Numerical Simulation and Experimental Verification of Mechanical Displacements in Piezoelectric Transformer

Since its invention, piezoelectric transformers (PTs) have been extensively studied and its performances have been continuously improved. Nowadays, such devices are designed in sophisticated architectures with associated models describing their behavior quite accurately. However, the different studies usually carried out on such devices mainly focus on their electrical characteristics induced by direct piezoelectric effect such as voltage gain and efficiency. In this work, a particular interest is given to the characterization of mechanical displacements induced by inverse piezoelectric effect, in a PT in vibration. For this purpose, a detailed 3D finite element analysis is proposed to examine the mechanical behavior of a Rosen type transformer made of a single bar of soft PZT (P191). At the first three modes of vibration, output voltage and mechanical displacements along the length, the width and the thickness are calculated. The amplitude of displacements varies in a range from a few nanometers to a few hundred nanometers. The validity of the simulations is successfully confirmed by experiments carried out on a prototype using a laser interferometer. A good match is observed between simulation and experimental results despite some differences observed locally at the scanned sections. Such 3D-simulations thus appear as a helpful tool for a better understanding of mechanical phenomena in Rosen-type PT.