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.

中文翻译：

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表征SH0超声波的Halbach EMAT配置

电磁声换能器（EMAT）可以有效地生成水平剪切（SH）导波模式。在本文中，将探讨Halbach磁体阵列模式，以替代传统的周期性永磁体（PPM）结构。Halbach阵列的磁场强度在结构的一侧明显更高，而在阵列的另一侧则很弱。这种磁场分布使Halbach EMAT能够生成幅度较大的超声波。为了观察这种现象，本研究使用基于有限元的SH0超声波仿真模型，将多个单行Halbach EMAT与单行PPM EMAT配置生成的幅度进行了比较。然后，本文介绍了使用基于有限元的仿真模型通过各种双行Halbach EMAT配置生成的超声波场，并通过实验验证了铝板样本中生成的引导基本SH0模式。可以观察到，针对不同的双行Halbach EMAT配置，不同的超声导引的波束方向图是相关的和预测的。