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The applicability of the effective medium theory to the dynamics of cellular beams

The applicability of the effective medium theory to the dynamics of cellular beams
The applicability of the effective medium theory to the dynamics of cellular beams
The applicability and the limitations of the effective medium assumption for the dynamics of cellular beams are studied. Beams made of uniform triangular and regular hexagonal cells are analysed. The natural frequencies and modal distributions are calculated using the detailed finite element model of the cellular networks are compared with those predicted based on equivalent homogenous media of the same overall size and shape. It is observed that, for low mode number, a cellular beam behaves as a continuum, provided the cell size is significantly smaller than the external dimensions of the beam. Due to different deformation mechanisms triangular cells show frequencies independent of area fraction whereas hexagonal cells show this dependence clearly. As the wavelength starts to become of the order of the heterogeneity, the continuum behaviour begins to break down. With the increase in mode number, cellular beams exhibit inherent flexibility with a progressive increase in their modal densities as compared to those of a homogeneous continuum. The modal density increases further when the cell walls start to resonate. During resonance, an abrupt rise in the modal density is observed for the triangular cellsas the cell walls start deforming in the flexural mode instead of the axial mode. In contrast, for hexagonal cells, the predominant mode of cell wall deformationis always flexural.
cellular solids, structural vibration
0020-7403
598-608
Banerjee, S.
697c77ef-53c1-4370-8c21-cb7065815627
Bhaskar, A.
d4122e7c-5bf3-415f-9846-5b0fed645f3e
Banerjee, S.
697c77ef-53c1-4370-8c21-cb7065815627
Bhaskar, A.
d4122e7c-5bf3-415f-9846-5b0fed645f3e

Banerjee, S. and Bhaskar, A. (2009) The applicability of the effective medium theory to the dynamics of cellular beams. International Journal of Mechanical Sciences, 51 (8), 598-608. (doi:10.1016/j.ijmecsci.2009.06.001).

Record type: Article

Abstract

The applicability and the limitations of the effective medium assumption for the dynamics of cellular beams are studied. Beams made of uniform triangular and regular hexagonal cells are analysed. The natural frequencies and modal distributions are calculated using the detailed finite element model of the cellular networks are compared with those predicted based on equivalent homogenous media of the same overall size and shape. It is observed that, for low mode number, a cellular beam behaves as a continuum, provided the cell size is significantly smaller than the external dimensions of the beam. Due to different deformation mechanisms triangular cells show frequencies independent of area fraction whereas hexagonal cells show this dependence clearly. As the wavelength starts to become of the order of the heterogeneity, the continuum behaviour begins to break down. With the increase in mode number, cellular beams exhibit inherent flexibility with a progressive increase in their modal densities as compared to those of a homogeneous continuum. The modal density increases further when the cell walls start to resonate. During resonance, an abrupt rise in the modal density is observed for the triangular cellsas the cell walls start deforming in the flexural mode instead of the axial mode. In contrast, for hexagonal cells, the predominant mode of cell wall deformationis always flexural.

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e-pub ahead of print date: 12 June 2008
Published date: August 2009
Keywords: cellular solids, structural vibration
Organisations: Computational Engineering and Design

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Local EPrints ID: 69940
URI: http://eprints.soton.ac.uk/id/eprint/69940
ISSN: 0020-7403
PURE UUID: 759527db-064c-484b-aba8-c78552031dd2

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Date deposited: 05 Jan 2010
Last modified: 13 Mar 2024 19:50

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Contributors

Author: S. Banerjee
Author: A. Bhaskar

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