传统基于周期性永磁体的电磁超声换能器结构较复杂, 为此该文提出了一种由单一永磁体和导线阵列线圈构成的电磁超声换能器（EMAT）用于激发板中的SH0导波。首先叙述了设计的原理, 并采用有限元软件进行三维数值仿真分析, 利用水平极化永磁体垂直于板面的磁场在铝板中成功激发出SH0导波。为使EMAT换能效率达到最优, 研究长和宽为10 mm×25 mm的永磁体, 其高度及线圈匝数不同时EMAT激励的效率。仿真结果表明, 选用永磁体高度为25 mm及线圈匝数为37时EMAT换能效率和声场指向性较好。在此基础上, 通过实验研究了不同线圈匝数对换能器换能效率的影响, 实验结果与仿真结果一致, 充分验证了该文设计EMAT的方法具有可行性。

The structure of the traditional electromagnetic ultrasonic transducer(EMAT) based on periodic permanent magnets is relatively complicated. In order to overcome this shortcoming, this paper presents an EMAT composed of a single permanent magnet and a wire array coil to excite the SH0 guided wave in the plate.First, the principle of the design is described,and the finite element software is used for three-dimensional numerical simulation analysis.The SH0 guided wave is successfully excited in an aluminum plate by using the magnetic field of the horizontally polarized permanent magnet perpendicular to the surface of the plate.In order to optimize the energy conversion efficiency of EMAT,the EMAT efficiency of the permanent magnet with the length and width of 10 mm×25 mm is investigated when the height and the coil turns are different. The simulation results demonstrate that the EMAT energy conversion efficiency and sound field pointing performance are better when the height of the permanent magnet is 25 mm and the number of coil turns is 37. On this basis, the effect of different coil turns on the transducer efficiency is studied through experiments. The experimental results are consistent with the simulation results, which fully verify the feasibility of the EMAT design method in this paper.