Qiu Gongzhe, Song Xiaochun, Zhang Xu, Tu Jun, Chen Tao
Hubei Key Laboratory of Modern Manufacturing Quantity Engineering, School of Mechanical Engineering, Hubei University of Technology, Wuhan 430068, China.
Sensors (Basel). 2019 Jul 9;19(13):3019. doi: 10.3390/s19133019.
High frequency guided-waves offer a trade-off between the high sensitivity of local bulk ultrasonic thickness measurements and the large area scanning of lower frequency guided-waves, so it has been a growing interest for corrosion inspection with the dispersive SH1 mode. However, according to the dispersive curve, it is hard to generate the pure SH1 mode since the non-dispersive SH0 mode will be excited simultaneously. Thus, this paper investigates a transducer design method to generate a pure SH1 guided-wave, where the dual periodic-permanent-magnet electromagnetic acoustic transducers (PPM EMATs) are placed on exactly opposite positions either side of the plate symmetrically. The suppression effect for SH0 and the enhancement effect for SH1 of the dual PPM EMATs are mainly discussed by theoretical analysis and simulation analysis, and the influence of positioning errors of PPM EMATs placed on opposite sides of the plate on its performances are analyzed. Employing the proposed dual PPM EMATs, some experiments are performed to verify the reliability of finite element simulation. The results indicate that the dual PPM EMATs can suppress the SH0 mode and generate the pure SH1 mode effectively. Moreover, the longitudinal and lateral positioning errors can affect the dual PPM EMATs performances significantly.
高频导波在局部体超声厚度测量的高灵敏度与低频导波的大面积扫描之间提供了一种权衡，因此，利用色散SH1模式进行腐蚀检测越来越受到关注。然而，根据色散曲线，由于非色散SH0模式会同时被激发，很难产生纯SH1模式。因此，本文研究了一种产生纯SH1导波的换能器设计方法，即将双周期永磁电磁声换能器（PPM EMAT）对称地放置在板两侧完全相对的位置。主要通过理论分析和仿真分析讨论了双PPM EMAT对SH0的抑制作用和对SH1的增强作用，并分析了放置在板两侧的PPM EMAT的定位误差对其性能的影响。采用所提出的双PPM EMAT进行了一些实验，以验证有限元模拟的可靠性。结果表明，双PPM EMAT可以有效抑制SH0模式并产生纯SH1模式。此外，纵向和横向定位误差会显著影响双PPM EMAT的性能。
