表面波椭圆偏振测量电磁声传感器的研制

    Optimized Design of Electromagnetic Acoustic Sensors for Surface Wave Polarization Measurements

    • 摘要: 电磁声传感器(electromagnetic acoustic transducer,EMAT)因其具有非接触、可设计性强等优势,在无损检测领域得到了广泛的应用。本研究提出了一种表面波聚磁式偏振测量电磁声传感器(magnetic concentrate type polarization measurement EMAT,MC-PM-EMAT)。该传感器利用2种聚磁式永磁铁阵列的磁场分布特征,配合线性单线圈结构,可实现表面波椭圆偏振面内及离面位移分量的独立测量。首先,提出了MC-PM-EMAT的设计方法,分析了该传感器的磁场分布特征,验证了磁通密度的提升效果。其次,建立了MC-PM-EMAT的多物理场耦合仿真模型,研究了该传感器的面内位移和离面位移的测量能力,结果表明,相比于传统型EMAT,所提出的MCPM-EMAT的面内分量测量信号提高了6.17倍,离面分量测量信号提高了2.49倍。最后,研制了MC-PMEMAT,并搭建了表面波椭圆偏振实验测量系统,进一步实验验证了MC-PM-EMAT的偏振测量效果。所提出的MC-PM-EMAT显著提升了表面波的偏振测量能力,为基于偏振特性的力学性能表征和缺陷的无损检测提供了一种重要的传感测试手段。

       

      Abstract: Electromagnetic acoustic transducer (EMAT) has been widely exploited in the field of nondestructive testing due to its advantages of non-contact and designability. In this paper, a surface wave magnetic concentrate type polarization measurement EMAT (magnetic concentrate type polarization measurement, MC-PM-EMAT) is introduced. The sensor utilizes the magnetic field distribution characteristics of two magnetic concentrate type permanent magnet arrays combined with a linear singlecoil structure to enable independent measurements of the in-plane and out-of-plane displacement components of surface wave elliptical polarization. Firstly, the design method of MC-PM-EMAT was proposed, and the magnetic field distribution characteristics of this sensor were analyzed to verify the magnetic flux density enhancement. Secondly, a multi-physics field coupling simulation model of the MCPM-EMAT was established to investigate the measurement capability of the in-plane and out-of-plane displacements of the sensor, and the results show that the proposed MC-PM-EMAT boosts the measurement signals of the in-plane component by a factor of 6. 17 and the out-of-plane component by a factor of 2. 49, compared to that of the conventional type EMAT. Finally, MC-PM-EMAT was developed and the experimental measurement system of surface wave elliptical polarization was built to further experimentally verify the polarization measurement of MC-PM-EMAT. The proposed MC-PM-EMAT significantly improves the polarization measurement capability of surface waves and offers an important sensing test method for the characterization of mechanical properties and non-destructive testing of defects based on polarization characteristics.

       

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