Contact length prediction: mathematical models and effect of friction schemes on FEM simulation for conventional to HSM of AISI 1045 steel

Abstract

Toolchip contact length is an important factor in the machining process because it provides the interface for heat flux into the tool. Friction conditions at this toolchip interface strongly influence heat generation in the secondary deformation zone and one of the most important inputs for modelling and simulation of the machining process. In this paper, existing models predicting toolchip contact length and different rake face friction distribution schemes for the tool rake face are discussed. The effects of these friction distribution schemes on the toolchip contact length are then studied using an updated Lagrangian finite element code DEFORM 2D, simulating continuous chip formation. In addition, orthogonal cutting experiments are conducted for AISI 1045 steel to validate these results. The toolchip contact length was measured for cutting speeds ranging from conventional to high speed range. Existing toolchip contact length models and the FE modelling results are compared with those determined from cutting tests. While the flow stress is the dominant input factor for chip formation prediction, the results also show that contact length is sensitive to rake face friction distribution schemes. This paper clearly shows that realistic FE modelling of machining of AISI 1045 steel should be based on variable Coulomb and hybrid sticking-sliding friction models, for conventional to high cutting speed range.