czm内聚力模型ppt课件.ppt

TheoreticalandComputationalAspectsofCohesiveZoneModeling NAMASCHANDRADepartmentofMechanicalEngineeringFAMU FSUCollegeofEngineeringFloridaStateUniversityTallahassee Fl 32310 1 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 2 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 FractureMechanics Linearsolutionsleadstosingularfields difficulttoevaluateFracturecriteriabasedonNon lineardomain solutionsarenotuniqueAdditionalcriteriaarerequiredforcrackinitiationandpropagationBasicbreakdownoftheprinciplesofmechanicsofcontinuousmediaDamagemechanics caneffectivelyreducethestrengthandstiffnessofthematerialinanaveragesense butcannotcreatenewsurface 3 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 CZMcancreatenewsurfaces Maintainscontinuityconditionsmathematically despitethephysicalseparation CZMrepresentsphysicsofthefractureprocessattheatomicscale Itcanalsobeperceivedatthemeso scaleastheeffectofenergydissipationmechanisms energydissipatedbothintheforwardandthewakeregionsofthecracktip Usesfractureenergy obtainedfromfracturetests asaparameterandisdevoidofanyad hoccriteriaforfractureinitiationandpropagation Eliminatessingularityofstressandlimitsittothecohesivestrengthofthethematerial Itisanidealframeworktomodelstrength stiffnessandfailureinanintegratedmanner Applications geomaterials biomaterials concrete metallics composites 4 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 5 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 ConceptualFrameworkofCohesiveZoneModelsforinterfaces 6 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 Molecularforceofcohesionactingneartheedgeofthecrackatitssurface regionII Theintensityofmolecularforceofcohesion f isfoundtovaryasshowninFig a Theinteratomicforceisinitiallyzerowhentheatomicplanesareseparatedbynormalintermoleculardistanceandincreasestohighmaximumafterthatitrapidlyreducestozerowithincreaseinseparationdistance EisYoung smodulusandissurfacetension Barenblatt G I 1959 PMM 23 p 434 Barenblatt 1959 wasfirsttoproposetheconceptofCohesivezonemodeltobrittlefracture 7 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 ForDuctilemetals steel CohesivestressintheCZMisequatedtoyieldstressYAnalyzedforplasticzonesizeforplatesundertensionLengthofyieldingzone s theoreticalcracklength a andappliedloading T arerelatedintheform Dugdale D S 1960 J Mech Phys Solids 8 p 100 8 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 ThetheoryofCZMisbasedonsoundprinciples HoweverimplementationofmodelforpracticalproblemsgrewexponentiallyforpracticalproblemswithuseofFEMandadventoffastcomputing Modelhasbeenrecastasaphenomenologicaloneforanumberofsystemsandboundaryvalueproblems Thephenomenologicalmodelscanmodeltheseparationprocessbutnottheeffectofatomicdiscreteness Hillerborgetal 1976Ficticiouscrackmodel concreteBazantetal 1983crackbandtheory concreteMorganetal 1997earthquakerupturepropagation geomaterialPlanasetal 1991 concreteEisenmenger 2001 stonefragm entationsqueezing byevanescentwaves brittle biomaterialsAmruthrajetal 1995 composites Grujicic 1999 fracturebeha viorofpolycrystalline bicrystalsCostanzoetal 1998 dynamicfr Ghosh2000 Interfacialdebo nding compositesRahulkumar2000viscoelasticfracture polymersLiechti2001Mixed mode time depend rubber metaldebondingRavichander 2001 fatigue Tevergaard1992particle matrixinterfacedebondingTvergaardetal1996elastic plasticsolid ductilefrac metalsBrocks2001crackgrowthinsheetmetalCamachobiomaterials 9 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 CZMessentiallymodelsfractureprocesszonebyalineoraplaneaheadofthecracktipsubjectedtocohesivetraction Theconstitutivebehaviorisgivenbytraction displacementrelationship obtainedbydefiningpotentialfunctionofthetype where arenormalandtangentialdisplacementjump Theinterfacetractionsaregivenby y 10 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 11 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 12 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 Whatistherelationshipbetweenthephysics mechanicsoftheseparationprocessandshapeofCZM Thereareasmanyshapes equationsastherearenumberofinterfaceproblemssolved WhatistherelationshipbetweenCZMandfracturemechanicsofbrittle semi brittleandductilematerials WhatistheroleofscalingparameterinthefidelityofCZMtomodelinterfacebehavior Whatisthephysicalsignificanceof ShapeofthecurveC tmaxandinterfacestrength Separationdistance sepandCOD Areaunderthecurve workoffracture fracturetoughnessG localandglobal CriticalIssuesintheapplicationofCZMtointerfacemodels 13 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 CZMisanexcellenttoolwithsoundtheoreticalbasisandcomputationalease Lackspropermechanicsandphysicsbasedanalysisandevaluation Alreadywidelyusedinfracture fragmentation failure 14 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 15 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 16 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 17 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 Constructsymmetrictiltboundaries STDB byrotatingasinglecrystal reflection PeriodicboundaryconditioninXdirectionRestrainfewlayersinlowercrystalApplybodyforceontopcrystal 18 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 AsmallportionofCSLgrainbounarybeforeAndafterapplicationoftangentialforce ShetC LiH ChandraN InterfacemodelsforGBslidingandmigrationMATERSCIFORUM357 3 577 5852001 19 