Dissertation > Industrial Technology > General industrial technology > Materials science and engineering > Other materials

Investigation on the Band Structure and Transmission Properties of Two-Dimensional Phononic Crystal

Author HuangXiaoYi
Tutor PengJingCui
School Hunan University
Course Materials Physics and Chemistry
Keywords phononic crystal band gap defect state transmission scattering
Type PhD thesis
Year 2006
Downloads 419
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During the last few years, the propagation of electromagnetic waves in artificial periodic structures of dielectric materials, known as photonic crystals, has received a great deal of attention, of particular interest is the existence of forbidden frequency bands. This search for band gaps in photonic crystals and the mathematical analogy between electromagnetic waves and vibrations has spurred a renewed interest in the propagation of elastic waves in the so-called phononic crystals. The propagation of elastic waves in periodic or random composite materials is an old topic in condensed matter physics and/or acoustic. The present research activities focus on the design of band gap in the acoustic spectrum of composite media. Acoustic gap being frequency domains in which propagation of sound and phonons are forbidden, one can imagine for these phononic crystals numerous engineering applications such as frequency filters,vibrationless environments for high-precision mechanical systems or the design of new transducers.Spatial and frequency distributions of forbidden bands of both surface and bulk acoustic waves are studied theoretically for two-dimensional (2D) periodic elastic structures consisting of aluminum and polymer. The surface is perpendicular to the 2D periodic arrays of circular cylinders embedded in a background material. The dispersion relations of the surface and bulk modes with wave vectors parallel to the surface are calculated for triangular Lattice and the stop band distributions are plotted in a form relevant to the comparison with ultrasound imaging experiments.The band structure and its dependence on the physical parameters and structured parameters need further physical interpretations. The higher velocity ratio between the two components of the composite, the more favorable the condition for gaps. Similarly, the density contrast is very important. However, for elastic waves(EL),high-density scatters favor gaps,while for acoustic waves(AC), low-density inclusions in a high-density matrix is the preferable setup. The topology and volume fraction occupied are the important factors influenced the band structure of phononic crystal. The volume fraction occupied must be in a certain range for gaps to exist. It is very significant for us to work on phononic band structures, such work can result in further step on theoretic area and provides instruction to fabricate phononic devices.We present elastic band-structure results for a new geometry of two-dimensional

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