Free vibration analysis of the piezoceramic bimorph with theoretical and experimental investigation

This paper investigates the vibration characteristics of an asymmetric, three-layered piezoceramic circular bimorph under traction-free boundary conditions by applying the electroelasticity and Kirchhoff plate theory. The asymmetric, three-layered bimorph consists of an isotropic shim layer and two piezoceramic layers of equal thickness and same polarization. Two optical techniques, amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and laser Doppler vibrometer (LDV), are used to validate the theoretical analysis. The resonant frequencies of the piezoceramic bimorph also are measured by an impedance analyzer. Both theoretical and experimental results indicate that the transverse vibration modes cannot be measured by impedance analysis, and only resonant frequencies of extensional vibration modes are present. However, transverse vibration modes of the piezoceramic bimorph can be obtained by the AF-ESPI and LDV measurements. The numerical calculations also are obtained using the finite-element method (FEM), and the results agree comparatively well with the theoretical analysis and experimental measurements. According to the theoretical calculation, the variations in resonant frequencies and effective coupling factors versus the various layer-thickness ratios also are investigated in this work.