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【英文标准名称】:StandardTestMethodforMeasurementofCreepCrackGrowthTimesinMetals
【原文标准名称】:测量金属蠕变开裂增长次数的标准试验方法
【标准号】:ASTME1457-2007e2
【标准状态】:现行
【国别】:美国
【发布日期】:2007
【实施或试行日期】:
【发布单位】:美国材料与试验协会(US-ASTM)
【起草单位】:E08.06
【标准类型】:(TestMethod)
【标准水平】:()
【中文主题词】:
【英文主题词】:
【摘要】:CreepcrackgrowthrateexpressedasafunctionofthesteadystateC*orKcharacterizestheresistanceofamaterialtocrackgrowthunderconditionsofextensivecreepdeformationorunderbrittlecreepconditions.Backgroundinformationontherationaleforemployingthefracturemechanicsapproachintheanalysesofcreepcrackgrowthdataisgivenin(8,10,27-32).Aggressiveenvironmentsathightemperaturescansignificantlyaffectthecreepcrackgrowthbehavior.Attentionmustbegiventotheproperselectionandcontroloftemperatureandenvironmentinresearchstudiesandingenerationofdesigndata.ExpressingCCItime,t0.2andCCGrate,da/dtasafunctionofanappropriatefracturemechanicsrelatedparameter,asdiscussedin11.8generallyprovidesresultsthatareindependentofspecimensizeandplanargeometryforthesamestressstateatthecracktipfortherangeofgeometriesandsizespresentedinthisdocument(seeAnnexA1).Thus,theappropriatecorrelationwillenableexchangeandcomparisonofdataobtainedfromavarietyofspecimenconfigurationsandloadingconditions.Moreover,thisfeatureenablescreepcrackgrowthdatatobeutilizedinthedesignandevaluationofengineeringstructuresoperatedatelevatedtemperatureswherecreepdeformationisaconcern.Theconceptofsimilitudeisassumed,implyingthatcracksofdifferingsizessubjectedtothesamenominalC*(t),Ct,orKwilladvancebyequalincrementsofcrackextensionperunittime,providedtheconditionsforthevalidityforthespecificcrackgrowthraterelatingparameteraremet.See11.7fordetails.Theeffectsofcracktipconstraintarisingfromvariationsinspecimensize,geometryandmaterialductilitycaninfluencet0.2andda/dt.Forexample,crackgrowthratesatthesamevalueofC*(t),Ctincreep-ductilematerialsgenerallyincreaseswithincreasingthickness.Itisthereforenecessarytokeepthecomponentdimensionsinmindwhenselectingspecimenthickness,geometryandsizeforlaboratorytesting.Differentgeometriesasmentionedin1.1.6mayhavedifferentsizerequirementsforobtaininggeometryandsizeindependentcreepcrackgrowthratedata.Itisthereforenecessarytoaccountforthesefactorswhencomparingda/dtdatafordifferentgeometriesorwhenpredictingcomponentlifeusinglaboratorydata.Forthesereasons,thescopeofthisstandardisrestrictedtotheuseofspecimensshowninAnnexA1andthevalidationcriteriaforthesespecimensarespecifiedin11.2.3and11.7.HoweverifspecimensotherthantheC(T)geometryareusedforgeneratingcreepcrackgrowthdata,thentheda/dtdataobtainedshould,ifpossible,becomparedagainsttestdataderivedfromthestandardC(T)testsinordertovalidatethedata.CreepcrackshavebeenobservedtogrowatdifferentratesatthebeginningoftestscomparedwiththeratesatequivalentC*(t),CtorKvaluesforcracksthathavesustainedpreviouscreepcrackextension(9,10).Thisregionisidentifiedasx2018;tailx2019;.Thedurationofthistransientcondition,x2018;tailx2019;,varieswithmaterialandinitiallyapplie..........
【中国标准分类号】:H22
【国际标准分类号】:77_040_10
【页数】:24P.;A4
【正文语种】:英语