A Comparative Study of the Performance of IR Detectors vs. High-Speed Cameras Under Dynamic Loading Conditions

Background The conversion of plastic work to heat and its efficiency (the Taylor-Quinney coefficient - TQC), are traditionally measured using infrared single-detectors (named detectors from here on) which measure the temperature at a single point on the surface. Lately, fast infrared cameras (focal plane array of detectors that measures a 2-dimensional field of view on the surface) have been increasingly used for that purpose too, but no systematic study has been carried out yet to compare the respective performance of each monitoring system for impact loading conditions. Objective A comparison between the two techniques (infrared detector and infrared fast camera) is reported for commercial 316L stainless steel under dynamic loading in the Kolsky bar. The respective merits and limitations of each setup are compared and discussed. Methods Cylindrical specimens were loaded at a strain rate of about 3000 [1/s] in a split Hopkinson pressure bar (Kolsky bar) apparatus. The transient temperature change was monitored in two separate series of experiments: In the first, we used a liquid N 2 cooled Mercury-Cadmium-Telluride (MCT) detector made by InfraRed Associates (USA) with a 1.5 MHz sampling rate, and in the second, a Telops FAST M2K high-speed infrared camera made by Telops (Canada) based on Indium Antimonide (InSb) array-detector and with a sampling rate of up to 90 kHz. Results Temperature changes under impact were successfully measured and compared using the two distinct techniques. In addition, the IR camera rendered a satisfactory thermal and visual recording of dynamic shear failure of various specimens. Conclusions The integral Taylor-Quinney coefficient ( β int ) can be assessed using either infrared detector or fast infrared camera alike, under dynamic loading conditions. However, the evaluation of the differential TQC ( β diff ) necessitates high sampling rates such as those enabled by infrared single detectors as compared to infrared high-speed cameras. Graphical Abstract