Effect of speed ratio on shear angle and forces in elliptical vibration assisted machining

Abstract

Elliptical vibration-assisted machining (EVAM) has been employed in manufacturing industries to improve the machining performance of metal alloys. The mechanics of EVAM is dependent on the critical process parameters, including the horizontal speed ratio (HSR) defined as the ratio between the original cutting speed and the horizontal vibration speed. This paper presents a new mechanics model of EVAM, which reveals that the primary reason for shear angle variation at different HSR values is the strain-hardening property of the workpiece material instead of the friction reversal phenomenon. The model quantitatively determines the effect of the HSR on the shear angle, friction reversal, and instantaneous cutting forces in EVAM. A 2-D vibration assistance stage driven is developed to perform EVAM experiments on aluminum alloy with evident strain-hardening property and Zirconium-based bulk metallic glass that is less sensitive to strain-hardening. The chip morphology is examined at various speed ratios and uncut chip thicknesses to validate the shear angle prediction from the mechanics model. In addition, the model predicts the time instance corresponding to the friction reversal, which is also dependent on the shear angle and HSR in EVAM. Finite element simulations are performed to validate the predicted instantaneous cutting forces and friction reversal from the analytical mechanics model.