2 7 and Figure 2 8 for more details Part data Design Part ID The user needs to specify the design domain for topology optimization To facilitate the identification of design domain all elements in the design domain are put in a single part in the LS DYNA input deck The information about the design domain is then communicated through the corresponding part id Note For multiple load cases the user must ensure that the design domain mesh and the part id remain the same in al
15. be viewed from the View pulldown menu Use these commands as a template for scripts 28 3 EXAMPLE PROBLEMS The application of the topology code is demonstrated with the help of a few test examples below The examples are supplied together with the software executables 3 1 Fixed Beam with Central Load This example is used as a template to demonstrate 1 how to define a problem 2 howto add a case 3 how to optimize the topology for a non extrusion example 4 analysis of output 3 1 1 Problem Description This example simulates a beam that 1s fixed on both ends A pole with assigned initial velocity of 10m s hits the beam in the center The design part is meshed using 5mm brick elements The symmetry of the problem is used to design only half section of the beam The geometry and loading conditions of the beam are shown in Figure 3 1 The material model used in this example is defined previously H 80mm 4185 Symmetry W 100mm Figure 3 1 Geometry and loading condition of a single load case example 3 1 2 Input The problem has a case named BEAM The name of the DYNA input deck file is Beam dyn Part 101 is the design part A maximum of 100 iterations are used to find the optimal topology The desired mass fraction is 0 25 The project input data is saved to the file st_project lstasc as provided in the examples distribution Additionally scripts to recreate the database are also provided The project dat
16. can be defined for every part See the following table and Figure 2 9 for more details Geometry data Name Extrusion Set ID Symmetry Plane Cast direction Coordinate System ID The geometric property can assigned a name or a default name can be used To define an extruded part the user firstly creates a set of all solid elements that would be extruded SET_SOLID The id of this set is specified in the input deck to identify the extrusion set Specify a symmetry plane to define symmetry A cast direction is required for a casting constraint The direction can be negative This is the direction in which the material will be removed It is the opposite of the direction in which a casting die will be removed The geometric property can be defined in a specific coordinate system or the default Cartesian system can be used Geometric Constraint Name for constraint Eymmetry2 Coordinate system Symmetry plane Gobel M ce J c jJ Figure 2 9 Creating a geometry constraint 2 9 6 The Completion Panel The completion panel specifies how the optimization problem will be solved See the following table and Figure 2 10 for more details Completion data Number of design iterations Minimum mass redistribution This is the maximum number of iterations allowed The default value is 30 The minimum mass redistribution is the termination criterion used to stop the search
17. characters The following fields are used 4 name 6 status R for running or Q for queued 10 total wall clock time allowed 11 total wall clock time consumed Fields 10 and 11 are used to set the progress indicator If the indicator ever reaches 100 then it will terminate due to total wall clock time restrictions If a job cannot be found in the status file then it is assumed to be dead The job status entry is not looked for until a minimum of 3 seconds after the job has been started A status file is searched for a particular job status entry only if the status file has a modification time that is later than the start time of the job Since there is no way to determine the exit status of a job by looking only at this status file the determination of the final exit status depends on whether or not the job is an LS DYNA job If the job is an LS DYNA job then the messag file is parsed for the status statements N or mal and Error termination If no messag file is found 70 seconds after the job is no longer listed in the status file then we assume an error termination If the job is a non LS DYNA job then LsoptJobCheck see Section 7 10 is executed just once after the job no longer appears in the status file LsoptJobCheck should print either a FINISHED or b ERROR in order to communicate the final exit status If 72 LsoptJobCheck cannot be found or cannot be executed then ERROR is assumed The
18. definition in this linked list A value of NULL indicates that this is the final geometry definition 5 3 6 Ist Case The details of the simulation setup are given in this data structure struct lst Case Char Name Char SolverCommand Char InputFile Int AnalysisType Float Weight struct lst Constraints ConstraintList struct lst JobInfo JobInfo struct lst Case Next j Name Each case is identified with a unique name e g TRUCK The same name would be used to create a directory to store all simulation data SolverCommand The complete solver command or script e g complete path of LS DYNA executable is specified InputFile The LS DYNA input deck path is provided AnalysisType The topology optimization code can be used to solve both static and dynamic problems The user identifies the correct problem type by specifying the correct option Type Option STATIC 1 DYNAMIC 2 Weight The weight associated with a case is defined here This enables the user to specify non uniform importance while running multiple cases ConstraintList This data structure holds the information about different constraints associated with this case See the following section for more details JobInfo The user specifies details of the queuing system and number of simultaneous processes in this data structure Next The next case in this linked list A value of NULL indicates that this is the final geometry case 47
19. density varies from 0 to 1 where 0 indicates void and 1 represents full material A more detailed description of the material model parameterization one should refer to Bendsge and Sigmund 7 and Patel 8 The elements with design variable value less than a user defined minimum value are deleted to improve numerical stability 59 6 2 5 Design Objectives and Constraints The typical goal of topology optimization is to obtain maximum utility of the material Compliance and the strain energy density are the most commonly used objectives for linear static problems For dynamic problems like crashworthiness simulations the structure needs to absorb maximum energy while maintaining the structural integrity and keeping the peak loads transmitted to the occupants low Following the formulation proposed by Patel 8 the goal of obtaining uniform internal energy density in the structure is defined as the objective for optimization This concept is similar to the fully stressed design and uniform strain energy density approaches Haftka and Gurdal 9 Patnaik and Hopkins 10 that are well established in literature for linear static problems The optimization problem is formulated as min Y Y wu x v 7 i j l N subject to Y ex lt M i l I u Ee SL o ad 8 Xain E X STO where U represents the internal energy density of the i element V is the volume of i element U represents internal energy den
20. ei xod civi oic vc dorus 39 2 0 L JProblenrDGOfmtlong cot i ota D poti user ERR OD Iusta e 40 3 6 2 js 40 999 O Cs i S e mee o mE Wien atit 40 aj Convergence History 2a ees trii ea ec ve E ba teg occ E D e PR AES 40 by Pinal Shell TIGR SSCS cotra io OM tocius dopo s 41 Ay NM A sis A tutes e E tuse eda Cd mune 42 4 1 Executable failing or no oDDDUL io io boo ea dd 42 42 Design Parte ase eise eec aote tio ded te odedec tien edo t UA 42 437 JXEDf SIOB SOC iuao tug enun Mau qM d qe ia ana te uisi itae uis 42 44 Negative VOIDPHes sese o Ned lo 42 4 5 The LS DYNA analysis fails if a smaller mass fraction is requested 42 45 COMVERSE CS 07 shy unc rotuli ndun T eee AA aeta Ae LIU 43 4 LS RBPOST ta 43 4 8 Casting o ON 43 4 9 Mysterious Error when after calling LS DYNA and or Errors involving the ESOPT EnvronmentY anal does tr a eos 43 A A em SE ede ede cate aoi acumen 44 SJ The scripting 3090896 cipe a etra eid ea basis cile aai bel Aaa da 44 52 Code EXP ecdesiae tel em eH c dtt tii 44 Da AI A p ta os IM 44 5 3 1 A tes er a e do ed ds ite 44 5 3 2 MISION A ede aera 44 5 3 3 Ist Problemin Ra 45 5 3 4 Ps 45 5 3 5 IN 46 5 3 6 6o c PTT PETS 47 5 3 7 IR circi 48 5 3 8 ISE TODO i aee e edid bete Stet wie tse iv Sese e bos rn Y 48 5 4 Interactions with the Data StTUCt fes a ie eene euer oe i aea 49 BW De RMI OM se teer n neni bon NM esencia eee 49 54 2 O ier ee bu I UI E A Ea ANDA 49 a
21. example 29 Figure 3 2 Convergence history of the mass redistribution 30 Figure 3 3 Initial and final density contours seen 31 Figure 3 4 Evolution of the geometry shown using density contours ss 31 Figure 3 5 Evolution of the beam using extrusion and single sided casting constraints 32 Figure 3 6 Evolution of the beam using extrusion and two sided casting constraints 33 Figure 3 7 The geometry and loading conditions of the multiple load case example 33 Figure 3 8 Convergence history for multiple load case example 34 Figure 3 9 Initial and final density contours esee 34 Figure 3 10 Evolution of the geometry for multiple load case structure 35 Figure 3 11 The geometry and loading conditions of the multiple constraints example 35 Figure 3 12 Convergence history for the example with multiple constraints 36 Figure 3 13 Evolution of the geometry for multiple constrained clamped beam 37 Figure 3 14 The geometry and loading conditions of a statically loaded structure 37 Figure 3 15 Convergence history for linear static example sees 38 Figure 3 16 Initial and final density contours 39 Figure 3 17 Evolution of the geometry for statically loaded structure 39 Figure 3 18 The geometry and loading condi
22. factor and U denotes the internal energy density set point The design variable is updated as xi 2x Ad 12 The change in the variable is constrained by the bounds on the value of the design variable 1 e L if x lt LB then x LB IL if x gt UB then x UB and only certain discrete values are allowed 61 dX K U U 1 dX 0 Figure 6 2 Design variable update The mass of each element is then calculated by using the appropriate material model associated with the design variables If the total mass of the structure meets the constraint the total change in design variables in this iteration is calculated and the design variable update is considered completed If the mass constraint is not satisfied the IED set point is updated iteratively to accommodate the material constraint as U U U M M 13 where M is the mass of the structure 6 2 10 Stopping Criteria Two termination conditions are used to stop the optimization process 1 The number of iterations has exceeded the maximum number of iterations or 2 The change in the topology is smaller than the tolerance i e N dX Ax lt e 14 i l The numerical oscillations in convergence are limited by averaging the total change in topology over two iterations 6 3 References 1 A Tovar Bone Remodeling as a Hybrid Cellular Automaton Optimization Process PhD thesis University of Notre Dame 2004 2 NM Patel B S Kang JE Re
23. geometry constraints the variables are defined only on a subset of elements 2 6 2 Filtering of Results Structured grids are not always possible for industrial applications and the results should be mesh independent A radius based strategy is therefore used to identify neighbors In this strategy a virtual sphere of default or user defined radius is placed at the center of an element All elements that are within this sphere are considered the neighbors of the corresponding element The result at an element is computed scaled from its own value and of its neighbors For dynamic problems it was observed that accounting for the history of evolution induces stability by reducing the element deletion rate Hence the field variable internal 16 energy density of i cell at iteration is updated by defining a weighted sum on the field variable of three previous iterations 2 6 3 Initialization of the Design Variables The design variables are initialized to satisfy the mass fraction All variables in a part are assigned the same initial value All associated field variables are also initialized to zero 2 7 LS DYNA Specifics 2 7 1 The Contact Definition The contacts involving the design parts should be modeled using either CONTACT AUTOMATIC SURFACE TO SURFACE ID Or CONTACT AUTOMATIC SINGLE SURFACE ID options These contact options are general enough to accommodate the changes in the geometry of the design parts duri
24. information for casting constraints Files will be created which can be viewed in LS PREPOST showing the master face free elements and the elements chained to the master elements StoreFieldHist Set this to a non zero value to obtain the IED histories in the View panel 5 3 3 Ist Problem The details of the problem is given in this data structure The definition is as follows struct lst Problem struct lst Case CaseList struct Ist Part PartList Char Description CaseList The user provides the details of the simulation in this data structure As the name suggests the CaseList is the list of all load cases For multiple load cases the user would specify one case per load case A complete description is given in a following section PartList The user provides the details of the parts in this data structure As the name suggests the PartList is the list of all parts A complete description is given in the next section Description This optional string is used to describe the problem 5 3 4 Ist Part The details of a part are 45 struct lst Part Int ID Int Continuum Float MassFraction Float ProxTol Float MinVarValue struct lst Geometry GeometryList struct Let Part Next ID Each part is identified with a unique id as in the LS DYNA input deck The design domain for topology optimization is identified as all of the parts given ProxTol All elements within a radius of proximity tolerance would b
