An active viscoelastic metamaterial for isolation applications

Abstract

Abstract. Metamaterials are of interest due to their ability to produce novel acoustic behaviour beyond that seen in naturally occurring media. Of particular interest is the appearance of band gaps which lead to very high levels of attenuation within narrow frequency ranges. Resonant elements within metamaterials allow band gaps to form within the long wavelength limit at low frequencies where traditional passive isolation solutions suffer poor performance. Hence metamaterials may provide a path to high performance, low frequency isolation. Two metamaterials are presented here. An acoustic material consisting of an array of split hollow spheres is developed and its performance validated experimentally. The application of an acoustic/mechanical analogy allows the development of an elastodynamic metamaterial that could be employed as a high performance vibration isolator at low frequencies. A prototype isolator is manufactured and its performance measured. The passively occurring band gap is enhanced using an active control architecture. The use of the active control system in conjunction with the natural passive behaviour of the metamaterial enables high levels of isolation across a broad frequency range. An eventual goal of the work is to produce such materials on a small scale, and as such the metamaterials developed are designed for, and produced using, additive layer manufacturing techniques

Acoustic Metamaterials: A Potential for Cabin Noise Control in Automobiles and Armored Vehicles

“…Their work was, however, a small-scale study in the laboratory. Their pioneering work brought forth a new field of research in various disciplines such as transformation optics [Jiang et al, 2009;Kinsler and McCall, 2015;Lu et al, 2009] energy harvesting , noise barriers [Garcia-Chocano et al, 2012;Garcia-Chocano and Sanchez-Dehesa, 2013;Ho et al, 2003;Lagarrigue et al, 2013;Sanchez-Dehesa et al, 2011] and vibration/shock mitigation [Akl and Baz, 2012;Baravelli and Ruzzene, 2013;Huang and Sun, 2010;Kim et al, 2015;Pai et al, 2014;Peng and Pai, 2014;Reynolds and Daley, 2014;Sharma and Sun, 2015;Tan et al, 2012]. The consideration of using AMs specifically for cavity noise control has been reported recently in two separate works.…”

Transfer matrix modeling and experimental validation of cellular porous material with resonant inclusions

“…[7][8][9][10][11] Most of these works mainly focused on the transmission properties of the resonant material and highlighted the large transmission dip at the HR resonance frequency. [7][8][9] Boutin and B ecot, 11 Lagarrigue et al, 12 and Groby et al 13 recently investigated the sound absorption efficiency of rigid backed acoustic foams with resonant split hollow cylinder or HR inclusions and showed that it is greatly improved for frequencies with a wavelength much larger than the material thickness.…”

Enhancing the band gap of an active metamaterial

“…2a. As shown in Reynolds and Daley (2014) this can be explained using the Bloch dispersion relationship of a the periodic metamaterial given by Eq. 4, where kd is plotted in Fig.…”

“…Although an experimental metamaterial was produced by Reynolds and Daley (2014) that demonstrated the potential of the active control architecture, the paper contained only preliminary proof of concept results. Moreover the viscoelastic metamaterial was produced using additive layer manufacturing techniques that limited the passive performance of the isolation device.…”

“…In this paper a similar device is developed using conventional manufacturing techniques that has a behaviour that is very close to theoretical predictions. Methods for calculating the effective material parameters and to shape the passive band gap were described by Reynolds and Daley (2014) and these are used here to show that by coupling the natural frequency of the resonant elements with the natural frequency of the transmission elements a wide, symmetric band gap can be achieved. This idea is then used to create the prototype active metamaterial, designed to be used as a high performance vibration isolator.…”