金属材料失效在abaqus中的应用(2)

Ductileshearandductilepressure:thischoicecorrespondstopoint1inFigure18.2.8–1andmodelsthecaseinwhichthedeviatoricstresscomponentsareunaffectedandthepressurestressislimitedbythehydrostaticcutoffstress;i.e.,.

InputFileUsage:*TENSILEFAILURE,ELEMENTDELETION=NO,

SHEAR=DUCTILE,PRESSURE=DUCTILE

Brittleshearandductilepressure:thischoicecorrespondstopoint2inFigure18.2.8–1andmodelsthecaseinwhichthedeviatoricstresscomponentsaresettozeroandremainzerofor

DYNAMICFAILUREMODELS

cutoff

Figure18.2.8–1pTensilefailurechoices.

therestofthecalculation,andthepressurestressislimitedbythehydrostaticcutoffstress;i.e.,

.

InputFileUsage:*TENSILEFAILURE,ELEMENTDELETION=NO,

SHEAR=BRITTLE,PRESSURE=DUCTILE

Brittleshearandbrittlepressure:thischoicecorrespondstopoint3inFigure18.2.8–1andmodelsthecaseinwhichthedeviatoricstresscomponentsaresettozeroandremainzerofortherestofthecalculation,andthepressurestressisrequiredtobecompressive;i.e.,.

InputFileUsage:*TENSILEFAILURE,ELEMENTDELETION=NO,

SHEAR=BRITTLE,PRESSURE=BRITTLE

Ductileshearandbrittlepressure:thischoicecorrespondstopoint4inFigure18.2.8–1andmodelsthecaseinwhichthedeviatoricstresscomponentsareunaffectedandthepressurestressisrequiredtobecompressive;i.e.,.

InputFileUsage:*TENSILEFAILURE,ELEMENTDELETION=NO,

SHEAR=DUCTILE,PRESSURE=BRITTLE

Thereisnodefaultfailurecombinationforthespallmodels.Ifyouchoosenottousetheelementdeletionmodel,youmustspecifythefailurecombinationexplicitly.Ifthematerial’sdeviatoricbehaviorisnotde ned(forexample,theequationofstatemodelwithoutdeviatoricbehaviorisused),thedeviatoricpartofthecombinationismeaninglessandwillbeignored.Thespallmodelsarenotallowedwhenusingplanestress,shell,membrane,beam,andtrusselements.

Determiningwhentousethetensilefailuremodel

ThetensilefailuremodelinAbaqus/Explicitissuitableforhigh-strain-ratedynamicproblemsinwhichinertiaeffectsareimportant.Improperuseofthetensilefailuremodelmayresultinanincorrectsimulation.

DYNAMICFAILUREMODELS

Usingthefailuremodelswithrebar

Itispossibletousetheshearfailureand/orthetensilefailuremodelsinelementsforwhichrebarsarealsode ned.Whensuchelementsfailaccordingtothefailurecriterion,thebasematerialcontributiontotheelementstress-carryingcapacityisremovedoradjusteddependingonthetypeoffailurechosen,buttherebarcontributiontotheelementstress-carryingcapacityisnotremoved.However,ifyoualsoincludefailureintherebarmaterialde nition,therebarcontributiontotheelementstress-carryingcapacitywillalsoberemovedoradjustedifthefailurecriterionspeci edfortherebarismet.Elements

TheshearandtensilefailuremodelswithelementdeletioncanbeusedwithanyelementsinAbaqus/Explicitthatincludemechanicalbehavior(elementsthathavedisplacementdegreesoffreedom).Theshearandtensilefailuremodelswithoutelementdeletioncanbeusedonlywithplanestrain,axisymmetric,andthree-dimensionalsolid(continuum)elementsinAbaqus/Explicit.Output

Inadditiontothestandardoutputidenti ersavailableinAbaqus/Explicit(“Abaqus/Explicitoutputvariableidenti ers,”Section4.2.2),thefollowingvariablehasspecialmeaningfortheshearandtensilefailuremodels:

STATUSStatusofelement(thestatusofanelementis1.0iftheelementisactive,0.0ifthe

elementisnot).

POROUSMETALPLASTICITY

18.2.9POROUSMETALPLASTICITY

Products:Abaqus/Standard

ReferencesAbaqus/ExplicitAbaqus/CAE “Materiallibrary:overview,”Section16.1.1“Inelasticbehavior,”Section18.1.1*POROUSMETALPLASTICITY*POROUSFAILURECRITERIA*VOIDNUCLEATION

“De ningporousmetalplasticity”in“De ningplasticity,”Section12.8.2oftheAbaqus/CAEUser’sManual,intheonlineHTMLversionofthismanualOverview

Theporousmetalplasticitymodel:

isusedtomodelmaterialswithadiluteconcentrationofvoidsinwhichtherelativedensityisgreaterthan0.9;isbasedonGurson’sporousmetalplasticitytheory(Gurson,1977)withvoidnucleationand,inAbaqus/Explicit,afailurede nition;and

de nestheinelastic owoftheporousmetalonthebasisofapotentialfunctionthatcharacterizestheporosityintermsofasinglestatevariable,therelativedensity.

Elasticandplasticbehavior

Youspecifytheelasticpartoftheresponseseparately;onlylinearisotropicelasticitycanbespeci ed(see“Linearelasticbehavior,”Section17.2.1).

Youspecifythehardeningbehaviorofthefullydensematrixmaterialbyde ningametalplasticitymodel(see“Classicalmetalplasticity,”Section18.2.1).Onlyisotropichardeningcanbespeci ed.Thehardeningcurvemustdescribetheyieldstressofthematrixmaterialasafunctionofplasticstraininthematrixmaterial.Inde ningthisdependenceat nitestrains,“true”(Cauchy)stressandlogstrainvaluesshouldbegiven.Ratedependencyeffectsforthematrixmaterialcanbemodeled(see“Rate-dependentyield,”Section18.2.3).

Yieldcondition

Therelativedensityofamaterial,r,isde nedastheratioofthevolumeofsolidmaterialtothetotalvolumeofthematerial.Therelationshipsde ningthemodelareexpressedintermsofthevoidvolumefraction,f,whichisde nedastheratioofthevolumeofvoidstothetotalvolumeofthematerial.ItfollowsthatForametalcontainingadiluteconcentrationofvoids,Gurson(1977)proposed

POROUSMETALPLASTICITY

ayieldconditionasafunctionofthevoidvolumefraction.Thisyieldconditionwaslatermodi edbyTvergaard(1981)totheform

where

isthedeviatoricpartoftheCauchystresstensor

istheeffectiveMisesstress;

isthehydrostaticpressure;

istheyieldstressofthefullydensematrixmaterialasafunctionof

equivalentplasticstraininthematrix;andarematerialparameters.,the;,,

TheCauchystressisde nedastheforceper“currentunitarea,”comprisedofvoidsandthesolid(matrix)material.

f=0(r=1)impliesthatthematerialisfullydense,andtheGursonyieldconditionreducestotheMisesyieldcondition.f=1(r=0)impliesthatthematerialiscompletelyvoidedandhasnostresscarryingcapacity.Themodelgenerallygivesphysicallyreasonableresultsonlyfor0.1(0.9).

Themodelisdescribedindetailin“Porousmetalplasticity,”Section4.3.6oftheAbaqusTheor …… 此处隐藏：4532字，全部文档内容请下载后查看。喜欢就下载吧 ……