多匹配层空气耦合压电超声换能器*

该文针对超声无损检测与成像功能空气耦合换能器开展了分析计算和研制。为解决压电材料与空气间巨大的阻抗失配问题,进行了多匹配层设计,并基于有限元技术仿真设计了1-3压电复合材料参数。借助复数压电方程,导出考虑损耗的多匹配层压电复合材料换能器厚度振动等效电路,获得其等效导纳,以此计算电导谱,同时基于有限元技术数值计算相应电导谱,二者有较好的一致性。在此基础上分别设计制作复合压电材料,多匹配层材料以及由此构成的空气耦合超声换能器。换能器的实测电导谱与数值仿真结果一致。进一步的换能器回波信号测试及其谱分析结果表明,所研制的160 k Hz中心频率空气耦合换能器样品有较好灵敏度和带宽。这些结果说明,该文研制的空气耦合超声换能器的初样是成功的。

Multi-matching layer air-coupled piezocomposite ultrasonic transducer

This paper describes our work on the numerical analysis, design, fabrication for air-coupled piezocomposite ultrasonic transducer employed in the NDT and imaging or materials characterization. The parameters of multi-matching layer and 1-3 connectivity composite are designed through numerical simulation technique in order to overcome the enormous impedance mismatch between air and piezoelectric element. Using complex piezoelectric equation, the thickness vibration equivalent circuit with an introducing attenuation for multi-matching layer air-coupled piezocomposite ultrasonic transducer is deduced, its equivalent admittance is then obtained to calculate the conductivity spectrum of this kind transducer. This spectrum is also calculated by finite element method. Both results are in good agreement. Based on these numerical results and parameters, the piezocomposite, multi-matching layer, and the air-coupled ultrasonic transducer are designed and fabricated. The experimental testing result of the conductivity spectrum for the transducer is agreed with the numerical results. The echo signal of the transducer and its frequency spectrum are further tested and analyzed. These results show that the transducer with a central frequency 160kHz have fairly good sensitivity and frequency bandwidth, and the success on this development is also demonstrated by these results.