Pixel-removing digital image correlation − a universal method for speckle pattern image degradation and cracking

Digital Image Correlation (DIC) typically has poor accuracy when the speckle pattern is degraded, as in cases involving fractures, speckle melting or oxidation in high-temperature measurements, speckle slip, speckle obstruction due to surface roughness, pixel overexposure, or low-quality sensors with dead or defective pixels. We propose a pixel-removing DIC (PR-DIC) method that can accurately match the images with these challenging issues. The PR-DIC dynamically discards unreliable pixels within each subset and keeps only the good pixels for subset matching, enabling a better correlation. Numerical tests shows that PR-DIC has good matching accuracy and efficiency even under severe speckle pattern degradation, which obviously outperforms the classical DIC. A real test of joint root demonstrates reliable performance under practical fracture conditions when the images exhibit severe speckle degradation and crack-induced discontinuities.