Geophysics Group EES-17, Los Alamos National Laboratory, MS D446, Los Alamos, NM 87545, USA.
Ultrasonics. 2014 Jul;54(5):1409-16. doi: 10.1016/j.ultras.2014.02.017. Epub 2014 Mar 4.
An air-coupled ultrasonic transducer is created by bonding a bulk piezoelectric element onto the surface of a thick plate with a wedge of power-law profile. The wedge is used to improve the ultrasonic radiation efficiency. The power-law profile provides a smooth, impedance-matching transition for the mechanical energy to be transferred from the thick plate to the air, through the large-amplitude flexural waves observed in the thinnest region of the wedge. The performance of the proposed transducer is examined numerically and compared to that of a design where the piezoelectric element is isolated and where it is affixed to a thin plate of uniform thickness. The numerical analysis is first focused on the free-field radiation of the transducers. Then, time-reversal experiments are simulated by placing the transducers inside a cavity of arbitrary shape with some perfectly reflecting boundaries. In addition to time-reversal mirrors, the proposed concept could be integrated in the design of phased arrays and parametric arrays.
一种空气耦合超声换能器是通过将块状压电元件粘结到具有功率-law 轮廓的厚板表面上而制成的。该楔形物用于提高超声辐射效率。功率-law 轮廓为机械能从厚板传递到空气提供了一个平滑的、阻抗匹配的过渡，通过在楔形物的最薄区域观察到的大振幅弯曲波来实现。本文通过数值方法对所提出的换能器的性能进行了研究，并与将压电元件隔离和固定在均匀厚度的薄板上的设计进行了比较。数值分析首先集中在换能器的自由场辐射上。然后，通过在具有一些完全反射边界的任意形状的腔体内放置换能器来模拟时间反转实验。除了时间反转镜之外，所提出的概念还可以集成到相控阵和参量阵的设计中。
