Nonlinear constant evaluation in a piezoelectric rod from analysis of second harmonic generation

The design of transducers requires a clear understanding of their electromechanical behavior. This involves precise linear modeling as well as characterization. With the development of novel techniques such as harmonic imaging as well as high-power applications, nonlinear aspects must also be taken into account. In this study, harmonic generation in the mechanical displacement of a piezoceramic rod under high sinusoidal electric fields was measured. Theoretically, the nonlinearity can come from various sources: dielectric, mechanical, and electromechanical. The nonlinearity coming from external sources being eliminated or taken into account, it is shown here that the analysis, over a wide frequency range, of 2 parameters related to the harmonic distortion enables the respective identification of these sources and, at the same time, the evaluation of third-order constants of the material.