Verifiche a fatica di giunti saldati mediante criteri locali: Un confronto tra il criterio basato su un raggio di raccordo fittizio e il criterio della densità di energia di deformazione in un volume finito

The aim of the paper is to demonstrate the close correspondence between two local approaches to assess the fatigue strength of welded joints: Radaj's approach based on fictitious notch rounding and a recently proposed approach based on the local strain energy density (SED) averaged over a given control volume. This volume surrounds the weld root or weld toe, both modelled as sharp (zero radius) V-notches with different opening angles. The two approaches are applied to load carrying and nonload carrying cruciform joints and the theoretical fatigue notch factors Kf are compared. The SED averaged over the control volume is determined from finite element models with very fine meshes, as typically designed to evaluate the intensity of the asymptotic stress distributions, and also from coarse meshes, showing a surprisingly good correspondence. This fact is surely of interest in view of possible applications of the SED method to components of complex geometry.