Atomic-scale insight into damage and removal behaviors during ultrasonic elliptical vibration-assisted grinding of CaF₂ crystals

Brittle damages incurred during machining of CaF₂ crystals present a significant challenge to achieving high surface integrity. Ultrasonic elliptical vibration-assisted grinding (UEVAG) can enhance the ductile-to-brittle transition depth in brittle materials, thereby improving processing quality and potentially facilitating plastic deformation and removal in CaF₂ crystals. To elucidate the plastic damage and removal mechanisms of CaF₂ crystals induced by UEVAG at the atomic scale, molecular dynamics simulations were employed to investigate the effects of normal vibration amplitude and frequency on grinding force, grinding stress, material removal depth, surface formation characteristics, and subsurface damage behaviors. The results demonstrated that amorphization transition and dislocation slip dominated the plastic deformation of CaF₂ crystals. Compared with traditional grinding, UEVAG reduced the average grinding force, dispersed subsurface stress, enhanced surface quality, minimized subsurface damage, and improved material removal efficiency at appropriately elevated frequencies and amplitudes. These findings enhanced our understanding of plastic damage and removal mechanisms involved in UEVAG of CaF₂ crystals, facilitating advancements in low-damage processing for other brittle solids.