Fatigue investigation of complex weldments by the means of the local strain energy density approach

The paper investigates the use of an energetic approach based on the strain energy density failure criteria to predict the fatigue life of welded joints in aluminum alloy. The cited criterion has already been proved valid to assess the failure of components in presence of sharp and blunt notches, and several results are present in the literature for different materials. The geometry tested in the present work is a double V-grooved full penetration butt weld, subsequently heat treated, and loaded orthogonally to the welding direction with load ratio R=0. This configuration makes the weld toe a notch of great opening angle. The aim of the paper is to verify the soundness of the energetic criteria for this class of welded joints, comparing the tests results with the numerical predictions. In the computational part, the energy in a given volume can be computed directly from the nodal displacements, thus not needing the stress values. Differently from the stress intensity factor approach, this property allows to a fast computation of the strain energy density by the means of a coarse mesh. The results of different configurations of geometry and meshing are compared to find the simplest modeling scheme capable of providing an accurate estimate of the fatigue life of the joint.