New insights into the mechanical pre-stressing of piezotransducers

Although pre-stressing is a requirement for the operation of a high-power piezo transducers, its impact on the model, the performance and the design of such devices is still not yet fully covered in the literature. This work attempts to bridge this gap by analyzing how the components of the Butterworth-Van Dyke model, the resonances, electrical impedances, electromechanical coupling factor, mechanical losses, and the tuning inductance are determined as a function of mechanical pre-stress. We have employed the Butterworth Van-Dyke model to study piezoelectric transducers tightened with a range of pre-stressing levels (12.2–60.1 MPa). As expected, the experimental results indicate that the components of the Butterworth-Van Dyke model are dependent upon the mechanical pre-stressing. The conclusions point out that, under mechanical pre-stressing levels between a threshold value and 60.1 MPa, the transducers used in this work tend to stabilize and enhance their performances. Also, upon stabilization, the transducers can be tuned with a constant inductance, which may also aid the design of ultrasonic systems. Overall, this work contributes to the definition of pre-stressing levels and its relationship with the length of the transducer, the mechanical losses, and the tuning.