| Summary: | 碩士 === 國立臺灣大學 === 應用力學研究所 === 107 === The major application of piezoelectric ceramic on the market is to attach it to other structures for various engineering requirements. The mode shapes of the composite structures are usually more complicated than the uniform structures, which is due to the continuity conditions.
This thesis reports a developed analytical approach to analyze resonance frequencies and mode shapes of the composite structures, including one-dimensional structure and disc structure. They are common engineering structures and are chosen to study in this thesis. The theory was established by combining the piezoelectric constitutive equations and wave equation in Cartesian coordinate and cylindrical coordinate. Methods to solve continuity conditions and boundary conditions were constructed to identify resonant frequencies and mode shapes. Using numerical analysis, theoretical resonance frequencies and mode shapes were obtained. The structure characteristics were also simulated by finite element method to verify developed theory. Finally, a 1-D piezoelectric composite and a circular composite were fabricated to compare with theory and finite element analysis. The one-dimensional composite structure is designed for the application of a piezoelectric motor for carry an object. The positions of piezoelectric actuators are designed so that the resonant mode is not interfered by the other actuator. The driving method adopts the method of dual-frequency-dual-mode to excite two resonant modes in order to generate a traveling wave. Driving frequencies were controlled to have a integer multiplication relationship to create a continuous and steady traveling wave. Experimental results demonstrated that the displacement of a 31mg object can be moved for 50.3 mm and the maximum speed of a 20mg object can reach 3.1mm/s. On the other hand, the disc composite structure operated rapidly through the resonant frequency to atomize water droplets into air. This composite structure can be used as a high-speed oscillator and an atomizer. Both of these composite structures verified the developed analytical approach can be used to study piezoelectric composite for engineering applications.
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