Streak recording of shock velocity history in polymers around 0.5-GPa stress region

In this study, unsteady propagation of high-pressure shock waves in PMMA and polyethylene specimens was first observed. Shock velocity decreases with the propagation distance for almost all cases, but the rate of decay process may depend on the material, shock strength and propagation distance. To observe the shock decay process, a high-speed photographic method was developed. The results obtained in this study may be closely related to the shape of the shock Hugoniot compression curve for these materials. Furthermore, stress relaxation occurring behind the wave front and its development with propagation are considered to have a close connection with the above results. Some of the data are presented and discussed compared with the Hugoniot and relaxation structures.