Research Papers

Multicell Active Acoustic Metamaterial With Programmable Effective Densities

[+] Author and Article Information
W. Akl

Design and Production Engineering Department,  Ain Shams University, Cairo, 11571, Egypt

A. Baz

Mechanical Engineering Department,  University of Maryland, College Park, MD 20742

J. Dyn. Sys., Meas., Control 134(6), 061001 (Sep 13, 2012) (11 pages) doi:10.1115/1.4006619 History: Received August 03, 2009; Revised February 29, 2012; Published September 13, 2012; Online September 13, 2012

Considerable interest has been devoted to the development of various classes of acoustic metamaterials. Acoustic metamaterials are those structurally engineered materials that are composed of periodic cells designed in such a fashion to yield specific material properties (density and bulk modulus) that would affect the wave propagation pattern within in a specific way. All the currently exerted efforts are focused on studying passive metamaterials with fixed material properties. In this paper, the emphasis is placed on the development of a new class of composite one-dimensional acoustic metamaterials with effective densities that are programmed to vary according to any prescribed patterns along the volume of the metamaterial. The theoretical analysis of this class of multilayered composite active acoustic metamaterials (CAAMM) is presented and the theoretical predictions are determined for an array of fluid cavities separated by piezoelectric boundaries. These smart self-sensing and actuating boundaries are used to modulate the overall stiffness of the metamaterial periodic cell and in turn its dynamic density through direct acoustic pressure feedback. The interaction between the neighboring layers of the composite metamaterial is modeled using a lumped-parameter approach. One-dimensional wave propagation as well as long wavelength assumptions are adapted in the current analysis. Numerical examples are presented to demonstrate the performance characteristics of the proposed CAAMM and its potential for generating prescribed spatial and spectral patterns of density variation. The CAAMM presents a viable approach to the development of effective acoustic cloaks that can be used for treating critical objects in order to render them acoustically invisible.

Copyright © 2012 by American Society of Mechanical Engineers
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Figure 1

Types of fluid domains under consideration (a) fluid domain free from both ends and (b) fluid domain free from one end and coupled to compliant solid subdomain from the other end

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Figure 2

Electrical circuit analogy of the free–free acoustic cavity

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Figure 3

Acoustic domain comprising fluid and compliant solid parts

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Figure 4

Electric circuit analogy of the fluid/solid acoustic domain

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Figure 5

Acoustic domain comprising fluid and piezoelectric subdomains

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Figure 6

Electrical analogy for an acoustic domain comprising fluid subdomain coupled with open-loop piezoelectric subdomain

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Figure 7

Electrical analogy for an acoustic domain comprising fluid subdomain coupled with closed-loop piezoelectric compliant subdomain

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Figure 8

A schematic for a set of N cascading and coupled cells

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Figure 9

Analogous electric circuit for the set of N cascading and coupled cells

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Figure 10

Flowchart of the recursive algorithm

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Figure 11

Comparison between passive and active composite cells

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Figure 12

Relative density distribution for eight cascading coupled cells

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Figure 13

Relative density for the 8-cell system

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Figure 14

Control voltage for the 8-cell system

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Figure 15

Piezoelectric elements compliance for the 8-cell system



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