Abstract: Dynamic experiments were conducted on single cleavage drilled compression (SCDC) specimens of sandstone using large-diameter split Hopkinson pressure bar to obtain the whole dynamic fracturing process of Mode-I crack. A crack propagation gauge was used to measure the key moments of dynamic initiation, propagation, arrest and re-initiation, respectively. A fractal model of crack extension was applied to analyze the propagation speed of a tortuous crack. Finally, we determined the dynamic initiation toughness, dynamic propagation toughness, dynamic arrest toughness, and dynamic re-initiation toughness using the experimental-numerical-analytical method. The results demonstrate that the crack propagation path is torturous in the process of crack propagation. For this irregular curve path, the value of the universal function, which was characterized by the crack propagation velocity, was smaller than that with a straight path. It is found that the dynamic propagation toughness obtained by the fractal model was close to its real value. The dynamic initiation toughness was greater than the dynamic arrest toughness, and the dynamic initiation toughness was slightly greater than the dynamic re-initiation toughness. The reason probably was that the naturally formed crack at the second re-initiation was sharp, while the artificial notch for the first dynamic initiation was blunt at a certain degree.

Key words: dynamic fracture whole process, various kinds of dynamic fracture toughness, fractal crack, crack re-initiation；single cleavage drilled compression (SCDC)