Nassar H, Chen Y Y, Huang G L
Department of Mechanical and Aerospace Engineering, University of Missouri, Columbia, Missouri 65211, USA.
Phys Rev Lett. 2020 Feb 28;124(8):084301. doi: 10.1103/PhysRevLett.124.084301.
Rotationally resonant metamaterials are leveraged to answer a longstanding question regarding the existence of transformation-invariant elastic materials and the ad hoc possibility of transformation-based passive cloaking in full plane elastodynamics. Combined with tailored lattice geometries, rotational resonance is found to induce a polar and chiral behavior, that is, a behavior lacking stress and mirror symmetries, respectively. The central, and simple, idea is that a population of rotating resonators can exert a density of body torques strong enough to modify the balance of angular momentum on which hang these symmetries. The obtained polar metamaterials are used as building blocks of a cloaking device. Numerical tests show satisfactory cloaking performance under pressure and shear probing waves, further coupled through a free boundary. The work sheds new light on the phenomenon of resonance in metamaterials and should help put transformation elastodynamics on equal footing with transformation acoustics and optics.
利用旋转共振超材料来回答一个长期存在的问题，该问题涉及变换不变弹性材料的存在以及在全平面弹性动力学中基于变换的被动隐身的特殊可能性。结合定制的晶格几何结构，发现旋转共振会诱导出一种极性和手性的行为，也就是说，分别是一种缺乏应力和镜像对称性的行为。核心且简单的想法是，一群旋转的谐振器可以施加足够强的体扭矩密度，以改变这些对称性所依赖的角动量平衡。所获得的极性超材料被用作隐身装置的构建块。数值测试表明，在压力和剪切探测波作用下，通过自由边界进一步耦合时，具有令人满意的隐身性能。这项工作为超材料中的共振现象提供了新的见解，并应有助于使变换弹性动力学与变换声学和光学处于同等地位。
