Modulation of solitary waves in woodpile phononic crystals made of stacked cylindrical elements
Eunho Kim (University of South Carolina), Jinkyu Yang (University of South Carolina)
Mechanics and Dynamics of Periodic Structures
Wed 9:00 - 10:30
Salomon 101
We present experimental and numerical studies on the propagation of solitary waves in woodpile phononic crystals (WPCs) composed of slender, cylindrical elements. We systematically vary the longitudinal dimensions of stacked cylinders and measure transmitted mechanical waves under striker impact. We report the generation of nonlinear waves – in the form of compact-supported solitary waves – due to the nonlinear Hertzian contact among the cylindrical elements. Unlike conventional, monoatomic granular chains, however, we find that WPCs form and propagate groups of solitary waves. These wave packets exhibit unique oscillation and attenuation patterns in association with the aspect ratios of the stacked cylinders. In this study, we show that such wave modulation effects are strongly affected by the natural frequencies of the cylinders’ bending vibration modes, which can be in turn controlled by the materials and dimensions of the cylinders. By testing various geometrical configurations, we demonstrate that WPCs can efficiently transmit or attenuate external impact in a controllable manner. For numerical verifications, we first investigate the modulation effect of solitary waves using finite element method (FEM). Then, we introduce a simplified computational method based on a discrete element model (DEM), which simulates the local resonance phenomena of WPCs efficiently. We find that the numerical results based on FEM and DEM show good agreement with experimental results. The experimental and numerical findings in this study can be used to design and characterize a new type of protective structures in periodic architectures, which can mitigate external impact by modulating, redirecting, and attenuating mechanical waves.