Abstract
Equivalent circuits of piezoelectric structures such as bimorphs and unimorphs conventionally focus on the bending vibration modes. However, the longitudinal vibration modes are rarely considered even though they also play a remarkable role in piezoelectric devices. Losses, especially elastic loss in the metal substrate, are also generally neglected, which leads to discrepancies compared with experiments. In this paper, a novel equivalent circuit with four kinds of losses is proposed for a beamlike piezoelectric structure under the longitudinal vibration mode. This structure consists of a slender beam as the metal substrate, and a piezoelectric patch which covers a partial length of the beam. In this approach, first, complex numbers are used to deal with four kinds of losses—elastic loss in the metal substrate, and piezoelectric, dielectric, and elastic losses in the piezoelectric patch. Next in this approach, based on Mason’s model, a new equivalent circuit is developed. Using MATLAB, impedance curves of this structure are simulated by the equivalent circuit method. Experiments are conducted and good agreements are revealed between experiments and equivalent circuit results. It is indicated that the introduction of four losses in an equivalent circuit can increase the result accuracy considerably.
Highlights
Piezoelectric structures such as bimorphs and unimorphs are of great research interest for a wide variety of applications including ultrasonic motors [1], microgrippers [2], and microcantilever biosensors [3]
The above studies focus on the bending vibration modes of piezoelectric patches and related metal substrates; the motion equations which generate the equivalent circuits are of flexure vibrations of the structures, and do not take the longitudinal vibration modes into consideration because longitudinal vibrations are not the working condition of those bimorphs and unimorphs
This paper describes an equivalent circuit of a piezoelectric structure which consists of a slender aluminum beam and a PZT patch
Summary
Piezoelectric structures such as bimorphs and unimorphs are of great research interest for a wide variety of applications including ultrasonic motors [1], microgrippers [2], and microcantilever biosensors [3]. The above studies focus on the bending vibration modes of piezoelectric patches and related metal substrates; the motion equations which generate the equivalent circuits are of flexure vibrations of the structures, and do not take the longitudinal vibration modes into consideration because longitudinal vibrations are not the working condition of those bimorphs and unimorphs. “pure” piezoelectric ceramics are the targets when the equivalent circuits are related with losses and no metal substrates are concerned This approach simplifies the derivation of motion equations, while for practical applications, the metal substrates are included. Elastic loss in the metal substrate and three losses in the piezoelectric patch are built into the related parameters, and the longitudinal vibration mode is dealt with. The effectiveness of the equivalent circuit considering both elastic loss of the metal substrate and the three piezoelectric material losses is verified through experiments
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