仪器压痕法断裂韧性检测方法

Fast&PreciseSolutionsforQuality&ReliabilityEvaluationofFractureToughnessofMaterialsUsingInstrumentedIndentationTechnique:Ductile/BrittleFractureModels2013.08.30.WonJeJoContentsIntroductionIndentationFractureToughnessModels-Brittlefracturemodel-DuctilefracturemodelVerificationoftheModels-ComparisonbetweenfracturetestresultsandIITresults-ApplicationsatlowtemperatureBasicconceptofindentationfracturetoughnessFast&PreciseSolutionsforQuality&ReliabilityFracturetestCrackpropagationandfractureIndenterIITNocrackandnofractureIssueofindentationfracturetoughnessWhatisacorrelationbetweenfracturetestandIIT?Inthecaseofmetals,2Fast&PreciseSolutionsforQuality&ReliabilityConstrainteffectaheadofacracktipPlasticregionconstrainedbyelasticregionbeneathanindenterSimilarconstrainteffect3Fast&PreciseSolutionsforQuality&ReliabilityR=250mIndenter[Material:APIX70]loadingConstrainteffect0.00.10.20.30.40.50.601234563.0---y=3.01177[1-exp{-4.57486(x+0.31229)}]tmaxV/Vmax0.00.10.20.30.40.50.601234563.2---y=3.29831[1-exp{-3.65099(x+0.27357)}]tmaxhmax/R2.13.22.33.0TriaxialityofcracktipTriaxialityofindentationSENBIndentation4Fast&PreciseSolutionsforQuality&ReliabilityIndentationfracturetoughness)1(2EJKCJCAnalogoussituation?JCK5Fast&PreciseSolutionsforQuality&ReliabilityEnergyconcept)1(2EJKCJCCJ=RequiredenergyforcrackpropagationEquivalentfractureenergyinIndentationAnalysisofindentationprocess6Fast&PreciseSolutionsforQuality&ReliabilityIndentationprocessFormationofaplasticzonetothesurface7Fast&PreciseSolutionsforQuality&ReliabilityFormationofafully-developedplasticzone(c/aisconstant)Expansionofplasticzone(c/aincrease)cacaAssumptionOnsetofformationofafully-developedplasticzone=Maximumstrainenergybeneaththeindenter≈Formationofequivalentfractureenergyh*8c/ahh*Fast&PreciseSolutionsforQuality&ReliabilityBrittlematerialsDuctilematerialsFracturesurfaceDeformationRelativelylittleornodeformationLargeplasticdeformationCriterionStresscontrolledcriticalfracturestressatthecracktip(sf)Straincontrolledcriticalfracturestrainatthecracktip(ef)FormationoffractureenergyWhenstressreachedcriticalfracturestressWhenstrainreachedcriticalfracturestrainFractureBehavior9BrittleFractureModelDuctileFractureModelFast&PreciseSolutionsforQuality&ReliabilityBrittleFractureModel10Fast&PreciseSolutionsforQuality&ReliabilityCriterion11L(kgf)hmax(m)Criticalindentationdepth(h*)cmmppεrrCriticalstress(pressure)ath*CriterionFast&PreciseSolutionsforQuality&ReliabilityAssumptionOnsetofformationtoafully-developedplasticzone=FormationofEquivalentfractureenergydtdctimesizezoneplasticfinalexpansionofRateconstant/acdtdadtdcexpansioncoreofrate;dtdazoneplasticdeveloped-fully12Fast&PreciseSolutionsforQuality&ReliabilityApplicationofindentationtheoriesStep1Yieldingrightoutsidethecontactarea→FormationofaplasticzonetothesurfaceeorycontactthelasticHertzStep2Expansionoftheplasticzone→Formationoffully-developedplasticzonetheory)plastic-(elasticmodelcavityExpandingcah*13Fast&PreciseSolutionsforQuality&ReliabilityHertzelasticcontacttheoryStressoutsidethecontactarea(r≥a)m22rpr2a)21(ss0zsWhenaradialstressattheedgeofthecontactarea(r=a)satisfiedyieldingcriterionmrp221sByVonMises’yieldcriterionysymCps114Fast&PreciseSolutionsforQuality&ReliabilityExpandingcavitymodel(E-Ptheory)Stresswithinplasticzone(a≤r≤c)rips31)ln(2rcyyssss32)ln(2rcyrssysiysrpacsssln232Changeofthecorepressure(r=a)untilformingthefully-developedplasticzone1ac2CacbyK.E.Puttick(1977)imppysiacpsln23215coreFast&PreciseSolutionsforQuality&ReliabilityCriterionofequivalentfractureenergyStep1ysfcmCpsmymcmpppcmpThetotalpressurerequiredforequivalentfractureenergy,Step2iympp16Fast&PreciseSolutionsforQuality&ReliabilityFracturetoughnessforbrittlematerial020406080050010001500PcmIndentationdepth(m)h*Indentationmeanpressure(kgf/m2))1(2EwKfJCPm-hcurve0204060801001201401600102030405060L(kgf)hmax(m)Indentationload-depthcurve2cmaxmaLp-Meancontactpressureateachunloadingdepth*0hcfdhALw(1)Indentationtesting(6)Indentationfracturetoughness(KJC)(2)Measuringσys&DeterminingPmc-σysfromanalyzingL-hcurve(3)FittingPm-hcurveysfcmCps-(4)Determiningh*-InsertingdeterminedPmcintoPm-hcurve(5)Equivalentfractureenergyuntilh*17Fast&PreciseSolutionsforQuality&ReliabilityDuctileFractureModel18Fast&PreciseSolutionsforQuality&ReliabilityCriterion19L(kgf)hmax(m)Criticalindentationdepth(h*)crreeεrrCriticalstrainath*CriterionFast&PreciseSolutionsforQuality&Reliability20Criticalstrainath*CriteriontensionuniaxialinstrainfractureceAbsorbedstrainenergyuntilfracturestrain=Toughness(tensileenergy)Fast&PreciseSolutionsforQuality&ReliabilityAssumptionElasticenergyreleasedduetothecrackgrowthisequaltotheamountofplasticworkaheadofthecracktip.JEKG221[PeelandFrosyth,1973]PlasticworkdoneperunitareaTpUrW2r:theradiusoftheplasticzoneUT:plasticworkdoneperunitvolumeForsmallscaleyielding,Elasticenergyreleasedperunitarea〓)1(2)1()1(222EUrEWEJKTcpCJC21Fast&PreciseSolutionsforQu