| Summary: | 博士 === 臺灣大學 === 機械工程學研究所 === 98 === Three-dimensional and coupled dynamic characteristics of piezoelectric materials are studied in this disertation. The piezoelectric materials, which are including piezoceramic plate, shell, piezoelectric two-layer discs and rectangular bimorphs, are used experimental measurements, finite element method (FEM), and theoretical analyses to study the out-of-plane and in-plane vibration characteristics. Electrode design method is proposed to enhance the vibration mode efficiency for piezoelectric materials, and is applied to piezoelectric plate and shell in experimental measurement. The experimental results of vibration characteristics are verified with theoretical analysis and numerical calculation. Temperature field is also studied for the piezoceramic plate with segmented electrodes and with crack when the specimens vibrate at high frequency. Furthermore, multilayer piezoelectric component is composited of the same and opposite poling direction, and it has different vibration characteristics by series and parallel electrically connection. This investigation thoroughly understands three-dimentsional dynamic characteriscs of several piezoelectric materials by experimental measurements, numerical calculations, and theoretical analyses.
Several experimental techniques are used to measure the dynamic characteristics of piezoelectric materials in this study. First, the full-filed optical technique, amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI), can measure simultaneously the resonant frequencies and mode shapes for in-plane and out-of-plane vibration. The excited voltages for mode shapes refer to the efficiency of three-dimensional vibration. Second, the point-wisely measurement system, laser Doppler vibrometer (LDV), can obtain resonant frequencies not only by dynamic signal swept-sine analysis, but also by the time-frequency transform from impulse signal excitation to the piezoceramic plates. Third, the correspondent in-plane resonant frequencies and anti-resonant frequencies are obtained by impedance analysis, and the electromechanical coupling coefficients can be calculated to perform the efficiency of resonance modes. Forth, infrared thermography is also full-field optical technique to measure the distribution of temperature filed. In theoretical analysis, the resonant frequencies, vibration displacements, and stress fileds of piezoceramic plate are derived by superposition method and its symmetric displacement properties of in-plane vibration are corresponding to the four kinds of electrode design in experiment. The transverse, extensional, and tangential vibration characteristics for piezoelectric two-layer discs of the parallel- and series-type polarization are also derived by theoretical analysis. All the results of the experimental measurements and theoretical solutions are compared with the FEM results. Besides, the electrode design method is provided by the summation of in-plane stresses in theoretical analysis, and the stress field is also corresponding with the electric flux of thickness direction in FEM. The vibration mode efficiency of piezoceramic plate and shell can be design by the stress and electric flux fields. It is excellent consistence between resonant frequencies, mode shapes, and normalized displacements on the dominant vibration motion by experimental measurements, finite element numerical calculations, and theoretical analyses.
|
|---|
