A Study on the Threshold Stress Intensity Factor and Fatigue Limit of Short Crack Growth

When a crack exceeds a certain size, the maximum stress intensity factor (K-max) is used to explain the occurrence condition of brittle crack, and the limit condition of hydrogen assisted and stress corrosion crack propagation. The fatigue crack can be explained through the stress intensity factor range (Delta K). However, as the stress intensity factor deals with only linear elastic bodies, it is necessary for the nonlinear range of crack tips to be small enough. It is known that this condition is not satisfied in the case of the microcrack problem, which became smaller than the threshold value of the long crack. This study evaluates the threshold stress intensity factor and fatigue limit of the input/output piping material STS316L for hydrogen storage tanks using the formula proposed by the author et al. to analyze the microcrack problem uniformly and using the formula proposed by Tange et al.