Author

Fariha Mir

Date of Award

Spring 2019

Document Type

Open Access Thesis

Department

Mechanical Engineering

First Advisor

Sourav Banerjee

Abstract

Harvesting unused and untapped energy from ambient vibration noise and acoustic sound waves is an emerging field of research in the recent years. Utilization of the energy with a wide band of the frequency spectrum from the vibrational sources alone stands as one of the most promising ways to power small electronic devices, smartphones, local structural health monitoring (SHM) sensors and home and workshop appliances. Various sources of ambient vibration and acoustic noise can be found around us in our everyday life. These sources are abundant in almost all the engineering industries and manufacturing facilities for example in aerospace, mechanical and civil sectors. Running machinery in a workshop, ambient vibration in a manufacturing facility, vibrating wings of an aircraft, high dB aircraft noise near airports, engine noise in a plant, vehicle noise near a roadside facility, etc. are few examples of the ambient source of energy that can be harvested which are otherwise wasted. If a suitable mechanism is devised, the vibration and acoustic noise sources can be tapped and equipped to reclaim the energy to create local power sources. First, in this thesis, a recently proposed method of creating Acoustoelastic Metamaterial (AEMM) is used to investigate further if that can be used to harvest energy from the industrial noise barriers. It is known that the noise barriers are designed to minimize the noise outside the boundary like we see the noise barriers beside the highways. Construction materials like concrete, steel, vinyl, wood or earth mounds are used in the industrial sound barriers that can reduce the sound pressure level (dB) on the other side of the barrier. In this thesis, a novel metamaterial wall (MetaWall) is proposed to redefine the industrial sound isolation wall using the integrated AEMM units. Purpose of the proposed MetaWall is to deliver two principal objectives, simultaneously, 1) provide enhanced sound isolation capability, which is closer to ~1.5 times the current state-of-the-art, and 2) make use of the isolated noise by transforming into usable electrical energy. Acoustic metamaterials are traditionally reported for guiding and isolating acoustic and elastic waves. In this article, wave isolation and energy harvesting capabilities of the acoustic metamaterial is fused to propose MetaWall unit bricks, which are made of rubber-metal-concrete composite, as an industrial building material. A numerical study shows that the designed prototype of a MetaWall brick can generate up to ~2mW of power against 10KΩ resistive load with just only 1 mm displacement depending on the type of smart material used in the composite while maintaining compressive strength greater than the minimum required strength 5 MPa. Such acousto-elastic metamaterial (AEMM) models can also be used in the aerospace sector to power the NDE/SHM sensors. Hence, further in this thesis, a rigorous study is made to find the required power to use traditional NDE / SHM sensors such that the power can be harvested with the AEMM model. The ultimate goal of this second study is to minimize the size of the proposed AEMM model to make it suitable for aerospace applications. With the change of the materials of the cell constituents, it is shown that the power outputs from a similar model can be significantly altered and further optimized (not performed in this thesis). A parametric study is performed to show the change in the output power pattern. A plate type metamaterial is proposed to harvest a significant amount of energy from the ambient vibration as low as 100Hz.

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