Molecular Dynamics Simulation of Cutting Processes: The Influence of Cutting Fluids at the Atomistic Scale

Abstract Molecular dynamics simulations are an attractive tool for studying the fundamental mechanisms of lubricated machining processes on the atomistic scale as it is not possible to access the small contact zone experimentally. Molecular dynamics simulations provide direct access to atomistic process properties of the contact zone of machining processes. In this work, lubricated machining processes were investigated, consisting of a workpiece, a tool, and a cutting fluid. The tool was fully immersed in the cutting fluid. Both, a simple model system and real substance systems were investigated. Using the simplified and generic model system, the influence of different process parameters and molecular interaction parameters were systematically studied. The real substance systems were used to represent specific real-world scenarios. The simulation results reveal that the fluid influences mainly the starting phase of an atomistic level cutting process by reducing the coefficient of friction in this phase compared to a dry case. After this starting phase of the lateral movement, the actual contact zone is mostly dry. For high pressure contacts, a tribofilm is formed between the workpiece and the cutting fluid, i.e. a significant amount of fluid particles is imprinted into the workpiece crystal structure. The presence of a cutting fluid significantly reduces the heat impact on the workpiece. Moreover, the cutting velocity is found to practically not influence the coefficient of friction, but significantly influences the dissipation and, therefore, the temperature in the contact zone. Finally, the reproducibility of the simulation method was assessed by studying replica sets of simulations of the model system.