Thermo-mechanical properties of metals at elevated temperatures

Results from novel DIC-based experiments focused on quantifying the high temperature thermo-mechanical properties of steel alloys at elevated temperatures are presented. In these studies, the vision-based high temperature measurement system is comprised of (a) an induction coil heating system, (b) blue and white light illumination of the specimen, (c) optical band-pass notch filters for each camera centered on the blue light illumination wavelength and (d) a stereo-camera configuration for acquisition of synchronized image pairs at the desired temperature. The entire system is portable and is sufficiently flexible such that it can be employed with a wide range of specimen geometries. Each pair of stereo images acquired at a specified temperature is analyzed using three-dimensional digital image correlation (stereo-DIC). Results from laboratory studies confirm that the blue light-illumination with optical notch filtering allows high contrast images to be obtained even when the specimen is glowing white hot. The effectiveness of the system is demonstrated by successfully performing experiments to obtain the coefficient of thermal expansion of a steel alloy as a function of temperature. Additionally, technical challenges (e.g., sensitivity, spatial resolution, and repeatability of the measurements) when performing high temperature experiments with the proposed methodology will be discussed.