The Effects of Integration Time and Size-of-Source on the Temperature Measurement of Segmented Chip Formation Using Infrared Thermography

This paper illustrates the errors due to integration time and size-of-source effects when measuring the temperature of segmented chip formation using infrared (IR) thermography. Segmented chip formation involves narrow periodic shear bands that experience rapid heating and move at high velocities and accelerations. As a result, the values of the measured temperatures depend strongly on the temporal and spatial measurement window used. In this study, an ideal infrared camera is simulated to understand the effects of integration time and size-of-source on the measurement. This analysis does not consider the temporal and spatial transfer functions of the camera system, thus simplifying the analysis to be applicable to all IR thermography users. Incorporating appropriate transfer functions would make the analysis specific to a given camera system. Finite element analysis (FEA) simulation results provide a reference cutting process which is manipulated to mimic motion blur and size-of-source effects. For this purpose, the FEA results adequately represent the cutting process with rapid heating and high chip velocities. For the studied cases, size-of-source has relatively little impact on the measurement results when compared to the effects of integration time. Results show integration times from 1 μs to 90 μs significantly affect the measurement results. The maximum temperature measured by the simulated IR camera decreases from an FEA maximum of 735 °C to 668 °C at 90 μs integration time. Integration time significantly affects temperature measurement in the periodic shear band but does not significantly affect the simulated measurement error of the chip temperature near the tool rake face.