Fatigue Strength Evaluation of Welded Joints Based on Notch Strains and the Influence of Weld Modelling

Abstract This study focuses on the estimation of the fatigue life of welded joints, considering elastic–plastic notch strains. Various finite element modelling approaches such as idealized geometries or measured geometries of weld toes will be discussed. By means of Monte Carlo simulations, partial safety factors are derived, which provide the possibility to account for the geometrical variability of the weld toe geometry. For computational efficiency, neural networks are employed to estimate notch stresses rapidly, revealing the influence of geometry parameters, like the notch radius or the flank angle at the weld toe and the weld throat thickness, but also variations of the wall thickness and angular misalignment. In addition, fatigue life evaluation using damage parameters applicable to low cycle, high cycle, and very high cycle fatigue will be presented.New experimental constant amplitude fatigue data from 84 tests on T- and butt joints made of X6CrNiTi18-10 stainless steel, including different sheet thicknesses, weld dimensions, weld types and weld seam variations, are used for validation of the proposed approach. Additionally, 144 tests from literature on materials S960M and X6CrNiTi18-10 are employed to validate the approach. For practical applications on component type specimen, 36 rectangular hollow section joints are used for additional validation. In summary, the study demonstrates that idealized weld modelling, following IIW-recommendations, coupled with an expanded effective notch stress approach, can enhance agreement between model predictions and experimental results. The derived partial safety factors facilitate the safe design of welded joints based on notch strains.