PREDICTION OF CRACK-GROWTH DIRECTION FOR MODE I II LOADING USING SMALL-SCALE YIELDING AND VOID INITIATION/GROWTH CONCEPTS/

Under the assumption that the processes which control the direction of crack growth in 2024-T3 aluminum are directly related to void initiat ion and growth, a theoretical framework is developed to predict the di rection of crack growth. The basic premise of the framework is that, d epending on the mode mixity of the remotely applied loading, either si gma(m)/sigma(eff) or sigma(eff) triggers the nucleation and growth of voids hence, fracture. The theoretical development uses linear elastic assumptions and two terms in the asymptotic expansion to describe the stress field in the vicinity of the crack tip for a mixed-mode I/II A RCAN specimen. Predictions based on the theory indicate that: (a) the transition from Mode I type to Mode II type crack propagation can be a ccurately quantified, and (b) the direction of crack growth is reasona bly well predicted for both types of crack propagation. In addition, a qualitative, but microstructurally based, physical rationale for the observed phenomena is presented.