Abaqus-User-Subroutines-Reference-Guide-用户材料子程序帮助文

1.1.41UMATUsersubroutinetodefineamaterial'smechanicalbehavior.Product:Abaqus/StandardWarning:Theuseofthissubroutinegenerallyrequiresconsiderableexpertise.Youarecautionedthattheimplementationofanyrealisticconstitutivemodelrequiresextensivedevelopmentandtesting.Initialtestingonasingle-elementmodelwithprescribedtractionloadingisstronglyrecommended.References“User-definedmechanicalmaterialbehavior,”Section26.7.1oftheAbaqusAnalysisUser'sGuide“User-definedthermalmaterialbehavior,”Section26.7.2oftheAbaqusAnalysisUser'sGuide*USERMATERIAL“SDVINI,”Section4.1.11oftheAbaqusVerificationGuide“UMATandUHYPER,”Section4.1.21oftheAbaqusVerificationGuideOverviewUsersubroutineUMAT:canbeusedtodefinethemechanicalconstitutivebehaviorofamaterial;willbecalledatallmaterialcalculationpointsofelementsforwhichthematerialdefinitionincludesauser-definedmaterialbehavior;canbeusedwithanyprocedurethatincludesmechanicalbehavior;canusesolution-dependentstatevariables;mustupdatethestressesandsolution-dependentstatevariablestotheirvaluesattheendoftheincrementforwhichitiscalled;mustprovidethematerialJacobianmatrix,,forthemechanicalconstitutivemodel;canbeusedinconjunctionwithusersubroutineUSDFLDtoredefineanyfieldvariablesbeforetheyarepassedin;andisdescribedfurtherin“User-definedmechanicalmaterialbehavior,”Section26.7.1oftheAbaqusAnalysisUser'sGuide.StorageofstressandstraincomponentsInthestressandstrainarraysandinthematricesDDSDDE,DDSDDT,andDRPLDE,directcomponentsarestoredfirst,followedbyshearcomponents.ThereareNDIdirectandNSHRengineeringshearcomponents.Theorderofthecomponentsisdefinedin“Conventions,”Section1.2.2oftheAbaqusAnalysisUser'sGuide.Sincethenumberofactivestressandstraincomponentsvariesbetweenelementtypes,theroutinemustbecodedtoprovideforallelementtypeswithwhichitwillbeused.DefininglocalorientationsIfalocalorientation(“Orientations,”Section2.2.5oftheAbaqusAnalysisUser'sGuide)isusedatthesamepointasusersubroutineUMAT,thestressandstraincomponentswillbeinthelocalorientation;and,inthecaseoffinite-strainanalysis,thebasissysteminwhichstressandstraincomponentsarestoredrotateswiththematerial.StabilityYoushouldensurethattheintegrationschemecodedinthisroutineisstable—nodirectprovisionismadetoincludeastabilitylimitinthetimesteppingschemebasedonthecalculationsinUMAT.ConvergencerateDDSDDEand—forcoupledtemperature-displacementandcoupledthermal-electrical-structuralanalyses—DDSDDT,DRPLDE,andDRPLDTmustbedefinedaccuratelyifrapidconvergenceoftheoverallNewtonschemeistobeachieved.Inmostcasestheaccuracyofthisdefinitionisthemostimportantfactorgoverningtheconvergencerate.Sincenonsymmetricequationsolutionisasmuchasfourtimesasexpensiveasthecorrespondingsymmetricsystem,iftheconstitutiveJacobian(DDSDDE)isonlyslightlynonsymmetric(forexample,africtionalmaterialwithasmallfrictionangle),itmaybelessexpensivecomputationallytouseasymmetricapproximationandacceptaslowerconvergencerate.AnincorrectdefinitionofthematerialJacobianaffectsonlytheconvergencerate;theresults(ifobtained)areunaffected.SpecialconsiderationsforvariouselementtypesThereareseveralspecialconsiderationsthatneedtobenoted.AvailabilityofdeformationgradientThedeformationgradientisavailableforsolid(continuum)elements,membranes,andfinite-strainshells(S3/S3R,S4,S4R,SAXs,andSAXAs).Itisnotavailableforbeamsorsmall-strainshells.Itisstoredasa3×3matrixwithcomponentequivalenceDFGRD0(I,J).Forfullyintegratedfirst-orderisoparametricelements(4-nodequadrilateralsintwodimensionsand8-nodehexahedrainthreedimensions)theselectivelyreducedintegrationtechniqueisused(alsoknownasthetechnique).Thus,amodifieddeformationgradientispassedintousersubroutineUMAT.Formoredetails,see“Solidisoparametricquadrilateralsandhexahedra,”Section3.2.4oftheAbaqusTheoryGuide.BeamsandshellsthatcalculatetransverseshearenergyIfusersubroutineUMATisusedtodescribethematerialofbeamsorshellsthatcalculatetransverseshearenergy,youmustspecifythetransverseshearstiffnessaspartofthebeamorshellsectiondefinitiontodefinethetransverseshearbehavior.See“Shellsectionbehavior,”Section29.6.4oftheAbaqusAnalysisUser'sGuide,and“Choosingabeamelement,”Section29.3.3oftheAbaqusAnalysisUser'sGuide,forinformationonspecifyingthisstiffness.Open-sectionbeamelementsWhenusersubroutineUMATisusedtodescribethematerialresponseofbeamswithopensections(forexample,anI-section),thetorsionalstiffnessisobtainedaswhereJisthetorsionalconstant,Aisthesectionarea,kisashearfactor,andistheuser-specifiedtransverseshearstiffness(see“Transverseshearstiffnessdefinition”in“Choosingabeamelement,”Section29.3.3oftheAbaqusAnalysisUser'sGuide).ElementswithhourglassingmodesIfthiscapabilityisusedtodescribethematerialofelementswithhourglassingmodes,youmustdefinethehourglassstiffnessfactorforhourglasscontrolbasedonthetotalstiffnessapproachaspartoftheelementsectiondefinition.Thehourglassstiffnessfactorisnotrequiredforenhancedhourglasscontrol,butyoucandefineascalingfactorforthestiffnessassociatedwiththedrilldegreeoffreedom(rotationaboutthesurfacenormal).See“Sectioncontrols,”Section27.1.4oftheAbaqusAnalysisUser'sGuide,forinformat