Study on Elastic-plastic fracture mechanics assessment method of a pipe having multiple circumferential surface cracks for the Rules on Fitness-for-Service of JSME

Abstract

This paper describes elastic-plastic fracture mechanics assessment methods of a pipe having multiple circumferential cracks. Ductile fracture strength of a multiple cracked pipe was evaluated using J-integral based on a reference stress method. Using this result and plastic collapse strength, Z-factor used in elastic-plastic fracture mechanics assessment methods was calculated. Z-factor for the multiple cracks was less than that for a single crack in all the analyzed cases. Although the position of bending axis where the minimum plastic collapse strength is given differs from that where the minimum ductile fracture strength is given, the minimum ductile fracture strength is not less than the value which divided the minimum of plastic collapse strength by Z-factor for a single crack. Based on these results, the elastic-plasticity fracture mechanics assessment methods for the Fitness-for-Service Codes were proposed.