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LinearandNonlinearAnalysiswithFemapandLS-DYNAAnintroductiontotheworldofLS-DYNAusingFemapforpreandpostprocessing
FemapSymposium–Cypress,CA–May15th,2018
AdrianJensen,PE|SeniorStaffMechanicalEngineer
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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TABLEOFCONTENTS1. WHATISLS-DYNA?..........................................................................................................................................................3
1.1 GENERALAPPLICATIONS...................................................................................................................................................................................3
1.2 SPECIFICAPPLICATIONS(COURTESYOFPREDICTIVEENGINEERING)...........................................................................................................................4
2. FEMAP–ANINTERFACETHATOPENSANALYSISPOSSIBILITIESACROSSMULTIPLEPLATFORMS................................102.1 MATERIALS.................................................................................................................................................................................................10
2.2 MESHING....................................................................................................................................................................................................11
2.3 CONTACT....................................................................................................................................................................................................12
2.4 ANALYSISMANAGER.....................................................................................................................................................................................13
3. FOUNDATIONSOFFINITEELEMENTANALYSIS.............................................................................................................143.1 SIMPLY-SUPPORTEDBEAM.............................................................................................................................................................................14
3.2 PLATEWITHAHOLE......................................................................................................................................................................................15
3.3 COMPOSITEANALYSIS...................................................................................................................................................................................17
3.4 LINEARCONNECTORS(EQUIVALENTNASTRANMULTI-POINTCONSTRAINTELEMENTS)...............................................................................................18
4. WHATABOUTNOT-SO-SIMPLEMODELS?....................................................................................................................194.1 COMPLEXCONSTRUCTIONFORCOMPLEXLOADING.............................................................................................................................................19
4.2 COMPOSITE-LAMINATEMATERIALMODELING...................................................................................................................................................20
4.3 SANDWICHPANEL-SURFACEANDSOLIDMESHING.............................................................................................................................................21
4.4 MULTI-STEPANALYSIS...................................................................................................................................................................................22
5. FEMAPAEROSPACEFROMINTERIORSTOSLEDTESTING.............................................................................................235.1 EVENWHENIT’SNOTAVAILABLE,IT’SSTILLAVAILABLEINFEMAP............................................................................................................................23
5.2 EXPORTANDREADYTORUN............................................................................................................................................................................24
6. GETTINGBYWITHALITTLEHELPFROMYOURFRIENDS..............................................................................................26
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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1. WHATISLS-DYNA?
1.1 GENERALAPPLICATIONSCrashworthiness DriverImpact TrainCollisions
EarthquakeEngineering MetalForming Military
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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1.2 SPECIFICAPPLICATIONS(COURTESYOFPREDICTIVEENGINEERING)Airplane16gCrashAnalysis SportingGoodsEquipment DropTestConsumerProducts
DropTestofComposites/Electronics HumanBiometrics LargeDeformationofPlastics
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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CrashAnalysisofCargoNet DropTestofNuclearWasteContainer ImpactAnalysisofFoams
PlasticThreadDesign PSD/ModalAnalysis DiggerToothFailure
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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ElectronBeamWelding Pyro-ShockAnalysis MedicalEquipment
FractureMechanicsofGlass BallisticShockLoadingofOpticalEquipment HyperelasticMedicalSealAnalysis
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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Blade-OutAnalysis DiscreteElementMethod(MiningIndustry) Drop-TestofHandHeldElectronics
BallisticPenetrationofAl/FoamPanel High-SpeedSpinningDiskContainment LocomotiveFuelTank
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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CrashAnalysisofBusSeats ImpactAnalysisofSafetyBlockDevice
Snap-FitAnalysis–AllPlasticMedicalDevice
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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9gCrashAnalysisofJetEngineStand TorqueAnalysisofEndoscopicMedicalDevice
Drop,RailImpactandPSDAnalysisofCompositeContainer
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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2. FEMAP–ANINTERFACETHATOPENSANALYSISPOSSIBILITIESACROSSMULTIPLEPLATFORMS
Let’sbuildasimplemodel.Thereareafewkeystepsthatarenecessarytogetyourmodelup-and-runninginLS-DYNA.
