为了减少多通道电磁超声换能器的磁铁数量,提高检测信号的信噪比,提出了一种组合型磁铁结构EMAT (电磁超声换能器),使用该EMAT可以在一次检测过程中完成超声测厚、轴向导波和周向导波扫查。通过仿真优化了换能器结构设计,分析了其结构参数对磁场强度的影响。设计换能器并搭建试验平台,验证了模型结构的正确性。与传统换能器的励磁效果相比,该换能器在工件近表面产生的磁场强度较大,可以在一次检测中同时完成测厚与轴向和周向两个方向的导波扫查;测厚信号的信噪比提升了2 dB,导波信号的信噪比提升了19.5%,检测效率得到提高。

In order to reduce the number of magnets of multi-channel electromagnetic ultrasonic transducer and improve the signal-to-noise ratio of detection signal, a combined magnet structure EMAT (electromagnetic acoustic transducer) is proposed. Using this EMAT, ultrasonic thickness measurement, axial guided wave and circumferential guided wave scanning can be completed in one detection process. The structural design of the transducer is optimized by simulation, and the influence of its structural parameters on the magnetic field intensity is analyzed. The transducer is designed and the test platform is built to verify the correctness of the model structure. Compared with the excitation effect of the traditional transducer, the magnetic field intensity generated by the transducer near the surface of the workpiece is relatively strong, and the thickness measurement and guided wave scanning in both axial and circumferential directions can be completed at the same time. The signal-to-noise ratio of thickness measurement signal is increased by 2 dB, the signal-to-noise ratio of guided wave signal is increased by 19. 5%, and the detection efficiency is improved.