【英文标准名称】:StandardTestMethodforDeterminationofReferenceTemperature,To,forFerriticSteelsintheTransitionRange
【原文标准名称】:确定铁素体钢在转变范围内的基准温度的标准试验方法
【标准号】:ASTME1921-2010e1
【标准状态】:现行
【国别】:美国
【发布日期】:2010
【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】:E08.07
【标准类型】:(TestMethod)
【标准水平】:()
【中文主题词】:
【英文主题词】:Ferriticsteel;Fracturetesting--metals/alloys;Referencetemperature
【摘要】:Fracturetoughnessisexpressedintermsofanelastic-plasticstressintensityfactor,KJc,thatisderivedfromtheJ-integralcalculatedatfracture.Ferriticsteelsareinhomogeneouswithrespecttotheorientationofindividualgrains.Also,grainboundarieshavepropertiesdistinctfromthoseofthegrains.Bothcontaincarbidesornonmetallicinclusionsthatcanactasnucleationsitesforcleavagemicrocracks.Therandomlocationofsuchnucleationsiteswithrespecttothepositionofthecrackfrontmanifestsitselfasvariabilityoftheassociatedfracturetoughness(13).Thisresultsinadistributionoffracturetoughnessvaluesthatisamenabletocharacterizationusingstatisticalmethods.DistributionsofKJcdatafromreplicatetestscanbeusedtopredictdistributionsofKJcfordifferentspecimensizes.Theoreticalreasoning(9),confirmedbyexperimentaldata,suggeststhatafixedWeibullslopeof4appliestoalldatadistributionsand,asaconsequence,standarddeviationondatascattercanbecalculated.DatadistributionandspecimensizeeffectsarecharacterizedusingaWeibullfunctionthatiscoupledwithweakest-linkstatistics(14).Anupperlimitonconstraintlossandalowerlimitontesttemperaturearedefinedbetweenwhichweakest-linkstatisticscanbeused.TheexperimentalresultscanbeusedtodefineamastercurvethatdescribestheshapeandlocationofmedianKJctransitiontemperaturefracturetoughnessfor1Tspecimens(15).Thecurveispositionedontheabscissa(temperaturecoordinate)byanexperimentallydeterminedreferencetemperature,To.Shiftsinreferencetemperatureareameasureoftransitiontemperaturechangecaused,forexample,bymetallurgicaldamagemechanisms.ToleranceboundsonKJccanbecalculatedbasedontheoryandgenericdata.Foraddedconservatism,anoffsetcanbeaddedtotoleranceboundstocovertheuncertaintyassociatedwithestimatingthereferencetemperature,To,fromarelativelysmalldataset.FromthisitispossibletoapplyamarginadjustmenttoTointheformofareferencetemperatureshift.Forsomematerials,particularlythosewithlowstrainhardening,thevalueofTomaybeinfluencedbyspecimensizeduetoapartiallossofcrack-tipconstraint(5).Whenthisoccurs,thevalueofTomaybelowerthanthevaluethatwouldbeobtainedfromadatasetofKJcvaluesderivedusinglargerspecimens.1.1Thistestmethodcoversthedeterminationofareferencetemperature,To,whichcharacterizesthefracturetoughnessofferriticsteelsthatexperienceonsetofcleavagecrackingatelastic,orelastic-plasticKJcinstabilities,orboth.Thespecifictypesofferriticsteels(3.2.1)coveredarethosewithyieldstrengthsrangingfrom275to825MPa(40to120ksi)andweldmetals,afterstress-reliefannealing,thathave10%orlessstrengthmismatchrelativetothatofthebasemetal.1.2Thespecimenscoveredarefatigueprecrackedsingle-edgenotchedbendbars,SE(B),andstandardordisk-shapedcompacttensionspecimens,C(T)orDC(T).Arangeofspecimensizeswithproportionaldimensionsisrecommended.Thedimensiononwhichtheproportionali......
【中国标准分类号】:H42
【国际标准分类号】:77_040_10
【页数】:22P.;A4
【正文语种】:英语