A novel phosphorescence-based thermometry technique for the measurement of tool temperature distribution in metal cutting

Abstract

Precise knowledge of the temperature during cutting processes is of high interest as the temperature of a cutting tool dictates the performance, and for the workpiece it controls the quality and integrity of the generated surface. For the first time, in this study, a novel technique has been developed utilizing phosphor thermometry for 2D surface temperature measurement of a cutting tool in metal cutting. More specifically, lifetime-based phosphor thermometry was used as it has several advantages in accuracy over pyrometry-based methods, including being independent of emissivity and absolute optical signal intensity. The phosphor material, ruby (Al₂O₃:Cr), was coated on zirconia toughened alumina (ZTA) tools and used in orthogonal machining of hardened AISI 1045 (HRC 38). 2D surface temperature measurements with varying cutting speed, feed, and offset were performed to investigate their impact on the temperature. The phosphor thermometry results were also compared to infrared thermography measurements, and the results demonstrate issues for infrared thermography with the emissivity being temperature dependent and dynamically changing across the tool surface and time. Hence, phosphor thermometry offers a highly accurate alternative, yet at the cost of higher experimental complexity.