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1、試驗應力疲勞分析本文由yangxj0713貢獻ppt文檔可能在WAP端瀏覽體驗不佳。建議您優(yōu)先選擇TXT，或下載源文件到本機查看。mFatigueAnalysisConceptsforGroundVehicleDurabilityTestingPage1mFatigue?WhatisFatigue??TheFatigueProcessinStructuralMetals.?AnalyticalLifePrediction:––––Stress-Life.Strain-Life.Notches.VariableAmplitudeLoading.Page2mF
2、atigue–AStandardDefinition“Theprocessofprogressivelocalizedpermanentstructuralchangeinamaterialsubjectedtoconditionsthatproducefluctuatingstressesandstrainsatsomepointorpointsandthatmayculminateincracksorcompletefractureafterasufficientnumberoffluctuations.”–ASTME-1823,StandardTer
3、minologyRelatingtoFatigueandFractureTesting.Page3mFatigue–KeyConcepts?Acyclicloadisrequired.?Fatigueisaprocessthatstartsonthefirstloadingcycle.?Fatiguedamageislocalized.?Fatiguedamageispermanentandirreversible.?Crackformationmayoccur.?Cracksmaygrowandcausefracture.Page4mFatiguePro
4、cessSlipoccursinareasofconcentratedstress/strain.?Intrusions/extrusionsmaybeformedwhereslipbandsintersectsurface.?Slipbandsintensifyandcracksdevelopalongthem.?Dominantcrack(s)propagatethroughmultiplegrains.?Crackgrowthproceedsapproximatelyperpendiculartoappliedload.?Fractureoccurs
5、whenremainingligamentcannotsupportload.Page5mFatigueProcessSlipBands:–Extrusionsandintrusionsmaydevelopatsurface.–Highlyconcentratedshearstrain.–Fatiguecracksforminslipbands.Page6mFatigueProcess?Slipbandsincoppersinglecrystal.(Hoeppner)CrackPage7mFatigueProcessSlipbandprofiles,alu
6、minumsinglecrystal.(Mughrabi)StageI(shear)fatiguecrackinaslipband(coppersinglecrystal).(Mughrabi)Page8mFatigueProcess(Hoeppner)Page9mInitiationandPropagationInitiationPropagationWhatisInitiation?––––FractureTimeLifespentdevelopingan“engineeringsize”crack.Lifetofirstdetectablecrack
7、.Crackformation.Initiationisnotpreciselydefined;thereisnostandarddefinition(e.g.ASTM).WhatisPropagation?–Portionoflifespentgrowinganexistingcracktofinalfracture.Theboundarybetweeninitiationandpropagationisarbitrary,notphysical.Page10mFatigueProcessFractureCrackSizeStressdominatedc
8、rackgrowthLifeCrackformationphase