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 AsmallportionofCSLgrainboundarybeforeAndafterapplicationofnormalforce 20 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 Summarycompletedebondingoccurswhenthedistanceofseparationreachesavalueof2to3 For 9bicrystaltangentialworkofseparationalongthegrainboundaryisoftheorder3andnormalworkofseparationisoftheorder2 6 For 3 bicrystal theworkofseparationrangesfrom1 5to3 7 Roseetal 1983 havereportedthattheadhesiveenergy workofseparation foraluminumisoftheorder0 5andtheseparationdistance2to3Measuredenergytofracturecopperbicrystalwithrandomgrainboundaryisoftheorder54andfor 11copperbicrystaltheenergytofractureismorethan8000 ImplicationsThenumericalvalueofthecohesiveenergyisverylowwhencomparedtotheobservedexperimentalresultsAtomisticsimulationgivesonlysurfaceenergyignoringtheinelasticenergiesduetoplasticityandothermicroprocesses Itshouldalsobenotedthattheexper imentalvalueoffractureenergyincludestheplasticworkinadditiontoworkofseparation J RRiceandJ SWang 1989 21 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 22 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 Energybalanceandeffectofplasticityintheboundingmaterial 23 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 Motivation ItisperceivedthatCZMrepresentsthephysicalseparationprocess Asseenfromatomistics fractureprocesscomprisesmostlyofinelasticdissipativeenergies Therearemanyinelasticdissipativeprocessspecifictoeachmaterialsystem someoccurwithinFPZ andsomeintheboundingmaterial Howtheenergyflowtakesplaceundertheexternalloadingwithinthecohesivezoneandneighboringboundingmaterialnearthecracktip Whatisthespatialdistributionofplasticenergy Istherealinkbetweenmicromechanicsprocessesofthematerialandcurve 24 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 Plasticityvs otherDissipationMechanisms Sinceboundingmaterialhasitsowninelasticconstitutiveequation whatistheproportionofenergydissipationwithinthatdomainandfractureregiongivenbyCZM Roleofplasticityintheboundingmaterialisclearlyunique andcannotbeassignedtoCZM 25 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 Al2024 T3alloyTheinputenergyinthecohesivemodelarerelatedtotheinterfacialstressandcharacteristicdisplacementasTheinputenergyisequatedtomaterialparameterBasedonthemeasuredfracturevalue Cohesivezoneparametersofaductilematerial 26 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 E 72GPa 0 33 Stressstraincurveisgivenby where andfractureparameter Materialmodelfortheboundingmaterial Elasto plasticmodelforAl2024 T3 27 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 Geometryandboundary loadingconditions a 0 025m b 0 1m h 0 1m 28 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 Finiteelementmesh 28189nodes 24340planestrain4nodeelements 7300cohesiveelements widthofelementalongthecrackplanis m 29 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 Globalenergydistribution areconfinedtoboundingmaterial 30 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 Globalenergydistribution continued Analysiswithelasto plasticmaterialmodel 31 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 WhatarethekeyCZMparametersthatgoverntheenergetics 32 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 Globalenergydistribution continued Variationofcohesiveenergyandplasticenergyforvariousratios 2 3 4 33 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 Relationbetweenplasticworkandcohesivework 34 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 VariationofNormalTractionalongtheinterface Thelengthofcohesivezoneisalsoaffectedbyratio Thereisadirectcorrelationbetweentheshapeofthetraction displacementcurveandthenormaltractiondistributionalongthecohesivezone Forlowerratiosthetraction separationcurveflattens thistendtoincreasetheoverallcohesivezonelength 35 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 Local spatialEnergyDistribution 36 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 VariationofCohesiveEnergy ThevariationofCohesiveEnergyintheWakeandForwardregionasthecrackpropagates ThenumbersindicatetheCohesiveElementPatchnumbersFallingJustBelowthebindingelementpatches 37 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 VariationofElasticEnergy VariationofElasticEnergyinVariousPatchofElementsasaFunctionofCrackExtension ThenumbersindicatePatchnumbersstartingfromInitialCrackTip Considerableelasticenergyisbuiltuptillthepeakofcurveisreachedafterwhichthecracktipadvances AfterpassingC thecohesiveelementsnearthecracktipareseparatedandtheelementsinthispatchbecomesapartofthewake Atthisstage thevaluesofnormaltractionreducesfollowingthedownwardslopeofcurvefollowingwhichthestressinthepatchreducesaccompaniedbyreductioninelasticstrainenergy Thereductioninelasticstrainenergyisusedupindissipatingcohesiveenergytothosecohesiveelementsadjoiningthispatch Theinitialcracktipisinherentlysharpleadingtohighlevelsofstressfieldsduetowhichhigherenergyforpatch1Cracktipbluntsforadvancingcracktipleadingtoalowerlevelsofstress resultinginreducedenergylevelinotherpatches 38 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 Variationofdissipatedplasticenergyinvariouspatchedasafunctionofcrackextension Thenumberindicatepatchnumbersstartingfrominitialcracktip 39 课件部分内容来源于网络 如有异议侵权的话可以联系删除 可编辑版 VariationofPlasticWork VariationofPlasticworkandElasticworkinvariouspatchofelementsalongtheinterfaceforthecaseof Thenumbersindicatesth