基于Leach模型的空气耦合超声换能器声阻抗匹配特性研究

Research on Characterization of Acoustic Impedance Matching of Air-Coupled Ultrasonic Transducers Based on the Leach Model

摘要:

压电陶瓷与空气之间的声阻抗差异巨大,导致声波在固-气介质间的能量传输效率低,研究匹配层特性对提升换能器能量传输效率具有重要意义。文章通过Leach模型仿真,研究了空气耦合超声换能器阻抗与瞬态响应,并搭建实验平台进行测试验证。仿真和实验结果表明,增加一层匹配层可将接收信号幅值增大约280%,增加两层匹配层可将接收信号幅值增大约363%。通过采用经声阻抗匹配后的换能器对碳纤维板缺陷进行检测,能明显检测出深度为0.5mm、直径为1mm凹槽缺陷的变化,验证了通过等效电路模型研究换能器匹配特性方法的有效性。

Abstract:

The acoustic impedance difference between air-coupled ultrasonic transducers is huge, resulting in low energy transfer efficiency between air-solid medium. Therefore, studying the characteristics of the matching layer of the transducer is of great significance to improve the sensitivity of the transducer to defects. By simulation through Leach, the impedance and transient response of the transducer were studied, and the acoustic impedance matching characteristics of the air-coupled ultrasonic transducer was analyzed. An air-coupled ultrasonic experimental platform was built to verify the simulation results. Experimental and simulation results show that, firstly, the Leach model can accurately describe the behavior of the air-coupled ultrasonic transducer. After matching the acoustic impedance of the transducer, reflections and interference occur in the presence of the matching layer, resulting in a second resonance phenomenon in the impedance. Secondly, the matching layer designed in this paper can increase the amplitude of the ultrasonic signal and improve the detection accuracy of the ultrasonic signal. Finally, the small defects that can not be identified by the unimpedance matching transducer were detected, and the practicality of the acoustic impedance matching transducer in detecting small defects in composite plates is verified.