Evaluating Fatigue Life in Energy Pipelines Subject to Residual Stress and Dent-Gouge Coupling Using Stress-Based Predictive Models

The integrity of energy pipelines is of paramount importance to the global economy, yet it faces persistent threats from mechanical defects such as dent-gouge coupling, the severity of which is exacerbated by residual stresses originating from plastic deformation, this research aims to provide a precise quantitative evaluation of the fatigue life of pipelines made from API X52 steel containing these combined defects. An integrated methodology was adopted, relying on advanced numerical simulation using the Finite Element Method (FEM) via the Ansys application, wherein a comprehensive parametric study was conducted to assess the impact of varying defect dimensions (dent depth, and gouge depth and length), the model was developed to simulate the indentation and spring-back process to implicitly incorporate residual stresses, followed by the application of operational pressure, the results demonstrated that the gouge depth is the most dominant geometric factor governing stress concentration, as its increase led to a sharp rise in the maximum stress at the gouge root, resulting in a catastrophic reduction in fatigue life of up to 43% within the scope of the studied variables, by linking the simulation outputs with analytical stress-based fatigue models, this work presents a predictive model that provides a robust engineering tool for risk assessment and proactive pipeline integrity management.