Experimental study on a Mach cone and trailing Rayleigh waves in a stress wave chasing running crack problem

This paper focuses on a blast-induced Mach cone followed by trailing Rayleigh waves during blast stress waves chasing a running crack in an epoxy plate, using the photoelasticity method and high-speed photography. A Mach cone and trailing Rayleigh waves were visualized and interpreted based on isochromatic fringes, agreeing well with theoretical wave paths. The Mach cone was the coalescence of shear wavelets generated by P waves on crack surfaces, which was verified by the half-cone angle, equal to arcsin (C-S/C-P). Effects of the Mach cone and trailing Rayleigh waves on the running crack were evaluated by measuring crack velocity and dynamic stress intensity factors (SIFs) of the crack tip. It was found that the Mach cone decreased both crack velocity and SIFs, while trailing Rayleigh waves had the opposite effect. Finally, because of similarities, the findings in our experiments were discussed with those in the supershear rupture. In particular, effects of the Mach cone and trailing Rayleigh waves on the running crack were consistent with particle motion near the fault in the supershear rupture.