Investigation of thickness and bead profile effects on fatigue strength of welded joints based on relative stress gradient

•Relative stress gradient at weld toe depends only on weld toe radius.•A geometric effect function on fatigue strength of welded joints was proposed.•Typical trends of the geometric effect were revealed based on our method. In this study, by focusing on the relative stress gradient at weld toes, a prediction method was derived for the thickness and bead profile effects on fatigue limit for welded joints. Based on the results of stress analyses for several types of welded joints, relative stress gradient was clarified as contingent only on weld toe radius, regardless of welded joint, and loading types. Accordingly, the proposed prediction method represents a unified approach that does not depend on welded joint types. The proposed method indicated as being able to successfully predict geometric effect via comparison of experimental data.