【英文标准名称】:StandardPracticeforSizeScalingofTensileStrengthsUsingWeibullStatisticsforAdvancedCeramics
【原文标准名称】:高级陶瓷用Weibull统计拉伸强度的尺寸缩放比例用标准实施规程
【标准号】:ASTMC1683-2008e1
【标准状态】:现行
【国别】:
【发布日期】:2008
【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】:C28.01
【标准类型】:(Practice)
【标准水平】:()
【中文主题词】:高级陶瓷;经过检查的数据;有效区域;有效体积;金属断面的显微镜观察;断裂原因;尺寸缩放比例;强度;Weibull特性强度;Weibull模数;Weibull尺度参数;Weibull统计
【英文主题词】:advancedceramics;censoreddata;effectivearea;effectivevolume;fractography;fractureorigin;sizescaling;strength;Weibullcharacteristicstrength;Weibullmodulus;Weibullscaleparameter;Weibullstatistics
【摘要】:Advancedceramicsusuallydisplayalinearstress-strainbehaviortofailure.Lackofductilitycombinedwithflawsthathavevarioussizesandorientationstypicallyleadstolargescatterinfailurestrength.Strengthisnotadeterministicpropertybutinsteadreflectstheintrinsicfracturetoughnessandadistribution(sizeandorientation)offlawspresentinthematerial.Thisstandardisapplicabletobrittlemonolithicceramicswhichfailasaresultofcatastrophicpropagationofflaws.PossiblerisingR-curveeffectsarealsonotconsidered,butareinherentlyincorporatedintothestrengthmeasurements.Two-andthree-parameterformulationsexistfortheWeibulldistribution.Thisstandardisrestrictedtothetwo-parameterformulation.Tensileandflexuraltestspecimensarethemostcommonlyusedtestconfigurationsforadvancedceramics.Ring-on-ringandpressure-on-ringtestspecimenswhichhavemulti-axialstatesofstressarealsoincluded.Closed-formsolutionsfortheeffectivevolumeandeffectivesurfacesandtheWeibullmaterialscalefactorareincludedfortheseconfigurations.ThispracticealsoincorporatessizescalingmethodsforC-ringtestspecimensforwhichnumericalapproachesarenecessary.AgenericapproachforarbitraryshapedtestspecimensorcomponentsthatutilizesfiniteelementanalysesispresentedinAnnexA3.Thefractureoriginsoffailedtestspecimenscanbedeterminedusingfractographicanalysis.Thespatialdistributionofthesestrengthcontrollingflawscanbeoveravolumeoranarea(asinthecaseofsurfaceflaws).Thisstandardallowsfortheconversionofstrengthparametersassociatedwitheithertypeofspatialdistribution.Lengthscalingforstrengthcontrollingflawslocatedalongedgesofatestspecimenisnotcoveredinthispractice.ThescalingofstrengthwithsizeinaccordancewiththeWeibullmodelisbasedonseveralkeyassumptions(5).Itisassumedthatthesamespecificflawtypecontrolsstrengthinthevariousspecimenconfigurations.Itisassumedthatthematerialisuniform,homogeneous,andisotropic.Ifthematerialisacomposite,itisassumedthatthecompositephasesaresufficientlysmallthatthestructurebehavesonanengineeringscaleasahomogeneousandisotropicbody.Thecompositemustcontainasufficientquantityofuniformly-distributed,randomly-oriented,reinforcingelementssuchthatthematerialiseffectivelyhomogeneous.Whisker-toughenedceramiccompositesmayberepresentativeofthistypeofmaterial.Thispracticeisalsoapplicabletocompositeceramicsthatdonotexhibitanyappreciablebilinearornonlineardeformationbehavior.ThisstandardandtheconventionalWeibullstrengthscalingwithsizemaynotbesuitableforcontinuousfiber-reinforcedcompositeceramics.Thematerialisassumedtofractureinabrittlefashion,aconsequenceofstresscausingcatastrophicpropagationofflaws.Thematerialisassumedtobeconsistent(batchtobatch,daytoday,etc.).ItisassumedthatthestrengthdistributionfollowsaWeibulltwoparameterdistribution.Itisassumedthateachtestpiecehasastatisticallysignificantnumberofflawsandthattheyarerandomlydistributed.Itisassumedthattheflawsaresmallrelativetothespecimencrosssectionsize.Ifmultipleflawtypesarepresentandcontrolstrength,thenstrengthsmayscaledifferentlyforeachflawtype.ConsultPracticeC1239andtheexamplein9.1forfurtherguidanceonhowtoapplycensoredstatisticsinsuchcases.Itisalsoassumedthatthespecimenstressstateandthemaximumstressareaccuratelydetermined.Itisassumedthattheactualdatafromasetoffracturedspecimensareaccurateandprecise.(SeeTerminology