Unidirectional emission and detection of Lamb waves based on a powerful and compact coils-only EMAT
Unidirectional emission and detection of Lamb waves based on a powerful and compact coils-only EMAT
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DOI：
10.1016/j.ndteint.2021.102492
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发表时间：
2021-06-27
影响因子：
4.2
通讯作者：
Rueter, Dirk
中科院分区：
文献类型：
--
作者：
Rieger, Kai;Erni, Daniel;Rueter, Dirk
本研究探讨了一种紧凑的非接触式电磁声换能器（EMAT），没有笨重的磁铁或单独的电磁铁的超声兰姆波在1 mm厚的钢板单向传输和接收。换能器头仅由两个紧密相邻的细长扁平线圈组成。强大的传感器技术桥接了高达1.5 mm的气隙。两个1 kV振幅的相位调整1 MHz脉冲增强了一个方向上的侧向投影超声场;其他脉冲则通过相消干涉衰减。一个5毫米的超声波波长与1毫米厚的钢板用于测试，波场计算结果吻合良好。作为一种可能的应用，扫描钢板的不可接近的边缘，其中难度增加了一个额外的边缘在一个类似的距离代表竞争的干扰反射。除了这种特定的非接触式应用之外，更普遍的进展是通过高功率和连续高偏置电流（1 kA）的相互耦合电感器的紧凑系统来演示相位精确的超声发射和灵敏的回波接收，从而实现基于单层密集排列线圈的紧凑而强大的EMAT相控阵列。
This study investigated a compact noncontact electromagnetic acoustic transducer (EMAT) without bulky magnets or separate electromagnets for unidirectional transmission and reception of ultrasonic Lamb waves in 1 mm thick steel plates. The transducer head consists of only two, closely adjacent and elongated flat coils. The powerful sensor technology bridged air gaps up to 1.5 mm. Two phase-adjusted 1 MHz pulses at 1 kV amplitude enhanced the sideways-projected ultrasound field in one direction; others were attenuated by destructive interference. A 5 mm ultrasound wavelength with 1 mm thick steel plate was used for testing; wave field calculations were in good agreement with results. As a possible application, an inaccessible edge of a steel plate was scanned, where the difficulty was increased by an additional edge at a similar distance representing competing interfering reflections. More general progress beyond this specific non-contact application is the demonstration of phase-accurate ultrasound transmission and sensitive echo reception with a compact system of mutually coupling inductors at high power and continuous high-bias currents (1 kA), allowing compact and powerful EMAT phased arrays based on single-layer densely arranged coils.