High-temperature strain field measurement using digital image correlation

A method is presented for obtaining good images of sample surfaces at high temperatures, suitable for strain measurement, by digital image correlation (DIC) without the use of surface markers or speckles. This is accomplished by suppressing black-body radiation through the use of filters and blue illumination. Using only relatively low levels of illumination the method is demonstrated to be capable of providing accurate DIC measurements up to 1100 degrees C, and the potential to monitor strains to 1400 degrees C is identified. The capability of the method is demonstrated by measuring the Young's modulus and coefficient of thermal expansion of a nickel-base superalloy at temperatures from ambient to 1000 degrees C; two parameters that are well established in the literature and that require high strain sensitivity for their reliable determination.