A new digital image correlation method for discontinuous measurement in fracture analysis

The Digital Image Correlation (DIC) method is commonly used in fracture analysis, but it has limitations in measuring discontinuities, which is crucial in fracture analysis. To address this issue, this paper proposes the Adaptive Discontinuous Digital Image Correlation (AD-DIC) method, which is explicitly designed to measure discontinuous displacement fields effectively and accurately in fracture analysis. The AD-DIC method both overcomes the limitations of previous methods by incorporating an adaptive subset tracking technique, which adaptively adjusts the binarization threshold, and improves the traditional Reliability Guided-Digital Image Correlation algorithm to reconstruct the displacement field near cracks. According to high-precision discontinuous displacement fields measured by AD-DIC method, we can accurately identify cracks, measure crack opening, and calculate inclination angles. To validate the effectiveness of the AD-DIC method, theoretical images of type I and mixed-mode I/II cracks are analyzed, as well as four actual experiments. The results show that the AD-DIC method achieves a high level of accuracy in calculating crack opening, with an error of less than 0.1 pixels. The actual experiments presented in this study demonstrate the wide-ranging applications of the AD-DIC method in fracture analysis, including identifying cracks that are difficult to detect with the naked eye, measuring crack opening and inclination angle, and tracking crack propagation processes over time. This study provides an effective tool for brittle fracture analysis, and the relevant algorithms can serve as a reference for discontinuous measurement.