Fracture analysis of three‐point bending notched granite beams under prepeak and postpeak cyclic loading by digital image correlation and acoustic emission techniques

In rock engineering, cyclic loading may occur before and after the loading forces reach the load‐carrying capacities of rocks. This investigation aims to comprehensively present the fracture behavior of cracked rocks subjected to prepeak and postpeak cyclic loads. In the experiments, fracture mechanisms of notched granite beams were analyzed in‐depth through digital image correlation (DIC) and acoustic emission (AE) technologies. The experiments showed that the specimen deformation gradually developed from elastic to elastic–plastic in the prepeak loading–unloading cycles, and microcracking was dominated by tension. In the postpeak cycles, the horizontal strain, horizontal displacement, and effective crack length generally increased cumulatively with the cycle number but locally decreased with unloading. Interestingly, many microcracks were still produced and the proportion of shear‐type AE signals increased during the unloading processes in the postpeak cycles.