25. iteration and the structure was fully developed in a largely 0 1 type structure by the 30 iteration Further redistribution of the material refined this structure between the 30 and the 40 iteration Wax ves Figure 3 13 Evolution of the geometry for multiple constrained clamped beam 3 5 Linear Static Loading The next example demonstrates the topology optimization of a statically loaded structure 3 5 1 Problem Definition 52 5mm H 7 L 52 5mm v Figure 3 14 The geometry and loading conditions of a statically loaded structure The geometry and loading conditions for the example are shown in Figure 3 10 The design part was meshed with 1 05mm elements such that there were approximately 125 000 elements 37 3 5 2 Input In this example a unit load is applied in the center of the structure The structure was fixed on the bottom The problem has a case named TopLoad The simulations are carried out using the double precision SMP version of LS DYNA s971 double The name of the DYNA input deck file is LinearStructure dyn Part 102 is the design part A maximum of 100 iterations are used to find the optimal topology and the desired mass fraction is 0 30 The project input data is saved to the file st_project lstasc as provided in the examples distribution Additionally scripts to recreate the database are also provided The project database can be investigated using the scripts use the script in exa
26. script is expected to print a status statement that LS TaSC can use to update its status information The only valid status statements are String Description WAITING The job has been submitted and is waiting to start RUNNING The job is running RUNNING N M After RUNNING the script may also report the progress as a fraction RUNNING 75 100 means that the job has 4 to go The progress information will be relayed to the user but not used in any other way by LS TaSC FAILED The job failed This is only to be used when the underlying queueing system reports some kind of problem Hence a solver that has terminated in error does not have to be deteceted by the LsoptJobCheck script FINISHED The job has completed and any output files needed for extraction has been copied back to the run directory Any amount of white space may appear at the beginning of a status statement and anything may appear after these statements The optional N M argument for RUNNING is interpreted as an estimate of the progress in this case N and M are integers and N M is the fractional progress N must be not be larger than M If LsoptJobCheck terminates without printing a valid status statement then it is assumed that Lsopt JobCheck does not function properly and LS TaSC terminates the job using the LsoptJobDel script All output from the LsoptJobCheck script is logged to the job log file Logx
27. solver command Istevm_run remote solver command For example solver command Istcvm run 1s971 single would be the appropriate solver command in LS TASC if you want to run the 1s971 single command on the remote LSTCVM server 2 LSTCVM and LS TaSC do not share a common file system In this case you may still execute remote commands on the LSTCVM server but you must select the following option in the Advanced GUI tab for the Solver Use LSTCVM proxy LS TASC will take care of prepending the 1st cvm run command So in this case if you want to execute 18971 single on the remote LSTCVM server then your solver command should simply be solver command 1s971 single All necessary input files will be transferred to the remote LSTCVM server using LS TASC runqueuer wrapper commands Extraction results are automatically brought back to the local side once the job has finished Note In order for this option to work you must install the LS TaSC wrapper on the LSTCVM proxy server and you must add the following entry to the executable map file 1stcvm exemap wrapper gt full path to wrapper The wrapper command is architecture specific So be sure to obtain the correct program for the LSTCVM architecture REMOTE FILES We do not currently delete files on the LSTCVM server after the job has completed This must be done by the LSTCVM proxy server administrator 7 14 2 LSTCVM server installation The LSTCVM server is distribute
28. studies 3 4 in topology optimization have focused on designing structures with static loading conditions but there is relatively little work on handling problems involving dynamic loads like those observed in crashworthiness optimization 5 The topology optimization in the context of crashworthiness is a very complex problem due to non linear interactions among material non linearities geometry and transient nature of boundary conditions The most efficient topology optimization methods use sensitivity information optimality criterion based methods Rozvany 1 Bendsee and Kikuchi 6 to drive the search for an optimum Sensitivity calculations are computationally inexpensive for linear static problems but not for the problems that involve non linearities To use the same set of topology optimization methods one needs to explicitly calculate sensitivities which is practically infeasible due to very high computational cost involved with simulations Thus the theory used to solve the linear static load cases though quite mature is not practical for the crashworthiness problems and alternate methods need to be explored Previously different approaches have been adopted by authors to solve topology optimization with nonlinearities Pedersen used the Method of Moving Asymptotes for crashworthiness optimization of two dimension structures 7 They used a quasi static nonlinear FEA to account for geometric nonlinearities to handle large deformation
29. then you must specify the port number N with the command Istcvm run s N lstcvm server name After setting the server name then you can test for connectivity using Istcvm run info You should see information about the current configuration of the LSTCVM server To test the installation cd to a directory where you are allowed to run the lstcvm run client and issue the command Istcvm run ls al It is possible that this command will fail if the LSTCVM administrator does not allow the 1s command to be run If that is the case then check with the administrator about which commands are available Once you know that the 1st cvm run command is properly configured and able to execute commands remotely then you are ready to use 1st cvm run with LS TaSC Only commands which are allowed and enabled by the LSTCVM administrator will function properly For example 18971 single is not available unless the remote administrator has enabled this command 80
30. 5 for dynamic problems and 0 001 for linear are deleted to improve numerical stability 2 4 2 Design of Shells For shells the thickness are changed to achieve a uniform internal energy density in the part The upper bound on the design variable is the original shell thickness while elements with design thickness values less than a user defined minimum value 0 05 for dynamic problems and 0 001 for linear are deleted to improve numerical stability 2 4 3 Element types Solid elements must be eight noded solid elements or four noded tetrahedral elements Elements shapes close to perfectly cubic are the best for the current neighbor selection algorithm Shell elements may be four noded shell elements or three noded shell elements The triangular elements must be specified as four noded shell elements by specifying the last node twice Elements shapes close to perfectly square or an equilateral triangle are the best for the current neighbor selection algorithm Tetrahedral and triangular elements cannot be extruded 2 4 4 Material data The part must be modeled using MAT PIECEWISE LINEAR PLASTICITY The load curve option LCSS is not supported use the EPSi ESi variables Test the material using LS DYNA before using it in LS TaSC For some material data the topology algorithm SIMP algorithm can only create materials for which the slope of the stress strain curve is higher in plastic regime than in the elastic one in this case the er
31. 75 TASA Edit DIS id 71 7 13 5 How the browse list is used by LS TaSC sse aL 7 14 Enabling LSTCVM job proxy support cocococooccooccononconncconoconocono nono nocnocnncnonnnos 79 TALA TSS CM MS Opti ia a i 79 7 14 2 LSTCVM server installation ia p bea mir a iadda 79 7 14 3 Environment Variables AA O ia me eeaoas 79 7 14 4 Configuring the Lstcvm_run client 80 TABLE OF FIGURES Figure 2 1 Geometry DIO Eto 15 Figure 2 2 The faces selected for design in a casting definition are all the faces facing the material removal direction The extra faces will cause the algorithm to fail 16 Figure 2 5 The information panel os iaa 19 BBS 2 4 The cases panelas e ad ten at a 20 Figure 2 5 The constraints overview panel eee tete eee tide therein 21 Figure 2 6 The constraints creation panel secas neiges nel aree hie te Ian DUS HEAR N ARM 21 Fapure 2 7 The parts panel a e ned 23 Figure 2 8 The panel to create part and geometry sse 23 Figure 2 9 Creating a geometry constraint 5 esee in el ce Rd NR du 24 Figure 2 10 The completion panel ea eec eee tee eren o tno et S ern 25 rere Dall Phe run Dale lose ecu Sateen eb en dte REED rotuli ssa edet e dH 26 Figure 2 12 The view panel with histories 4n ease e ER Res erii a uet iue 21 Figure 2 13 Viewing the model evolution in LS PREPOST see 21 Figure 3 1 Geometry and loading condition of a single load case
32. Conn struct lst Part const char name long set struct lst _ Geometry lst_PartAddGeometrySymmetryXY struct lst Part const char name long CID struct lst Geometry lst_PartAddGeometrySymmetryYZ struct lst Part const char name long CID struct lst Geometry lst_PartAddGeometrySymmetryZX struct lst Part const char name long CID struct lst Geometry lst PartAddGeometrylSideCasting struct lst Part const char name long dir long CID struct lst Geometry lst PartAddGeometry2SideCasting struct st Part const char name long dir long CID g Adding Job Distribution Data Details about running the simulation job for each case can be added by creating a JobInfo structure and using 1st_CaseSetJobInfo function The syntax is as follows lst JobInfo ji 1st JobInfoNew ji NumProc 1 ji Queuer 3 lst CaseSetJobInfo aCase ji For jobs submitted using a queuing system the values of the environment variables can be set on the remote system if required using the 1st_JobInfoAddEnvVar command The command has the following syntax lst JobInfoAddEnvVar struct JobInfo ji char variableName char value lst JobInfoDeleteEnvVar struct JobInfo ji char variableName 51 Example Adding simulation information to the two cases 1 Adding JobInfo to the case LEFT LOAD that uses PBS queuing system lst_JobInfo ji lst_JobInfoNew ji gt NumProc
33. LEVELER 2 AQS 6 PBSPRO 10 PBS 3 SLURM 7 HONDA 11 By default no queuing system would be used 48 EnvVarList These parameters are passed to the remote machine by the queuing system The 1st_JobInfoAddEnvVar command is used to set the values 5 4 Interactions with the Data Structures To specify the input data the user needs to communicate with the program data structures These data structures are accessed by the user via a script that follows the syntax of C programming language So the user needs to first define the data structure and then populate the input data 5 4 1 Definition Each script must include the following command to access necessary data structures lst Root root lst RootGet The root data structure encapsulates both problem and method data and therefore always needs to be accessed 5 4 2 Initialization During initialization the user provides the necessary input data a Adding Case Data The solver information is added to the problem data using the 1st_ProblemAddCase function defined as follows lst ProblemAddCase lst Problem Char CaseName Char SolverCmd Char InputFileName Int analysisType Float Weight The last two arguments analysisType and weight are optional If not specified then the program will determine whether it is a non linear analysis and set the weight to 1 0 Example Add two load cases 1 This load case uses a queuing system for a nonlinear structural problem lst
34. LS TaSC TOPOLOGY AND SHAPE COMPUTATIONS FOR LS DYNA USER S MANUAL April 2011 Version 2 0 Copyright O 2009 2011 LIVERMORE SOFTWARE TECHNOLOGY CORPORATION All Rights Reserved Corporate Address Livermore Software Technology Corporation P O Box 712 Livermore California 94551 0712 Support Addresses Livermore Software Technology Corporation Livermore Software Technology Corporation 7374 Las Positas Road 1740 West Big Beaver Road Livermore California 94551 Suite 100 Tel 925 449 2500 Fax 925 449 2507 Troy Michigan 48084 Email sales Istc com Tel 248 649 4728 Fax 248 649 6328 Website www lstc com Disclaimer Copyright O 2009 2011 Livermore Software Technology Corporation All Rights Reserved LS DYNA LS OPT and LS PrePost are registered trademarks of Livermore Software Technology Corporation in the United States All other trademarks product names and brand names belong to their respective owners LSTC reserves the right to modify the material contained within this manual without prior notice The information and examples included herein are for illustrative purposes only and are not intended to be exhaustive or all inclusive LSTC assumes no liability or responsibility whatsoever for any direct of indirect damages or inaccuracies of any type or nature that could be deemed to have resulted from the use of this manual Any reproduction in whole or in part of this manual is prohibited withou
