dc.contributor.advisor |
Tang, L |
en |
dc.contributor.advisor |
Calius, E |
en |
dc.contributor.advisor |
Das, R |
en |
dc.contributor.author |
Nacario Junior, Marlon |
en |
dc.date.accessioned |
2018-04-20T02:39:15Z |
en |
dc.date.issued |
2017 |
en |
dc.identifier.uri |
http://hdl.handle.net/2292/37080 |
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dc.description |
Full text is available to authenticated members of The University of Auckland only. |
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dc.description.abstract |
Metamaterials are artificial materials that exhibit paranormal properties not present in nature. Essentially, they are architectured materials that have been carefully designed to bend the rules of nature and provide exotic properties such as negative stiffness, negative refractive index, and negative effective mass. Metamaterials used in the acoustic-elastic field employ the effect of local resonances to artificially impart materials with properties such as negative stiffness and negative effective mass. This leads to some interesting phenomena such as attenuation band gap to occur. Linear systems often have limited applications due to the restriction of their narrow attenuation bandwidth. By introducing nonlinearity to metamaterials, the attenuation bandwidth can potentially be widened. Based on the research completed at Callaghan Innovation about a bistable curve beam resonator, indications imply that decreasing the potential barrier height can improve the vibration attenuation performance of the metamaterial. Based on this principle, the concept to study the effects of a flat potential energy well was introduced, i.e. effectively reducing the separation barrier height to zero. To produce a bistable resonator with a symmetric potential energy well proved to be very difficult with 3D printing means. A system that utilized a slack string system is to be investigated. By applying a slackness, the system becomes a piecewise function that has two sections; a tension zone where the string is taut and a slack zone where the tension is zero. The piecewise nonlinear system is modelled with the assumption that the resonator mass governs the characteristics of the system. For simplicity, the effects of gravity on the system are ignored. A numerical parametric study is investigated varying three parameters that were determined to affect the response of the system; slackness of the string, the mass ratio between the primary mass and resonator mass and the stiffness of the resonator mass. An experimental study was done to validate the system using a shaker as the force actuation. From these studies, the potential energy well was found to also include a discontinuity point at the slackness length, a property that was not factored in during the preliminary proposal. When comparing to linear 2DOF systems, the numerical studies showed that attenuation of the transmission peak could occur. Furthermore, in some cases, the second eigenfrequency inherently present in linear 2DOF systems was eliminated. Experimental studies showed that at lower frequencies, there were discrepancies between numerical and experimental results. However, at higher frequencies, numerical and experimental results correlated with each other. |
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dc.publisher |
ResearchSpace@Auckland |
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dc.relation.ispartof |
Masters Thesis - University of Auckland |
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dc.relation.isreferencedby |
UoA |
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dc.rights |
Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. |
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dc.rights |
Restricted Item. Available to authenticated members of The University of Auckland. |
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dc.rights.uri |
https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm |
en |
dc.rights.uri |
http://creativecommons.org/licenses/by-nc-sa/3.0/nz/ |
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dc.title |
Capability of Enhancing Vibration Attenuation of Nonlinear Resonant Metamaterials |
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dc.type |
Thesis |
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thesis.degree.discipline |
Mechanical Engineering |
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thesis.degree.grantor |
The University of Auckland |
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thesis.degree.level |
Masters |
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dc.rights.holder |
Copyright: The author |
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pubs.elements-id |
737868 |
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pubs.record-created-at-source-date |
2018-04-20 |
en |
dc.identifier.wikidata |
Q112934538 |
|