Nonlinear behavior of an ultrasonic transducer

A transducer model, based on nonlinear piezoelectric constitutive equations, has been developed to describe the harmonic generation that occurs on current or velocity signal analysis when the transducer is driven at high voltage. The symmetrical Langevin transducer studied close to its resonance frequency is composed of Navy III type power ceramics. The nonlinearities create an energy spread over the frequency spectrum and consequently result in an amplitude saturation effect at the driving frequency, which can be interpreted in terms of the loss mechanism. Experiments have been carried out to measure the nonlinear losses and the harmonic amplitude evolutions. Results are given and discussed. Eventually, by experimental means, identification of the influential nonlinear coefficients permits comparison between theoretical predictions and experimental results.