An Introduction for Machining Researchers to Measurement Uncertainty Sources in Thermal Images of Metal Cutting

Published: July 31, 2012


Eric P. Whitenton


Thermal imaging yields valuable information which improves our understanding of the metal cutting process. This understanding may be used to improve and verify the accuracy of machining models. There are three main steps involved when measuring the 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 uncertainty sources are familiar to anyone performing thermography measurements, such as uncertainties in the basic 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 as chips form. This paper is an introduction based on a readily available report. The focus is on thermal, though visible spectrum images are also shown. Both qualitative and quantitative examples of using these images to perform temperature measurements are presented. Some examples illustrate very basic concepts, while others are more complex. Images of a number of cutting experiments with different cutting conditions and materials are shown. For brevity, the specifics of the cutting experiments are not given, as this paper has a measurement focus. The examples presented were acquired using MADMACS, the MAnufacturing Deformation MACro videography System. It consists of a high speed visible light camera, a medium speed thermal camera, and a common primary lens so the two cameras are imaging the same scene. Timing signals for the cameras, as well as other signals such as cutting forces, are recorded so researchers may review the images and signals synchronized to each other.
Citation: International Journal of Machining and Machinability of Materials
Volume: 12
Pub Type: Journals

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uncertainty, metal cutting, dual-spectrum, high-speed imaging, infrared thermography
Created July 31, 2012, Updated February 19, 2017