Research on the Behavior and Mechanism of Three-Dimensional Crack Growth under Uniaxial Loading

Table 2

Description of the failure process of the sample with different angles of crack.

Angle (°)	Failure process	Schematic diagram of sample failure
Crack-free	Most of the induced cracks grew along the direction parallel to loading, and failure mode was the simple extension mode.
0	Because the preexisting crack was parallel to the loading direction, induced cracks also grew along the loading direction. Compared with the failure mode of the crack-free sample, the failure mode for this type of samples was more complex, presenting a multiple extension mode.
30	With the angle of preexisting crack increasing, shear failure is gradually strengthened and the failure mode was the multiple shear mode.
45	When the angle of preexisting crack reached 45°, sample failure mode presented obvious shear failure characteristics (simple shear mode).
60	As the angle of the preexisting crack continued to increase, shear failure characteristics gradually weakened and there was a significant increase in the number of the induced cracks. The failure mode was similar to the multiple fracturing mode.
90	When the angle of the preexisting crack reached 90°, the preexisting crack was perpendicular to the loading direction. It is challenging to form stress concentration at the crack tip, and shear failure characteristics were further weakened. However, its failure mode was different from that of the crack-free sample (simple extension mode) due to the preexisting crack, presenting a multiple fracturing mode.