Implementation of Advanced Frictional Laws for Modelling of High Speed Machining
Résumé
High-speed machining is submitted to economical and ecological constraints. Optimization of cutting processes must increase productivity, reduce tool wear and control residual stresses in the workpiece. Developments of numerical approaches to simulate accurately high-speed machining process are therefore necessary since in situ optimization is long and costly. To get this purpose, rheological behaviour of both antagonists and representative friction models at tool-chip interface has to be studied as encountered during high-speed machining process. The study is led with AISI 1045 steel and an uncoated carbide tool. An experimental device has been first designed to simulate the friction behaviour at the tool-chip interface only in the zone near the cutting edge. Several tests are then performed to provide experimental data and these data are used to define the friction coefficient versus to the contact pressure, the sliding velocity and the interfacial temperature by a new formulation frictional law given by Brocail et al (2010). A two-dimensional finite element model of orthogonal cutting is developed with Abaqus/explicit software. An Arbitrary Lagrangian-Eulerian (ALE) formulation is used to predict chip formation, temperature, chip-tool contact length, chip thickness, and cutting forces. This numerical model of orthogonal cutting is then validated by comparing these process variables to experimental and numerical results obtained by Filice et al. (2006). This model makes possible qualitative analysis of input parameters related to cutting process and frictional models. A sensitivity analysis has been performed on the main input parameters (coefficients of the Johnson-Cook law, contact and thermal parameters) with the finite element model. The interfacial law determined by Brocail et al (2010) is implemented on this finite element model of machining and leads to improve numerical approaches of machining. Nevertheless, even if this law enables to reduce results between experimental and numerical approaches, some differences are still substantial. The advanced friction law must be complemented for higher sliding velocities and this work using a new specific experimental device will be presented in the second part of this paper.