电磁超声电声转换效率的影响因素分析

电磁超声是一种非接触超声检测方法，因不需要耦合剂，在一些常规超声无法实施的特殊检测领域发挥着重要作用。但是，由于电磁超声电声转换效率低，制约着电磁超声的广泛应用。分析了几种参数对电磁超声电声转换效率的影响，包括探头的提离、激励信号的电流幅值、频率、周期个数和仪器的输出功率等几个因素。研究表明：随着探头提离的增大，电磁超声的信号几乎成指数衰减；通过优化激励信号的电流幅值、周期个数和激励频率以及在探头两端增加阻抗匹配单元，可以提高电磁超声的电声转换效率。

Analysis of Influencing Factors in Electromagnetic Acoustic Electro-acoustic Conversion Efficiency

EMAT is a non-contact ultrasonic testing method,with no need coupling,and plays an important role in a number of special routine ultrasonic testing fields.However,the lower elec-tro-acoustic conversion efficiency restricts the usage of electromagnetic acoustic.The influences of several parameters on the electro-acoustic conversion efficiency are analyzed,such as the probe lift-off,the current excitation signal amplitude,frequency,cycle number,output power of in-strument,and so on.The results show that with the increase of probe lift-off,the electromagnet-ic acoustic signal decreases almost exponentially,and the electromagnetic acoustic electro-acoustic conversion efficiency can be improved by optimizing the current excitation signal amplitude,the cycle number,the excitation frequency,and adding the impedance matching unit in the probe ends.