Simulation of the Cutting Process Basic Instability Using Molecular Dynamics Technique

Cutting processes are unstable machining processes. The influence of the instability on the deformation mechanism that leads to the chip formation at the atomic scale is analysed in this paper. Fundamental aspects of the crystalline networks deformation are underlined by using molecular dynamics technique applied to the microscopic level of the deformed material and are defined as basic instability. Thus, the goal of this research is to determine the influence of the basic instability in cutting processes on the crystalline networks belonging to the workmaterial area which participates at the chip formation. The simulation using molecular dynamics technique uses the external conditions of the cutting processes as periodic boundary conditions for a selected crystalline network of the workmaterial. Moreover, the influence of the network integrity is studied as a possible cause of instability at the atomic scale that further, it is added to the global process instability. A measure of the atomic instability is the evolution of the kinetic energy at the atomic level. Three different crystalline networks are considered with free defects, vacation and interstitial atom – to estimate the differences in kinetic energies at the atomic level and the influence on the cutting force – time evolution. The fluctuations of the forces at the atomic level are considered one of the causes of the macroscopic perturbation of the cutting process itself named basic instability. Key-Words: molecular dynamics, micro-cutting process, basic instability, simulation, cutting force, chip formation