Acquiring the hot spot stress (HSS) in dangerous points of the structure (normally the welding seams of the structure) is the foundation of the offshore platform fatigue strength design. Because of the fact that it is very difficult and unpractical to install sensors in the welding seams, the most widely used method of acquiring the HSS currently is extrapolation, a method that obtains the HSS by extrapolating from stress of distant points. In order to figure out the feasibility of the method of extrapolation as well as the best ways to implement extrapolation in real practice, it is important to carry out numerical calculation of welded tubular joints in advance. To study the tubular joints, the finite element method (FEM) is the most widely adopted approach. In previous studies, shell elements are utilized to simulate tubular joints instead of solid elements concerning the difficulty. However, shell element simulation merely simulates the mid-surfaces of the tube walls so that shear stress in the direction of tube thicknesses are ignored, making the calculation of the stress concentration factor (SCF) inaccurate. In this study, the recommended ways of simulating the tubular Y- and T-joints are displayed and then the comparison of calculation results between different weld type, different mesh situations as well as different elements are given in order to bring up advice on numerical calculation for the study of extrapolation. The results of numerical calculation show that the extrapolation results are more accurate when we only consider the change of parameter α (chord length-to-chord radius ratio) and also, it is suggested to do the fitting in the area of 2t-4t away from the welding seam. These suggestions are verified by applying the method of extrapolation to a real jacket platform, which turns out that the fitting degree of extrapolation is very pleasant.
Aiming at the flexible hinge is often affected by external random variable loading operating noise fluctuation and complex factors, the fatigue degradation or failure is lack of analysis methods and that causes weak link of fatigue life analysis is difficult to find in the engineering practice. This paper introduces fatigue analysis method combines the fatigue of rain flow counting method and Pam Glen palmgren Miner theory. The article uses random loadtime history to deal with cyclic loadings by rain flow counting method. Calculate the flexible hinge fatigue damage with the S-N curve in different stress. The fatigue life and the design of the weak link are obtained under random variable loading through simulation with ANSYS. The strategies are given to improve the anti-fatigue for rectangular flexible hinge which improve the deficiencies in the design. This method has instruction and reference value to actual project.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.