Development of a Three-Dimensional CFD Model to Determine Convective Heat Transfer During Orthogonal Cutting

During machining, most of the process energy dissipates into process heat, which leads to high temperature gradients, especially in the cutting zone that forms between tool and workpiece. High temperature gradients lead to thermal stresses in tool and workpiece and reduce the overall manufacturing quality. Therefore, cutting fluids are commonly used to decrease high local temperatures at the tool-workpiece interface. In an earlier approach, a two-dimensional CFD model has been developed to determine the resulting convective heat transfer coefficients between tool and cutting fluid. The results of this simulation reveal a fluid stagnation near the cutting zone. This effect is expected to be overestimated by the flow restrictions of the two-dimensional domain, leading to an underestimation of the local convective heat transfer. In order to model the flow behaviour and local convective heat transfer coefficients more accurately, this work aims to extend the existing CFD model to a third spatial dimension. Compared to the two-dimensional setup, the simulation results show higher overall convective heat transfer coefficients resulting from the reduced stagnation effect of the fluid near the cutting zone. Following, a sensitivity analysis is performed regarding the impact of varying Reynolds and Prandtl numbers on the convective heat transfer. Further, the influence of chip evolution on the flow behaviour is considered by performing simulations with varying chip geometries. Finally, the results of the sensitivity analysis are summarized in a Nusselt correlation.