In this presentation, we propose a novel design of elastic metamaterial that possesses unique anisotropic mass density and hyperbolic dispersion, which enables subwavelength-scale flexural wave manipulation. The metamaterial unit cell is inspired by kirigami, an ancient art of paper cutting and folding. A three-dimensional kirigami microstructure can be obtained by simply cutting and folding a thin metallic plate. By attaching the resonant kirigami microstructures periodically on the top of a host plate, a hyperbolic metamaterial plate can be manufactured without any perforation that degrades the strength of the pristine plate. A theoretical model based on the classic plate theory and mass-spring model is developed to understand the working mechanism of the elastic metamaterial. Dispersion curves are obtained by using an extended plane wave expansion method. An anisotropic effective mass density tensor is retrieved based on effective medium theory, which explains the different couplings between the local resonance of kirigami microstructure and the global flexural wave propagations in the host plate along two in-plane principal directions. Finally, numerical simulation on an elastic hyperlens is conducted to demonstrate the subwavelength-scale flexural wave control and super-resolution imaging abilities. The advantages of the proposed kirigami-based elastic hyperbolic metamaterial are twofold: (i) simple manufacturing process without perforation in the pristine plate and (ii) subwavelength flexural wave manipulation providing a high signal-to-noise ratio in plate-like engineering structures. Therefore, the proposed elastic hyperbolic metamaterial could be highly promising for high resolution damage imaging in nondestructive evaluation and structural health monitoring.
Rui Zhu, Hiromi Yasuda, Guoliang Huang, and Jinkyu Yang, "Control of subwavelength flexural waves via kirigami-based hyperlens (Conference Presentation)," Proc. SPIE 10170, Health Monitoring of Structural and Biological Systems 2017, 101700K (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 27, 2017; Published: 11 May 2017); https://doi.org/10.1117/12.2258671.5427850812001.
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