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Calibrated Thermal Microscopy of the Tool–Chip Interface in Machining

This paper presents the results of calibrated, microscopic measurement of the temperature fields at the tool–chip interface during the steady‐state, orthogonal machining of AISI 1045 steel. The measurement system consists of an infrared imaging microscope with a 0.5 mm square target area, and a spatial resolution of less than 5 µm. The system is based on an InSb 128 × 128 focal plane array with an all‐reflective microscope objective. The microscope is calibrated using a standard blackbody source from NIST. The emissivity of the machined material is determined from the infrared reflectivity measurements. Thermal images of steady state machining are measured on a diamond‐turning class lathe for a range of machining parameters. The measurements are analyzed by two methods: 1) energy flux calculations made directly from the thermal images using a control–volume approach; and 2) a simplified finite‐difference simulation. The standard uncertainty of the temperature measurements is ± 52°C at 800°C.