Influence factor analysis for fatigue crack propagation life prediction of subsea pipelines
Fatigue is one of the main failure modes due to the complex loading environment of submarine pipelines.Due to manufacturing or environmental factors,crack defects are inevitable in submarine pipelines.For submarine pipelines in service,it is more practical to predict the residual fatigue life and study influence factor of prediction results.On the premise of the Conservative Estimation Method,the MTS criterion is used to analyze the crack propagation mode of submar-ine pipelines.Solving crack stress intensity factor by FEM combined with 1/4 node displacement method,and then the fa-tigue life of submarine pipelines is predicted by da method based on Paris formula.Finally,the influence factors of numeric-al prediction results are discussed.The results show that when the crack size increment △a is set reasonably,the predicted value of crack propagation life of submarine pipeline is close to the experimental value,and this numerical method can ef-fectively predict the fatigue residual life of submarine pipelines.The choice of the crack size increment has a large impact on the life prediction,and the method of reasonable selection of the crack size increment is given in terms of both prediction ac-curacy and calculation time consumption.The effect of crack shape ratio on fatigue life is related to the initial crack size.When the crack size expansion continues to increase after a certain value,the fatigue propagation life change rate is slower.The results obtained provide a reference for the safety assessment of pipelines in service.
submarine pipelinenumerical predictionfatigue propagation lifecrack size incrementshape ratio