The concept of brittle crack arrest has recently become an internationally focused issue for container ships. The International Association of Classification Society (IACS) also prescribed the unified requirement (UR) for brittle crack arrest design, and brittle crack arrest design has been internationally authorized. As one of the methods to evaluate brittle crack arrestability, the crack arrest temperature (CAT) concept, by isothermal crack arrest test, has been proposed since the 1990s. The concept has been applied mainly for tank design. However, no standard has been specified to describe the detailed evaluation procedure. This means that only limited organizations can evaluate CAT and it is considered to be a problem when arrest evaluation is mandated as an international standard. In the background of such circumstances, Japanese research groups including the Japan Welding Engineering Society (JWES) and Nippon Kaiji Kyokai (ClassNK) started the standardization for CAT test in 2016. In the research programme, various aspects of control factors have been investigated based on the test results from many experiments and numerical calculations. The CAT test shall include the embrittled zone to initiate a brittle crack. Either electron beam (EB) line remelting or a local temperature gradient (LTG) can be applied to the embrittled zone. Even if we focus on EB welding only, welding defects in the embrittled zone can be an influencing factor. In this report, we investigate the effects of residual stress by EB welding on the crack driving force, which is quantified as the K value using a 3D finite element method (FEM). As a result, we confirmed the existence of the residual stress which cannot be ignored that is formed on the surface of the EB-welded portion; however, the influence of that on the K value is considered to be small if the CAT test conditions can sufficiently secure the arrest crack length. This result shows that the driving force at the arrested point in the CAT test can be simply evaluated by the LEFM formula without consideration of the residual stress of the EB weld for embrittlement.

中文翻译：

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EB焊缝残余应力对裂纹止裂温度（CAT）的影响

脆性裂纹止裂的概念最近已成为集装箱船的国际关注焦点。国际船级社协会（IACS）还规定了脆性裂纹止裂设计的统一要求（UR），并且脆性裂纹止裂设计已得到国际认可。自1990年代以来，就提出了通过等温裂纹抑制试验来定义裂纹抑制温度（CAT）的概念，这是一种评估脆性裂纹抑制能力的方法之一。该概念主要应用于油箱设计。但是，尚未指定任何标准来描述详细的评估程序。这意味着只有有限的组织才能评估CAT，而当将逮捕评估作为国际标准强制执行时，这被认为是一个问题。在这种情况下，日本焊接工程学会（JWES）和Nippon Kaiji Kyokai（ClassNK）等日本研究小组于2016年开始进行CAT试验的标准化。在该研究计划中，根据许多实验和试验结果对控制因素的各个方面进行了研究。数值计算。CAT试验应包括脆性区域以引发脆性裂纹。电子束（EB）线重熔或局部温度梯度（LTG）均可应用于脆化区。即使我们仅专注于EB焊接，脆性区的焊接缺陷也可能是影响因素。在本报告中，我们研究了EB焊接残余应力对裂纹驱动力的影响，量化为 基于许多实验和数值计算的测试结果，研究了控制因素的各个方面。CAT试验应包括脆性区域以引发脆性裂纹。电子束（EB）线重熔或局部温度梯度（LTG）均可应用于脆化区。即使我们仅专注于EB焊接，脆性区的焊接缺陷也可能是影响因素。在本报告中，我们研究了EB焊接残余应力对裂纹驱动力的影响，量化为 基于许多实验和数值计算的测试结果，研究了控制因素的各个方面。CAT试验应包括脆性区域以引发脆性裂纹。电子束（EB）线重熔或局部温度梯度（LTG）均可应用于脆化区。即使我们仅专注于EB焊接，脆性区的焊接缺陷也可能是影响因素。在本报告中，我们研究了EB焊接残余应力对裂纹驱动力的影响，量化为 电子束（EB）线重熔或局部温度梯度（LTG）均可应用于脆化区。即使我们仅专注于EB焊接，脆性区的焊接缺陷也可能是影响因素。在本报告中，我们研究了EB焊接残余应力对裂纹驱动力的影响，量化为 电子束（EB）线重熔或局部温度梯度（LTG）均可应用于脆化区。即使我们仅专注于EB焊接，脆性区的焊接缺陷也可能是影响因素。在本报告中，我们研究了EB焊接残余应力对裂纹驱动力的影响，量化为使用3D有限元方法（FEM）的K值。结果，我们确认了在EB焊接部分表面上形成的残余应力的存在，这是不容忽视的。但是，如果CAT测试条件能够充分确保止裂裂纹的长度，则对K值的影响很小。该结果表明，可以通过LEFM公式简单地评估CAT测试中止点处的驱动力，而无需考虑EB焊缝脆化的残余应力。