The Effect of Misalignment on Stress Concentration and Fatigue Life for Circumferential Weld Joints of Pipeline

Abstract

Misalignment has a significant impact on the fatigue performance of circumferential weld joints in pipelines, which can significantly reduce the fatigue life. Misalignment generates a structural stress concentration on the pipeline, which proportionally reduces its fatigue strength. Moreover, due to the misalignment, the reinforcement of the root and the transition angle of the pipeline inwall are significantly reduced, increasing its notch stress concentration factor and further reducing its fatigue performance. This work investigates the effect of misalignment on stress concentration in the circumferential welds of pipelines, and it is used to predict the fatigue life. The structural stress method is proposed in the present work, and finite element analysis technology with Abaqus is used to calculate the structural stress concentration factor kj at the root-pass toe of misaligned circumferential weld joints, and a formula for the relationship between the structural stress concentration factor kj and the misalignment is established. The total stress concentration factor k of weld joints with different misalignments under several welding processes are calculated, and are compared with the structural stress concentration factor kj. The fatigue test data of weld joints with different misalignments are studied, and it is shown that the fatigue performance could be predicted by the fitting result.