Understanding the effects of adhesive layer on the electromechanical impedance (EMI) of bonded piezoelectric wafer transducer

This paper investigates the effects of the adhesive layer on the admittance of bonded piezoelectric wafer active sensors (PWASs) through mode identification, parametric studies, and experimental verification. Based on the time-frequency analysis of the broadband ultrasound pitch-catch signal, we discovered that the resonances of the PWAS actuator bonded on a thin slender structure are associated with the longitudinal and flexural modes of the structure. Subsequently, a physics-based shear transfer parameter was introduced to establish a multi-mode analytical model. Parametric studies were carried out to study the effects of the adhesive layer on the frequencies and amplitudes of the PWAS resonances. Based on the insights gained from the parametric studies, the simulated resonant frequencies of the PWAS were matched with the experimental measurements by adjusting the unknown adhesive layer parameters.