Ultraviolet digital image correlation (UV-DIC) for high temperature applications

A method is presented for extending two-dimensional digital image correlation (DIC) to a higher range of temperatures by using ultraviolet (UV) lights and UV optics to minimize the light emitted by specimens at those temperatures. The method, which we refer to as UV-DIC, is compared against DIC using unfiltered white light and DIC using filtered blue light which in the past have been used for high temperature applications. It is shown that at low temperatures for which sample glowing is not an issue all three methods produce the same results. At higher temperatures in our experiments, the unfiltered white light method showed significant glowing between 500 and 600 °C and the blue light between 800 and 900 °C, while the UV-DIC remained minimally affected until the material began nearing its melting point (about 1260 °C). The three methods were then used to obtain the coefficient of thermal expansion as a function of temperature for the nickel superalloy Hastelloy-X. All three methods give similar coefficients at temperatures below which glowing becomes significant, with the values also being comparable to the manufacturers specifications. Similar results were also seen in uniaxial tension tests.