35. Mn Js i i 1 define int Print Case lst_Case cse char whitespace struct lst JobInfo jInf print whitespace Cage n print whitespace tName t t cse gt Name n print whitespace tSolverCommand t cse gt SolverCommand n Es print whitespace tInputFile t cse gt InputFile n print whitespace tWeight t t cse gt Weight Mn print whitespace tAnalysisType t cse gt AnalysisType Mn jInf cse JobInfo Print JobInfo jInf t t define int Print Geom lst Geometry geom char whitespace 55 whitespace Geometry n whitespace tName t t geom gt Name Mn print whitespace tType t t geom gt Type Mn whitespace tCID t t geom gt CID n whitespace tExtructionDir t t geom gt ExtructionDir n print whitespace tMirrorPlane t t geom gt MirrorPlane An define int Print Part lst Part prt char whitespace struct lst Geometry geom print whitespace Part n print whitespace tID t t prt gt ID n print whitespace tMassFraction t prt gt MassFraction Mn print whitespace tMinVarValue t prt gt MinVarValue n print whitespace tProxTol t t prt gt ProxTol n geom prt gt GeometryList while geom Print Geom geom t t geom geom gt Next define int Print Pr
36. ProblemAddCase root Problem LEFT LOAD Sub pst My Input kt 2y rus 2 Second load case uses a standalone DYNA program for a linear structural problem lst ProblemAddCase root Problem ROUGE Tes GOAD So sino Lei imputi Um b Accessing a Specific Case Structure The cases are stored in a linked list in the 1st__Problem structure Also a pointer to the lst Case structure is returned when it is created Note that the word case is a reserved word in the C programming language lst Case csel lst Case cse2 root Problem CaseList root Problem CaseList Next 49 lst Case cse4 csel gt Next gt Next gt Next lst Case cse 1st ProblemAddCase root gt Problem RIGHT LOAD 1s971 single MyInputR k 2 1 c Adding Constraints A user can add constraints to each case using the following command lst CaseAddConstraint struct lst Case cse Char constraintName Float UpperBound Float LowerBound Char constraintCommand Example Adding two constraints to a case 1 Adding a displacement constraint Maximum resultant displacement of part defined by id 101 should be less than 7 25 units lst_CaseAddConstraint root gt Problem gt CaseList gDisp 7 25 pS Ue OSE TOURS Ose mud ree eye ney Clips bectl Gadi spa cemento selec MAR Sica bathe Oi 2 Adding a force constraint Maximum y force on the master side of the interface defined by id 9 should be smaller than 2 0e5 units lst C
37. TaSC reserved name for the chosen solver e g for LS DYNA use DynaOpt inp 7 5 Example Example The LS TaSC command relating to the queue nec00a mike project submit pbs The submit pbs file is bin csh f Run jobs on a remote processor remote disk set newdir pwd sed n s N1N N2 p Run jobs on a remote processor local disk no transmission set newdir pwd echo Snewdir cat dynscr EOF bin csh f PBS 1 nodes 1 ncpus 1 setenv LSOPT nec00a mike codes LSOPT EXE setenv LSOPT_HOST LSOPT_HOST setenv LSOPT PORT LSOPT PORT Run jobs on a remote processor remote disk mkdir p lsopt newdir cd lsopt newdir The input file name is required for LS OPT 1s 65 nec00a mike codes wrapper nec00a mike codes 1s980 single i DynaOpt inp EOF qsub dynscr It is also possible to specify the queuer command directly on the command line Environment variables can be specified on the solver command line e g for the PBS queuing system as well as LS TaSC input data Example This example shows how the required environment variables LSOPT PORT and LSOPT HOST set by the runqueuer program are specified on the solver command line whereas the two user variables LSDYNA971 MPP and LSOPT WRAPPER are defined and stored as special input entities see Section 7 13 These can also be set on the command line using the Linux setenv command qsub is a PBS queue submi
38. _getpwd fout dirName A String with the name of the current directory in the database Do not free this 53 string handle An Int identifying the Isda database Print the content of the current directory Command Int numItems Isda_Is Int handle Example Int n Isda_Is fout numltems An Int specifying the number of items directories and data vectors in this directory handle An Int identifying the Isda database Get Integer data Command Int data lsda getI4data Int handle Char variableName Int numValues Example Int results Isda getl4data fout elementLabels amp numV data A pointer to Int containing the data You must free this pointer after using handle An Int identifying the Isda database variableName The name of the results numValues The length of the data vector the number of items Get Float data Command Float data Isda_getR4data Int handle Char variableName Int numValues Example Float results lsda getR4data fout xx stress amp numV data A pointer to Float containing the data You must free this pointer after using handle An Int identifying the Isda database variableName The name of the results numValues The length of the data vector the number of items 5 6 Example Script 5 6 1 Retrieving a value from the project database Retrieving a value from the database is simple opened the project database and the value is avallable
39. abase can be investigated using the scripts use the script in example 5 6 4 to print the project data The advanced user can conduct the simulations using the LS DYNA MPP version and hence using a script named submit pbs for the PBS queuing system 29 3 1 3 Output The output of the code is written in the file named Ist output txt The error and warning messages are echoed in Ist error and Ist Warning files respectively The typical output in the Ist output txt is ls dyna analysis time 161s it dz total IED 9 933e 03 Mf 0 250 ls dyna analysis time 177s it 2 total IED 9 495e 03 Mf 0 250 dX 0 074627 target 0 001 ls dyna analysis time 183s it 3s total IED 8 983e 03 Mf 0 250 dX 0 077542 target 0 001 ls dyna analysis time 187s it 4 total IED 9 252e 03 Mf 0 250 dX 0 072176 target 0 001 ls dyna analysis time 193s it 5 total IED 9 156e 03 Mf 0 250 dX 0 063345 target 0 001 ls dyna analysis time 193s a Convergence History The convergence is quantified using the change in topology characterized by the normalized density redistribution and the total internal energy density as shown in Figure 3 2 Density Redistribution Iteration Figure 3 2 Convergence history of the mass redistribution The simulation converged after 57 iterations It was observed that initially there were significant changes in the topology upto 30 iterations Afterwards small changes were made in the topolo
40. ariable at iteration f 6 2 6 Constraint Handling In presence of constraints other than the mass constraints the target mass constraint is adjusted to satisfy the structural constraints The mass target M is increased in proportion to the constraint violation for all constraints except force constraints for which the mass target is reduced M M AM AM xs a J where J is the total number of constraints Kj is the coefficient used to scale the 10 constraint violation of the j constraint and e is the violation of the j constraint The total change in mass target AM is bounded to allow gradual changes in the structure 6 2 9 State Update Rules This is the heart of topology optimization method In this step the state of a variable is updated based on the state of its neighbors The state update is carried out in two steps 1 Field variable update The field variable internal energy density of a variable is updated as accounting for the field variable values of its n neighbors as U Yu Y 10 j 0 j 0 2 Variable Material Update Once the field variable state of each variable is defined the design variable is updated to reflect the changes While numerous rules are proposed in literature 6 to update design variables a control based rule used by Patel 8 is implemented here Figure 6 2 The change in the design variable of i variable Ax is computed as Ax K U u iv 11 where K is a scaling
41. aseAddConstraint root gt Problem gt CaseList rForce 2 0e5 1 0e 30 BinoutResponse res type RCForc cmp y_force id 9 side MASTER select MAX start_time 07007 It is recommended to obtain the command definition using the GUI The LS OPT manual can also be consulted on how to create the string d Adding Part Data A user can add parts to the problem using the following command struct lst Part lst ProblemAddPart struct lst Problem prob Int partId Float massFracB Double minx Double proxTol with the items in the command as explained for the part structure The last two arguments the minimum variable value and the neighbor radius are optional Example Adding a part struct let Beart pre let Proolemcceart rout gt Problem 102 0 3 50 e Accessing a Part The parts are stored in a linked list in the 1st_Problenm structure In addition a pointer to the 1st_Part structure is returned when it is created lst Part partl root gt Problem gt PartList lst Part part2 root Problem PartList Next lst Part part4 partl Next Next Next lst Part prt lst ProblemAddPart root gt Problen 1015 13 29 f Adding Geometry Data A user can add geometry constraints to the problem using the following commands struct lst Geometry lst PartAddGeometryExtrusion struct lst Part const char name long set long CID long dir struct lst Geometry lst PartAddGeometryExtrusion
42. ast line survives echo A B C D Running the browse command shown above will import two variables A and C into the browse list 76 NOTE Strings in the Env Vars List appearing above the browse line are all part of the Browse List Strings in the Env Vars tab that appear below browse are never part of the Browse List User defined environment variables will always follow after the browse variable definition e g last first in the figure above was not defined by the browse command 7 13 4 Edit browse list Select the Edit Browse list button Choosing this option does nothing unless a Browse List has been previously created If a valid Browse List is present in the Env Vars tab then selecting this option will run the original program that created the Browse List together with all of the current Browse List options passed as command line arguments one per existing environment variable Each command line argument has the form name value However value is not single quoted because each name value argument is a separate command line argument The customer supplied browse command should offer the user an opportunity to edit the existing variables and the browse command should return the newly edited list on one line in the same format as described above This would normally be done through some sort of graphical user interface The returned list will be used to replace all of the previous Browse List The next example script returns an
43. chnology Corporation Technology Corp C copyright 2008 2010 All Rights Reserved Problem description Current working directory C LSTC TaSC stasc_2 Current project file none Last modified none Figure 2 3 The information panel 2 9 2 The Cases Panel The cases panel contains all of the load cases to be analyzed using LS DYNA See the following table and Figure 2 4 for more details Cases data Name Each case is identified with a unique name e g TRUCK The same name would be used to create a directory to store all simulation data Execution The complete solver command or script e g complete path of LS Command DYNA executable is specified Input File The LS DYNA input deck path is provided Weight The weight associated with a case is defined here This enables the user to specify non uniform importance while running multiple cases Number of This parameter indicates the number of processes to be run jobs simultaneously A value of zero indicates all processes would be run simultaneously This parameter only makes sense if multiple cases must be evaluated The program will allow as many processes as defined for the current case being evaluated Queue system This parameter is used to indicate the queuing system The options are Isf loadleveler pbs nqs user aqs slurm blackbox msccp 19 pbspro Honda By default no queuing system would be used See the appendix for a des
44. cription of setting up the queuing systems The system is the same as used in LS OPT so a queuing system definition is the same File view Plot Help Info Cases Parts Constraints Completion Run View Name Input file Weight Queuer DYN LOAD Beam dyn 1 none E H Edit Case x General Scheduling Name Weight DYN LOAD 1 Input file name Beam dyn Browse Execution command without i parameter 15971 single memory 100m Edit X cancel Bok New zy Edit Copy SF Delete Figure 2 4 The cases panel 2 9 3 The Constraints Panel The constraint panel contains the global constraints on the structure See the following table and Figure 2 4 for more details Cases data Name Each constraint is identified with a unique name e g MAX DISP Case Each constraint is associated with a load case Constraint One of NODOUT or RCFORC Type Lower and The weight associated with a case is defined here This enables the upper bound user to specify non uniform importance while running multiple cases ID This is the ID of the node in the FE model at which the results must be collected Select This parameter indicates which value over time must be selected It can be the last value the maximum value the minimum value or at a specific time A time or a time interval can also be specified Filtering If filtering is desired select the type of filter frequency and time units LS PREPOST can
