An analytical cutting force model for elliptical vibration texturing of nano-grating surfaces

Although the direct texturing processes using dynamic cutting depth modulation have been widely demonstrated for generating micro/nano-structured surfaces, the material shearing removal dominates the surface topography generation that inevitably inhibits the machining feasibility of high-aspect textures. This paper proposes a novel nano-grating generation mechanism governed by the combined effect of shearing-based material removal and compressive forming-based deformation in elliptical vibration texturing. A newly dynamic cutting force model is established to reveal its transient cutting mechanics that incorporating the process elastic rebounding behaviors and essential local cutting characteristics in three deformation zones. The model fully considers the complex transient shear angle variation, friction reversal phenomenon on tool-chip interface as well as the unique flank-waviness interaction. A series of texturing experiments are delicately designed to modulate the contribution of material shearing removal and flank compressive forming on nano-grating generation mechanism. The measured dynamic cutting force show good agreements with the simulated results, based on which the model accuracy and main process assumptions are well validated. Furthermore, the relationship between the cutting force characteristics and nano-grating topography is analyzed to guide the optimal elliptical trajectory designs for simultaneously achieving high-quality nano-gratings and smaller dynamic cutting forces. The outcomes of this paper not only lay the scientific foundations for machining capability extension of direct texturing processes, but also contribute to the understandings of combined surface generation mechanisms of other intermittent cutting processes in nano-scale domain.