Frictional instability: A nonlinear mechanism to control shear wave responses in rough contact-based metamaterials

Abstract

Incorporating nonlinearity in periodic media not only enables enriched wave dynamics but also allows passive tunability of the wave responses. However, studies so far have been mostly focused on nonlinear mechanisms and responses of longitudinal wave propagation whereas shear propagation in the presence of strong nonlinearity is yet to be fully understood. In this talk, we study shear wave propagation through metamaterials with rough contacts including friction. The roughness of contacting surfaces results in structural instability causing the contacts to switch between different regimes—stick, partial slip, and gross slip—giving rise to strong nonlinearity. Moreover, due to the presence of friction, the contacts exhibit hysteretic nonlinearity, i.e., history-dependent response. In this study, we first experimentally evaluate the frictional properties of rough contacts by measuring high-frequency friction hysteresis loops. Then, we develop metamaterial with a periodic arrangement of these rough contacts and use the obtained frictional properties to numerically study nonlinear shear wave signatures. We evaluate higher harmonic generation and demonstrate how they can be tuned through excitation wave amplitude, external precompression, and surface roughness. These fundamental understandings can open new avenues for designing tailored material with memory-dependent nonlinearity for controlling shear wave propagation.