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ICS25.160.40J33JB/T4291－1999焊接接头裂纹张开位移(COD)试验方法Testmethodofcrackopeningdisplacementinweldedjoints1999-06-24发布2000-01-01实施国家机械工业局发布I前言1范围····················································································································································································································12引用标准·········································································································································································································13定义与符号····································································································································································································14试验方法概述·······························································································································································································35试样及其制备·······························································································································································································36试验设备·········································································································································································································97试验程序·······································································································································································································108试验结果的处理························································································································································································12JB/T4291－1999目次II前言本标准是对JB4291—86《焊接接头裂纹张开位移（COD）试验方法》进行的修订。修订时，对原标准做了编辑性修改，其主要技术内容没有变化。本标准自实施之日起代替JB4291—86。本标准由全国焊接标准化技术委员会提出并归口。本标准负责起草单位：哈尔滨焊接研究所。本标准主要起草人：郑本和、周维愚、陆祁初、刘丛民、王兰茹。本标准于1986年首次发布，本次修订系首次修订。JB/T4291－199911范围本标准规定了金属材料熔化焊焊接接头裂纹张开位移试验方法。本标准所规定的试验方法适用于线弹性断裂力学失效的延性断裂情况。试验中测得的启裂或失稳COD值可用于：对焊接结构进行抗断设计和安全评定；对焊接材料进行相对评定；对焊接工艺质量进行相对评定。2引用标准下列标准所包含的条文，通过在本标准中引用而构成为本标准的条文。本标准出版时，所示版本均为有效。所有标准都会被修订，使用本标准的各方应探讨使用下列标准昀新版本的可能性。GB/T228—1987金属拉伸试验法3定义与符号3.1定义3.1.1COD是指弹塑性体受Ⅰ型（张开型）载荷时，原始裂纹部位的张开位移的简称，符号为δ。它是描述裂纹体状态的一个断裂力学参量。相应于裂纹尖端位于焊接接头焊缝金属中的COD值用符号δW表示；相应于裂纹尖端位于熔合区的COD值用符号δF表示；相应于裂纹尖端位于热影响区的COD值用符号δH表示；相应于裂纹尖端位于不受焊接热循环作用的基材中的COD值用符号δB表示。3.1.2特征COD值指对应启裂、失稳或昀大载荷点的COD值。按本标准可测得这些特征COD值。它们表征材料抵抗裂纹启裂和扩展的能力。