LSDYNA高级求解策略\elforms-12

ElementTypeSelectionCriteriaStructuralGeometryLoadingConditionsObjectiveofAnalysisEconomicsPointElements*ELEMENT_MASSmasselementID(EID)nodeIDmassvalue*ELEMENT_INERTIAelementIDnodeIDcoordinatesystemIDforinputofinertiatensor6termsofinertiatensor*ELEMENT_DISCRETEMasslessspringsanddampersInput:elementIDpartID2nodelID’s(onecanbeground)orientationoptionN1toN2Alongavector(*define_sd_orientation)–NOTRECOMMNEDED,usebeamformulation6insteadscalefactorforforceortorqueprintflagforDEFORCfileoffset(foranonzeroforceortorqueattimezero)*ELEMENT_DISCRETEUsesspecialmaterialmodels*MAT_SPRING_optionForce=F(displacement)elasticandnonlinearelasticinelasticgeneralnonlinearMaxwell(exponentialdecayofstiffness)*MAT_DAMPER_optionForce=F(velocity)viscousnonlinearviscous*SECTION_DISCRETETranslationorrotationalDynamicmagnificationfactor(optiontoscalestaticforcesbasedonrateofdeformation)Clearance(“slack”thatmustbetakenupbeforeforces(torques)aregenerated)Tensionandcompressionlimitsbeforelocking(can’tbeusedforadjacentspringsinseries)Failuredeflection/rotation*ELEMENT_BEAMUsedinmodelinglongslenderobjectssteeringcolumn,suspensioncomponents,buildingframes,rebarInput:elementIDpartID3nodepointID’s(3rdnodeisfororientationonlyandisnotrequiredforallbeamtypes)optionallycanoverridesectionpropertiesspecifiedin*section_beamBeamDefinitionn3rn2tsn1*SECTION_BEAMBeamFormulations6degreesoffreedompernodeHughes-Liu(default)-integratedbeamstressesincrosssectionarecalculatedatmidlengthofbeamBelytschko-Schwerresultantbeamnostressescomputed-onlyforcesandmomentsatnodesDiscretebeam(maybezerolength)Stiffness/dampinggivenin6DOFIfnonzerolength,setSCOORto-3,-2,2,or3fortruebeam-likebehaviorDeformablespotwelduses*mat_spotweld;includesplasticityandfailure*SECTION_BEAMBeamFormulations3degreesoffreedompernodeTruss(tensionorcompression)cable(tensiononly)Mustuse*mat_cable*SECTION_BEAMSectioninputsaredependentontheformulationchosenIntegratedbeamanddeformablespotweldtypeofintegration(userintegrationruleisoneoption)sectionshape(rectangular,tubular,W,C,T,Z,user-defined)outsidedimensions(orinnerandouterdiameter)Resultantbeamarea,momentsofinertia,shearareaDiscretebeamvolume,extrarotaryinertia,coordinatesystemIDfororientation,constraintsforrotationoflocalcoordinatesystemCableandTrussareaoffsetforcabletoindicationinitialslackorinitialtension*ELEMENT_SOLIDModelcomponentsthathavesignificantthicknessinallthreedimensionsRequiredinput:elementIDpartID8nodeID’sn1,n2,n3,n4,n4,n4,n4,n4fortetrahedronn1,n2,n3,n4,n5,n5,n6,n6forpentahedron(wedge)CanoptionallygivematerialaxesorientationfororthotropicoranisotropicmaterialsSolidElements423163421573264185Activate*control_solidiftetsorpentahedronsaremixedwithhexahedronsSolidElementFormulationsElementformulationspecifiedin*SECTION_SOLID1.Constantstresssolid(default)Cheapestandmostrobust8-nodebrick1pointintegrationwithhourglasscontrol(needatleast2elementsthruthicknessofpartforbendingbehavior)Massofdegenerateelements(tetrahedrons,pentahedrons)isincorrect2.FullyintegratedS/Rsolid8-nodebrick2x2x2integration(nohourglassing)NovolumetriclockingduetoSelectivelyReducedintegration(constantpressureelement)NotrobustforlargedeformationsMaybebestforsolidspotweldsSolidElementFormulations3.Fullyintegratedquadraticsolidwithnodalrotations8-node,14I.P.solidderivedfrom20-nodesolid6dofateachnode(bendingacrosssingleelementpossible;compatiblewithshellelements)AccuracyrelativelygoodforlinearelasticitybutdegradesapproachingincompressibilityVeryexpensiveandNOTrecommended4.S/Rquadratictetrahedronwithnodalrotations5integrationpoints6dofateachnodeNohourglassingTetsaregenerallystifferthanhexahedronsinincompressibleregimes,e.g.,plasticity.Stiffbehaviormostevidentinbendingmodes.Usefinemeshtominimizestiffbehavior.Preferredformulationfortets(lesspronetostiff/lockingbehavior)unlessincludedincontactSolidElementFormulations8,14.AcousticelementSingledegree-of-freedom(pressure)Usedwith*MAT_ACOUSTICtotransmit(low)pressurewavesthroughfluids10