AN ANALYSIS OF NONPLANAR CRACK-GROWTH UNDER MIXED-MODE LOADING

A method is presented for calculating stress intensity factors at the tip of a slightly wavy three-dimensional crack. The solution is used to calculate the direction of propagation of all initially planar semi-infinite crack, which is subjected to uniform remote loading. In particular, the combinations of remote load which cause the crack to deviate from its original plane are found. For the particular case of a two-dimensional crack subjected to combined mode I and mode II loading, we recover the results of Cotterell and Rice [1980, Int. J. Fract. 16(2), 155]. For a crack loaded by combined mode I and mode III loading, it is shown that there is a critical ratio of K(III)/K(I) which causes the crack to deviate from its original plane. The influence of T-stresses, which act parallel to the crack plane, is also investigated. Finally, the predictions of the perturbation theory are compared with full-field numerical simulations which predict the path of a crack propagating under mixed mode remote loading.