Prediction of Tensile Strain Capacity of Spiral-Welded Pipes With Varying Initial Crack Sizes Using Extended Finite Element Method

Structural integrity assessments are essential for the reliability and safety of energy transportation pipelines. Predicting the fracture resistance of pipes with flaws and defects generated during manufacturing and installation procedures is necessary for improving pipeline designs’ structural integrity. This study employs the Extended Finite Element Method (XFEM) to analyze mixed-mode fracture behavior and tensile strain capacity of API X70 spiral-welded pipe. Single-edge notched tension (SENT) specimens were used to calibrate XFEM parameters due to their fracture toughness similarity to full-scale spiral-welded pipes. The behavior of pipe under operational conditions was studied, focusing on mixed-mode fracture mechanisms specific to the helical geometry of spiral welds. In addition, the impact of initial flaw sizes on the tensile strain capacity and fracture behavior of spiral-welded pipes were evaluated. Results demonstrate that larger flaw sizes reduce fracture toughness and influence mixed-mode crack propagation, as reflected by the significant reduction in remote strain at failure (εfailure) for flaws with larger sizes. These findings provide valuable insights for improving pipeline design, assessing operational reliability, and enhancing structural integrity under real-world loading conditions.