.OnepointtetrahedronFasterthanformulation4butpronetolockingPreferredoverdegeneratetetrahedron(formulation1)13.Avg.nodalpressuretetrahedronforbulkformingNovolumetriclockingunderplasticflowconditions16.10-nodetetrahedron(mid-sidenodes)UnderevalulationAutomaticcontactbreakseachfaceinto4triangularsegmentsTimestep=halfthatofothertetformulationsSolidElementFormulations0and9.Co-rotationalsolidformulationsfor*MAT_MODIFIED_HONEYCOMBDevelopedforcrushablebarriersCanundergoextremedeformationwithoutlosingstabilityLikenonlinearsprings;elementcaninvertandremainstableFormulation0:localcoordinatesystemtransformedwithelementrotationFormulation9:localcoordinatesystembasedonaxespassingthroughcentroidofelementfaces;maybehavepoorlyinshearSolidElementFormulationsALEandEulerformulations(5,6,7,11,12)Generallyreservedforfluids(Lagrangeformulationsill-suitedtofluidflow)Materialadvectsfromcelltocell(cell=element)Formulation5:ALE(meshissmoothed)Formulation6:Eulerian(nodesdonotmove)Formulation7:Eulerianambient(constantpressureinfloworoutflow)Formulation11:Euler/ALEmulti-material(upto3materialgroupsallowed)Formulation12:Euler/ALEsinglematerialwithvoidShellElementsUsedtomodelcomponentsthatarerelativelythininonedirectionandmaybesubjecttoout-of-planebending.6dofateachnode(moreexpensiveonperelementbasisthandefaultsolid).Planestresscondition,thatis,s33iszero.Can’tthinelementbysqueezingtransversely(requiressolidelement)Incrementallyobjectivefortreatmentoffinitestrains(rigidbodyrotationsdonotproducestrain)Numerousformulationsandoptionstosuitapplication.*CONTROL_SHELLGlobalcontrolparametersaffectingALLshellsectionsautomaticallysetelementformulationtoC0fortrianglesturnonthicknesschangeduetomembranestrainB-W-CwarpingstiffnessforB-TshellsetdefaultshellformulationelementwarpagewarningHughes-Liushellnormalupdateflag(setto-2ifreferencesurfaceofH-LshellisNOTatmidplane)Newin970Thermalshellactivationflagforthrough-thicknessvariationoftemperationFlagtocheckforhighlydistortedshellsanddeleteelementorterminate*SECTION_SHELLControlparametersaffectingeachshellsectionindividuallynumberofthrough-thicknessintegrationpoints(IP)(default=2pointGauss)thicknessateachnodeshearfactor(default=1.0,5/6isrecommended;correctsforassumptionofconstanttransverseshearstressthroughthickness)referencesurface-top,mid,bottomsurface(Hughes-Liushellformulations1,6,7only)materialangleateachthrough-thicknessIP(applicableonlytoorthotropicincludingmaterialmodels22,23,33,34,36,54,55,56,59,103)*ELEMENT_SHELLRequiredinputelementIDpartID(pointstosection,material,eos,hourglasscontrol)4nodesforaquad(repeat3rdnodefortriangle)Optionalinputcanoverridethicknessateachnodegivenin*SECTION_SHELLcanspecifyanothermaterialanglefororthotropicmaterials(addedtomaterialanglesgivenin*SECTION_SHELL)ShellFormulations2=Belytschko-Tsay(B-T)Thisdefaultformulationisefficientandgenerallythemostrobustformulationforlargedeformations1in-planeintegrationpointsubjecttohourglassmodesnumberofthrough-thicknessintegrationpointscontrolledbyuserCo-rotationalstressupdate(ref:Sec.6ofLS-DYNATheoreticalManual)elementcoordinatesystemembeddedatelementcentroidupdatedelementcoordinatesysteminfluencedbyorderingofnodes(unlessinvariantnodenumberingflaggedwith*CONTROL_ACCURACY)notwell-suitedtowarpedgeometriesunlessBWCwarpingstiffnesswithfullprojectionisinvokedin*CONTROL_SHELLBelytschko-Wong-ChiangShell(10)AdvantagesoverB-Tshellaccurateforwarpedelements(solvestwistedbeamproblemimprovedtreatmentoftransverseshear(passesKirchhoffpatchtest)DisadvantagesslightlymorecostlythandefaultB-TformulationnotasrobustasB-TformulationforlargedeformationsAlternative:InvokeB-W-CwarpingstiffnessforB-Tshellusing*CONTROL_SHELLrecommendedforwarpedgeometriessomewhatmorerobustandcheaperthanformulation10ShellFormulations1=Hughes-LiuFirstshellformulationimplementedinLS-DYNALikeB-Tshell,has1in-planeintegrationpointsubjecttohourglassmodesnumberofthrough-thicknessintegrationpointscontrolledbyuserUsescostlyJaumannstressrateupdate(ref:Sec.9,LS