六、缺陷评定标准断裂力学在工程中的应用,最早和最多的就是损伤容限,或允许裂纹尺寸分析。1973年以来,国际上相继出现若干缺陷评定标准,为了便于工程应用和总结,积累经验,其中常用的有:1.ASME 方法(1973年)美国机械工程师学会提出,编在“锅炉及压力容器设计规范”中,第Ⅲ篇的附录 G“防止无延性破坏”和第Ⅺ篇“核动力部件运转中的检查”,都是采用了断裂力学的方法。ASME 方法是线弹性断裂力学方法,当σ>σ_s 时,采用线性内插,图6.1中的Ⅰ区断裂应力σ_c≤σ_s,它由线弹性断裂力学的 K 判据给出,随裂纹尺寸减小,断裂应力σ_c增高,直到 Six, defect assessment standards Fracture mechanics in engineering applications, the earliest and most is the damage tolerance, or allow crack size analysis. Since 1973, a number of international standards for defect assessment have emerged. In order to facilitate the application and summarization of engineering experiences, some commonly used ones are as follows: 1.ASME Method (1973) The American Society of Mechanical Engineers proposed in “Boiler and Pressure Vessel Design The ”Code“, Part III of Appendix G ”to prevent non-ductile damage“ and XI ”inspection of nuclear power components in operation, are using the method of fracture mechanics. The ASME method is a linear elastic fracture mechanics method. When σ> σ_s, linear interpolation is used. The fracture stress in region Ⅰ in Fig. 6.1 σ_c≤σ_s is given by K criterion of linear elastic fracture mechanics. As the crack size decreases , Fracture stress σ_c increased until