Abstract

Dynamic fracture toughness is an important material parameter that can be applied in the prediction of a cracked structure’s stability under dynamic loads. Large single cleavage semicircle compression specimens were used to evaluate rock dynamic fracture toughness by a drop weight impact test system. Crack propagation gauges, which consist of a group of fine wires, were glued along a crack propagation path to measure crack propagation speed and propagation time. The finite difference code Autodyn (ANSYS, Canonsburg, PA) was used to simulate the crack propagation path and to analyze the crack propagation mechanism. A group of gauge points were set up along the propagation path, and the stresses at these points were calculated and analyzed. The dynamic stress intensity factors were calculated by numerical models using the finite element code ABAQUS (Dassault Systèmes, Vélizy-Villacoublay, France). Finally, the dynamic fracture toughness, including initiation toughness and propagation toughness, was determined according to crack propagation speed and propagation time. The results show that crack propagation speed varies during dynamic propagation under impact loads, and the propagation toughness is inversely proportional to the crack propagation speed. In addition, the phenomena of cracks temporarily arresting could be observed during crack dynamic propagations.

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