45. cture 3 4 Force Displacement Constraints The next example demonstrates a simulation with multiple constraints 3 4 1 Problem Definition M H wuIooZz wuIooZz L 800mm Figure 3 11 The geometry and loading conditions of the multiple constraints example The geometry and loading conditions for the example are shown in Figure 3 11 This is a fixed fixed beam with a central load The design part was meshed with 10mm elements 3 4 2 Input The center load was assigned at the location of the pole hitting the beam The desired mass fraction for this example was 0 25 A maximum of 100 iterations were allowed The maximum displacement of the indenter was constrained at 34 units and the maximum y component of the interface force was limited at 1 45e6 units The project input data is saved to the file st_project lstasc as provided in the examples distribution Additionally scripts to recreate the database are also provided The project database can be investigated using the scripts use the script in example 5 6 4 to print the 35 project data The advanced user can conduct the simulations using the LS DYNA MPP version and hence using a seript named submit_pbs for the PBS queuing system 3 4 3 Output a Convergence History 2 2E 06 2 1E 06 34 2E 06 1 9E 06 1 8E 06 38 1 7E 06 CLAMPED gDisp CLAMPED rForce 40 1 6E 06 1 5E 06 42 1 4E
46. d separately from LS TASC and in addition to the executables contains detailed information and installation instructions This server installation is usually handled by a systems administrator 7 14 3 Environment Variables All solver environment variables defined in the LS TASC EnvVar tab of the Solver are automatically passed to the remote job on the LSTCVM server PATH is not passed for security reasons This provides a convenient way to define licensing variables for LS DYNA For example you can pass the following variables to the remote proxy server job 79 LSTC LICENSE network LSTC LICENSE SERVER license server name 7 14 4 Configuring the 1s8tcvm run client The 1stcvm run client should be supplied with the LS TaSC distribution If you do not have such a command in the LS TaSC installation directory then your version of LS TaSC is probably not LSTCVM ready We suggest obtaining a later version of LS TaSC in that case In order to configure the 1st cvm run client you should execute Istcvm run s Istcvm server name The information will be saved so that this step never needs to be repeated If you are running on a Microsoft Windows platform then you should execute this command from within a command prompt the server information will be saved in the Windows registry If you are running on a Linux UNIX platform then the server information is stored in HOME Istcvm If for some reason a port other than the default is used
47. e bar indicating that the command failed 7 13 5 How the browse list is used by LS TaSC The Browse List indeed the complete Env Vars List is used to set environment variables before running the solver command specified by LS TaSC However if the first variable returned by the browse command is exe then a pre processing command is run T before running the actual solver command The pre processing command is the value of the exe variable The pre processing command has a command line Sexe varl varl var2 Svar2 varN SvarN That 1s the command executed is the value of the exe variable additional command line arguments consist of all Browse List strings with a comma delimiter appended to each intermediate one The final argument is not followed by a comma Note Such a pre processing command is always run from within the current LS TaSC Job Directory Therefore any file that the pre processing command references must be specified by a fully qualified path or must be interpreted relative to the current LS TaSC Job Directory So the LS TaSC Case Directory will be and the LS TaSC Project Directory will be 78 7 14 Enabling LSTCVM job proxy support 7 14 1 LSTCVM options There are two ways that LS TaSC can work with the LSTCVM job proxy 1 LSTCVM and LS TaSC share a common file system If LSTCVM and LS TASC share a common file system then you may run LS TASC jobs from within the shared file system by using the
48. e considered as the neighbors of an element MinVarValue Elements with a density of less than this will be deleted MassFractionBound The material constraint for the topology optimization is necessary for the optimization An appropriate value 0 05 x 0 95 is supplied here Continuum Whether the part is a solid or a shell Solids have a value of 1 while shells have a value of 2 GeometryList These are the geometry and manufacturing constraint on a part A complete description is given in the next section Next The next part in this linked list A value of NULL indicates that this is the final part 5 3 5 Ist Geometry The details of a geometry definition are struct lst Geometry Char Name Int Type Int CID Int Set Int ExtructionDir Int MirrorPlane struct lst Geometry Next Name Each geometry definition is identified with a unique name The name is used to identify the geometry constraint in the output Type The type of extrusion 2 is an extrusion 3 is a symmetry constraint 4 is a single sided casting constraint and 5 is a double sided casting constraint Set To design an extruded part the user firstly creates a set of all solid elements that would be extruded SET_SOLID The id of this set is specified in the input deck to identify the extrusion set 46 ExtrusionDir X Y 2 Z 3 MirrorPlane The mirror plane for a symmetry constraint XY 1 YZ 2 ZX 3 Next The next geometry
49. e system t Honda gt Environment variables Name Value project home t browse willem X cancel Bok new E Edit copy Delete A valid browse command must print environment variable definitions to standard output in the form name value the single quotes are optional if value does not contain spaces A valid sample output is shown below the line is wrapped because of its length exe home trent LSTC PERL lsdyna caecOl1 pbs sub pl menu batch time 1 00 host abcdefgh07 procs 1 jobname My Job project isd email No delay No preemptable No version LS DYNA 970 MPP SP 6763 ioloc home trent inpfile DynaOpt inp meml auto mem2 auto pfile Generic dumpbdb No dynamore No clean No tail No copycont No optimization LsOpt All of the name value strings are directly imported into the Env Vars tab in bulk In addition to these Browse List variables a special browse variable is created that should not be edited This variable records the program name used to create the Browse List NOTE All variables must be printed on one line which must be the last line of output from the program Lines before the last line are ignored WARNING The user supplied browse program should never define the browse variable in its output The name browse should be treated as a reserved name A simple Linux browse command could be a shell script bin bash echo This line is ignored Only the l
50. e that a lot of material was removed as early The final geometry evolved by considering the geometry 32 definitions was significantly different than the case when no manufacturing constraints were considered The I section evolved makes intuitively sense Figure 3 6 Evolution of the beam using extrusion and two sided casting constraints 3 3 Multiple Load Cases This example demonstrates a simulation with multiple load cases 3 3 1 Problem Definition H fame Fixed L 800mm Figure 3 7 The geometry and loading conditions of the multiple load case example The geometry and loading conditions for the example are shown in Figure 3 7 This is a fixed fixed beam with three loads The design part was meshed with 10mm elements 3 3 2 Input The three load cases were identified according to the location of the pole hitting the beam Side load cases were assigned a unit weight and the center load was assigned a weight of three units The desired mass fraction for this example was 0 3 A maximum of 100 iterations were allowed All simulations were run simultaneously 33 The project input data is saved to the file st_project lstasc as provided in the examples distribution Additionally scripts to recreate the database are also provided The project database can be investigated using the scripts use the script in example 5 6 4 to print the project data The advanced user can conduct the simulations using the LS DYNA MPP v
51. eometric definitions are given here e Constraints This optional information prescribes the stiffness or compliance of the whole structure e Completion These are methodology data such as the convergence criterions 2 4 The Design Parts The design domain is specified by selecting parts the optimum parts computed will be inside the boundaries delimited by these parts The part must be defined using PART not PART OPTION The parts may contain holes a structured mesh is accordingly not required 13 2 4 1 Elementwise Material Density and Element Deletion for Solids The shape of a solid part is described by the subset of the initial elements used The shape of a solid element is controlled by changing the amount of material in the element This is achieved by assigning a design variable to the density of each element The material is parameterized using a so called density approach In this approach a design variable is directly linked to the individual material element such that each cell has its own material model The design variable x also known as relative density varies from 0 to 1 where 0 indicates void and 1 represents the full material The material properties corresponding to the values of design variables are obtained using an appropriate interpolation model as described in the theoretical manual The upper bound on the design variable is 1 while elements with design variable value less than a user defined minimum value 0 0
52. ersion and hence using a seript named submit_pbs for the PBS queuing system 3 3 3 Output a Convergence History Density_Redistribution 20 40 60 Iteration Figure 3 8 Convergence history for multiple load case example The convergence history for the multiple load example is shown in Figure 3 8 The simulation converged after 67 iterations though miniscule changes were noted after 40 iterations As observed before monotonic reduction in the change in topology was observed The final structure absorbed approximately 8 less total internal energy b Density Contours The initial and final structures are shown in Figure 3 9 The final structure evolved in a tabular structure with the two cross members as legs The structure had more material in the center section due to the high importance assigned to the center weight There were many cavities in the structure such that the final structure could be considered equivalent to a truss like structure as one would expect Figure 3 9 Initial and final density contours 34 The evolution of the topology under multiple loading conditions is shown in Figure 3 10 While the final form of the structure was largely evolved by 28 iteration row 2 column 1 the material was re distributed to remove the low density material and evolve a largely 0 1 no material or full density material structure Figure 3 10 Evolution of the geometry for multiple load case stru
53. fied in the Scheduling panel when defining a Case The command to queue the job must return a job identifier that has one of the following two forms Job Any Quoted String has been submitted Job AnyUnquotedStringWithoutSpaces has been submitted The Word Job must be the first non white space on the line and must appear exactly as shown Any amount of white space may appear between Job and the job identifier as well as after the job identifier and before has been submitted The Blackbox queuer requires the presence of two executable scripts Lsopt JobCheck and LsoptJobDel These scripts must be located in either in the current LS TaSC project directory or in the directory where the running LS TaSC program is located For Windows the scripts must have an added extension exe vbs cmd or bat If the Blackbox queuer option is invoked for some solver then LS TaSC checks for the existence of executable scripts in one of these locations and refuses to run if the LsoptJobCheck and or Lsopt JobDel scripts cannot be found or are not executable The project directory is searched first LsoptJobCheck script The user supplied Lsopt JobCheck script is run each time LS TaSC tries to update the current status of a job The LsoptJobCheck script is run with a single commandline argument 70 LsoptJobCheck job identifier The working directory of the LsoptJobCheck script is set to the job directory associated with job identifier The
54. gy There was a drop in the total internal energy density during the early phase of the optimization but it increased during the later iterations The final topology is visualized in LS PREPOST b Density Contours The initial and final topologies are shown in Figure 3 3 and the topologies at different iterations during the evolution process are shown in Figure 3 4 30 Figure 3 3 Initial and final density contours The final topology evolved in a truss like structure Many holes were carved to satisfy the mass constraint while reducing the non uniformity in the distribution of the internal energy density The final structure was also found to have a reasonably homogenous distribution of the material as was desired Figure 3 4 Evolution of the geometry shown using density contours Topologies at different stages of the evolution process show that the main features of the structure were evolved by iteration 20 row 2 column 1 Further iterations were necessary to bolster the structure by removing the material from relatively non contributing zones and redistributing it to the desirable sections such as a 0 1 type topology was evolved 3 2 Beam using geometry definitions This example demonstrates how to setup a problem with geometry definitions The same fixed beam with a central load example is analyzed with an extrusion and two casting definitions The symmetry face is also defined as the extruded face In the input deck f
