An introduction for machining researchers to measurement uncertainty sources in thermal images of metal cutting

Abstract

Thermal imaging yields valuable information which improves and verifies the accuracy of machining models. There are three main steps involved when measuring temperature distribution of the tool, workpiece, or chip during metal cutting; acquiring a thermal image, converting imaged temperature to apparent temperature, and converting apparent temperature to true temperature. There are many error sources to consider. It is important to understand how these error sources affect measurement uncertainty. Some are familiar to anyone performing thermography measurements, such as uncertainties in camera calibration. However, metal cutting presents unique measurement challenges due to factors such as the high magnification required, high surface speeds, micro blackbody effects, and changing emissivity. This paper is an introduction, focusing on thermal images, though visible spectrum images are also shown. Some examples illustrate basic concepts, while others are more complex. For brevity, specifics of cutting experiments are not given, as this paper has a measurement focus.