Figure 1. Phononic crystal model.
(a) Cylinders stacked helically to form a one-dimensional chain. Insets show the two types of wave modes the structure supports. fL and fα are the frequencies of longitudinal and torsional travelling waves, respectively. (b) Contact stiffness dependence on the angle between two cylinders (Δα), which is perturbed by the torsional wave. (c) Uniform contact stiffness for the longitudinal wave propagation in the system without torsional excitation. (d) Spatio-temporal variation of the same stiffness with torsional excitation. The spatial distribution of stiffness moves by ds distance in time dt.