Grinding force characteristics in elliptical ultrasonic assisted grinding (EUAG) of monocrystal sapphire

The characteristics of grinding forces in elliptical ultrasonic assisted grinding (EUAG) of monocrystal sapphire were experimentally investigated. A series of grinding experiments are carried out to reveal the effects of the ultrasonic vibration and the process parameters on the grinding forces and the force ratio F_n/F_t. The obtained grinding forces during EUAG were lowered by 50% and the force ratio was reduced by 33% compared with that during conventional grinding (CG). The grinding forces during EUAG have lower variation rate than those during CG as grinding parameters change, but the force ratio has higher variation rate as depth of cut and grinding speed change. Higher grinding speed causes larger grinding forces in CG, but has little effect on the variation of grinding forces in EUAG. Although greater worktable feed rate has little effect on the variation of grinding forces both in CG and EUAG, but it leads to lower force ratios. These results show that the grindability of sapphire material is improved by using EUAG method.