Effect of welding residual stress on load-carrying capacity of girth-welded pipelines with cracks

To address the unclear effects of welding residual stress on the load-carrying capacity of girth-welded pipelines with cracks, a dynamic fracture finite element model was established to investigate the bearing capacity of girth-welded pipelines with cracks under welding residual stress. The dynamic fracture finite element model was based on a residual stress field validated through full-scale pipeline welding experiments and utilized submodeling techniques to transfer the welding residual stress field. Additionally, by considering the material property differences between the base metal, weld metal, and heat-affected zone in the girth-welded pipeline, small punch tests were conducted to obtain the elastic-plastic mechanical properties of each region. The Gurson-Tvergaard-Needleman (GTN) damage parameters for the corresponding regions were calibrated through finite element simulations of three-point bending tests. Based on the dynamic fracture finite element model, the influence of welding residual stress on the bearing capacity of girth-welded pipelines with cracks was investigated. The results have shown that welding residual stress is concentrated in the weld metal, with the distance between the axial compressive stress on the inner surface and the weld center first increasing and then decreasing. The hoop stress rapidly transitions from tensile to compressive stress. The welding residual stress has a minimal effect on the maximum tensile load that the pipeline could withstand and the crack mouth opening displacement at failure. However, the pipeline’s critical displacement and tensile strain capacity (TSC) decrease by 12.42% and 13.04%, respectively, due to welding residual stress, indicating that its presence reduces the pipeline’s resistance to tensile fracture.