Crack Initiation Prediction in Rock Samples using Digital Image Correlation

Crack initiation is important in rock mechanics because it is the first stage in the process of rock failure. Understanding the mechanisms of crack initiation can help engineers predict when and where rock failure is likely to occur, which can inform decisions about design and safety. Crack initiation in rocks can be studied using image processing techniques. Image processing involves the analysis and manipulation of digital images to extract meaningful information. This can be done through techniques such as digital image correlation (DIC), which allows for the measurement of displacement and strain fields in rocks under different loading conditions. Therefore, this paper presents a study aimed at predicting tensile crack initiation in rock samples using DIC. The study used rock specimens of Marble and Travertine and performed direct tensile strength tests to determine their strength characteristics. To do that, the DIC technique was employed to measure the rock surface displacement field under direct tensile stress. Afterwards, the divergence of this field was calculated to identify the location of crack initiation. The results showed that the regions with the maximum positive divergence value reflect the pure relative expansion of the surface, thereby helping in identifying the location of crack initiation.