Interference mechanism and damage accumulation in high-speed cross scratches on hard brittle materials

Precision and low damage grinding of aviation optical elements can effectively improve the overall processing efficiency. The mechanism of high-speed cross scuffing of multiple abrasive particles has become an important factor affecting the forming quality of workpiece. Interaction of abrasive trajectory determines machined surface and subsurface morphology and damage. According to the relative motion trajectory of wear particles on the workpiece surface, a theoretical model of the trochoidal trajectory intersection angle is proposed. High-speed scratches with different cross angles are experimentally obtained to explore the interference mechanism and damage accumulation of cross scratches. The results indicate that the Crack system I and Crack system II, produced by the two cross scratches, are mainly based on the stress principle and the strength principle, respectively. An increase in the damage radius is observed with a decrease in the crossing angle. Furthermore, as the duration of the normal cutting force decomposition curve at the entrance/exit of the intersection increases, the half-peak width also increases. The accumulation of cross-scratch damage promotes the propagation of deep subsurface lateral and median cracks. In other words, damage accumulation and interference mechanism formed by the cross scratches increase the longitudinal depth and lateral length of the damage.