Numerical Assessment of Pipeline Damage Due to an External Circumferential Semi-Elliptical Crack

This paper presents a numerical evaluation of pipeline damage caused by an external circumferential semi-elliptical crack. The study utilizes the Abaqus software and the Extended Finite Element Method (XFEM) to model and analyze the crack behavior. Various parameters such as crack size, internal pressure, and loading conditions are investigated to assess their influence on pipeline integrity.   The results reveal that as internal pressure increases from 300 to 600 bar, the pipe’s bearing capacity significantly decreases due to heightened stress concentrations around crack tips, leading to increased hoop stress and Stress Intensity Factors (SIFs), which accelerate crack propagation. Higher pressures also promote crack nucleation and growth, further reducing the effective cross-sectional area and weakening the pipe's load-carrying ability. Additionally, the analysis highlights the critical influence of defect size (a/t ratio) on stress distribution and residual strength: as the a/t ratio increases, the pipe becomes more vulnerable to failure at lower stress levels. The critical crack size is identified at the intersection of the resistance curve and the ultimate stress line, beyond which failure occurs before reaching the material’s full strength. Non-physical regions, where resistance exceeds ultimate stress, are disregarded to ensure realistic defect assessments. Under an internal pressure of 30 MPa, pipes with a/t ratios of 0.50 and 0.62 remain within the safety zone, while those with a/t ratios of 0.75 and 0.80 enter the failure zone, indicating a substantial loss of structural integrity and an increased risk of fracture.