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我国“压力容器缺陷评定规范(CVDA)”拟采用1983年日本WES2805新版修改中所增的三类表面裂纹疲劳扩展形貌变化等有关计算公式,分别采用三个计算式的合理性是显而易见的,但其可靠性如何?为对此进行验证试验,并探讨今后能否以统一表达式代替三个公式,我们进行了单向拉伸载荷下的三类表面裂纹疲劳扩展规律的实验研究和理论分析.结果表明:当用Rajn和Newman公式计算表面裂纹应力强度因子时,裂纹深度(a)向和表面(c)向(见图4)的疲劳裂纹扩展速率数据都可用Paris公式整理,当用△K_c=0.9△K_c代替△K_c时.c向的扩展速率数据落入a向的da/dN～△K_a的分散带内。针对三类表面裂纹采用三个公式是合理的,在不太深的表面裂纹情况下与试验结果相符,为CVDA规范公式提供了验证。另外,从Rajn and Newman应力强度因子出发,应用Paris公式,从理论上导出了三类表面裂纹形貌的统一表达式。借助于形貌表达式,得出了工程aN～N计算式。这些公式与实验结果吻合良好。
China’s “Pressure Vessel Defects Evaluation Criteria (CVDA)” to be adopted in 1983 WES2805 new version of the amendment to the three types of surface fatigue crack growth morphology changes and other relevant formulas, respectively, the rationale for using three formulas is obvious, But how about its reliability? In order to verify the experiment and discuss whether the three formulas can be replaced by the unified expression in the future, we carried out experimental research and theoretical analysis on the fatigue propagation law of the three kinds of surface cracks under uniaxial tensile load The results show that the fatigue crack growth rate data of crack depth (a) and surface (c) (see Fig. 4) can be sorted by Paris formula when the surface crack stress intensity factor is calculated by Rajn and Newman’s formula. When K_c = 0.9ΔK_c instead ofΔK_c, the expansion rate data in c direction fall into the dispersion of da / dN ~ △ K_a in a direction. The use of three formulas for the three types of surface cracks is reasonable, consistent with the test results in the case of not too deep surface cracks, proving the CVDA specification formula. In addition, starting from the Rajn and Newman stress intensity factor, Paris formula is applied to theoretically derive the unified expression of three types of surface crack morphology. With the help of morphology expression, the formula of engineering aN ~ N is obtained. These formulas are in good agreement with the experimental results.