Approximate evaluation method for ductile fracture analysis of circumferentially through-wall-cracked pipe subjected to combined bending and tension

To estimate the structural integrity of the Light Water Reactor piping, combined loading consists of tensile load due to internal pressure and bending load under seismic condition should be considered as a basic loading mode. However, theoretical investigation on the methodology to evaluate ductile fracture behavior is not adequate to date. In this study, an approximate evaluation method for ductile fracture analysis of circumferentially through-wall-cracked pipe subjected to combined bending and tension was newly developed. This method can explicitly incorporate the contribution of both tension and bending. The effect of growing crack is also considered in the method. This method was then applied to the full-scale pipe fracture tests. Based on the comparison with experimental results as well as finite element calculations, it could be ascertained that the proposed method could well predict ductile fracture behavior under combined loading. The effect of combined loading on ductile fracture was sensitivity-studied using the proposed method. As a result, it was quantitatively found that the superposition of internal pressure reduced the maximum load of cracked pipe. (author)