Perturbation Decay Experiments on Granular Materials

Sakharov and co-workers proposed an experiment 1965 in which a sinusoidal perturbation to a planar wave evolves as it travels through a sample. More recently, Liu et al. used gas guns rather than explosives to drive the shock wave, resulting in better defined input conditions. Previous work involved study of solids such as aluminum and liquids such as water and mercury. Here, the approach is applied to granular materials in a wedge geometry so that a broad range of sample thicknesses is sampled in one experiment. This experimental approach is attractive since it probes phenomena in a different manner than planar shock experiments, and the length scales involved can be varied by changing the perturbation wavelength and amplitude. A novel optical diagnostic approach is developed to provide increased data return. In addition, continuum and grain-scale simulations are used to understand the main material parameters affecting the observed behavior.