DETERMINATION OF K_I AND K_II FOR CURVILINEAR CRACKS UNDER A NON‐UNIFORM BIAXIAL STRESS FIELD

Abstract— Any structural element subjected to a static or alternating biaxial load with variable or random amplitudes may suffer from damage that can be described by fracture mechanics parameters. Brittle fracture conditions, fatigue crack growth rate and direction, as well as corresponding safety margins, are the most important unknowns which have to be predicted. A method is presented for estimating stress intensity factors K_I and K_II for a curvilinear crack subjected to a non‐uniform biaxial stress field. The method is based on the assumption of an equivalent arc crack, determined separately for each of the real crack tips. The K_I and K_II values are estimated by means of a modified weight function, called a unitary weight function, evaluated here for the arc crack by using the boundary element method (BEM). According to the principle of superposition any form of non‐uniform stress field may be considered. Accuracy of the method and associated problems of curvilinear crack analysis are also discussed.