Date of Completion

3-29-2019

Embargo Period

3-28-2020

Keywords

Metasurface, Piezoelectric transducer, Wave guiding, Particle damping

Major Advisor

Jiong Tang

Associate Advisor

Horea Ilies

Associate Advisor

Xu Chen

Associate Advisor

George Lykotrafitis

Associate Advisor

Ying Li

Field of Study

Mechanical Engineering

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

The overarching goal of structural dynamic analysis is usually to facilitate regulation of energy flows in terms of vibration and acoustic wave transmission. Such regulation of vibratory energy flows can yield effective designs of vibration suppression, energy harvesting, and vibration/wave based health monitoring, etc. This dissertation research employs the concept of built-up structure, i.e., constructing secondary oscillatory sub-systems and incorporating them into the underlying host structure to realize new ways of energy flow regulation. In particular, we propose to develop three distinct designs of sub-systems to realize unusual wave transmission and to dramatically improve damping performance, i.e., electro-mechanical local scatter for wave guiding, multi-field adaptive metasurfacing, and cantilevered coupling design to enhance energy dissipation.

The first built-up sub-system design is based on the electro-mechanical local coupling, aiming at realizing adaptive elastic metasurfaces capable of arbitrarily manipulating refracted wave energy. By adjusting the negative capacitances properly, accurately formed, discontinuous phase profiles along the elastic metasurfaces can be achieved. Based on different phase profiles, anomalous refractions, planar focal lenses, self-accelerating beams and source illusion can be realized on the transmitted elastic wave energy. The second sub-system, multi-field adaptive metasurfacing, combines the membrane-type acoustic metasurface with piezoelectric integration able to tune the initial stress on the membrane with different voltages such that different resonant frequencies of the membranes can be realized to accomplish proper phase profiles along metasurfaces. Applications, such as acoustic cloaking, are illustrated to feature the acoustic wave energy manipulation. To dissipate the vibrational energy, tuned mass particle damper is designed based on cantilevered coupling, where the particle damping mechanism is integrated into a tuned mass damper configuration. The essential idea is to utilize the tuned mass damper configuration as a motion magnifier to amplify the energy dissipation capability of particle damper. While these built-up sub-system designs are distinctly different, they share the common feature that, by properly adjusting the sub-system oscillatory effects, the impedance at the region of interest of the host structure can be altered as desired. Consequently, effective energy flow regulations are realized. The outcome of this research can directly benefit vibration control and structural health monitoring.

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