The moiré method for the study of explosions

Explosives have been used to produce weak shock waves in central cavities of Plexiglas spheres. Shock pressures engendered were less than the so-called stable shock threshold and they resulted in a decomposition of the shock wave into an elastic precursor preceding the so-called plastic shock wave. The differential moiré method has been used to measure simultaneously the precursor and shock-wave velocities, as well as the velocity of the cavity interface. Moreover, the displacement field given by the moiré pattern yields the components of strains and the particle velocity behind each shock.