试验应力疲劳分析

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1、试验应力疲劳分析本文rtlyangxjO713贡献ppt文档可能在WAP端浏览体验不佳。建议您优先选择TXT,或下载源文件到本机查看。mFatigueAnalysisConceptsforGroundVehicleDurabilityTestingPage1mFatigue?WhatisFatigue??TheFatigueProcessinStructuralMetals・？AnalyticalLifePrediction:----Stress-Life・Strain-Life・Notches・VoridbleAmplitudeLoading・Page2mFatigu

2、e-AStandardDefinition"Theprocessofprogressivelocalizedpermanentstructuralchangeinamaterialsubjectedtoconditionsthatproducefluctuatingstressesandstrainsatsomepointorpointsandthatmayculminateincracksorcompletefractureafterasufficientnumberoffluctuations.”-ASTME-1823,StandardTerminologyRela

3、tingtoFatigueandFractureTesting・Page3mFatigue-KeyConcepts?Acyclicloadisrequired.?Fatigueisaprocessthatstartsonthefirstloadingcycle・？Fatiguedamageislocalized.?Fatiguedamageispermanentandirreversible・?Crackformationmayoccur・?Cracksmaygrowandcausefracture・Page4FatigueProcessSlipoccursinarea

4、sofconcentratedstress/strain・？Intrusions/extrusionsmaybeformedwhereslipbandsintersectsurface・?Slipbandsintensifyandcracksdevelopalongthem・?Dominantcrack(s)propagatethroughmultiplegrains・？Crackgrowthproceedsapproximatelyperpendiculartoappliedload・？Fractureoccurswhenremainingligamentcannot

5、supportload・Page5mFatigueProcessSlipBands:-Extrusionsandintrusionsmaydevelopatsurface・-Highlyconcentratedshearstrain.-Fatiguecracksforminslipbands・Page6mFatigueProcess?Slipbandsincoppersinglecrysta1.(Hoeppner)CrackPage7mFatigueProcessSlipbandprofiles,aluminumsinglecrysta1.(Mughrabi)Stage

6、I(shear)fatiguecrackinaslipband(coppersinglecrystal)・(Mughrabi)Page8mFatigueProcess(Hoeppner)Page9mInitiationandPropagationInitiationPropagationWhatisInitiation?FractureTimeLifespentdevelopingan^engineeringsize”crack・Lifetofirstdetectablecrack・Crackformation.Initiationisnotpreciselydefin

7、ed;thereisnostandarddefinition(e.g.ASTM)・WhatisPropagation?-Portionoflifespentgrowinganexistingcracktofinalfracture・Theboundarybetweeninitiationandpropagationisarbitrary,notphysica1.Page10mFatigueProcessFractureCrackSizeStressdominatedcrackgrowthLifeCrackformationphase(no