Due to the poor conversion efficiency and signal-to-noise ratio (SNR) of Electromagnetic Acoustic Transducer (EMAT) testing, the defect detection sensitivity is limited, which restricts the extensive industrial applications. A finite element model for the testing process of a meander-coil EMAT wasestablished that considers the simplified excitation and detection circuits for the EMAT. Based on this model, the effect of the connection methods (parallel or series) of the coils in the generating and receiving EMATs on their generating and receiving efficiency was investigated, and the simulation results were validated experimentally. Subsequently, the pulse compression technique with a 13-bit Barker code was used for the EMAT detection, and improvements of the SNR and range resolution were established through numerical simulation and experimental measurement. The results show that compared with the traditional EMAT design, which comprises single-layer transmitting and receiving coils, the conversion efficiency of the optimized EMAT with two excitation and receiving coils in the parallel connection can be improved by 52.8%. With the application of the Barker-coded pulse compression to detect the ultrasonic A-scan signal with no synchronous average, the SNR of the defect echo can be improved by 9.5 dB compared with the A-scan signal with 128 synchronous averages.

中文翻译：

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增强表面波EMAT高灵敏度检测的方法

由于电磁声换能器（EMAT）测试的转换效率和信噪比（SNR）差，缺陷检测灵敏度受到限制，从而限制了广泛的工业应用。建立了曲流式EMAT测试过程的有限元模型，其中考虑了EMAT的简化激励和检测电路。在此模型的基础上，研究了线圈在生成和接收EMAT中的连接方式（并联或串联）对其生成和接收效率的影响，并通过仿真验证了仿真结果。随后，将具有13位巴克码的脉冲压缩技术用于EMAT检测，通过数值模拟和实验测量，确定了信噪比和距离分辨率的提高。结果表明，与传统的单层发射和接收线圈的EMAT设计相比，具有两个并联的激励和接收线圈的优化EMAT的转换效率可提高52.8％。通过使用Barker编码的脉冲压缩来检测没有同步平均值的超声A扫描信号，与具有128个同步平均值的A扫描信号相比，缺陷回波的SNR可以提高9.5 dB。通过并联连接两个励磁和接收线圈，优化后的EMAT的转换效率可提高52.8％。通过使用Barker编码的脉冲压缩来检测没有同步平均值的超声A扫描信号，与具有128个同步平均值的A扫描信号相比，缺陷回波的SNR可以提高9.5 dB。通过并联连接两个励磁和接收线圈，优化后的EMAT的转换效率可提高52.8％。通过使用Barker编码的脉冲压缩来检测没有同步平均值的超声A扫描信号，与具有128个同步平均值的A扫描信号相比，缺陷回波的SNR可以提高9.5 dB。