非铁磁性金属材料螺旋线圈电磁超声换能器接收效率场路耦合分析

摘要

Considering that the receiving signals of an electromagnetic acoustic transducer (EMAT) are extremely weak, a circuit-field coupled finite element model based on the receiving progress of a spiral coil EMAT and a reception equivalent circuit was established. The influence patterns of impedance matching parameters, coil conductor diameter, input resistance of pre-amplifier and backplate-to-coil distance were investigated with respect to the receiving efficiency. The results show that the amplitude of the receiving shear wave from experiments can be enhanced by at least 3 times when coil conductor diameter is 0.25 mm, input impedance of the pre-amplifier is 1 kΩ, and the backplate-to-coil distance is 0.5 mm. The circuit-field coupled analysis method, which takes the output gain of the reception circuit and the conversion efficiency of the receiving EMAT into consideration, can be used to guide the design of the receiving EMAT system more accurately.%针对电磁超声换能器(electromagnetic acoustic transducer,EMAT)接收信号十分微弱的问题,建立包括螺旋线圈EMAT换能过程和接收等效电路的场路耦合有限元模型;分析阻抗匹配参数、线圈导线直径、前置放大器的输入阻抗和铜背底至线圈间距对EMAT接收效率的影响规律.研究结果表明:当线圈导线直径为0.25 mm,前置放大器输入阻抗为1 kΩ,铜背底至线圈距离为0.5 mm时,实验接收横波信号幅值可以提高3倍以上;场路耦合分析方法能够综合考虑接收电路的输出增益和接收EMAT的换能效率,可以更准确地指导EMAT系统设计.