Investigation of the interaction mechanism of two dynamic propagating cracks under blast loading

Crack interactions significantly influence the propagation behavior of cracks, and further alter the crack coalescence characteristic. Caustic experiments, combined with numerical simulations, are carried out to further investigate the interaction mechanism between cracks. The results show that the local stress field significantly superposed when the distance between the two opposite propagating cracks is within a critical distance, resulting in an increase in both the dynamic stress intensity factors and the crack velocities during the crack interactions, and further control the fracture behaviors between the two cracks. During the crack interactions, both the absolute values of dynamic stress intensity factor KdII and T-stress increased significantly, indicating that the cracks turned from tensile fracture to mixed tensile-shear fracture conditions, and deflected from its original direction. Moreover, it is found that before the two cracks overlap, the sign of KdII was negative, T-stress was positive, and leading the cracks propagated in an anticlockwise direction. Whereas after the two cracks overlap, the sign of KdII turned to positive, T-stress turned to negative, and further inducing the cracks propagated in an clockwise direction. In addition, the results also implies that the two opposite propagating cracks first exhibit repulsion effect, then turn to attraction effect, and finally form a clasping shape between the two cracks. However, both the repulsion effect and the attraction effect decrease with the increase of the vertical distance between cracks. And the interactions between cracks decreased significantly after the initial vertical distance between two cracks is beyond a critical value. Results may shed lights on the interaction behaviors between two opposite propagating cracks.

Automated summary

The interaction between cracks significantly influences the stress intensity factors and crack velocities, as well as the fracture behaviors. During crack interactions, cracks may transition from tensile to mixed tensile-shear fracture conditions, leading to changes in crack propagation direction.