FEM study on the stress concentration factors of K-joints with welding residual stress

K-joint is widely used on offshore platforms; its strength is very important for safety evaluation of platforms and the welding residual stress is inevitable. According to the thermo-effect of welding process, based on ANSYS, using the birth-death element technology, numerical simulation was performed for the welding process by coupling the temperature field and stress field. The nonlinear changes of material properties were considered and the distribution of temperature and stress was obtained. Considering that annealing treatment is generally performed for K-joint after welding, the process of annealing treatment was also simulated in this paper and the influence of it on welding residual stress was analyzed. Based on this, axial loads were applied on two different K-joint models, one with welding residual stress and the other without welding residual stress while just considering the influence of welding seam structure on the K-joint. The stress concentration factors (SCFs) of these two models were calculated and thus the influence of the welding residual stress on stress concentration factor was analyzed. Furthermore, considering the influence of welding residual stress, 105 models of K-joints with different geometric parameters and loading conditions were generated and the effects of them on the SCFs were discussed, results presented in this paper provide references for safety analysis of K-joints.