Calculation Of The Stress Intensity Factor Of Tubular Joints Based On Maximum Crack Opening Displacement

Tubular joints are the typical structures of offshore platforms,and they are prone to fatigue damage due to the high stress concentration at the intersection of brace member and chord member,the hot spot region.The fatigue life of tubular joints is critical to the lifespan of offshore structures,and therefore it's of great necessity to predict the fatigue life for the tubular joints.For practical engineering applications,a quick and simple approach has been constantly researched.Some researchers have proposed simple evaluation method based on maximum crack opening displacement,but their application range is only restricted to finite plate and T-butt weld joints.In this study,a new approach for predicting the stress intensity factor of welded tubular joints based on maximum crack opening displacement is proposed.The main contents of the essay are presented below:Finite element model of T-tubular joint has been established using ANSYS APDL,and the modified modeling process can improve the universality and mesh quality.Modeling method using APDL can guarantee the efficiency of parametric modeling;Separately validate the accuracy of the stress intensity factor both on the deepest point and the deepest point;According to parametric modeling method,large amounts of models with different parameters have been established and data of the stress intensity factor on the deepest and the surface point is then utilized for the analysis of the relationship between stress intensity factor and parameters including crack size and the whole model parameter.Eventually function relationship between them is given.Train the data of stress intensity factor on the deepest and surface point using neural network,and finally the error between the forecast and the true value is within 6.8%,which to some extent is acceptable in engineering application;furthermore,crack depth is substituted with maximum crack opening displacement,and nearly the same validation result is achieved,which proves that the method based on the maximum crack opening displacement is applicable in practical engineering.