疲劳裂纹扩展速率试验中裂纹曲率修正方法研究

针对目前疲劳裂纹扩展速率试验标准中仅提出裂纹长度需进行曲率修正但未给出具体修正方法及步骤的问题,作者推荐了线性插值法和等比例法两种裂纹曲率修正方法,并通过分析两种方法的修正原理,结合试验结果,将两种曲率修正方法进行对比。结果表明,在双对数坐标系上,修正后的da/dN-ΔK曲线向低ΔK方向偏移,最大偏移量约15%,在利用da/dN-ΔK曲线进行选材对比或疲劳寿命评估时,修正后的曲线与未修正的曲线相比是偏安全的。基于两种方法修正后的da/dN-ΔK曲线之间差异较小,最大相差约2%,两种方法均可作为疲劳裂纹扩展速率试验中裂纹长度的曲率修正方法。

Study on Crack Curvature Correction Method in Fatigue Crack Growth Rate Test

The fatigue crack length should be modified based on crack curvature correction according to the fatigue crack growth rate test standard. However, the specific correction method and calculation procedures are not given. Thus, two crack curvature correction methods are recommended in the paper, i.e. linear interpolation method and equal proportion method. The two curvature correction methods are compared by analyzing their correction principles combining with the experimental results. The results indicate that the modified da/dN-ΔK curve has an offset up to 15% toward to the low ΔK direction in the log-log coordinates system. When using da/dN-ΔK curve to conduct material selection and fatigue life evaluation, the modified da/dN-ΔK curve is safer than the unmodified. The difference between the da/dN-ΔK curves corrected by the two methods is not significant, and the maximum difference is about 2%.Both methods can be used as the curvature correction method in the fatigue crack growth rate test.