Effect of Thickness Eccentricity on the Stress Intensity Factors for a Pipe with a Single Internal Radial Crack under Internal Pressure

Abstract

The thickness eccentricity of a pipe occurs due to manufacturing limitations and may be exacerbated by service-induced degradation mechanisms. Fracture and remaining life assessments of a cracked eccentric pipe require a solution for the crack-tip parameters, e.g., the stress intensity factors (SIFs). However, the SIFs for this problem have not been examined. This study aimed to develop SIFs for an eccentric pipe with an infinitely longitudinal crack nucleated from an inner wall at the thinnest location of the pipe cross-section subjected to internal pressure. The problem was simplified to a cracked eccentric ring in a plane-strain condition, and finite element analysis was utilized for the determination of the SIFs, which were presented in tabulated form and empirical relation. The SIFs included a wide range of configuration parameters, i.e., a thin to thick-walled pipe, a shallow to deep crack, and a concentric pipe to a pipe with moderate thickness eccentricity. The need to consider the effect of eccentricity in SIFs calculation increased when the relative thickness of a pipe decreased and the relative crack depth increased.