Ultrasound based Structural Health Monitoring (SHM) commonly uses surface-bonded piezoelectric wafer active transducers (PWaTs) for ultrasound wave generation and sensing. Both the electromechanical impedance (EMI) of the surface bonded PWaT and the ultrasound pitch-catch signal have been studied extensively for damage detection. However, these two signals were studied separately. The correlation between the EMI and the pitch-catch signal has not been studied in detail. In this paper, a broadband spectral analysis method is presented to analyze the influence of the EMI resonances on the fundamental symmetric (S0) pitch-catch signal. First, the broadband responses of the PWaT actuator and sensor are measured and analyzed in the time-frequency domain. The results clearly demonstrate that the S0 pitch-catch signal can deviate significantly from the excitation signal when the excitation frequency is above a threshold. Next, a simulation model was implemented to explain the observed distortions. The simulation model was first validated by adjusting the adhesive parameters to reproduce the experiment measurements. The resonant characteristics of the PWaT actuator and sensor were then analyzed separately. The study reveals that the S0 deviations are due to the resonances and anti-resonances of the PWaT EMI. Furthermore, this study demonstrates that the resonance characteristics of surface-bonded PWaTs are more complicated than previously known. The research framework presented in this paper lays the theoretical foundation for future more in-depth analysis of the PWaT resonances.

基于超声波的结构健康监测（SHM）通常使用表面结合的压电晶片有源换能器（PWaT）来产生和感测超声波。表面结合的PWaT的机电阻抗（EMI）和超声音高捕获信号已被广泛研究以用于损伤检测。但是，分别研究了这两个信号。尚未对EMI与音高捕捉信号之间的相关性进行详细研究。本文提出了一种宽带频谱分析方法，用于分析EMI谐振对基本对称（S0）基音捕获信号的影响。首先，在时频域中对PWaT执行器和传感器的宽带响应进行了测量和分析。结果清楚地表明，当激励频率高于阈值时，SO音高捕获信号可能会明显偏离激励信号。接下来，实施了一个仿真模型来解释观察到的变形。首先通过调整粘合剂参数以重现实验测量值来验证仿真模型。然后分别分析了PWaT执行器和传感器的谐振特性。研究表明，S0偏差是由于PWaT EMI的谐振和反谐振引起的。此外，这项研究表明，表面键合的PWaT的共振特性比以前已知的更为复杂。本文提出的研究框架为将来对PWaT共振进行更深入的分析奠定了理论基础。