Ductile-brittle coupled cutting of a single-crystal silicon by ultrasonic assisted diamond turning

Ultrasonic assisted diamond turning (UADT) is a significant machining technology for the fabrication of a crack-free surface on single-crystal silicon. However, due to insufficient understanding of intermittent cutting characteristic, most researches have been only focused on the mechanism of ductile-regime machining rather than the improvement of surface quality and machining efficiency. Therefore, the novel machining model in UADT, ductile-brittle coupled cutting, is proposed to reveal how to realize the high-precision optical surface with larger processing parameters. Two quantitative performance indices, crack length projection and maximum tolerance length, are employed to evaluate whether a smooth surface can be achieved. And the variation of microscopic crack is analyzed and discussed in a single vibration cycle with different machining and tool parameters. In the experiments, the odd cosine surface is fabricated and the surface roughness Ra can reach 1.739 nm after measuring. The results show that better surface quality and higher machining efficiency can be achieved on single-crystal silicon by ductile-brittle coupled cutting in UADT.