ORIGINAL ARTICLE On the contribution of primary deformation zone-generated chip temperature to heat partition in machining M. Fahad & P. T. Mativenga & M. A. Sheikh Received: 8 June 2012 / Accepted: 26 December 2012 / Published online: 11 January 2013 # Springer-Verlag London 2013 Abstract In machining, the percentage of heat flux that enters the cutting tool can have a critical impact on tool wear especially in dry cutting or high speed machining. In previous work, heat partition was evaluated by iteratively reducing the secondary deformation zone heat flux to the tool until the finite element simulated temperatures matched the experimental measured rake face temperatures. This follow-on work quantifies the contribution of primary zone heat flux to heat partition in machining. In this study, an analytical model was used to evaluate the rise in chip temperature due to primary deformation zone heat source. The heat partition and thermal modelling on the rake face was then conducted with an appropriate initial rake face temperature. Thus primary zone heat loads and shear- force-derived secondary zone heat flux were applied in finite element transient heat transfer analysis to evaluate heat flux into the cutting tool. External dry turning of AISI/SAE 4140 with tungsten carbide-based multilayer TiCN/Al 2 O 3 -coated tools was conducted for a wide range of cutting speeds between 314 and 879 m/min. Results further support the dominance of secondary zone heat flux on heat partition. The contribution of primary zone heat generation to the cutting tool heat flux in machining was less than 9.5 %. These findings suggest that, to address the thermal problem in machining, research and development should also focus on reducing friction on the rake face (e.g. coating innovations) and reducing contact areas (e.g. rake face design) in addition to the modification of shear angle and hence primary zone heat intensity. Keywords High-speed machining . Heat partition . Multilayer-coated tools . Finite element modelling Nomenclature a w Thermal diffusivity of workpiece material 1 w Thermal conductivity of workpiece material a Tool rake angle ϕ Shear angle a p Width of cut F v Cutting force F f Feed force F fr Frictional force along the rake face h Convective heat transfer coefficient K ο Bessel function of zero order second kind L s Length of shear plane heat source l st Contact length of sticking zone L c Tool–chip contact length q s Heat flux due to shear plane heat source q st Heat flux due to sticking contact zone R T Heat partition coefficient into cutting tool t ch Chip thickness C sh Shear stress in secondary deformation zone V ch Chip velocity 1 Introduction Metal cutting appears to be a simple process of removing material which involves a relative motion between the work- piece and the cutting tool. However, the underlying physics of the process is much more complex. A significant amount of power is consumed in overcoming the ultimate shear strength of the workpiece material. This deformation at the shear plane takes place at high strain rates and generates a large amount of heat. Furthermore, during high-speed ma- chining (HSM), the temperature in the chip formation region can be equally high with the higher energy required for higher values of cutting speeds [1]. Moreover, the mating of the chip with the tool rake face and the tool and the M. Fahad (*) : P. T. Mativenga : M. A. Sheikh School of Mechanical, Aerospace, and Civil Engineering, The University of Manchester, Manchester M13 9PL, UK e-mail: mufahad786@hotmail.com Int J Adv Manuf Technol (2013) 68:99–110 DOI 10.1007/s00170-012-4711-1