55. i E willem 1 willem TOPO EXAMPLES Z il LITT id villem 1 villem TOPO EXAMPLES S Feomp History Views ies Matrix size furdistributior deplacemer Title Off Tims Trial Beolr Unode Prin Isos Leon Acen Zin 10 Rx Deon ERN Top Front Right Redw Home Hide Shad View Wire Fear Edge Grid Mesh Shm Poen Zow w Cip an EMEN Dota Back Left Anim Reset BDC First Last 20 Inc 1 W Loop SF J Time 0 a m PrP om i an gt States Y A Finished reading command filef op Front Bottom Dack Left show Figure 2 13 Viewing the model evolution in LS PREPOST 27 2 10 Databases and Files The important files and directories are shown in the figure below Four files are important to know about e The project database e The project results in the st binout binary file e The optimal design in the case directory The d3plot files in the run directory inside the case directory Work Directory database stasc Ist output txt Ist errors txt Ist binout CASE 1 CASE 2 lt CASE_1 gt _OptDesign lt n gt k lt CASE_2 gt _OptDesign lt n gt k 2 11 Opening and Saving Projects The standard File pulldown is provides the ability to open and save projects The name of the database can also be specified on the command line when staring the GUI as stasc Ist project lstasc 2 12 Script Commands The script commands issued to create the database can
56. ial hence care must be exercised in defining master and slave penalty stiffness factors 2 Specify SOFT 2 option on the control card 3 Increase minimum density fraction default 0 05 for dynamic problems 4 5 The LS DYNA analysis fails if a smaller mass fraction is requested Possibly the structure is not strong enough to support the load 42 Inspect the d3plot results in the failed iteration to understand what happens in the LS DYNA analysis Fixes are to reduce the load increasing the mass fraction changing the FE model to be more robust using a finer mesh modify your approach keeping in mind that you cannot get a solution from that starting mass fraction or accepting that a design does not exist at that mass fraction 4 6 Convergence For some problems the code does not converge instead oscillations set in The user must look at the geometry to understand why oscillations are observed Mostly oscillations indicate that there is more than one possible optimal solution 4 7 LS PREPOST You may need to install another version of LS PREPOST into the LS TaSC installation directory Please follow the instructions on the LS PREPOST web site The name of the executable must be sprepost Do not use a symbolic link You may need to investigate the latest version of LS Prepost 2 4 and 3 1 4 8 Casting definitions Using the scripting interface you can set a debug flag on the st Method structure which will dump a defini
57. ibed in Section 2 9 2 The internal densities of the cells are extracted at the end of the analysis for use in the design procedure 17 2 8 Global constraints Global responses depend on the design of the whole structure Two types of global responses are e Stiffness This is specified as displacement constraint e Compliance This is specified as a reaction force constraint Local effects such as stress concentrations are not handled by this algorithm The algorithm is actually a search for the mass of the structure If the displacements are too large then mass are added to the structure to increase the stiffness If the reaction forces are too large then mass is removed from the structure to reduce the force Multiple global constraints may be specified If the constraints are in conflict then a trade off is done and a design is selected resulting in the minimum violation of any given constraint 2 9 Setting up the Problem The GUI consists of a number of panels Complete the panels from left to right as described in the following subsections 2 9 1 The Information Panel The information contains only information such as the software version the name of the current database file and a description of the problem 18 LS TaSC File View Plot Help Info Cases Parts Constraints Completion Run View LS TaSC gt LSTC Version 2 0 Beta Revision 63888 Livermore Software PY Livermore Software Te
58. ile the elements on the extrusion face were grouped in a solid set SET SOLID Two different casting conditions were applied in two separate design runs 1 in the first run casting definition was applied in the Z direction and 11 in the second run a two sided casting definition was applied in the Z direction All other parameters were kept the same 31 3 2 1 Input The main differences in this example compared to the non extrusion example are e An extrusion definition is provided e Acasting definition in Z direction is provided The project input data is saved to the file Extr Cast Ilstasc and Extr Cast2 lstasc as provided in the examples distribution in the directory Beam extr cast Additionally scripts to recreate the database are also provided The project database can be investigated using the GUI or a script use the script in example 5 6 4 to print the project data 3 2 2 Output a Extrusion and Casting Figure 3 5 Evolution of the beam using extrusion and single sided casting constraints Different phases in the evolution are depicted in Figure 3 5 One can see that a lot of material was removed as early The final geometry evolved by considering the geometry definitions was significantly different than the case when no manufacturing constraints were considered The C section evolved makes intuitively sense b Extrusion and two sided casting Different phases in the evolution are depicted in Figure 3 5 One can se
59. imization Topometry optimization a methodology closely related to topology optimization changes the element properties on an element by element basis With the LS TaSC program the shell thicknesses can be designed 1 1 3 Size Optimization In this mode the designer has already finalized the configuration of the system but improvements are sought by changing the thickness of members of the structure on a part basis instead of an element by element basis as done for topometry optimization There is usually no need to re mesh the geometry This class of optimization problems is the most amenable to meta model based optimization The LS OPT program should be used for this instead of this program 1 1 4 Shape Optimization Shape optimization further expands the scope of design domain by allowing changes in the geometry of the structure for example the radius of a hole While there is more freedom to explore the design space the cost of optimization increases due to the possible need to mesh different candidate optimum designs Use the LS OPT program together with a preprocessor such as LS PREPOST instead of this program 1 2 Brief Overview Topology optimization in structures has been studied since the 1970s resulting in many books and numerous papers The books by Rozvany 1 and Bendsee and Sigmund 2 provide a very comprehensive and contemporary survey of optimization techniques used 10 in topology optimization Most previous
60. ing down the Control key The plot ranges can be set under the View pulldown menu The histories can be printed or saved to file using the Plot pulldown menu The history data can be exported and postprocessed using the scripting interface 26 Info Cases Parts Constraints Completion Run View 1 ElFracUsed_Part_102 MassFraction_Part_102 Mass_Redistribution Topology histories ElFracDel Part 102 ElFracUsed Part 102 MassFraction Part 1C Mass Redistribution Model plots Single Matrix 0 84 0 6 9 S S G f o 2 E z 0 4 0 4 5 10 15 20 25 TEIL Iteration Figure 2 12 The view panel with histories LS PREPOST 2 Beta 19Feb2009 14 49 BEAM SO 1 d3plot Ux T 2 4 Bet b BEA d3pl File Misc Toggle Background Applications Settings Help LS DYNA USER INPUT mmes o Contours of Hestery Vanatiess 6750 10 max pi vaine a willem on deliwr AAA 7500 10 Anno Light FLD prr 2g SPlame Setting State Follow Splitw Particle Fringe Levels Output Trace Xyplot Ele dit yew Terminal Tabs Help 6740010 Range Vector Moasur T Find Idem ASCII rw r r 1 willem staff 45 rw r r 1 willem staff 1509 r will xr x 1 willen pesa willem 1 willem villem 1 villem AM 675010 willem 1 willem Appear Coler Model willem 1 villem 2XAMP i a Blank SelPar prat y Es HS T 2 3 4 5 6 7 D lat errors txt T
61. initial Browse List consisting of two variables A and C Invoking the editing feature appends a new variable tN N to the list bin bash echo This line will be ignored Only the last line survives TE P OSSIA Sa ie ENE echo A B C D else echo t fi When this script is invoked using the Create by Browse feature there are no command line arguments and the script prints A B C D to standard output However when the script is invoked using the edit feature for the first time two command line arguments A B and C D are passed to the script This time the return line consists of the original command line arguments printed using and tN N where N is the PID of the shell process If the editing feature is invoked a second time then three command line arguments are passed to the script A B C D and tN N Another new variable tN is appended where N is the newest PID of the script process This sample script has little practical value except to illustrate how existing variable settings are passed by command line to the previous browse command and to illustrate how one can use the editing feature to modify or add new variables Note The browse command can ABORT the replacement operation by printing a blank line to the standard output and immediately terminating Otherwise the current Browse List may be deleted If the browse command abnormally terminates then an error box will appear with a titl
62. int normal termination signal to screen echo No rma l which is submitted by the wrapper command in submit_pbs as home john bin wrapper home john bin runscript Note Adding echo N o r m a 1 atthe end of the wrapper command after a semicolon does not work which is why it should be part of the script run by the wrapper 7 9 User defined queuing systems To ensure that the LS TaSC job scheduler can terminate queued jobs two requirements must be satisfied 1 The queuer must echo a string Job Stringa Stringb Stringc has been submitted or Job Stringa has been submitted e g Job Opteron Ags4832 has been submitted Job aqs4832 has been submitted The string will be parsed as separate arguments in the former example or as a single argument in the latter example The string length is limited to 1024 characters The syntax of the phrases Job and has been submitted must be exactly as specified If more than one argument is specified without the double quotes the string will not be recognized and the termination feature will fail 2 A termination script or program LsoptJobDel must be placed either in the main working directory first default location or in the directory containing the LS TaSC binaries second default This script will be run with the arguments stringA stringB etc and must contain the command for terminating the queue An example of a Unix C shell termination script that uses two arguments i
63. ion converged after 28 iterations 3 6 Shell Example This example shows how to work with shell structures 39 3 6 1 Problem Definition Figure 3 18 The geometry and loading conditions of the shell example The left side is built in while a downward load is applied to the right back corner The geometry and loading conditions for the example are shown in Figure 3 18 3 6 2 Input The project input data is saved to the file Shell Istasc as provided in the examples distribution Additionally scripts to recreate the database are also provided The project database can be investigated using the scripts use the script in example 5 6 4 to print the project data 3 6 3 Output a Convergence History 0 0 0 0 0 04 0 0 0 02 Mass_Redistribution 0 01 10 Iteration Figure 3 19 Convergence history for the shell example 40 The convergence history for the shell example is shown in Figure 3 19 The simulation converged after 14 iterations There was largely monotonic reduction in the density redistribution b Final Shell Thicknesses The final design is shown in Figure 3 20 The final structure had many cavities and resembled an optimized truss like structure Figure 3 20 Final geometry and thicknesses for the shell problem 41 4 TROUBLESHOOTING This chapter lists some of the most common errors and suggested remedies 4 1 Executable failing or no output For the example prob
