Quasi-static finite element modelling of thermal distribution and heat partitioning for the multi-component system of high speed metal cutting

Higher cutting speeds are desired for an enhanced manufacturing productivity. However, this is limited by the increased wear rate at the elevated cutter-chip interface temperature. To achieve the optimal cutting speed and cutter design for a prolonged tool life, a high fidelity thermal model is indispensable. In this paper, the thermal distribution for a multi-component system of cutter, workpiece and chip is modelled in a single mesh with realistic geometries and thermal boundary conditions. Directly modelling the multi-component system avoids the problem of inter-component heat partitioning. In order to dispense the computational cost of a 3D transient simulation, a multi-component system in a thermal equilibrium is modelled in a quasi-static way, i.e. heat taken away by the moving material is treated as advection heat transfer in the flow. This reduced-order model is achievable by imposing a mapping boundary condition dealing with temperature continuity and velocity discontinuity at the shear plane such that the numerical error in heat flux crossing the curly air-material boundaries is eliminated. After validation against Ivester et al. (2000)’s experimental data, a wide range of cutting speeds, shear zone and friction zone thicknesses are investigated. This quasi-static model was found to perform better than Lalwani et al. (2009)’s semi-empirical tuned analytical model in predicting the maximum interface temperature, while also applying non-linear material properties and realistic thermal boundaries. It was found that heat partitioning into the tool was over-predicted by using this empirical formula and the maximum temperature at the tool-chip interface was sensitive to the friction zone geometry. Furthermore, convective and radiative surface heat loss was found to be insignificant when compared to the heat taken away by the moving material. Therefore, a high-fidelity thermal distribution can be calculated within several seconds using a quasi-static 2D model. This reduced order model can not only be used to optimise the cutter design, but also to model the thermal distribution of any multi-component system with moving components in a thermal equilibrium.