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Finite element-boundary elements modelling of acoustic scattering from viscoelastic anechoic structures

Di Meglio, Alberto (2000)
Ph.D. thesis, University of Birmingham.

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This research work focuses on the analysis of multi-layered, anechoic tiles for underwater applications, especially in the field of communications.
It is firstly shown how the sound absorbing properties of viscoelastic materials can be modified and enhanced by the proper use of fillers, such as lead oxide and mica. Successively, a new method for identifying the viscoelastic frequency-dependent properties of such materials from experimental data is presented. The method is based on a variational method analogous to the Hamilton Principle. It allows calculating hard-to-find properties such as the complex viscoelastic response functions and the complex Poisson ratio.
After the materials properties have been determined, it is shown how they can be incorporated into the combined finite-element-boundary element method to provide accurate numerical solutions to the acoustic scattering problem.
A tile made of three layers, a reflecting aluminium layer, an absorbing butyl rubber layer and a matching layer made of a regular grid of polyurethane cones is finally analysed in several scattering and geometrical configurations.
The scattering patterns produced by a plane wave incident on the tile are plotted, discussed and compared with experimental data obtained from in-tank scattering measurements of a model tile.

Type of Work:Ph.D. thesis.
Supervisor(s):Wang, Lian Sheng and Smith, Brian and Atkins, Phil
School/Faculty:Schools (1998 to 2008) > School of Engineering
Department:School of Electronic and Electrical Engineering
Subjects:TK Electrical engineering. Electronics Nuclear engineering
Institution:University of Birmingham
Library Catalogue:Check for printed version of this thesis
ID Code:488
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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