| Summary: | 碩士 === 國立成功大學 === 機械工程學系碩博士班 === 100 === Phononic crystals are periodically composed of two or more materials, regardless of the elastic waves in solids or sound waves, band gap phenomenon are generated due to the cyclical relationship for the wave propagation. Destruction will make periodic structure to the defect formations, common defects are point defect and line defect. Point defect is the common phononic crystal resonant cavity, while the phononic crystal waveguide that is, the line defect. Phononic crystals have a lot of discussion to the frequency gap phenomenon. In addition, there has abnormal dispersion phenomenon in the propagation area, such as negative refraction characteristics of these features for further improvement and progress on the design of subsequent components. Thus, this aspect of the study becomes a hot topic of recent academia.
Firstly, using the plane wave expansion method and finite element method to obtain phononic crystal dispersion curves, and then combined with the supercell method to get dispersion curve of phononic crystal waveguide to predict the coupling between the waveguide, such as energy pass, coupling length and so on. In general, the coupling phenomenon occurs when the two waveguides between certain distance. Namely, the distance between the two waveguides are close, the mode will affect each other. Coupling between waveguide structure and the surface of waveguide produced the acoustic surface wave phenomena, and discussing the relationship between surface waveguide structure and surface wave behavior. In the past, most of the acoustic surface wave excited by interdigital electrodes combined with piezoelectric material, via this novel phononic crystal structure would bring the different thinking for the technology industry.
|
|---|
