Techniques of speckle fabrication and imgae processing for high temperature digital image correlation

According to requirement of the high-temperature application from the digital image correlation (DIC) method, the speckle fabrication methods and high-temperature speckle image processing technique are studied in this paper. Taking high-temperature structural materials as the studied objects, a high-temperature speckle fabrication technique based on parametric template is developed. The technique is mainly based on a parametric template, which can adjust the parameters such as particle size, distribution density, and randomness in the template. As a result, the quality of the speckle can be optimized. A high-temperature speckle pattern was successful fabricated on the C-SiC composite substrate by the proposed technique, and the experiment verifies the speckle carrier can endure high temperature up to 1 200℃. At the same time, the influence factors of thermal disturbance and thermal radiation on DIC measurement results are analyzed. The high-temperature speckle images are corrected with approaches of image grayscale-average, circulating thermal disturbance and optical filtering method. And a test for measuring the thermal expansion coefficient is designed to verify the feasibility of the correction methods. © 2019, Tsinghua University Press. All right reserved.