采用弹性壳声学超材料元件的高透射宽带梯度折射率透镜
A high transmission broadband gradient index lens using elastic shell acoustic metamaterial elements
摘要：
利用圆柱形弹性壳作为声学超材料器件的元件，通过圆柱-平面波透镜的模拟和水下测量来证明。圆形区域到正方形的变换声学（TA）指示透镜中的有效密度保持恒定并且等于水的有效密度。分段近似所需的有效压缩性是使用一个正方形阵列与元素的基础上，弹性壳超材料的概念，在[30]。元件的尺寸是根据壳体的可用性来选择的，以最大限度地减少制造难度。被测试的装置是中性浮力的，包括由铝、黄铜、铜和聚合物制成的九种不同类型的商业外壳的48个元件。模拟表明，在宽带范围内，该设备作为一个圆柱形平面波透镜。实验结果证实了从大约20到40 kHz的宽带四极响应，在四个平面波方向上具有辐射图案的正增益。
英文摘要：
The use of cylindrical elastic shells as elements in acoustic metamaterial devices is demonstrated through simulations and underwater measurements of a cylindrical-to-plane wave lens. Transformation acoustics (TA) of a circular region to a square dictates that the effective density in the lens remain constant and equal to that of water. Piecewise approximation to the desired effective compressibility is achieved using a square array with elements based on the elastic shell metamaterial concept developed in [30]. The size of the elements are chosen based on availability of shells, minimizing fabrication difficulties. The tested device is neutrally buoyant comprising 48 elements of nine different types of commercial shells made from aluminum, brass, copper, and polymers. Simulations indicate a broadband range in which the device acts as a cylindrical to plane wave lens. The experimental findings confirm the broadband quadropolar response from approximately 20 to 40 kHz, with positive gain of the radiation pattern in the four plane wave directions.
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