On the fatigue design strength of steel butt welded joints: Size and geometrical effects

This paper addresses the issue of the influence of geometry and size on the fatigue strength of steel butt weld joints. It aims to develop a series of continuously defined influencing factors, similar to the stress concentration factors in conventional un-welded notches. Such coefficients are mainly based on theoretical outcomes from Fracture Mechanics and Notch Mechanics and, where necessary, they are defined by the extensive use of parametrical numerical investigations. The relationship between stress raising factors and strength assessment reduction is explored by using local stress approaches as well as Notch Stress Intensity Factors and local effective stress. The main result is a clear definition of the size effect related to the dimensions and opening angle. Further secondary factors are investigated: bead shape, thickness over bead dimension ratio and toe radius.