Effect of the Nonlinear Properties of Piezoactive Materials on the Characteristics of Radiating Transducers
I.Golyamina (N.N. Andreev Acoustics Institute, Moscow, Russia)
Electromechanically active materials - piezoceramics and magnetostrictive compounds of different metals, are characterized by a nonlinear relation between the mechanical and electric (magnetic) state parameters. Such a relation is caused by the domain structure of these materials, and for its linearization, a bias electric (magnetic) field should be applied. In these conditions, the nonlinear properties manifest themselves as a decrease in the efficiency of the radiating transducers. However, the main effect caused by the nonlinear properties of material is the limitation on the growth of acoustic radiation power with increasing excitation level. For magnetostrictive radiating transducers, this limitation is determined by magnetostrictive saturation, whereas for piezoceramic transducers, by excessive heating and, hence, by depolarization and electric breakdown. The report presents the data, which were obtained from experimental studies and numerical estimates, on the nonlinear behavior of the most used ceramic and metallic active materials and transducers made of them. The conditions of their application are considered from the point of view of the dominance of one or another limiting factor. Particular attention is paid to the new active materials: the PMN-PT electrostrictive ceramics and the magnetostrictive compounds of rare earths with iron.
Section : 11