A three-dimensional transient numerical model of milling

Abstract

This paper presents a transient numerical model of metal cutting using a milling operation. This finite element model takes into account dynamic effects, thermomechanical coupling with a damage criterion and contact with friction. The yield stress takes into account the strain, the strain rate and the temperature in order to reflect realistic behaviour in metal cutting. The simulation of an unsteady process needs a separation criterion (chip criterion), and thus many of the models in the literature use an arbitrary criterion based on either the effective plastic strain, the strain energy density or the distance between nodes of parts and the tool edge. The damage criterion adopted in the model presented here allows the definition of advanced simulations of tool penetration into the workpiece and of chip formation. The originality of such a criterion is that it is applied on all the workpiece and enables complex tool trajectories. This damage criterion has been defined from tensile tests for 4140 steel (corresponding to 42CD4 in the French standard), and it has been used for the machining process. Stress distributions, chip formation and tool forces are shown at different stages of the cutting process.