Numerical Investigation of the Influence of Geometric Features and Weld Metal Properties on Stress and Strain States in X80 Girth Welds

In the design and integrity assessment of long-distance natural gas pipelines, it is critical to assess how geometrical features and material properties influence the stress and strain states of girth welds. This study conducted an extensive three-dimensional finite element analysis for X80 pipeline girth welds with varying geometric features and material properties to examine stress triaxiality and strain distribution phenomena. The effect of the wall thickness ratio, misalignment, strength matching coefficient, and yield-to-tensile ratio of the weld metal was analyzed under both unloaded and internal pressure-loaded conditions. The results demonstrate that stress triaxiality and local strain increase with the wall thickness ratio, amplified by increasing misalignment, yield-to-tensile ratio, and internal pressure. Enhancing weld metal strength correspondingly improves root stress and strain states; nevertheless, greater wall thickness ratios and misalignment diminish this improvement. Based on these findings, design recommendations were proposed, including suitable wall thickness ratio design, strict misalignment control and the optimization of weld material properties. The findings of this study offer valuable insights into the design and assessment of pipeline girth welds exhibiting intricate geometric features.