2.1 MATERIALS
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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2.2 MESHING
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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2.3 CONTACT
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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2.4 ANALYSISMANAGER
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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3. FOUNDATIONSOFFINITEELEMENTANALYSIS3.1 SIMPLY-SUPPORTEDBEAM
Asimply-supportedhalf-symmetricbeamisanalyzedusingbeam,shellandsolid(8-nodebrickand10-nodetetrahedral)elements.ThisbasicexampleisusedtodemonstratethatLS-DYNAcansolvethemostbasicoflinearelasticproblems.
StandardFEAImplicitCode(Nastran) LS-DYNAImplicitAnalysis
Table1:Summaryoflinearelasticimplicitverificationresults
Model Hex 10-nodeTet Shell BeamStress Disp Stress Disp Stress Disp Stress Disp
Standard 999.0 4.185e-3 1000. 4.194e-3 999.1 4.192e-3 1000. 4.190e-3LS-DYNA 999.3 4.184e-3 1000. 4.192e-3 999.0 4.192e-3 1000. 4.192e-3
%Difference 0.03 0.02 0.00 0.05 0.01 0.00 0.00 0.05
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3.2 PLATEWITHAHOLEForauniformlyloaded,infiniteplatewithahole,themaximumstressconcentrationis3xthefarfieldstress.
PlatewithHoleUnderUniformTension Courtesyofwww.fracturemechanics.org
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Thefollowinggraphicsshowstressresultsforthesolidandshellelementformulations.Asinthepriorexample,thesamemesheswereusedbetweenthetwoprograms.IncontouringsolidelementstresseswithinLS-PrePost,severaloptionsareavailableforaveragingnodalstresses:mid,aveandmax.Themidoptiontakesasimpleaveragebetweenconnectednodesandwasusedinthehexandtetmodels.Fortheshellmodel,extrapolate1wasusedwithinLS-PrePosttoextrapolatethestressesfromtheintegrationpointsandthenaveragedusingthedefaultsetting(mid).
StandardFEAImplicitCode(Nastran)-Hex LS-DYNAImplicitAnalysis-Hex
Table2:SummaryoflinearelasticresultsforQSplatewithhole
Hex Tet Shell
Standard 2898 3063 2865LS-DYNA 2919 3063 2865
%Difference 0.72 0.00 0.00
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3.3 COMPOSITEANALYSISTheimagesbelowprovideacomparisonbetweenthefirstpliesofaneightplylaminatecompositeplatewithahole.Theanalysisislinearelastic.FortheLS-DYNAmodel,theshellformulationisELFORM=-16(minussign16).Torequestplyinformation,usethe*DATABASE_EXTENT_BINARYsettingmaxint=8towriteoutintegrationpointdataforeachply.Thereasonfornotrequestingallintegrationpointsoneachlayer(i.e.,ply)using-8isthatNastranonlyreportsthecentroidvalueasadefaultandwedon’twishtomakethiscomparisonmoredifficultthannecessary.
Nastran–Ply1 LS-DYNAPly1
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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3.4 LINEARCONNECTORS(EQUIVALENTNASTRANMULTI-POINTCONSTRAINTELEMENTS)InNastranimplicitanalysis,itisquitecommontouseconnectorsthatarebasedonconstraintrelationshipsbetweenstiffnesstermswithinthestiffnessmatrix.InNastrantheyaretermedmulti-pointconstraintelements(MPC’s)anddependingupontheirformulationarealsoknownasrigidelements(e.g.,RBE1andRBE2)orforceinterpolationelements(e.g.,RBE3).
MPC–RBE2(Rigid6DOF’s) LS-DYNACNRB(Rigid6DOF)
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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4. WHATABOUTNOT-SO-SIMPLEMODELS?
4.1 COMPLEXCONSTRUCTIONFORCOMPLEXLOADINGAlargecompositeshippingcontainerwasanalyzedfordrop,impact,PSDrandomvibrationandgeneralstressanalysis.Themainshellofthecontainerwasaglass-fibervacuuminfusedcompositewithclosuresmadeofaluminum.Liftingringsandothermajorstructuralloadpointswereattachedtothecompositecontainerusingthickaluminumplateswithpreloadedboltstodistributepointloadsintotheshell.