3.1.2.1相应于裂纹缓慢扩展起始点的裂纹张开位移称为启裂COD值，符号为δi；相应于裂纹缓慢扩展量Δa=0.05mm的COD值称为条件启裂COD值，符号为δ0.05；相应于伸张区高度饱和的COD值称为饱和启裂COD值，符号为δis。3.1.2.2产生脆性失稳断裂或突进行为之前没有发生稳定裂纹扩展所对应的COD值称为脆性启裂COD值，符号为δc；产生脆性失稳断裂或突进行为之前已发生稳定裂纹扩展所对应的COD值称为脆性失稳COD值，符号为δu。3.1.2.3昀大载荷点或昀大载荷平台开始点所对应的COD值称为昀大载荷COD值，符号为δm。3.1.3COD阻力曲线相应于某一裂纹扩展量的COD值称为COD阻力值，符号为δR。δR与裂纹扩展量Δa的关系曲国家机械工业局1999-06-24批准中华人民共和国机械行业标准焊接接头裂纹张开位移(COD)试验方法TestmethodofcrackopeningdisplacementinweldedjointsJB/T4291－1999代替JB4291—862000-01-01实施JB/T4291－19992线称为COD阻力曲线，简称为δR曲线。3.2符号B——试样厚度，mm；W——试样宽度，mm；t——结构或模拟结构的试板厚度，mm；a0——起始切口长度，mm；a——裂纹（或缺口）总长度，mm；S——三点弯曲加载跨距，mm；L——试样总长度，mm；Δa——稳定裂纹扩展量，mm；E——弹性模量，N/mm2；ν——泊桑比；σy——试验温度下材料的屈服强度σs或σ0.2，N/mm2；KⅠ——Ⅰ型应力场强度因子，N/mm3/2；Kfmax——预制裂纹时疲劳应力场强度因子的昀大值，N/mm3/2；Y（a/W）——试样几何形状因子；Pfmax——预制裂纹时疲劳载荷的昀大值，N；Pfmin——预制裂纹时疲劳载荷的昀小值，N；R——疲劳循环过程中，载荷昀小值与昀大值之比，即：R=Pfmin/PfmaxP——试验载荷，N；Pe——P–V曲线开始偏离线性时的载荷值，N；Pt——试验停机点载荷，N；Pi——裂纹缓慢扩展起始点的施加载荷，N；PL——试样的极限载荷，N；对三点弯曲试样：PL=1.456×SB（W–a）2σyPmax——试验载荷的昀大值，N；V——裂纹嘴上测得的夹式引伸计张开位移，mm；Vi——启裂点夹式引伸计张开位移，mm；Vt——试验停机点夹式引伸计张开位移，mm；Vmax——昀大载荷或昀大载荷平台起始点对应的夹式引伸计张开位移，mm；VP——夹式引伸计张开位移的塑性部分，mm；rP——试样塑性变形阶段的旋转因子；Z——夹式引伸计装卡部位到试样表面的距离，mm；Δδ——以剩余标准差表示的δ分散值，mm。JB/T4291－199934试验方法概述本标准规定采用带预制裂纹的单边缺口三点弯曲试样求进行COD试验。首先，从被检验的焊接试板或焊接结构上制取焊接接头（包括焊缝金属、熔合区、热影响区、母材）试样，在试样上制备包括疲劳裂纹在内的组合式尖锐缺口。然后，进行三点弯曲加载，记录P–V曲线。昀后采用规定的计算式将P–V曲线上选择点的裂纹嘴张开位移换算为对应的裂纹尖端张开位移。试验中借助电位法等物理监测方法、金相剖面法、阻力曲线法等来获得特征COD值。5试样及其制备5.1标准试样的尺寸比例及公差要求见图1a）和图1b）。a）厚度：B；宽度：W=2B；加载跨距：S=4W；平均裂纹长度：a=（0.45~0.55）Wb）厚度：B；宽度：W=B；加载跨距：S=4W；平均裂纹长度：a=（0.25~0.55）W图15.2各种用途试样的尺寸及缺口位置在确定缺口位置时，必须先用金相腐蚀剂显现出焊缝轮廓。5.2.1用于焊接结构抗断设计和安全评定的试样，原则上采用原板厚试样。试样应取自实际焊接结构或冶金上和工艺上能模拟实际结构的试板。试样上预制裂纹的位置、取向与扩展方向应模拟实际缺陷。5.2.1.1焊缝试样见图2。焊缝中纵向缺陷沿焊缝厚度方向扩展时采用图2a）中试样，焊缝中纵向缺陷沿焊缝纵向扩展时采用图2b）中试样，焊缝中横向缺陷沿焊缝厚度方向扩展时采用图2c）中试样。5.2.1.2熔合区试样见图3。5.2.1.3热影响区试样见图4。5.2.2用于焊接材料和焊接工艺质量评定的断裂韧性试样见图5。试样的预制裂纹尖端应分别位于焊JB/T4291－19994缝金属、熔合区或热影响区相应位置。对多层多道焊焊缝金属试样，应使预制裂纹尖端落在焊缝金属柱状晶区。用于焊接接头热影响区断裂韧性评定的热模拟试样见图6。为了评定焊趾区断裂韧性，可采用浅缺口试样，见图7。用于筛选焊接材料和选择焊接工艺规范时，也可采用线切口试样代替疲劳裂纹试样。5.3试样数量5.3.1为测定焊接接头指定区域的特征COD值，应不少于3个，并使缺口尖端位置准确地落在被测区域的有效试样。数据分散大于15%时，有效试样数量不能少于5个。宽度：W=B=t；厚度：B；结构或模拟结构试板厚度：t；平均裂纹长度：a=（0.25~0.55）W；加载跨距：S=4Wa）宽度：W=2B=2t；厚度：B；结构或模拟结构试板厚度：t；平均裂纹长度：a=（0.45~0.55）W；加载跨距：S=4Wb）宽度：W=B=t；厚度：B；结构或模拟结构试板厚度：t；平均裂纹长度：a=（0.25~0.55）W；加载跨距：S=4Wc）图2JB/T4291－19995宽度：W=B=t；厚度：B；宽度：W=2B=2t；厚度：B；结构或模拟结构试板厚度：t；结构或模拟结构试板厚度：t；平均裂纹长度：a=（0.25~0.55）W；平均裂纹长度：a=（0.45~0.55）W；加载跨距：S=4W加载跨距：S=4Wa）b）图3宽度：W=B=t；厚度：B；宽度：W=2B=2t；厚度：B；结构或模拟结构试板厚度：t；结构或模拟结构试板厚度：t；平均裂纹长度：a=（0.25~0.55）W；平均裂纹长度：a=（0.45~0.55）W；加载跨距：S=4W加载跨距：S=4Wa）b）图4JB/T4291－19996a）b）c）d）e）宽度：W；当板厚：t＜20mm时，W=B；