In this paper, molecular dynamics simulations are carried out to investigate the cutting mechanism during the hybrid machining process combined the thermal and vibration assistants. A modified cutting model is applied to study the material removal behavior and subsurface damage formation in one vibration cycle. The results indicate that during the hybrid machining process, the dominant material removal mechanism could transform from extrusion to shearing in a single vibration cycle. With an increase of the cutting temperature, the generation and propagation of cracks are effectively suppressed while the swelling appears when the dominant material removal mechanism becomes shearing. The formation mechanism of the subsurface damage in one vibration cycle can be distinct according to the stress distribution. Moreover, the generation of the vacancies in workpiece becomes apparent with increasing temperature, which is an important phenomenon in hybrid machining process.

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Tool wear is one of the bottlenecks that decrease the machinability of hard and brittle materials in single point diamond turning (SPDT). Specifically, a microgroove generated on the cutting edge is an important character of tool wear, which leads to the formation of subcutting edges and facilitates the ductile to brittle transition in machining. However, the mechanism of the groove wear influence on the machined workpiece, especially the subsurface damage, is not clear just by the experimental investigations. In this paper, molecular dynamic simulations were carried out to explore the influence of groove wear on workpiece subsurface damage in SPDT of single crystal silicon. The propagation of grooves was also investigated by discussion of the stress and temperature distribution on the cutting edge. The Weierstrass-Mandelbrot function was adopted to set up groove wear on the tool flank face. It is concluded that grooves improve the atomic flowing ability and the plastic deformation in the workpiece. Moreover, the grooves can also cause polycrystal transition in the workpiece subsurface. The thickness of the subsurface damaged region is increased when groove wear becomes severe. This study contributes to the understanding of the details involved in the interaction between tool groove wear and workpiece, which is advantageous to improve the machined surface quality.