Experimental study on the influence of explosive stress wave on the dynamic crack propagation characteristics under biaxial confining pressure

The effect of biaxial confining pressure on dynamic crack and the interaction between explosive stress wave and dynamic crack are studied based on dynamic photoelastic method in this experiment. The experiment consists of five groups, primarily focusing on the angle at which the stress wave encounters the crack. The experimental results reveal two main fractures: mode I fracture and mixed-mode fracture. The influence of biaxial confining pressure on stress waves and dynamic cracks differs between these two fracture modes. Additionally, the Newton-Raphson iteration method is employed to analyze and calculate the fringe pattern of the crack tip at various stages. Subsequently, the calculation results are used to reconstruct the photoelastic fringe. To validate the accuracy of the calculation method, the reconstructed photoelastic fringe pattern is compared with the experimental results. The results show that the presence of confining biaxial pressure enhances the crack initiation toughness, propagation toughness and propagation speed. It also improves the crack's resistance to the impact of the incident stress wave from all directions. When the stress wave interacts with the crack, the photoelastic fringe patterns at the crack tip can be categorized into two main types. One is primarily influenced by the stress wave, while the other is primarily influenced by the stress field at the crack tip. To extract accurate crack tip information, it is essential to analyze the fringe pattern dominated by the stress field at the crack tip.