64. job log file will contain a message indicating any problem that may exist which prevents LsoptJobCheck from being run The HONDA queued jobs do not use LsoptJobDel as defined in the Blackbox queuing selection Jobs are deleted using the standard PBSPro qdel command Various statements concerning how status information is gathered are logged to the job log files These are 1 Job status for LSDYNA jobs found in messag file HONDA Termination status found in messag file HONDA exact termination statement 2 The job status line for the current job found in SHONDA STATUSFILE is saved HONDA status line 3 The job is assumed finished if there is no status line found HONDA Job 23551 not found in STATUS file assuming job is finished 4 Indication that LsoptJobCheck is run at the end of a non LS DYNA job HONDA Non LS DYNA job Running LsoptJobCheck to determine exit status 5 Status returned from LsoptJobCheck HONDA Job finished LsoptJobCheck reports normal termination HONDA Job finished LsoptJobCheck reports error termination Any errors while gathering status information are logged to the job log files such as log12345 6 Missing messag file after LSDYNA terminates HONDA Failed to find messag file while FINISHING HONDA Assuming ERROR termination for LSDYNA job 7 Found no termination status statement in messag file HONDA Found no termination status in messag file HONDA
65. l input decks Mass Fraction This parameter describes the fraction of the mass of the part to be retained The rest will be removed A part with an initial welght of 5 designed using a Mass Fraction of 0 3 will have a final weight of 1 5 Neighbor Radius All elements within a sphere of radius of this value are considered the neighbors of an element The design variable at an element is updated using the result at the element averaged together with that of its neighbors Smaller values of this parameter yield finer grained structures The default value depends on the average element size Minimum variable Ifthe design variable value associated with and elements is fraction too small then that element is deleted to preserve the stability of the model An appropriate value 0 05 x lt 0 95 is supplied here The default is 0 05 for non linear problems and 0 001 for linear problems 22 Figure 2 7 The parts panel r Edit Part Design part ID Mass fraction between 0 0 and 1 0 Minimum variable fraction for deleting element Neighbor radius Geometry definitions Name Definition Symmetryl Symmetry about x y plane in global coordinate system Symmetry2 Symmetry about y z plane in global coordinate system Casting Two way casting along z axis in global coordinate system A esa e im Figure 2 8 The panel to create part and geometry 23 2 9 5 Part Geometry The geometric properties
66. lems check that you changed the name of the LS DYNA executable in the example problem to what is used on your computer Provide the complete path for the solver command instead of using alias You may also specify necessary DYNA options in the command e g home Tushar bin 1s971 single memory 100m 4 2 Design Part The design part is not found check that the DYNA input deck has the same part id for the design part as specified in the input file In the case of the multiple load cases the design domain must remain the same 4 3 Extrusion Set The extrusion set is not found check that the set of elements on the extruded face are grouped under the SET SOLID option in the DYNA input deck The ID of the set is same for all load cases as specified in the input file Unable to find all the slaved elements if the node numbering order is different for some elements are not the same then the algorithm may fail Using a different node number will for example cause face 1 to be the top face on one element and to be the left face on another element the algorithm depends on this not happening 4 4 Negative Volumes While care has been taken to avoid running into negative volume errors sometimes the simulation terminates due to negative volume errors A user can take several actions to correct this error 1 Check the CONTACT cards Note that the failed run probably has elements with soft material interface with elements with harder mater
67. m its neighbors No gradient information was required The simplicity and effectiveness of this method for both two and three dimensional problems made it an attractive choice for our initial implementation The methodology has however been enhanced using more established approaches as well currently amongst others it gives mesh independent results 11 This manual is divided into parts The user s manual describes how to do topology optimization using LS TaSC A few examples are provided to cover different options in the topology optimization program The scripting section lists the command language used to interact with the topology optimization code together with some examples Some common errors and tips on troubleshooting are provided in a separate chapter In the theory section the method for topology optimization is described Setting up queuing systems is described in an appendix 1 4 ER 10 11 12 13 References GIN Rozvany Structural Design via Optimality Criteria Kluwer London 1989 MP Bendsee O Sigmund Topology Obptimization Theory Methods and Applications Springer Verlag Heidelberg 2003 HA Eschenaur N Olhoff Topology Optimization of Continuum Structures A Review Applied Mechanics Review 54 4 331 390 2001 GIN Rozvany Topology Optimization in Structural Mechanics Springer Verlag Vienna 1997 CA Soto Applications of Structural Topology Optimization in the Automotive Industry Past P
68. mple 5 6 4 to print the project data 3 5 3 Output a Convergence History The convergence history for the statically loaded structure topology optimization example is shown in Figure 3 15 The simulation converged after 28 iterations though only minor changes were noted after 20 iterations As observed before monotonic reduction in the change in topology was observed The total internal energy of the structure also decreased with topology evolution Density Redistribution Iteration Figure 3 15 Convergence history for linear static example b Density Contours The initial and final structures are shown in Figure 3 16 The final structure evolved in a column like structure with wider supports on the faces The shape of the structure also resembled the best stress design 38 Figure 3 16 Initial and final density contours Fringe Levels 8201e 10 B201e 10 8201e 10 8201 10 8201 10 8201 10 B2010 10 B201e 10 82016 10 B201e 10 82016 10 581 Figure 3 17 Evolution of the geometry for statically loaded structure The evolution of the topology under the static loading conditions is shown in Figure 3 17 While the final form of the structure was largely evolved by 17 iteration first structure in the second row the material was re distributed to remove the low density elements that were not contributing sufficiently to support the load and obtain a homogenous material distribution such that the simulat
69. naud Crashworthiness Design using a Hybrid Cellular Automata Algorithm Jn Proceedings of the 2006 International Design Engineering Technical Conference DETC 2006 99566 Philadelphia PA Sep 10 13 2006 3 P Hajela B Kim On the Use of Energy Minimization of CA Based Analysis in Elasticity Structural and Multidisciplinary Optimization 23 23 33 2001 4 J Forsberg L Nilsson Topology Optimization in Crashworthiness Design Structural and Multidisciplinary Optimization 33 1 12 2007 5 http mathworld wolfram com Last accessed 23 March 2008 62 10 11 MP Bendsge O Sigmund Material Interpolation Schemes in Topology Optimization Archives of Applied Mechanics 69 635 654 1999 MP BendsOe O Sigmund Topology Optimization Theory Methods and Applications Springer Verlag Berlin 1989 NM Patel Crashworthiness Design Using Topology Optimization PhD thesis University of Notre Dame 2004 RT Haftka Z Gurdal MP Kamat Elements of Structural Optimization Kluwer Academic Publishers Dordrecht The Netherlands 2 ed 1990 SN Patnaik DA Hopkins Optimality of Fully Stressed Design Computer Methods in Applied Mechanics and Engineering 165 215 221 1998 JO Hallquist LS DYNA Manual version 971 Livermore Software Technology Corporation October 2007 63 7 APPENDIX C USING A QUEUING SYSTEM 7 1 Relationship with the LS OPT queuing system This queuing system is the same as used in LS OPT If your queue setu
70. ng the optimization to maintain valid contacts It is also recommended to specify the contact options e g friction coefficients appropriately accounting for the changes in the geometry may result in significantly different material properties for some elements near the contacts Too restrictive values may cause instabilities in the LS DYNA simulations for intermediate geometries 2 7 2 Disallowed keywords The INCLUDE keyword is not supported in the current version The portions of the FE model related to the design part are extensively edited by the optimization algorithm In these segments of the FE model only specific versions of PART SET and CONTACT keywords may be used as described in the relevant sections Portions of the model not edited by the optimization algorithm are not subjected to this rule 2 7 3 LS DYNA Simulation The elements in the finite element model are modified by changing the material models adding or deleting elements at each iteration The input deck is accordingly re written for every iteration The relevant field variables for all elements are obtained from the output to completely define the state of each cell For multiple load case conditions the state variable is based on the output from simulations of different load cases This modified input deck is analyzed using LS DYNA One can take advantage of multiple processors using the MPP version of LS DYNA Queuing system can also be used as descr
71. oblem l1st_Problem prob char whitespace struct lst Case cse struct lst Part prt print whitespace Problem n print whitespace tDescription t t prob gt Description Mn print whitespace tNumCase t t t prob gt NumCase Mn print whitespace tNumPart t t t prob NumPart An cse prob CaseList while cse Print Case cse Nt cse cse gt Next prt prob gt PartList while prt Print Part prt Nt prt prt Next define int Print Method lst Method meth char whitespace print whitespace Method n print whitespace tNumIter t t t meth NumIter Mn print whitespace tConvTol t t t meth gt ConvTol An print whitespace tNumDiscreteLevels t meth NumDiscreteLevels Anat ys print whitespace tDebugGeomDef t t meth gt DebugGeomDef Mn RRR KKK ke ke ke ke ke ke ke ke e e ke k k k k k PROGRAM TO PRINT LST DATABASE HAHAHA AAA ke ke ke ke KK e e KK x x 56 struct lst Root root struct lst Problem prob struct lst Method meth root lst RootReadDb prob root gt Problem Print Problem prob meth root gt Method Print Method meth 5 6 5 Printing the content of the results database Int flag numV iter 1 Char dirName 1024 Float data wmEID aveChng print ItNum Total_IED Density Redistribution n Int handle
72. ogether with Willem Roux The project architecture was the responsibilities of Willem Roux and David Bj rkevik David had the lead role with regard to the graphical user interface aspects while Willem had the senior role looking after the overall project and the project management Thanks are also due to Nielen Stander from LSTC who helped to coordinate the efforts in the LS OPT group and sourced the initial version of the technology John Renaud and Neal Patel for discussion regarding topology optimization Kishore Pydimarry and Ofir Shor for evaluating the alpha version and Fabio Mantovani and Stefano Mazzalai for their help with LS DYNA simulations Willem Roux Livermore CA January 2010 TABLE OF CONTENTS Preface t0 MEM ad Cox oe ean atat aceto tdt O aute ut et nace 3 Preface to Version 13 iet Ds 4 Table oft Contents ue Herba Ee bu b He QU M ipea kept Ebo cdd eps co Y 5 Table of ETDUIOS ud pua M tei decus dns iubes oia or RM 9 T nttOdBetlOfi s a e aiti auo 10 1 1 Classification of Structural Optimization Techniques sess 10 1 1 1 Topology Optimization vers iae e pix a ea epa tiq esi dae 10 1 1 2 Topometry OpUtfizatlofi ties 10 1 1 3 Size OPI dolia 10 1 1 4 Shape Opti za io da 10 A A A A RS 10 1 3 Topology Optimization Method in LS TaSC sese 11 Td lt Referentes oscuro ACA eins on o ues ues ites 12 X User s Mantal ta a 13 2 JRun the Pro ad 13 23 A cam umen ue xL C nets 13
73. p works for LS OPT then it should work for LS TaSC as well This appendix mostly repeats the information for people not using LS OPT In the LS TaSC GUI the queuing is defined in the Scheduling tab of the Case definition LS OPT on the other hand define the queuing system in the run panel Also you do not need to reinstall the wrapper program if it is already installed for LS OPT 7 2 Experience may be required Experience with the queuing system and help from the system administer may be required The queuing systems are not provided by LSTC Getting the queue system to work may therefore require work and insight from the customer 7 3 Introduction The LS TaSC Queuing Interface interfaces with load sharing facilities e g LSF or LoadLeveler to enable running simulation jobs across a network LS TaSC will automatically copy the simulation input files to each remote node extract the results on the remote directory and transfer the extracted results to the local directory The interface allows the progress of each simulation run to be monitored via the GUI The README queue file should be consulted for the most up to date information about the queuing interface 7 4 Installation To run LS TaSC with a queuing load sharing facility the following binary files are provided in the LSOPT_EXE directory which un tars or unzips from the distribution during installation of LS TaSC LSOPTOPO EXE wrapper LSOPTOPO EXE runqueuer The
