【英文标准名称】:StandardTestMethodforTensionTestingofStructuralAlloysinLiquidHelium
【原文标准名称】:液氦中结构合金抗拉试验的标准试验方法
【标准号】:ASTME1450-2009
【标准状态】:现行
【国别】:美国
【发布日期】:2009
【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】:E28.04
【标准类型】:(TestMethod)
【标准水平】:()
【中文主题词】:
【英文主题词】:adiabaticheating;cryogenicproperties(ofmaterials);cryostats;discontinuousyielding;liquidhelium;lowtemperaturetests;mechanicalproperties(ofmaterials);tensileproperties;tensiontest
【摘要】:Tensiontestsprovideinformationonthestrengthandductilityofmaterialsunderuniaxialtensilestresses.Thisinformationmaybeusefulforalloydevelopment,comparisonandselectionofmaterials,andqualitycontrol.Undercertaincircumstances,theinformationmayalsobeusefulfordesign.Theforce-timeandforce-extensionrecordsforalloystestedinliquidheliumusingdisplacementcontrolareserrated(1).Serrationsareformedbyrepeatedburstsofunstableplasticflowandarrests.Theunstableplasticflow(discontinuousyielding)isafree-runningprocessoccurringinlocalizedregionsofthereducedsectionathigherthannominalratesofstrainwithinternalspecimenheating.Examplesofserratedstress-straincurvesforatypicalausteniticstainlesssteelwithdiscontinuousyieldingareshowninFig.2.Aconstantspecimentemperaturecannotbemaintainedatalltimesduringtestsinliquidhelium.Thespecimentemperatureatlocalregionsinthereducedsectionrisestemporarilyabove4Kduringeachdiscontinuousyieldingevent(seeFig.2),owingtoadiabaticheat.Thenumberofeventsandthemagnitudeoftheassociateddropsinmagnitudeofforceareafunctionofthematerialcompositionandotherfactorssuchasspecimensizeandtestspeed.Typically,alteringthemechanicaltestvariablescanmodifybutnoteliminatethediscontinuousyielding(2-4).Therefore,tensilepropertymeasurementsofalloysinliquidhelium(especiallytensilestrength,elongation,andreductionofarea)lacktheusualsignificanceofpropertymeasurementsatroomtemperaturewheredeformationismorenearlyisothermalanddiscontinuousyieldingtypicallydoesnotoccur.Thestress-strainresponseofamaterialtestedinliquidheliumdependsonwhetherforcecontrolordisplacementcontrolisused(3).Crossheaddisplacementcontrolisspecifiedinthisstandardsincethegoalismaterialcharacterizationbyconventionalmethods.Thepossibilityofadifferentandlessfavorablematerialresponsemustbetakenintoaccountwhendataareusedfordesigninactualapplicationssubjecttoforce-controlledconditions.FIG.2TypicalEngineeringStress-StrainCurvesandSpecimenTemperatureHistories,atFourDifferentNominalStrainRates,forAISI304LStainlessSteelTestedinLiquidHelium(4)1.1Thistestmethoddescribesproceduresforthetensiontestingofstructuralalloysinliquidhelium.TheformatissimilartothatofotherASTMtensionteststandards,butthecontentsincludemodificationsforcryogenictestingwhichrequiresspecialapparatus,smallerspecimens,andconcernforserratedyielding,adiabaticheating,andstrain-rateeffects.1.2Toconductatensiontestbythisstandard,thespecimeninacryostatisfullysubmergedinnormalliquidhelium(HeI)andtestedusingcrossheaddisplacementcontrolatanominalstrainrateof10x2212;3sx2212;1orless.Testsusingforcecontrolorhighstrainratesarenotconsidered.1.3Thisstandardspecifiesmethodsforthemeasurementofyieldstrength,tensilestrength,elongation,andreductionofarea.ThedeterminationoftheelasticmodulusistreatedinTestMethodE111.Note18212;Theboilingpointofnormalliquidhelium(HeI)atsealevelis4.2K(x2212;269x00B0;Corx2212;452.1x00B0;For7.6x00B0;R).Itdecreaseswit......
【中国标准分类号】:H22
【国际标准分类号】:
【页数】:9P.;A4
【正文语种】:英语