Notch Stress Intensity Factors and fatigue behaviour of steel and aluminium welded joints

Weld bead geometry cannot, by its very nature, be precisely defined. Parameters such as bead shape and toe radius vary from joint to joint even in well-controlled manufacturing operations. In the Notch Stress Intensity Factor (N-SIF) approach the weld toe region is modelled as a sharp V-shaped corner and local stress distributions in planar problems can be expressed in closed form on the basis of the relevant Mode I and Mode II N-SIFs. Initially thought of as parameters suitable for quantifying only the crack initiation life, N-SIFs are shown able to predict also the total fatigue life, at least when a large part of the life is spent as in the propagation of small cracks in the highly stressed region close to the notch tip. A large amount of experimental data reported in the literature for steel and aluminium welded joints is used here to demonstrate the applicability of the N-SIF-based approach.