Evaluation of Stress Intensity Factors from elliptical notches under mixed mode loadings

In this paper, by starting from the Inglis solution, the stress along the free border of an ellipse in a finite plate is investigated. The stress, divided into symmetric and skew-sym- metric terms, is approximated by means of a linear combination of three independent stress equations. The coefficients of the combination are calculated by FE analysis and the proposed equations appear to be suitable for different elliptical notches in a plate under general loading conditions. Then, the J-integral (namely J Vq) of an ellipse under general load conditions is evaluated analytically. Finally, in order to estimate the Stress Intensity Factors of cracks under mixed mode loading, FE analysis of equivalent ellipses is performed. This is possible because the terms of J Vq with null contribution when the ellipse becomes a crack are neglected. The errors in SIF predictions are approximately a few per cent, which is also the case for an ellipse close to a circle.