A tunable gradient impedance matching layer based on piezoelectric materials with external circuits

Abstract

The impedance step between different materials inevitably leads to serious energy loss during acoustic emission, transmission, and receiving. In this paper, a tunable gradient impedance matching layer (TGIML) was designed and fabricated to eliminate the impedance step. The TGIML was composed of periodical piezoelectric disks with shunting capacitors. Through the elaborate modulation of the capacitances of the shunting capacitors, the proposed TGIML can adapt interfaces formed by different materials. Two interfaces formed by solid rods were constructed to demonstrate the performance of the TGIML. The simulated and experimental results verified that, after inserting the TGIML, the transmission could be enhanced significantly in a wide frequency range for both interfaces. We believe that the proposed TGIML has great potential for wide applications in the development of ultrasound transducers, nondestructive testing, and energy harvesting.

Smart piezoelectric phononic crystals and metamaterials:State-of-the-art review and outlook

“…波导是一种能够改变波传播方向的器件。波导大多依赖于缺陷态，但已有的缺陷很难改变其位 置、尺寸等等，因而大大限制了波导的应用。而利用分流电路可调特性，可通过分流电路制成电路 缺陷，从而便捷的制成任意方向、宽频率的波导。Casadei 等人 [114] 通过将压电片贴在波导内拓宽了 波导的工作频率。Chen 等人 [115] 则通过改变压电复合板的电路，在不改变原始弹性板结构的前提下 等人 [116] 以及 Alshaqaq 和 Erturk [117] 通过将电路参数沿空间方向梯度分布，进而拓宽带隙；Wu 等人 [118] 通过梯度布置压电复合杆外接电路的电感提高了弯曲波透射率； Li 等人 [119] 通过梯度布置电路参 数改变了弯曲波的相位，为后续制作弯曲波超表面提供了理论基础；Xia 等人 [120] 通过梯度布置负 电容电路实现了反平面 SH 剪切波的转向和聚焦；Chen 等人 [121,122] 通过梯度布置分流电路的电路参 数，提高了弯曲波感应器的灵敏度，实现了弯曲波转向、聚焦透镜和隐身斗篷；Yi 等人 [123,124] 通过 在二维弹性板表面周期的粘贴压电片， 使用负电容电路改变等效折射率实现了平面透镜； Li 等人 [125] 通过将压电片贴在弹性板的边界上，用于改变弯曲波的传播方向。 Li 等人 [126] 将压电片贴在特定的边界上，如图 7(a)和 7(b)所示，通过反馈控制算法实现了弯曲 波吸收和弯曲波斗篷(见图 7(c)和 7(d)) 。Ning 等人 [127,128] 通过将压电片呈放射状粘贴在弹性基体板 表面，如图 7(e)所示，外接控制电路并使其参数按照指定规则由内向外梯度排布，制成了弯曲波黑 洞(见图 7(f)) 。 图 7.主动弯曲波斗篷、黑洞示意图。 (a)、(b)弯曲波隐身斗篷示意图和实验图 [126] 。(c)、(d)分别为…”