Modelling for prediction of time-varying heat partition coefficient at coated tool-chip interface in continuous turning and interrupted milling

Abstract

Knowing heat partition coefficient at tool-chip interface is important for accurate estimating the distribution of heat flux and temperature field in metal cutting process. The heat partition coefficient in steady metal cutting has been widely analyzed. However, the time-varying effect of heat partition coefficient is rarely investigated in metal cutting with coated tool. In this research, a novel model for prediction of the transient heat partition coefficient at coated tool-chip interface was proposed. The time-varying heat partition coefficient was quantitatively calculated. The new proposed model fully considered the coating thickness and material thermal properties compared with current models including Shaw's model, Kato-Fujii's model and Reznikov's model. The time-varying heat partition coefficients in continuous turning and interrupted milling process were comparatively analyzed. Results showed that the time needed for attaining quasi-steady-state of heat partition was about tens of milliseconds. The heat partition coefficient was mainly dependent on tool coating and workpiece thermal properties rather than tool substrate thermal properties. The heat partition coefficient was decreased with the increase of interrupted cutting speed. The new proposed model was verified accurate compared with former research and cutting experiment. The proposed methodology can guide for design and selection of coated tool in metal cutting production.