Analysis of ultrasonic assisted machining (UAM) on regenerative chatter in turning

Ultrasonic assisted machining (UAM) is an advanced technology for improving the machining process, especially for hard materials. This paper presents an experimental and theoretical study toward the effect of UAM on chatter. Theoretical explanation of the effect of UAM on chatter is not fully presented in the available literature yet. In this paper, considering fixed tool geometry, theoretical dynamic equations for UAM are represented. The approach is demonstrated by deriving dynamic formulation of UAM in turning, considering both turning equation and Merchants ultrasonic machining equations. A time domain analysis is fulfilled on each machining condition to verify whether it has a stable vibration or an unstable chatter vibration. Subsequently, an experimental setup is designed and manufactured to investigate UAM effect on regenerative chatter. Special conical shape for workpiece is designed to experimentally generate different points of stability lobe. The generated oscillation by a piezoelectric actuator is transferred, amplified, and concentrated on the tip of the tool by appropriate design of a cutting tool, which is vibrated in its bending mode. The obtained results are encouraging, and indicating good agreement between experimental and theoretical results.