Thermal Modeling of Stick-Slip Frictional Contact in High-Speed Machining

Segmented or shear-localized chip is a type of cyclic chip formation mode that is commonly observed in high-speed machining of metals. In contrast to the classical continuous chip, segmented chip shows a serrated chip morphology and often exhibits periodic localization of plastic flow inside thin shear bands. This type of chip formation is characterized by periodically varying forces, stick-slip motion at the tool-chip interface, and a non-steady temperature field. In this study, an analytical framework is developed to model the non-steady temperature field at the tool-chip interface using planar heat source models, of moving and stationary type. Based on direct in situ imaging observations of the segmented chip formation process, sliding at the tool-chip contact is decoupled into two periodically occurring phases – the stick phase described by little relative sliding between the chip and the tool, and the slip phase where the chip slides with a uniform velocity across the tool face. Spatiotemporal variation in the tool-chip contact temperature distribution is modeled based on this stick-slip dynamics. Using Ti-6Al-4V alloy as a model material, the modeling framework is used to elucidate the following aspects: oscillatory nature of tool-chip interface temperature distribution, time-dependent variation of the heat partitioning coefficient, and periodic cooling and heating of the tool face during stick-slip cycles.