System design and experimental research on ultrasonic assisted elliptical vibration grinding of Nano-ZrO2 ceramics

Abstract

Aiming at the low toughness, high hardness and difficult machining of hard and brittle materials such as Nano-ZrO2 ceramics, a new type of ultrasonic assisted elliptical vibration grinding (UAEVG) system was designed to improve its machinability and grinding quality. The overall frequency equation of the ultrasonic grinding cup-shaped tool transformer (UGCTT) was derived by the integrated nonresonant design method and the length of the conical horn was optimized. The trajectory of abrasive particles was simulated by finite element software and verified by ultrasonic resonance test. Finally, through the experiment of UAEVG Nano-ZrO2 ceramics, the effects of UAEVG method on its surface morphology, roughness and residual stress were explored. The results showed that when the length of the horn was 65 mm after optimization, the transformer had good vibration mode. Simulation and ultrasonic resonance test results showed that the abrasive particles periodically moved in an elliptical shape in the longitudinal radial plane, and the radial and longitudinal amplitude were AR = 7.5 μm and AL = 3.1 μm. The grinding experiments of Nano-ZrO2 ceramics showed that UAEVG could change the grinding mechanism of conventional grinding (CG), reduce the generation of grinding debris and material fracture. When the grinding depth was increased, the plastic processing ratio of the material under UAEVG was significantly larger than that of CG, which could form a better surface topography. The surface roughness increased with the increase of the grinding depth and feed rate, and the surface compressive stress decreased with the increase of grinding depth. UAEVG could reduce the surface roughness by about 30% and increase the residual compressive stress by about 20% compared with CG, which could achieve better grinding surface quality. Therefore, it can be concluded that UAEVG could expand the plastic processing domain, improve the surface integrity and fatigue strength of Nano-ZrO2 ceramics to some extent.