Axial and composite ultrasonic vibration-assisted face grinding of silicon carbide ceramics: grinding force and surface quality

Axial ultrasonic vibration-assisted face grinding (AUVAFG) of SiC has the characteristics of high efficiency and serious damage. With the aim of solving the problem of serious surface damage in AUVAFG of SiC ceramics, a composite ultrasonic vibration-assisted face grinding (CUVAFG) method involving axial vibration and elliptic vibration is proposed, which not only ensures the high efficiency but also maintains high quality of the machined surface. In this paper, the grinding forces and the surface quality were investigated by conducting comparative experiments on axial and composite ultrasonic vibration-assisted face grinding using a single diamond. The effects of ultrasonic vibration amplitude and wheel speed on grinding forces, ground surface roughness, and ground surface morphology were analyzed to reveal the brittle-ductile removal behavior of SiC ceramics during the micro-cutting process caused by elliptic ultrasonic vibration. The results show that CUVAFG can effectively reduce the grinding forces by about 15%, reduce the ground surface roughness by approximately 40.7%, and induce ductile removal to acquire good surface finish with predominantly facets in comparison to AUVAFG. More specifically for CUVAFG, with increased elliptic ultrasonic vibration amplitude along the long axis, the grinding forces are reduced by minor amplitude, but remain constant in the case of major amplitude. When the elliptic vibration amplitude is close to the critical chip thickness of brittle-ductile transition, the number of facets on workpiece surface is the highest, but the grinding forces and the surface roughness are relatively low. Meanwhile, with the increase of wheel speed, the number of facets and the proportion of ductile removal are both increased, but the grinding forces and the surface roughness are decreased. In order to realize low-damage machining of SiC ceramics by CUVAFG, it is suggested to keep the elliptic ultrasonic vibration amplitude around the critical chip thickness of brittle-ductile transition and use minor axial ultrasonic vibration amplitude and high wheel speed to achieve lower grinding forces and good surface quality.