linear and nonlinear analysis with femap and ls …...linear and nonlinear analysis with femap and...

LinearandNonlinearAnalysiswithFemapandLS-DYNAAnintroductiontotheworldofLS-DYNAusingFemapforpreandpostprocessing

FemapSymposium–Cypress,CA–May15th,2018

AdrianJensen,PE|SeniorStaffMechanicalEngineer

LinearandNonlinearAnalysiswithFemapandLS-DYNA

FemapSymposium–Cypress,CA–May15th,2018 Page2of28

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



1. WHATISLS-DYNA?

1.1 GENERALAPPLICATIONSCrashworthiness DriverImpact TrainCollisions

EarthquakeEngineering MetalForming Military



1.2 SPECIFICAPPLICATIONS(COURTESYOFPREDICTIVEENGINEERING)Airplane16gCrashAnalysis SportingGoodsEquipment DropTestConsumerProducts

DropTestofComposites/Electronics HumanBiometrics LargeDeformationofPlastics



CrashAnalysisofCargoNet DropTestofNuclearWasteContainer ImpactAnalysisofFoams

PlasticThreadDesign PSD/ModalAnalysis DiggerToothFailure



ElectronBeamWelding Pyro-ShockAnalysis MedicalEquipment

FractureMechanicsofGlass BallisticShockLoadingofOpticalEquipment HyperelasticMedicalSealAnalysis



Blade-OutAnalysis DiscreteElementMethod(MiningIndustry) Drop-TestofHandHeldElectronics

BallisticPenetrationofAl/FoamPanel High-SpeedSpinningDiskContainment LocomotiveFuelTank



CrashAnalysisofBusSeats ImpactAnalysisofSafetyBlockDevice

Snap-FitAnalysis–AllPlasticMedicalDevice



9gCrashAnalysisofJetEngineStand TorqueAnalysisofEndoscopicMedicalDevice

Drop,RailImpactandPSDAnalysisofCompositeContainer



2. FEMAP–ANINTERFACETHATOPENSANALYSISPOSSIBILITIESACROSSMULTIPLEPLATFORMS

Let’sbuildasimplemodel.Thereareafewkeystepsthatarenecessarytogetyourmodelup-and-runninginLS-DYNA.

2.1 MATERIALS



2.2 MESHING



2.3 CONTACT



2.4 ANALYSISMANAGER



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



3.2 PLATEWITHAHOLEForauniformlyloaded,infiniteplatewithahole,themaximumstressconcentrationis3xthefarfieldstress.

PlatewithHoleUnderUniformTension Courtesyofwww.fracturemechanics.org



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



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



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)



4. WHATABOUTNOT-SO-SIMPLEMODELS?

4.1 COMPLEXCONSTRUCTIONFORCOMPLEXLOADINGAlargecompositeshippingcontainerwasanalyzedfordrop,impact,PSDrandomvibrationandgeneralstressanalysis.Themainshellofthecontainerwasaglass-fibervacuuminfusedcompositewithclosuresmadeofaluminum.Liftingringsandothermajorstructuralloadpointswereattachedtothecompositecontainerusingthickaluminumplateswithpreloadedboltstodistributepointloadsintotheshell.

ExampleofLargeCompositeTransportationContainer



4.2 COMPOSITE-LAMINATEMATERIALMODELINGTheuniquenessofthisworkwasthatonebasemodelcouldaddressprogressivecompositefailurewhetherunderstaticconditions(implicit)orduringdroptestanalysis(explicit)alongwithboltpreloadandextensivenonlinearcontactbehavioratclosures,skidplatesandloadrings.Analysisrecommendationsareprovidedforgeneralimplicitanalysisfor:(i)PSDrandomvibrationwithboltpreload;(ii)progressivefailureofcompositeswith*MAT_54;(iii)contactmodelingand(iv)optimizationofruntimesusingMPPLS-DYNA.Theexplicitanalysisofthecontainerwasrathersimplisticbutsomecommentswillbemadeabouttheanalysissetupandruntimes.

SandwichandSolidLaminateCompositeswithTransitionRegion



4.3 SANDWICHPANEL-SURFACEANDSOLIDMESHINGGiventhatthemodelwasgoingtoberuninexplicit,theaimedtimestepwas1μs.Withanominalcompositewavespeedof3500m/s,elementsizescouldbeassmallas3.5mmifneeded,butingeneral,themeshsizingwassetto25mm.Themodelcontains150kelementsand125knodes.

SandwichandSolidLaminateCompositeswithTransitionRegion



4.4 MULTI-STEPANALYSISThetopimageshowsthepreloadstatepriortoinitialvelocityinitializationwhilethesecondimageshowstheimpactstresses.Scalingisaswithpriorwork.

BoltPreloadFollowingbyImpact(Implicit/Explicit)



5. FEMAPAEROSPACEFROMINTERIORSTOSLEDTESTING

5.1 EVENWHENIT’SNOTAVAILABLE,IT’SSTILLAVAILABLEINFEMAPIt’satallordertoaskthatapreandpostprocessorkeeps100%up-to-datewithallthedevelopmentsforaportfolioofsolvers.ForfeaturesnotyetincorporatedintotheFemapGUI,theabilitytoaddanalysistextallowsonetoaccessevenmoreLS-DYNAfeatures.

AnalysisTexttoIncorporateAdditionalAnalysisControl



5.2 EXPORTANDREADYTORUNForevenmoreflexibilityinanalysisfilemanagement,theanalystcanusethe*INCLUDEkeywordtopointtheanalysismanagertoexternalfiles.Thisisespeciallywellwhenworkingwithcomplicated3rdpartymodels,likeanATD.

Using*INLCUDEtoIntegrateExternalAnalysisFiles



Consideringthegeometrypreparationtoolsandmeshingtoolbox;theabilitytocreateLS-DYNAmaterialmodelsandsetelementformulations,andtheaddedflexibilityofanalysistextandincludefiles,-FemapallowsyoutoworkfromCADgeometryandgeneratearun-readyLS-DYNAanalysisdeck.

FullNonlinearDynamicTranisentAnalysis–StraightfromFemap



6. GETTINGBYWITHALITTLEHELPFROMYOURFRIENDS

ItseemsthatoutsidethecoreLSTCstaff(whichincludestheDYNAmoreteam),truemasteryofLS-DYNAisquiteelusive.Onecouldspendyearsstudyingthemanualsandexamplesandonlyscratchthesurfaceofcapabilities.However,itdoesn’tmeanthatonecan’tgetmeaningfulresultsinareasonabletimeframe.Withtherighttrainingandresources,agoodsimulationengineercanuseFemapandLS-DYNAwithouttoomuchblood,sweatandtears.



ThankyouforyourTime!Questions?AdrianJensenSr.StaffEngineerPredictiveEngineering,Inc.Phone:(503)206-5571E-mail:[email protected]

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linear and nonlinear analysis with femap and ls …...linear and nonlinear analysis with femap and...

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