Fatigue life estimation of welded structures: A new modified hot-spot stress method

Welding is a joining technique that still maintains its importance in today's automotive, transportation, civil and industrial structure designs. Fatigue life of welded structures is generally estimated by considering the stress field near the weld. However, even for the same loading conditions, the stress gradient near the weld toe will vary from one specimen to another due to imperfections. This in turn causes large scatters in the S-N curves of fatigue life estimation methods. A successful fatigue life estimation is considered to have a reduced scatter of the corresponding S-N curve under variable geometry and loading conditions. The Hot-spot Stress (HSS) method is a commonly used estimation method owing to its practical approach and ability to include the effect of geometric details. In this paper, an improvement of this method using optimization techniques is presented. The modified HSS method is then used to estimate the fatigue life of welded structures with different thicknesses and loading conditions. The results show that the proposed method will noticeably reduce the scatter in S-N curves by increasing the coefficient of determination value (R2) 9.1% compared to the classical method. Keywords: Fatigue Life Estimation, Hot-spot Stress Method, Extrapolation Points, Surrogate Models, Optimization