Stability analysis of finite amplitude chatter in turning considering tool wear and process damping effects

Abstract

Due to the nonlinear characteristics of tool wear and process damping, these factors are often neglected when establishing the differential equations for machining chatter dynamics, resulting in the predicted stability lobe diagrams (SLD) not accurately guiding the actual machining. Furthermore, the influence of tool wear on turning stability and its relationship with process damping effect are still unclear. Based on the traditional turning machining dynamics model, this paper establishes a dynamics model suitable for sharp tools and worn tools, producing SLD that evolve with cutting time. Considering the influence of process damping effect, the calculation formula of process damping coefficient is derived based on the energy equivalence principle, and both process and system damping are incorporated into the dynamic differential equations. According to the limit loop theory, this paper proposes a construction method of finite amplitude chatter SLD, which features both upper and lower boundaries instead of the traditional single-boundary SLD. In the region between the upper and lower boundaries, the machining process is in a finite amplitude stable state. Finally, the results are verified by turning experiments, which show that the finite-amplitude chatter SLD proposed in this paper can guide the machining more accurately and efficiently compared with the traditional SLD. At the same time, this paper reveals the evolution law of the influence of tool wear on the machining stability, and the interaction relationship between tool wear and process damping.