G Meneghetti et alii, Frattura ed Integrità Strutturale, 34 (2015) 109-115; DOI: 10.3221/IGF-ESIS.34.11 109 Focussed on Crack Paths A link between the peak stresses and the averaged strain energy density for cracks under mixed-mode (I+II) loading G. Meneghetti, B. Atzori University of Padova, Department of Industrial Engineering, Via Venezia 1, 35131, Padova (Italy) , A. Campagnolo, F. Berto University of Padova, Department of Management and Engineering, Stradella S. Nicola 3, 36100, Vicenza (Italy), A BSTRACT . In this work, a link between the averaged strain energy density (SED) approach and the peak stress method in the case of cracks subjected to mixed mode (I+II) loading has been investigated. Some closed-form expressions of the strain energy density, averaged in a volume of radius R 0 , as function of the stress intensity factors are provided for plane strain conditions under mixed mode I+II loadings. On the basis of the peak stress method (PSM) some expressions useful to estimate the mode I and mode II stress intensity factors (SIFs) have been recently derived. These relationships take advantage of the elastic peak stresses from FE analyses carried out by using a given mesh pattern where the element size and type are kept constants. The evaluation of the SIFs from a numerical analysis of the local stress field usually requires very refined meshes and then large computational effort. The usefulness of the PSM-based expressions is that (i) only the elastic peak stresses numerically evaluated at the crack tip are needed and not a set of stress–distance data; (ii) the employed meshes are rather coarse if compared to those necessary for the evaluation of the whole local stress field. By substituting the PSM-based relationships in the closed-form expressions of the averaged SED it appears that the latter can be directly estimated by means of the elastic peak stresses evaluated at the crack tip. Several FE analyses have been carried out on cracked plates subjected to tension loading considering different geometrical combinations, varying the length 2a and the inclination ϕ of the crack (i.e. the mode mixity) as well as the size d of the adopted finite elements, with the aim to evaluate the local SED and the elastic peak stress components σ peak and τ peak . In all cases the numerical values of the SED derived from the FE analyses have been compared with those analytically obtained by using the expressions for the SED based on the elastic peak stresses, in order to verify the range of applicability of the proposed relationships. K EYWORDS . Local approaches; Stress intensity factors; Strain energy density; Finite elements; Coarse mesh. I NTRODUCTION otch stress intensity factors (NSIFs) play an important role in static strength assessments of components made of brittle or quasi-brittle materials and weakened by sharp V-shaped notches [1]. This holds true also for components made of structural materials undergoing high cycle fatigue loading [2] as well as for welded joints N