Effect of loading rate and arc boundary on dynamic crack arrest behavior of brittle material under dynamic loads

The development and extension of microcracks in rocks affect the integrity and stability of rock mass construction. External dynamic loads with different loading rates lead to different dynamic fracture characteristics of rock fractures. In this study, a large-sized PMMA specimen with an arc boundary was proposed. The time at which the crack started and spread was determined using drop hammer impact testing and crack growth meter testing. Subsequently, the microscopic characteristics of the crack fracture surfaces were analyzed using a scanning electron microscope. Finally, the dynamic fracture toughness of the crack tip of the PMMA specimen was calculated using the finite-element method. Both experimental and numerical studies indicated that the arc boundary of the specimen demonstrated effective capabilities for arresting propagating cracks, and as the loading rate increased, the crack velocity also increased, while the crack initiation time decreased. The crack no longer propagated along the original crack surface after the crack arrest. The peak compressive stress along the crack trajectories increased with the loading rate. During the early stages of crack propagation, the highest compressive stress was observed for the 65° specimen. Conversely, during the later stages of the crack propagation, the 125° specimen exhibits the highest compressive stress. The dynamic arrest toughness of the crack is greater than the dynamic initiation and propagation toughness of the crack. As the loading rates increased, the dynamic initiation and propagating toughness of the crack also increased, while the dynamic arrest toughness of the crack changed little with the loading rate.