Access Type

Open Access Embargo

Date of Award

1-1-2010

Degree Type

Thesis

Degree Name

M.S.

Department

Mechanical Engineering

First Advisor

Golam M. Newaz

Abstract

The effects of negative effective mass density and negative effective elastic modulus on energy absorption have been investigated experimentally and numerically. It is noteworthy that the classical continuum mechanics support the concept of negative effective elastic modulus of artificially designed vibro - acoustic metamaterial. Both the negative effective mass density and the effective negative elastic modulus are frequency dependent and are shown up near the natural frequencies of the complex structure. The physical structure has been designed in such a fashion so that only longitudinal planar waves at a frequency of 0 - 20 kHz can propagate throughout the system. The free - free vibration testing has been conducted to evaluate the natural frequencies of the complex system and to determine the negative effective mass density near resonances. Moreover, the numerical platform is based on acoustic - structural interaction physics. By performing frequency analysis, the negative effective elastic modulus of the complex structure, which demonstrates the energy absorption phenomenon, has been found numerically.

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