74. rategy is used to identify neighbors In this strategy a virtual sphere of user defined radius is placed at the centroids of an element All elements that are within this sphere are considered the neighbors of the corresponding element and the results are averaged over the elements in the neighborhood U YU Yi 2 j l j l 6 2 4 Material Parameterization The material model is parameterized using a so called density approach In this approach a design variable is directly linked to the individual material element such that each variable has its own material model The material properties corresponding to the values of design variables are obtained using an appropriate interpolation model The solid isotropic material with penalization SIMP model 6 is the most popular interpolation method This model is power law approach that drives the intermediate material properties towards the boundaries to obtain a 0 1 topology According to SIMP model the material properties are defined as P X Xpo 6 E x x E 4 o x x 0 5 E EX E 6 where p denotes the density of the material E represents the Young s modulus o is the yield stress and E is the strain hardening modulus The last two material properties represent material non linearities and are required for dynamic problems like crash that involve material yielding The subscript 0 refers to the base material properties The design variable x also known as relative
75. resent and Future in HA Mang FG Rammerstorfer J Eberhardsteiner eds Proceedings of the Fifth World Congress on Computational Mechanics Vienna 2002 MP Bendsoe N Kikuchi Generating Optimal Topologies in Optimal Design using a Homogenization Method Computer Methods in Applied Mechanics and Engineering 71 2 197 224 1988 CBW Pedersen Topology Optimization Design of Crushed 2d Frames for Desired Energy Absorption Structural and Multidisciplinary Optimization 25 368 282 2003 CA Soto Structural topology optimization from minimizing compliance to maximizing energy absorption International Journal of Vehicle Design 25 1 2 142 163 2001 CA Soto Structural Topology Optimization for Crashworthiness International Journal of Numerical Methods in Engineering 9 3 277 283 2004 CBW Pedersen Crashworthiness Design of Transient Frame Structures Using Topology Optimization Computer Methods in Applied Mechanics in Engineering 193 653 678 2004 J Forsberg L Nilsson Topology Optimization in Crashworthiness Design Structural and Multidisciplinary Optimization 33 1 12 2007 MK Shin KJ Park GJ Park Optimization of Structures with Nonlinear Behavior Using Equivalent Loads Computer Methods in Applied Mechanics and Engineering 196 1154 1167 2007 A Tovar Bone Remodeling as a Hybrid Cellular Automaton Optimization Process PhD Thesis University of Notre Dame 2004 12 2 USER S MANUAL Topology optimization con
76. rors and warnings should be consulted for feedback on how to modify the material stress strain curve in the input deck 14 2 5 Geometry and manufacturing definitions For each part geometry and manufacturing constraints such as being an extrusion may be specified The geometry definitions as shown in Figure 2 1 are e Symmetry For these the geometry is duplicated across a symmetry plane The part as supplied by the user must be symmetric an element must have a matching element on the other side of the symmetry plane e Extrusion An element set is extruded in a certain direction Allowable set definitions are SET SOLID SET SOLID LIST SET SHELL and SET SHELL LIST The part as supplied by the user must be an extrusion with every element in the elements set must have the same number of extruded elements Only hexahedrons and quadrilateral elements can be extruded e Casting Material is removed only from a given side of the structure The structure therefore will have no internal holes The casting constraints can be one sided or two sided This capability is available only for solids Yo Extrusion Symmetry Rm One sided Casting Two sided Casting Figure 2 1 Geometry definitions Multiple geometry constraints can be specified for each part Some combinations of geometry constraints may however not be possible A maximum of three geometry definitions per part is possible The symmetry planes must be orthogonal to each other
77. runqueuer executes the command line for the purpose of queuing and must remain in the LS TaSC environment the same directory as the Isopt executable The following instructions should then be followed Registered Trademark of Platform Computing Inc Registered Trademark of International Business Machines Corporation 64 a Installation for all remote machines running LS DYNA 1 Create a directory on the remote machine for keeping all the executables including 1sdyna Copy the appropriate executable wrapper program to the new directory e g if you are running lsdyna on a Linux machine place the wrapper appropriate for the architecture and operating system on this machine You do not need to reinstall the wrapper program if it is already installed for LS OPT b Installation on the local machine 2 Select the queuer option in the GUI for the Case definition To pass all the jobs to the queuing system at once select zero concurrent jobs in the GUI or command file In this example the arguments to the rundyna hp script are optional and can be hard coded in the script 3 Change the script you use to run the solver via the queuing facility by prepending wrapper to the solver execution command Use full path names for both the wrapper and executable or make sure the path on the remote machine includes the directory where the executables are kept The argument for the input deck specified in the script must always be the LS
78. s H bin csh f aadmin c 1 j 2 stop 7 10 Blackbox queueing system The Blackbox queueing system is another flavor of the User defined queueing system It can be used when the computers running the jobs are separated from the computer 69 running LS TaSC by means of a firewall The key differences between User defined and Blackbox are 1 It is the responsibility of the queueing system or the user provided scripts to transfer input and output files for the solver between the queueing system and the workstation running LS TaSC LS TaSC will not attempt to open any communications channel between the compute node and the LS TaSC workstation 2 Extraction of responses and histories takes place on the local workstation instead of on the computer running the job 3 LS TaSC will not run local placeholder processes i e extractor runqueuer for every submitted job This makes Blackbox use less system resources especially when many jobs are run in each iteration When using the Blackbox queueing system a LsoptJobDel script is required just as in the User defined case Furthermore another script named LsoptJobCheck must also be provided This script takes one parameter the job ID as returned by the submission script The script should return the status of the given job as a string to standard output The Blackbox queuer option requires the user to specify a command that will queue the job The Blackbox option can also be speci
79. s Hybrid Cellular Algorithm 1 2 but we found older views of the technology to be more representative of what is currently actually implemented 6 2 Implementation The algorithm for structural optimization is shown pictorially in Figure 6 1 After defining the problem the topology is evolved using the simple rules defined on the variables The constraints are accommodated during the state update procedure Read input data Indentify neigbours Create geometry defiritions No Evaluate objective and constraints Initialize variables Update field and design variables Figure 6 1 The topology optimization algorithm 6 2 1 Definition The input data is used to identify the design domain and design material model The input data comprises of method data e g number of iterations convergence tolerance and the problem data e g load cases design part etc 58 6 2 2 Creating the variables The finite element model is mapped to design variables Each design variables is assigned to a solid element in the design domain For extrusion and symmetry constraints the equality constraints are defined between the variables For casting constraints inequality constraints are established 6 2 3 Filtering of results Past work were based on the structured grid arrangement of cells This assumption would breakdown for industrial applications where structured grids are not always possible Hence a radius based st
80. sign Objectives and Constraints oooooononnnncnnoncconncconncnnnnnnnnconncconocancnonnnos 60 6 2 6 Design Variable Initialization indi id aii 60 6 2 7 Simulation to Obtain Field Variables sss 60 6 2 8 Constramt Handling iue a UR RI YO iia 61 6 2 9 State Update Res er odes a i heo dadie vermute Ron ROS 61 6 2 10 Stopping CHITI oi panas A adv ds 62 Gide ca PL 62 Appendix C Usine a queuing Md 64 7 Relationship with the LS OPT queuing system seen 64 7 2 Experience may De TEQUES A eias edes 64 qu MO O Adi 64 TA Instalan is tasa ver aid oae wi uc Roa pa 64 a Installation for all remote machines running LS DYNA 65 b Installation on the local machine oooonooccnnonocconoccconncconanononanononanonnonononanos 65 Ts Example m 65 7 6 Mechanics of the queuing process arde 67 Tels Environment variables sedit D ticos ast E a a a a 68 dus A a a e a sai abeat mds aad 68 7 9 User defined queuing systems a ga e IDEO de eae 69 7 10 Blackbox queueing system cita di las 69 7 11 Honda queuing O a dis 72 eld Microsoft Windows Compute Cluster server sse 74 7 13 Passing environment variables sss 74 7 13 1 Adding a new environment variable definition sss 74 7 13 2 Editing an existing environment variable definition 75 Paes Set Dy DROW SII 0 e e e o etu a e Ru E a na
81. sists of describing the topology design problem together with the solution methodology the scheduling the automated design and the evaluation of the results 2 1 Running the Program The LS TaSC GUI is launched from the command prompt by running the executable Istasc If a project already exists then the project database name stasc can be supplied in two ways 1 With the execution command lstasc myProject lstasc 2 The file open dialogue available from the File pulldown menu 2 2 Design Goal The goal of topology optimization is to find the shape of a structure with the maximum utility of the material For dynamic problems like crashworthiness simulations this is achieved by designing for a uniform internal energy density in the structure while keeping the mass constrained 2 3 Problem Definition The topology design problem is defined by 1 the allowable geometric domain 11 how the part will be used and 111 properties of the part such as manufacturing constraints Additionally you have to specify methodology requirements such as termination criteria and management of the LS DYNA evaluations In the GUI provide this information using the following headings e Cases These store the load case data such as the LS DYNA input deck and executable to use The Cases data therefore contain the information on how to simulate the use of part e Parts The properties of the parts such as the part ID mass reduction and g
82. sity set point and C is the j constraint There are L load cases with a total of J constraints The superscripts l and u represent lower and upper bounds on the constraints respectively 6 2 6 Design Variable Initialization The design variables are initialized to satisfy the material constraint All elements are assigned the same design variable values All associated field variables are also initialized to zero 6 2 7 Simulation to Obtain Field Variables The elements in the finite element model are modified by changing the material models adding or deleting elements at each iteration So the input deck is re written at each iteration This modified input deck is analyzed using LS DYNA 11 One can take advantage of multiple processors using the MPP version of LS DYNA The relevant field variables for all elements are obtained from the output to completely define the state of each variable For multiple load case conditions the state variable is based on the output from simulations of different load cases For dynamic problems it was observed that accounting for the history of evolution induces stability by reducing the element deletion rate Hence the field variable internal energy density of i variable at iteration is updated by defining a weighted sum on the field variable of three previous iterations as follows 60 U 25 0 Ur 3 y 9 j 0 where x is the design variable associated with the i v
83. stc com 1s opt QUEUING MSCCS Before using the scripts the variables in the beginning of the file submit cmd needs to be changed to fit your local environment Most users do not need to change the submit vbs file The example shows how the queue related parts of an LS TASC command file look when using the CCP scripts when they are placed in the same directory as the command file 7 13 Passing environment variables LSOPT provides a way to define environment variables that will be set before executing a solver command The desired environment variable settings can be specified directly in the com file with solver commands They can be specified within the Scheduling tab when defining a Case 7 13 1 Adding a new environment variable definition Select the New button After selecting this option an empty editable environment variable definition will appear We do not allow the names of variables to contain anything other than upper or lower case letters numbers and underscore characters Variable values are not so limited 74 File View Plot Help Info Cases Problem Method Run View E Edit Case x Name Input file Weight Qui mem TOPLOAD bcS0 ext 1 noi General Scheduling M Limit number of concurrent jobs Queue system 1 Ej Honda Environment variables Name Value tail No copycor No optimize LsOpt Set by browsing Edit browse lig X cancel Dok New
