Research on fatigue crack propagation life prediction method for subsea pipelines

Abstract Subsea pipelines are subject to complex loading environments, and fatigue damage is one of the main failure modes. Due to manufacturing or environmental factors, crack defects are inevitable in submarine pipelines. For subsea pipelines in service, it is of practical importance to predict the residual fatigue life. On the premise of the conservative estimation method, the MTS criterion is used to analyze the crack propagation mode of subsea pipelines. In the numerical prediction method, the crack stress intensity factor is solved by the finite element method combined with the 1/4 node displacement method, and then the fatigue life of the subsea pipeline is predicted by the da/dN method based on the Paris formula. The results show that when the crack size increment Δa is set reasonably, the predicted results of crack propagation life of subsea pipeline are close to the experiment results, which verifies the accuracy of the numerical prediction method. The choice of the crack size increment has a large impact on the life prediction and needs to be considered in terms of both calculation accuracy and time consumption. The results obtained provide a reference for the safety assessment of pipelines in service.