增强SH波电磁超声传感器信号的方法与实验

摘要

Electromagnetic acoustic transducer ( EMAT) technology is a non-contact nondestructive testing method which can be used under harsh condition. The driving and receiving of shear horizontal (SH) wave can be implemented by EMAT. The conventional EMAT for SH wave is based on magnetostrictive effect, but its signal is weak. In order to obtain stronger SH wave signals and improve the signal-to-noise ratio, a method to enhance the EMAT signal is presented. The additional permanent magnets are added to the closed magnetic circuit of the main permanent magnets to improve the magnetization in the specimen under the EMAT coil,so the signal amplitude is improved significantly. Experiment verifies that this method is beneficial to increase the signal amplitude, and thereby improving the detectability.%电磁超声传感器技术作为一种非接触无损测量方法,可用于恶劣工况的无损检测,尤其是可以实现水平剪切(SH)波的激励和接收.基于磁致伸缩效应的常规SH波电磁超声传感器信号较弱,为得到较强SH信号,改善信噪比,提出了一种增强电磁超声传感器信号的方法.该方法是在主永久磁铁闭合磁路上施加辅助永久磁铁,提高电磁超声线圈下部构件磁化强度,从而增强信号.实验证明:此方法可以使信号得到明显增强,并且有助于提高缺陷检测能力.