Fracture mechanics analysis method for cracked components under very low cycle fatigue loading

In this study, fracture mechanics analysis was performed to calculate crack growth under very low cycle fatigue loading conditions. The calculation results are compared with 11 experimental datasets concerning through-wall cracked pipes made from three different materials under fully reversed large-amplitude cyclic loading. In the analysis, it was assumed that the crack growth rate under large-amplitude cyclic loading is the linear summation of the fatigue crack growth rate and ductile tearing rate. Relevant fracture mechanics parameters were determined using the reference stress approach. It was found that the calculated failure cycles are around half of those using the experimental data regardless of the material and load amplitude. The most important factors affecting the calculation results were the accuracy of estimating J and ΔJ, and the crack closure coefficient when calculating ΔJ. Their effects on the analysis results are discussed herein.