Study on the Key Influencing Factors of Fatigue Life Evaluation for Dented Pipelines

Pipeline transportation is the core lifeline of the global energy supply system, but dent defects caused by third-party damage, construction errors, and other factors seriously threaten the safe operation of pipelines. As one of the most common defects in pipelines, dents will lead to local stress concentration and residual stress, accelerate fatigue crack initiation and propagation under cyclic service loads, and significantly shorten the pipeline fatigue life, even inducing leakage and explosion accidents. To accurately grasp the key factors affecting the fatigue life of dented pipelines and provide theoretical and engineering support for pipeline integrity management, this study systematically investigates the influencing factors of the fatigue life of dented pipelines through the combination of theoretical analysis, experimental testing, and numerical simulation. The research focuses on three categories of key factors: dent's own parameters (depth, length, width, shape, composite defects), pipeline's own parameters (material, diameter, wall thickness, location), and external related factors (internal pressure fluctuation, temperature change, corrosive environment, third-party loads). The results show that dent depth is the most critical influencing factor, and the fatigue life decreases exponentially with the increase of depth; composite defects (dent + crack, dent + corrosion pit) have a significant synergistic damage effect; high-grade steel materials, larger pipe diameter and wall thickness can effectively improve fatigue resistance; internal pressure fluctuation, high/low temperature, and corrosive environment will accelerate fatigue damage. Based on the research results, quantitative models of fatigue life related to key influencing factors are established, and corresponding engineering suggestions for inspection, maintenance, design, and construction are put forward. This study clarifies the intrinsic mechanism of fatigue failure of dented pipelines, improves the theoretical system of pipeline fatigue evaluation, and provides a reliable technical tool for the safe operation and integrity management of dented pipelines.