金属材料失效在abaqus中的应用

DYNAMICFAILUREMODELS

18.2.8DYNAMICFAILUREMODELS

Product:Abaqus/ExplicitReferences

“Equationofstate,”Section17.9.1“Classicalmetalplasticity,”Section18.2.1“Rate-dependentyield,”Section18.2.3“Johnson-Cookplasticity,”Section18.2.7“Materiallibrary:overview,”Section16.1.1“Inelasticbehavior,”Section18.1.1*SHEARFAILURE

*TENSILEFAILUREOverview

Theprogressivedamageandfailuremodelsdescribedin“Damageandfailureforductilemetals:overview,”Section19.2.1,aretherecommendedmethodformodelingmaterialdamageandfailureinAbaqus;thesemodelsaresuitableforbothquasi-staticanddynamicsituations.Abaqus/Explicitofferstwoadditionalelementfailuremodelssuitableonlyforhigh-strain-ratedynamicproblems.Theshearfailuremodelisdrivenbyplasticyielding.Thetensilefailuremodelisdrivenbytensileloading.Thesefailuremodelscanbeusedtolimitsubsequentload-carryingcapacityofanelement(uptothepointofremovingtheelement)onceastresslimitisreached.Bothmodelscanbeusedforthesamematerial.

Theshearfailuremodel:

isdesignedforhigh-strain-ratedeformationofmanymaterials,includingmostmetals;usestheequivalentplasticstrainasafailuremeasure;offerstwochoicesforwhatoccursuponfailure,includingtheremovalofelementsfromthemesh;canbeusedinconjunctionwitheithertheMisesortheJohnson-Cookplasticitymodels;andcanbeusedinconjunctionwiththetensilefailuremodel.isdesignedforhigh-strain-ratedeformationofmanymaterials,includingmostmetals;usesthehydrostaticpressurestressasafailuremeasuretomodeldynamicspallorapressurecutoff;offersanumberofchoicesforwhatoccursuponfailure,includingtheremovalofelementsfromthemesh;canbeusedinconjunctionwitheithertheMisesortheJohnson-Cookplasticitymodelsortheequationofstatematerialmodel;and

canbeusedinconjunctionwiththeshearfailuremodel.Thetensilefailuremodel:

DYNAMICFAILUREMODELS

Shearfailuremodel

TheshearfailuremodelcanbeusedinconjunctionwiththeMisesortheJohnson-CookplasticitymodelsinAbaqus/Explicittode neshearfailureofthematerial.

Shearfailurecriterion

Theshearfailuremodelisbasedonthevalueoftheequivalentplasticstrainatelementintegrationpoints;failureisassumedtooccurwhenthedamageparameterexceeds1.Thedamageparameter,,isde nedaswhereisanyinitialvalueoftheequivalentplasticstrain,isanincrementoftheequivalentplasticisthestrainatfailure,andthesummationisperformedoverallincrementsintheanalysis.strain,

Thestrainatfailure,,isassumedtodependontheplasticstrainrate,;adimensionlesspressure-deviatoricstress(wherepisthepressurestressandqistheMisesstress);temperature;andprede ned eldvariables.Therearetwowaystode nethestrainatfailure,.Oneistousedirecttabulardata,wherethedependenciesaregiveninatabularform.theanalyticalformproposedbyJohnsonandCookcanbeinvoked(see“Johnson-Cookplasticity,”Section18.2.7,formoredetails).

Whendirecttabulardataareusedtode netheshearfailuremodel,thestrainatfailure,,mustbegivenasatabularfunctionoftheequivalentplasticstrainrate,thepressure-deviatoricratio,temperature,andprede ned eldvariables.ThismethodrequirestheuseoftheMisesplasticitymodel.

FortheJohnson-Cookshearfailuremodel,youmustspecifythefailureparameters,–(see“Johnson-Cookplasticity,”Section18.2.7,formoredetailsontheseparameters).Theshearfailuredatamustbecalibratedatorbelowthetransitiontemperature,,de nedin“Johnson-Cookplasticity,”Section18.2.7.ThismethodrequirestheuseoftheJohnson-Cookplasticitymodel.InputFileUsage:UsebothofthefollowingoptionsfortheMisesplasticitymodel:

*PLASTIC,HARDENING=ISOTROPIC

*SHEARFAILURE,TYPE=TABULAR

UsebothofthefollowingoptionsfortheJohnson-Cookplasticitymodel:

*PLASTIC,HARDENING=JOHNSONCOOK

*SHEARFAILURE,TYPE=JOHNSONCOOK

Elementremoval

Whentheshearfailurecriterionismetatanintegrationpoint,allthestresscomponentswillbesettozeroandthatmaterialpointfails.Bydefault,ifallofthematerialpointsatanyonesectionofanelementfail,theelementisremovedfromthemesh;itisnotnecessaryforallmaterialpointsintheelementtofail.Forexample,ina rst-orderreduced-integrationsolidelementremovaloftheelementtakesplaceassoonas

DYNAMICFAILUREMODELS

itsonlyintegrationpointfails.However,inashellelementallthrough-the-thicknessintegrationpointsmustfailbeforetheelementisremovedfromthemesh.Inthecaseofsecond-orderreduced-integrationbeamelements,failureofallintegrationpointsthroughthesectionateitherofthetwoelementintegrationlocationsalongthebeamaxisleads,bydefault,toelementremoval.Similarly,inthemodi edtriangularandtetrahedralsolidelementsfailureatanyoneintegrationpointleads,bydefault,toelementremoval.Elementdeletionisthedefaultfailurechoice.

Analternativefailurechoice,wheretheelementisnotdeleted,istospecifythatwhentheshearfailurecriterionismetatamaterialpoint,thedeviatoricstresscomponentswillbesettozeroforthatpointandwillremainzerofortherestofthecalculation.Thepressurestressisthenrequiredtoremaincompressive;thatis,ifanegativepressurestressiscomputedinafailedmaterialpointinanincrement,itisresettozero.Thisfailurechoiceisnotallowedwhenusingplanestress,shell,membrane,beam,andtrusselementsbecausethestructuralconstraintsmaybeviolated.

InputFileUsage:Usethefollowingoptiontoallowelementdeletionwhenthefailurecriterionis

met(thedefault):

*SHEARFAILURE,ELEMENTDELETION=YES

Usethefollowingoptiontoallowtheelementtotakehydrostaticcompressive

stressonlywhenthefailurecriterionismet:

*SHEARFAILURE,ELEMENTDELETION=NO

Determiningwhentousetheshearfailuremodel

TheshearfailuremodelinAbaqus/Explicitissuitableforhigh-strain-ratedynamicproblemswhereinertiaisimportant.Improperuseoftheshearfailuremodelmayresultinanincorrectsimulation.

Forquasi-staticproblemsthatmayrequireelementremoval,theprogressivedamageandfailuremodels(Chapter19,“ProgressiveDamageandFailure”)ortheGursonporousmetalplasticitymodel(“Porousmetalplasticity,”Section18.2.9)arerecommended.

Tensilefailuremodel

ThetensilefailuremodelcanbeusedinconjunctionwitheithertheMisesortheJohnson-Coo …… 此处隐藏：6267字，全部文档内容请下载后查看。喜欢就下载吧 ……