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This dissertation is mainly on the theoretical analysis of vibrating crystal plates for acoustic wave resonator and sensor applications. The frequency and mode effects of different surface structures on either or both sides of the crystal plates are the main concerns in this dissertation. These effects are fundamental to the improvement of existing acoustic wave devices, or to the design of new acoustic wave devices, especially new sensors based on these effects.
At first, two-dimensional equations of motion for an anisotropic crystal plate with two thin films on its surfaces are derived by reduction from the three-dimensional equations of anisotropic elasticity and joining separate equations for the crystal plate and the thin films through interface continuity conditions. The thin films possess multiphysical effects, including inertia, stiffness, intrinsic stress, electric and magnetic couplings. The equations derived are used to analyze the perturbation of the resonant frequencies of the crystal plate under the influence of the surface films.
After that, two relatively more complicated but really existing problems in acoustic wave devices are analyzed. One is the effects of a surface film with nonuniform thickness, either stepped or gradually varying. The other is a crystal plate carrying an array of thin films which may be periodic or nonperiodic. In addition to the effects of surface films, vibrations of crystal plates with arrays of surface attached fibers in extensional or flexural motions and surface attached particles are investigated to explore the possibility of using crystal resonators for fiber and particle characterizations.
Finally, the effects of material property variation of thin film piezoelectric actuators are also studied.
Adviser: Jiashi Yang