Abstract
In this paper, we designed and analyzed a piezo-lens to focus flexural waves in thin plates. The piezo-lens is comprised of a host plate and piezoelectric arrays bonded on the surfaces of the plate. The piezoelectric patches are shunted with negative capacitance circuits. The effective refractive indexes inside the piezo-lens are designed to fit a hyperbolic secant distribution by tuning the negative capacitance values. A homogenized model of a piezo-mechanical system is adopted in the designing process of the piezo-lens. The wave focusing effect is studied by the finite element method. Numerical results show that the piezo-lens can focus flexural waves by bending their trajectories, and is effective in a large frequency band. The piezo-lens has the ability to focus flexural waves at different locations by tuning the shunting negative capacitance values. The piezo-lens is shown to be effective for flexural waves generated by different types of sources.
Highlights
Wave focusing is a method which promises to be useful in applications such as structural health monitoring (SHM) [1], energy harvesting [2], etc
It is reported that acoustic waves [3, 4] and elastic waves [5, 6] can be focused by a flat slab composed of phononic crystals (PCs) at a certain frequency band
In order to obtain more broadband wave focusing, methods based on the gradient index (GRIN) were proposed
Summary
Wave focusing is a method which promises to be useful in applications such as structural health monitoring (SHM) [1], energy harvesting [2], etc. A GRIN lens was realized by periodically arranging the local resonators on the plate surface and tuning them to fit a required refractive index variation pattern. Multi-mode techniques [16, 17], negative capacitance circuits [18, 19] and distributed shunted piezoelectric patches [20] In another kind of passive technique, the piezoelectric patches are periodically distributed on the controlled structures and are interconnected with an electric network. Later research shows that when piezoelectric patches are shunted with negative capacitance circuits [29], their effective material parameters are independent of the frequency and can be modified to a great extent [32].
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