Crack extension mechanism and scratch stress field model of hard and brittle materials caused by curvature effect

Abstract

Inhibition of subsurface crack growth under contact loading is key to enhancing the service performance of brittle materials. However, the understanding of crack extension mechanism under complex conditions is still limited. In this paper, scratch experiments and stress field analysis were used to investigate the damage evolution of glass materials induced by the curvature effect of abrasive trajectories. A cycloid or trochoid analytical model was developed to identify curvature-sensitive paths. On this basis, Curvature scratching experiments were conducted on the self-developed scratching experimental platform. The results revealed that surface cracks appeared outside the scratch grooves at the maximum curvature. Scratches with higher curvature peaks demonstrated less depth of crack initiation, and deeper cracks were induced inside the scratch. A novel finite-length, curved stress field model is proposed to evaluate the damage evolution from the inner and outer sides of the scratch. Based on the theory of maximum principal stress and tensile stress, the mechanism of crack extension under the curvature effect is revealed. This study improved the understanding of abrasive scratching and cracks extension under broad physical conditions.