An asymmetric elastic metamaterial model for elastic wave cloaking

TL;DR

This paper introduces a novel elastic metamaterial with asymmetric elastic tensor properties enabled by rotational resonance, allowing full control of elastic waves for cloaking applications without external torque.

Contribution

It demonstrates the feasibility of asymmetric elastic materials through rotational resonance, providing a new pathway for elastic wave manipulation and cloaking device design.

Findings

Asymmetric elastic tensor achieved via rotational resonance.

Metamaterial can be tuned for transformation-based wave control.

Numerical validation of elastic wave cloaking.

Abstract

Elastic material with its elastic tensor losing minor symmetry is considered impossible without introducing artificially body torque. Here we demonstrate the feasibility of such material by introducing rotational resonance, the amplified rotational inertia of the microstructure during dynamical loading breaks naturally the shear stress symmetry, without resorting to external body torque or any other active means. This concept is illustrated through a realistic mass-spring model together with analytical homogenization technique and band structure analysis. It is also proven that this metamaterial model can be deliberately tuned to meet the material requirement defined by transformation method for full control of elastic wave, and the relation bridging the microstructure and the desired wave functionality is explicitly given. Application of this asymmetric metamaterial to design elastic wave cloak is demonstrated and validated by numerical simulation. The study paves the way for material design used to construct the transformation media for controlling elastic wave and related devices.