Uniform scatter bands to analyse the fatigue strength of welded joints

This paper analyses the possibilities of a rational and uniform interpretation of the fatigue strength of welded joints, as a necessary basis for the development of sound and easily applicable design procedures. The re-analyses of experimental data here considered refer to as-welded joints, in steel and aluminium alloys, fabricated by using arc-welding, under axial or bending loads, under different stress ratios and modelled with the assumption of a null notch tip radius at the crack initiation location. The first part of the paper gives a synthetic presentation of the principal unifying parameters proposed in the literature and of the fatigue scatter bands derived with their application. The second part applies to welded joints a new parameter, recently introduced as an extension of the averaged Strain Energy Density approach. This parameter, which has been called the Strain Energy Density Intensity Factor, does not depend on the radius of the chosen control area, since it is not related to the fatigue strength of a specimen without geometrical notches. For this reason, it should make the averaged strain energy density concept more easily applicable to welded structures and give more general validity to the scatter bands derived with its application.