Shankar Siddharth, Balasubramaniam Krishnan
IEEE Trans Ultrason Ferroelectr Freq Control. 2021 May;68(5):1866-1875. doi: 10.1109/TUFFC.2021.3049507. Epub 2021 Apr 26.
Electromagnetic acoustic transducers (EMATs) can efficiently generate the shear horizontal (SH) guided wave modes. In this article, the Halbach magnet array pattern is explored as an alternate to the conventional periodic permanent magnet (PPM) structure. The magnetic field strength of a Halbach array is significantly higher on one side of the structure while it is weak on the opposite side of the array. This magnetic field distribution enables Halbach EMATs to generate ultrasonic waves with relatively large amplitude. To observe this phenomenon, this study compares the amplitude generated from multiple single-row Halbach EMATs with single-row PPM EMAT configurations using finite-element-based simulation models for SH0 ultrasonic wave generation. This article then presents the ultrasonic wave fields generated by various double-row Halbach EMAT configurations using finite-element-based simulation models and experimentally validated for guided fundamental SH0 mode generated in an aluminum plate specimen. It is observed that distinct ultrasonic guided wave beam patterns be associated and predicted for different double-row Halbach EMAT configurations.
电磁声换能器（EMATs）能够高效地产生水平剪切（SH）导波模式。在本文中，研究了哈尔巴赫磁体阵列模式，以替代传统的周期性永磁体（PPM）结构。哈尔巴赫阵列的磁场强度在结构的一侧显著更高，而在阵列的另一侧则较弱。这种磁场分布使哈尔巴赫电磁声换能器能够产生振幅相对较大的超声波。为了观察这一现象，本研究使用基于有限元的SH0超声波生成模拟模型，比较了多个单排哈尔巴赫电磁声换能器与单排PPM电磁声换能器配置所产生的振幅。本文接着使用基于有限元的模拟模型展示了各种双排哈尔巴赫电磁声换能器配置所产生的超声波场，并通过实验验证了在铝板试样中产生的基本SH0导波模式。研究发现，不同的双排哈尔巴赫电磁声换能器配置会产生并预测出不同的超声导波束模式。
