Anisotropy monitoring of ultra-precision grinding force and acoustic emission signal of monocrystalline sapphire

The significant anisotropy and exceptional mechanical properties of sapphire pose substantial challenges in achieving uniform grinding quality. Moreover, the complexity of monitoring grinding signals complicates the understanding of sapphire's anisotropic behavior. For the first time, the grinding signals and quality of all crystal planes (R, N, C, M, A) during the ultra-precision grinding process of sapphire are comprehensively monitored. This study simultaneously investigates the anisotropy associated with sapphire grinding through the analysis of time domain and frequency domain signals. The roughness and surface damage resulting from sapphire grinding are characterized, and the characteristics of the grinding force and acoustic emission (AE) signals are analyzed in both the time and frequency domains to provide a deeper understanding of sapphire's anisotropic behavior during the grinding process. Furthermore, a grinding force model for ultra-precision grinding of sapphire has been developed, considering the effects of strain rate, the random distribution of abrasive tip radius, and the inherent anisotropy of sapphire. The results indicate that the simulated forces align closely with the experimental measurements, exhibiting an average error of approximately 7.78 %.