Development of 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 consist 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 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. The method was then applied to the actual pipe fracture tests. Based on the comparison with experimental results as well as finite element calculations, it could be ascertained that the 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)