Simulation of Residual Stress Effect on Stress Corrosion Crack Growth in Gas Pipelines

In this paper, a quantitative study on stress corrosion crack growth in large diameter gas pipelines is presented. Finite element method is applied for determining stress intensity factor at the crack tip. First a small semi-elliptical axial surface crack is assumed. Then internal gas pressure and residual stress, induced from welding process, are considered. Applied forces and crack growth rate are calculated as a function of stress intensity factor based on an empirical equation. Crack front shape is determined by calculating stress intensity factor distributions along the crack tip. As a result, the effect of residual stress on stress intensity factor and therefore crack growth is determined. In addition, minimum crack size that activates the stress corrosion cracking mechanism is determined. It is shown that the applied method could be used to estimate the reliable life of pipeline and the suitable time for inspection of the pipeline’s surface.