Full-field infrared thermography at tool-chip interface through transparent cutting tool while machining TI-6AL-4V

Abstract

This experimental study is aimed at obtaining the temperature distribution along the tool-chip interface in the steady state orthogonal machining of Ti-6Al-4V with a high level of accuracy. Yttrium Aluminum Garnet (YAG) is identified as a new transparent tool material which could successfully machine this ‘difficult-to-machine’ alloy. A unique fixture is developed to hold this transparent tool using which cameras sensitive to visible and infrared radiation observed the machining process in-situ and image, at a high speed, the radiation emitted from the tool-chip interface in a field less than 1 mm wide. The radiation intensity is converted to local temperature through a calibration process performed by imaging a blackbody in place of the chip at the tool-chip interface for the range of expected temperatures. The time averaged temperature maps show a hot region adjacent and parallel to the cutting edge. The temperature is uniform in the direction along the cutting edge, but decrease near the side boundaries of the chip. The time averaged temperature profiles show an increase of temperature with distance from cutting edge in the direction of chip flow. The temperature peaks 900 ⁰C to 1050 ⁰C at half of the contact length and then decreases. The uncertainty for reported values in maps is 10 K and that in profiles is 6 K. Time resolved temperatures are obtained using visible and IR camera systems using very low exposure times and the evolution of rake face temperature with respect to time is predicted. High resolution visible wavelength photography is used to obtain the chip velocity field along the interface. Shear stress of the deforming material is determined from predicted temperatures by imposing sticking friction.