84. t command and the v directive defined the names of environment variables to be exported to the job The qsub manual pages should also be consulted for more details Say we submit to qsub using the command qsub v LSOPT PORT LSOPT HOST dynscr2 The dynscr2 file in this case is This is the dynscr2 file bin csh f cwd pe mpi 2 setenv NP 2 setenv ROUNDROBIN 0 Define LSDYNA971 MPP environment variables in lsopt input or shell command setenv 1 represents i DynaOpt inp and is automatically tagged on as the last argument of the lsopt solver command setenv EXE SLSDYNA971_MPP 1 rm f mpd hostfile mpp appfile filter hostfile lt PE_HOSTFILE gt mpd hostfile This python script builds an HPMPI specific appfile telling it exactly what to run on each node gen appfile hpmpi mpd hostfile SGE O WORKDIR SNP SROUNDROBIN SEXE gt mpp appfile This actually executes the job SLSOPT WRAPPER opt hpmpi bin mpirun f mpp appfile The solver command data and environment variable input are displayed below 66 Info Cases Problem Method Run View a Edit Case x Name Input file Weight Qui pM TOPLOAD bc50 ext 1 noi General Scheduling M Limit number of concurrent jobs Queue system 1 Honda S Environment variables Name Value project home t menu batch time 1 00 host X hraocae procs 1 jobnam ajobnan lv Se
85. t by browsing Edit browse list New Delete X cancel ox New A Edit Copy Delete 7 6 Mechanics of the queuing process Understanding the mechanics of the queuing process should help to debug the installation 1 LS TaSC automatically prepends runqueuer to the solver command and executes runqueuer which runs the submit pbs script o The runqueuer sets the variables LSOPT HOST and LSOPT PORT locally o Inthe first example the submit pbs script spawns the dynscr script In Example 1 the queuing system then submits dynscr see qsub command at the end of the submit pbs script above on the remote node which now has fixed values substituted for LSOPT HOST and LSOPT PORT In Example 2 the LS TaSC schedules the qsub command directly with LSOPT HOST and LSOPT PORT as arguments and i DynaOpt inp appended at the end of the command It therefore serves as an argument to dynscr2 The wrapper executes on the same machine as LS DYNA opens a socket and connects back to the local host using the host port information The standard output is then relayed to the local machine This output is also written to the logxxxx file where xxxx is the process number on the local host To look at the log of any particular run the user can select a button on the Run page under the View Log heading The progress dialog is shown below followed by the popup log 67 An example of an error message resulting from a mistype of
86. t the prior written approval of LSTC All requests to reproduce the contents hereof should be sent to sales Istc com 2 Jun 11 PREFACE TO VERSION 2 Version 2 was started in spring of 2010 in response to industrial feedback regarding version 1 Version 2 is an important step forward containing the following major new features e Shell structure support Global constraints Multiple parts Symmetry definitions Casting direction definitions Some minor features are e Tetrahedral solid element and triangular shell element support e The speed of some algorithms was improved e Improved integration with LS DYNA Many thanks are due to David Bj rkevik for the GUI design and implementation Tushar Goel for the initial global constraints implementation and Trent Eggleston for assistance with distributed computing Valuable feedback from customers and co workers is also acknowledged Willem Roux Livermore CA January 2011 PREFACE TO VERSION 1 The development of the topology code started in the fall of 2007 in response to a request from a vehicle company research group The alpha version was released in the spring of 2009 to allow the vehicle company research groups to give feedback from an industrial perspective while the beta version was released in November 2009 Most of the methodology developments in version 1 0 are due to Tushar Goel who worked on the engine implementation and algorithm design Additionally he also wrote the manual t
87. teTopology root Interval d Cleaning the directory The files created in the directory can be removed lst CleanDir databaseFileName lstasc The filename was specified in this case if omitted the default of Ist_project Istasc will be used All of the files created for the analysis except the database will be removed 5 5 Accessing Results These commands access the LS TaSC database and the LS DYNA binout database using the LSDA LSTC Data Archival interface Read this section together with the LSDA documentation available from the LSTC ftp site Open a database Command Int handle lsda open Char filename Example Int fout Isda open Istasc Isda handle An Int used to indentify this file in further actions filename A string giving the filename or path to the database Close a database Command Int success Isda_close Int handle Example Int flag lsda close fout Success An Int specify whether the command succeeded 70 handle An Int identifying the Isda database Change to a database directory Command Int success Isda_cd Int handle Char dirName Example Int flag lsda_cd fout Design 4 Success An Int specify whether the command succeeded 70 handle An Int identifying the Isda database dirName A String specifying the database directory Get the current directory in a database Command Char dirName lsda_getpwd Int handle Example Char currDir Isda
88. tect this problem Make sure that the result database is produced in the same directory as where the wrapper is started otherwise the data cannot be extracted E g the front end program such as mpirun may have a specification to change the working directory wd dir Running on a remote disk Make sure that the file HostDirectory is not copied by a user script to the remote disk if the simulation run is done on a remote disk The HostDirectory file is a marker file which is present only on the local disk Its purpose is to inform the wrapper that it is running on the local disk and if found on a remote disk will prevent the wrapper from automatically transferring extracted results back to the local disk In general the user is not required to do any file copying since input files including LS DYNA include files are copied to the remote disk automatically The response and history files are recovered from the remote disk automatically 68 6 Termination of user defined programs LS DYNA always displays a N o r m a 1 at the end of its output When running a user defined program which does not have this command displayed for a normal termination the program has to be executed from a script followed by a command to write N o r m a 1 to standard output The example file runscript shown below first runs the user defined solver and then signals a normal termination mpiexec n 2 home john bin myprogram i UserOpt inp pr
89. tion of the faces to a file for display in LS PREPOST 4 9 Mysterious Error when after calling LS DYNA and or Errors involving the LSOPT Environment Variable Make sure the queuing is set correctly Specifying the use of a queuing system when none is available may cause 1 mysterious errors or 11 the LS DYNA execution not to return after finishing Make sure the LSOPT environment variable is not set 43 5 APPENDIX A SCRIPTING The scripting capability is provided to allow advanced users to customize the application Normal interaction with the topology optimization code is with the graphical user interface which issues the scripting commands driving the optimization process A script is provided to the program in a file The commands in a script can perform one of two functions e Define the problem and methodology data e Call the topology design functions 5 1 The scripting language The script commands use the C programming language syntax to manipulate data Detailed knowledge of the language is not required to use this manual the example scripts in this manual give enough information A complete syntax reference is given in the LS PREPOST customization manual titled SCRIPTO A new tool to talk with LS PREPOST available at http www2 lstc com lspp index shtml 5 2 Code Execution The LS TaSC code is executed from the command prompt by running the executable Istasc script The input command file script can be s
90. tions of the shell example The left side is built in while a downward load is applied to the right back corner 40 Figure 3 19 Convergence history for the shell example sees 40 Figure 3 20 Final geometry and thicknesses for the shell problem 4 Figure 6 1 The topology optimization algorithm eene 58 Figure 6 2 Design variable Update dais 62 1 INTRODUCTION 1 1 Classification of Structural Optimization Techniques Engineering optimization finds new designs that satisfy the system specifications at a minimal cost Different types of structural optimization are 1 1 1 Topology Optimization This is a first principle based approach to develop optimal designs In this method the user needs to provide the design domain load and boundary conditions only The optimal shape including the shape size and location of gaps in the domain is derived by the optimizer While the most flexible method topology optimization is indeed the most complex optimization method due to a multitude of reasons like large number of design variables ill posed nature of the problem etc Nevertheless the benefits of using topology optimization include the possibility of finding new concept designs that have become feasible due to recent advances in technology e g new materials The LS aSC program can be used to this design work 1 1 2 Topometry Opt
91. upplied in two manners 1 With the execution command and a script file name lstasc script lst script lss 2 The code prompts for the input file if no input was specified with the execution command lstasc script Please input command file name lst inp Additionally you can use the execution command and a database file name 1stasc script Ist project Istasc 5 3 Data structures 5 3 1 Ist Root All input data is encapsulated in a top level data structure st Root The input data is classified in two sub categories the problem definition that does not depend on the optimization method and the optimization method parameters struct lst Root struct lst Problem Problem struct lst Method Method 5 3 2 Ist Method The parameters used for optimization method are specified in this data structure 44 struct lst Method Int NumIter Float ConvTol Int NumDiscreteLevels Int DumpGeomDef Int StoreFieldHist NumIter The maximum number of iterations allowed is specified ConvTo1 The convergence tolerance is the termination criterion used to stop the search when the topology has evolved sufficiently If ConvTol lt 0 0 then this input would be ignored and the default will be used NumDiscreteLevels Resolution or the number of steps in the gradation of the material of the part being design The default value should suffice for almost all problems DumpGeomDef Set this to a non zero value to obtain debugging
92. when the topology has evolved sufficiently This value is compared with the Mass Redistribution history variable displayed in the view panel The default value is 0 002 24 File View Plot Help Info Cases Parts Constraints Completion Run view Number of design iterations Minimum mass redistribution 30 a or Auto w Figure 2 10 The completion panel 2 9 7 The Run Panel The control panel is used to submit the design problem In addition the LS DYNA jobs can also be stopped and old results deleted Use this panel and the Viewer panel to monitor job execution See Figure 2 11 for more details 25 LS TOPO OX File View Plot Help Cases Parts Constraints Completion Run View Info Job status Job ID PID Iter Case Status 1 10618 1 SOLVER_1 2 10622 2 SOLVER_1 3 10626 3 SOLVER 1 4 10630 4 SOLVER 1 S 10634 5 SOLVER 1 6 10638 6 SOLVER 1 z 10642 7 SOIVFR 1 v Optimimum design input deck written to SOLVER 1 SOLVER 1 OptDesign9 k Optimization converged ANALYSIS COMPLETED Wed Dec 15 14 33 44 2010 Run Q stop Clear results Figure 2 11 The run panel 2 9 8 The View Panel The view can be used to monitor both optimization progress and optimization results Both histories and plots in LS PREPOST are possible See Figure 2 12 and Figure 2 13 for more details For the histories note that Multiple histories can be plotted simultaneously by hold
93. xxx in the run directory for debugging purposes Note The LsoptJobCheck script may print more than one status statement but only the first one will be used to update the status LsoptJobDel script The user supplied Lsopt JobDel script is run whenever the user chooses to terminate a job or whenever LS TaSC determines that a job should be killed for example if LsoptJobCheck fails The LsoptJobDel script is run with a single commandline argument LsoptJobDel job identifier 71 The working directory of the LsoptJobDel script is set to the job directory associated with job_identifier 7 11 Honda queuing system The Honda queuing system interface is based on the Blackbox queuing system but is dedicated to the particular needs of this system Mechanics of the Honda queuing process The queuing system generates a status file for which an environment variable has been defined in LS TASC as SHONDA STATUSFILE The status file is the output of the PBS queue check command During the initialization phase LS TASC checks whether this variable setting points to a valid file If it does not LS TASC terminates before starting the scheduler and prints a standard LSOPT style error message The line which marks the fields in the status file is used to determine how to parse the file this line has the form Fields are extracted based on this line which consists solely of space and dash

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