Peridynamic Analysis of Fracture Failure in Girth Welds of X80 Pipeline

With the large-scale application of X80 high-grade, large-diameter, and high-pressure natural gas pipelines in China, girth weld regions are prone to fracture failure due to the deterioration of material properties caused by welding processes, posing a serious threat to pipeline safety. The traditional Finite Element Method (FEM) struggles to effectively capture the stress singularity at the crack tip . When modeling discontinuous problems such as crack propagation, and it relies on external criteria to predict fracture initiation. This study focuses on the girth weld of X80 pipelines and develops an improved bond-based peridynamic model, taking into account the structural characteristics of the weld region, to investigate the cracking behavior and evolution mechanisms. The effects of different initial crack lengths, angles, and locations on fracture failure are systematically analyzed. The results show that longer initial cracks exhibit slightly delayed crack initiation but shorter growth durations. When an angle exists between the initial crack and the pipe wall thickness direction, crack branching is more likely to occur, and the branching angle increases with the initial inclination angle. The sequence of crack propagation at different locations is: center of the heat-affected zone (HAZ), interface between HAZ and base metal, interface between HAZ and weld metal, and finally the weld metal.