Simultaneous Visible And Thermal Imaging Of Metals During Machining

摘要

In order to investigate temperatures reached during orthogonal metal cutting, a novel approach for measuring temperatures at the tool-chip interface has been developed based on high-speed thermography. A thermal infrared camera and a visible camera combined through a dichroic beam splitter form the basis for a synchronized visible and infrared imaging system. Pairing the infrared camera with a higher speed visible camera allows for assessment of thermal images with aberrant chip flow or an obstructed view of the tool/chip interface. This feature facilitates the use of the apparatus in machining environments where machining chips or other debris fly about. The measurement setup also includes a force dynamometer, custom timing circuitry, and a high-speed digital oscilloscope to enable timing of frames together with force measurements so that analysis of the infrared images can be compared against the energy levels measured through the cutting forces. The resulting infrared images were converted to radiance temperatures through comparison to a NIST calibrated blackbody. Emissivity was measured by thermally imaging the machining chips heated to known temperatures. Machining experiments were performed at various cutting speeds and at two different infrared wavelengths. Analysis of these experiments gives insight into the relationships between emissivity, temperature, surface condition, infrared wavelength and motion blur. The analysis shows that using the visible, thermal and force data together is a significant improvement over any of these alone. These insights lead to practical guidance for use of infrared imaging systems to image rapidly moving objects.