A Plastic Fracture Instability Analysis of Wall Breakthrough in a Circumferentially Cracked Pipe Subjected to Bending Loads

Abstract

A method of analyzing internal surface circumferential cracks in ductile reactor piping is presented. The method utilizes an alternate but equivalent definition of the J-integral based on nonlinear structural compliance. The analysis is valid for situations where the cross section containing the crack is fully yielded. Results are obtained for radial and circumferential crack growth for pipes subjected to bending. The stability of radial crack growth (wall breakthrough) is assessed using the J-integral-based Tearing Modulus approach. The analysis is shown to be in good agreement with experimental results on the stability of surface crack growth in Type 304 stainless steel pipes. Example quantitative results for fracture instabiltiy assessments for nuclear piping are presented to demonstrate the practical application of the approach.