A numerical investigation on coolant flow and heat transfer characteristics of cutting tool in spot cooled vibration assisted turning of Ti6Al4V alloy

Abstract

The present work is aimed to investigate the coolant flow and heat transfer of an uncoated carbide cutting tool in Spot Cooled Vibration Assisted Turning (SCVAT) of Ti6Al4V alloy. Initially, Ti6Al4V alloy was machined with SCVAT and the cutting temperature was determined using embedded thermocouple technique with a calibrated K-type thermocouple. This experimental data was utilized to validate the CFD model developed and the error in prediction is found to be within the satisfactory limits. A detailed CFD analysis is performed on dual nozzle impingement cooling system with CO2 as coolant. Then the effect of various nozzle variables viz. nozzle inclination (α), nozzle tool distance (β) and nozzle diameter (D) and coolant flow variables viz. coolant pressure (CP) and cold fraction (CF) on coolant flow pattern, temperature distribution, heat transfer coefficient and turbulence kinetic energy are investigated using the validated CFD model. Flow visualization revealed the formation of a recirculation zone in the vicinity of the cutting tool which may be attributed to the jet-to-jet spacing resulting from nozzle configuration. The maximum temperature at the tool work interface, temperature distribution along the flank and rake faces, heat transfer coefficient and Turbulence Kinetic energy are significantly affected by coolant pressure and cold fraction whereas the contribution of nozzle variables is comparatively less. This may be due to the significant influence of coolant pressure and cold fraction on coolant velocity and mass flow rate that result in efficient heat transfer from the cutting tool. Among the nozzle variables, nozzle diameter and nozzle tool distance are found to be significant whereas nozzle inclination is not significant. Furthermore, the effective nozzle configuration (α = 30⁰; β = 25 mm; D = 5 mm) and flow parameters (CP = 9 bar and CF = 30%) were determined for maximizing the heat transfer from the cutting tool.