ExampleofLargeCompositeTransportationContainer
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4.2 COMPOSITE-LAMINATEMATERIALMODELINGTheuniquenessofthisworkwasthatonebasemodelcouldaddressprogressivecompositefailurewhetherunderstaticconditions(implicit)orduringdroptestanalysis(explicit)alongwithboltpreloadandextensivenonlinearcontactbehavioratclosures,skidplatesandloadrings.Analysisrecommendationsareprovidedforgeneralimplicitanalysisfor:(i)PSDrandomvibrationwithboltpreload;(ii)progressivefailureofcompositeswith*MAT_54;(iii)contactmodelingand(iv)optimizationofruntimesusingMPPLS-DYNA.Theexplicitanalysisofthecontainerwasrathersimplisticbutsomecommentswillbemadeabouttheanalysissetupandruntimes.
SandwichandSolidLaminateCompositeswithTransitionRegion
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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4.3 SANDWICHPANEL-SURFACEANDSOLIDMESHINGGiventhatthemodelwasgoingtoberuninexplicit,theaimedtimestepwas1μs.Withanominalcompositewavespeedof3500m/s,elementsizescouldbeassmallas3.5mmifneeded,butingeneral,themeshsizingwassetto25mm.Themodelcontains150kelementsand125knodes.
SandwichandSolidLaminateCompositeswithTransitionRegion
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4.4 MULTI-STEPANALYSISThetopimageshowsthepreloadstatepriortoinitialvelocityinitializationwhilethesecondimageshowstheimpactstresses.Scalingisaswithpriorwork.
BoltPreloadFollowingbyImpact(Implicit/Explicit)
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5. FEMAPAEROSPACEFROMINTERIORSTOSLEDTESTING
5.1 EVENWHENIT’SNOTAVAILABLE,IT’SSTILLAVAILABLEINFEMAPIt’satallordertoaskthatapreandpostprocessorkeeps100%up-to-datewithallthedevelopmentsforaportfolioofsolvers.ForfeaturesnotyetincorporatedintotheFemapGUI,theabilitytoaddanalysistextallowsonetoaccessevenmoreLS-DYNAfeatures.
AnalysisTexttoIncorporateAdditionalAnalysisControl
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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5.2 EXPORTANDREADYTORUNForevenmoreflexibilityinanalysisfilemanagement,theanalystcanusethe*INCLUDEkeywordtopointtheanalysismanagertoexternalfiles.Thisisespeciallywellwhenworkingwithcomplicated3rdpartymodels,likeanATD.
Using*INLCUDEtoIntegrateExternalAnalysisFiles
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Consideringthegeometrypreparationtoolsandmeshingtoolbox;theabilitytocreateLS-DYNAmaterialmodelsandsetelementformulations,andtheaddedflexibilityofanalysistextandincludefiles,-FemapallowsyoutoworkfromCADgeometryandgeneratearun-readyLS-DYNAanalysisdeck.
FullNonlinearDynamicTranisentAnalysis–StraightfromFemap
LinearandNonlinearAnalysiswithFemapandLS-DYNA
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6. GETTINGBYWITHALITTLEHELPFROMYOURFRIENDS
ItseemsthatoutsidethecoreLSTCstaff(whichincludestheDYNAmoreteam),truemasteryofLS-DYNAisquiteelusive.Onecouldspendyearsstudyingthemanualsandexamplesandonlyscratchthesurfaceofcapabilities.However,itdoesn’tmeanthatonecan’tgetmeaningfulresultsinareasonabletimeframe.Withtherighttrainingandresources,agoodsimulationengineercanuseFemapandLS-DYNAwithouttoomuchblood,sweatandtears.
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ThankyouforyourTime!Questions?AdrianJensenSr.StaffEngineerPredictiveEngineering,Inc.Phone:(503)206-5571E-mail:[email protected]