Title: Wave propagation in soft granular materials

Author (Invited): Christopher MacMinn, Yale University

Abstract:

Granular materials exhibit anomalous mechanical behavior such as aging, hysteresis, and anharmonic vibrational modes. This complex macroscopic behavior stems from grain-scale dynamics such as rearrangement, avalanching, and contact-breaking, but the connection between these two scales is poorly understood. Here, we study the propagation of vibrational waves through a granular material using experiments in a quasi-two-dimensional packing of soft particles. The softness of the grains makes the characteristic wave speed accessible to visualization with a high-speed camera. We image the packing during vibration and use particle tracking to connect the grain-scale mechanisms of energy propagation and dissipation with the macroscopic motion of the packing in response to harmonic driving over a wide range of frequencies and amplitudes.