The Effect of Loading Rates on Crack Dynamic Behavior Under Medium-Low Speed Impacts

Rock structures are often subjected to dynamic loads, such as blasts, impacts and earthquakes, and their loading rates differ largely. To investigate the effect of loading rates on the dynamic behavior of crack propagation, impact tests were conducted on large single-cleavage semicircle compression (LSCSC) specimens using a drop weight impact test system. Five types of rock materials were selected to prepare the LSCSC specimens, and crack propagation gauges were mounted along the crack propagation paths to measure crack initiation time and propagation speeds. Finite element models were established by using ABAQUS code, and the dynamic stress intensity factors (SIFs) were calculated. The curves of dynamic SIFs versus time were obtained, and the initiation toughness was determined by using these curves and the initiation time measured in the impact tests. The results show that loading rate has a significant effect on crack propagation behavior, and both the crack propagation speed and initiation toughness increase with the loading rate, whereas the delayed fracture time decreases with the increase in loading rate.