-DYNATheoreticalManual)recommendedforelementsundergoingverylargein-planeshearingdeformationroughlytwiceascostlyasB-TshellOKforwarpedgeometriesifnodalfibersareincrementallyanduniquelyupdated(IRNXX=-2in*control_shell)Cansetreferencesurfacetoinsidesurface,midsurface(default),oroutsidesurfaceofshellShellFormulations1=Hughes-Liu(continued)Otherthanoffsetreferencesurfacefeatureandperhapstheabilitytoremainaccurateforlargein-planeshearstrains,noreasontousethisformulationoverB-T(formulation2)shellprovidedthefollowingareinvokedfortheB-TshellBWCwarpingstiffnessisactivated(*control_shell)withfullprojectionand...invariantnodenumberingisturnedon(*control_accuracy)ShellFormulationswith2x2IntegrationSometimesreferredtoasfullyintegratedshells4in-planeI.P.eliminate4of5hourglassmodes(notw-mode)Numberofthrough-thicknessI.P.controlledbyuserGenerallylessrobustforelementsundergoingseveredeformation/distortionFormulations:6=Hughes-LiuformulationwithJaumannratestressupdateapprox.10timesmorecostlythandefaultB-Tshell7=Hughes-Liuformulationwithco-rotationalstressupdateapprox.5timesmorecostlythandefaultB-TshellShellFormulationswith2x2IntegrationFullyIntegratedFormulations(continued):16=Belytschko-Tsayformulationwithco-rotationalstressupdateunlike6and7,includesBathe-Dvorkintransversesheartreatmenttoeliminatethew-modehourglassing(twistingmode)relativelycheap-only2.5to3timesmorecostlythandefaultB-TshellsuitableforwarpedgeometriesifHGformulation8isinvokedrecommendedformulationif2x2integrationiswarrantedcoarsemeshstubbornhourglassingproblemSlightstiffer(morerealistic)thandefaultB-TshellAbnormalTerminationsDuetoShellDistortionsAnabnormalterminationwilloccurifazeroornegativeJacobiandevelopsinashellelement.OftencausedbypoorinitialelementshapesMorecommonforfully-integratedshellsSuchterminationscanbehardtodebugtomakeappropriatemodelchanges.Specialcheckingisavailableinv.970toidentify“bad”elementsandeither,cleanlyterminate,ordeletetheelementandcontinuerunning.Twoflagscontrolthechecking,onefor1pointshellsandtheotherforfullyintegratedshells(*control_shell)MembraneShellsShellswithoutbendingmomentsortransverseshearforcesSingle,through-thicknessintegrationpointSpecialshellformulationsformembranesbasedonBelytschko-TsayelementFormulation5:singlein-planeintegrationpointcheaperthandefaultformulation(2)with1I.P.stillmustspecify1I.P.in*SECTION_SHELLFormulation9:Fullyintegrated(4in-planeintegrationpoints)recommendedforairbagsspecialversionofthisformulationisautomaticallyinvokedfor*MAT_FABRICTriangularShellsTypicallyusedformeshtransitions,avoidingwarpedquads,complexgeometriesTri’saregenerallystifferthanquads(NOTrecommended)Formuations1,2,10:degeneratequad(muchstiffer;avoid!)Formulation4:C0triangle(stiffnessincreaseinbendingisnegligible;increasedstiffnessmorenoticeableformembraneandshear)Formulation3:BCIZtriangle(morecostly;noappreciablegaininaccuracyoverC0)Tri’saremorecostlyreductionintimestep(defaultcharacteristiclengthistheshortestaltitude);moreelementsTri’sdonothourglass(thisisGOOD)Setflagin*CONTROL_SHELLtoautomaticallyuseC0formulationforalltrianglesRecommendedShellFormulations*recommendBWCwarpingstiffnesswithfullprojectionandinvariantnodenumberingifmaterialisorthotropic/anisotropic.2-DContinuumElementsInputasshellssincedefinedasquadsortrianglesShellformulationspertainingto2-Dcontinua12=Planestress13=Planestrain14=Axisymmetric(area-weighted)-recommendedforaxisymmetrichighexplosives15=Axisymmetric(volume-weighted)Elementsaremodeledinthex-yplane(y-axisisaxisofsymmetryforformulations14and15)SetNIP=4in*section_shelltoinvokefullyintegratedformulationsfortypes13and15Cannotbemixedwith3DelementformulationsOnlycontacttypes*CONTACT_2D_...canbeusedwiththeseelements.ThickShellElements8-nodeslikeasolidBehaviorismorelikea4-nodeshellPlanestressassumptioninformulations1and2Numberofthrough-thicknessintegrationpointsspecifiedbyuserMustpayspecialattentiontoelementconnectivityN1,N2,N3,N4definethelowersurfaceSeecommands*Section_Tshell,*Element_Tshell