Dynamics and stability of micro-cutting operations

In spite of considerable advances toward the understanding of the mechanics of micro-cutting operations their dynamics and stability that are dominated by the influence of nonlinear effects imposed by the minimum chip thickness and grain size effects and the dominance of ploughing over shearing still remain largely uncharted. Hence, the objective of this paper is to explore the fundamental mechanisms that lead to instabilities in micro-cutting. For dynamic stability analysis, linear stability theory was adopted to model regenerative chatter. The rationale for using linear stability theory is to perform a rigorous parametric study of the major factors that influence stability in light of the nonlinear phenomena that dominate micro-cutting processes. A linearized micro-cutting dynamic force model and a linear structural dynamics model are presented to formulate stability criteria for the different characteristic operating regimes encountered in micro-cutting. It has been shown that the three physical operating regimes, pure ploughing, simultaneous ploughing and shearing and the shearing dominant, govern the micro-cutting process. They are primarily a function of the relationship between the un-deformed chip thickness and cutting edge radius and exert different influences on process stability. Based on the linearized cutting dynamics models characterizing these regimes, a generalized approach to dealing with nonlinear force effects was proposed for process stability analysis. The method is applicable for cutting process nonlinearities at all scales if they are present. (C) 2016 Elsevier Ltd. All rights reserved.