Mechanical Engineering ETDs

Publication Date

7-1-2016

Abstract

In many areas of engineering such as telecommunications industry, lenses and optical cooling, waveguiding and the ability to control wave propagation is necessary. Phononic Crystals (PnCs) influence the propagation of mechanical waves by their periodic variation in elastic impedances. Depending on Lattice type and inclusion's spacing, one can manipulate the frequencies that are blocked or allowed to transmit through the crystal in a particular direction. In this work, two dimensional PnCs plates are design and also numerically and experimentally demonstrated. Finite Element Analysis (FEA) was performed to study the dispersion behavior and eigenmodes of a PnC. The simulations show the existence of a complete bandgap, thus acoustic PnC devices such as cavity, resonator and waveguide are created accordingly by introducing a line defect to the crystal. The experimental response of the devices was then measured by fabricating and then testing them. These results show excellent agreement with the FEA. For the first time waveguide and 90áµ’ bend is designed that have several isolated modes in the bandgap with transmission efficiencies above 90% for a specific frequency range. In this seminar also a few novel patents will be introduced. We consider a two-dimensional periodic square array of the air holes in a finite aluminum medium. The defect introduced to the crystals are acting as local acoustic resonances/guiding with the substrate and lead to the possibility of finding a low-frequency confined acoustic waves or guided modes. Studying the mode shapes will help to shed light on the origin of BG formation and as the results BG optimization. The numerical and experimental results presented here are related to the case of Aluminum-air devices, but the conclusions remain valid for other materials and compositions as well.

Keywords

Phononic Crystals, RF Devices, Finite Element Method, Waveguiding, Phononic Crystals, RF Devices, Finite Element Method, Waveguiding, Mode shape

Degree Name

Mechanical Engineering

Level of Degree

Doctoral

Department Name

Mechanical Engineering

First Advisor

Leseman, Zayd

First Committee Member (Chair)

Shen, Yu-lin

Second Committee Member

El-Kady, Ihab

Third Committee Member

Fatih Su, Mehmet

Fourth Committee Member

Hossein-Zadeh, Mani

Document Type

Dissertation

Language

English

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