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.