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Structure-acoustic analysis; finite element modelling and reduction methods

Davidsson, Peter LU (2004) In Report TVSM TVSM-1018.
Abstract (Swedish)
Popular Abstract in Swedish

Avhandlingen behandlar finita element analys av det kopplade problemet bestående av en akustisk fluid innesluten av en flexibel struktur. Det studerade problemområdet kan också innehålla poröst ljudabsorberande material.



Denna analys kan appliceras på flera olika ingenjörsproblem, till exempel vid bestäming av ljud nivån i ett fordon på grund av motorns vibrationer eller vid bestäming av ljudreduktionen hos en dubbelvägg som är placerad mellan två lägenheter. De geometriska parametrarna hos det studerade systemet och den maximala frekvens som analysen ska vara giltig vid bestämmer storleken på det genererade ekvationssystemet. Detta ekvationssystem blir ofta väldigt stort och... (More)
Popular Abstract in Swedish

Avhandlingen behandlar finita element analys av det kopplade problemet bestående av en akustisk fluid innesluten av en flexibel struktur. Det studerade problemområdet kan också innehålla poröst ljudabsorberande material.



Denna analys kan appliceras på flera olika ingenjörsproblem, till exempel vid bestäming av ljud nivån i ett fordon på grund av motorns vibrationer eller vid bestäming av ljudreduktionen hos en dubbelvägg som är placerad mellan två lägenheter. De geometriska parametrarna hos det studerade systemet och den maximala frekvens som analysen ska vara giltig vid bestämmer storleken på det genererade ekvationssystemet. Detta ekvationssystem blir ofta väldigt stort och tiden för att lösa det blir lång.



I denna avhandling utvecklas analysmetoder för detta kopplade problem baserade på substrukturering och modal reduktion. Målet är att minska storleken på ekvationssystemet som beskriver problemet och därmed få kortare beräkningstider. Med substrukturing menas att det studerade sytemet delas upp i ett antal geometriska delar, eller subdomäner. En reducerad modal beskrivning används sedan för att beskriva varje subdomän. Denna modala beskrivning består i ett antal bas vektorer som här bestäms genom att dels studera varje subdomän i fri svängning och också genom att ta hänsyn till de övriga subdomäner som är kopplade till den studerade subdomänen. En viktig del av avhandingen är att inkludera beskrivningen av porösa ljudabsorberande material i analyserna.



De beskrivna analysmetoderna används också i ingenjörsapplikationer; framför allt i analysen av ljudreduktionen hos lätta dubbelväggar i lågfrekvensområdet. Målet med denna analys är att med en detalierad geometrisk beskrivning av problemet genomföra en strukturerad analys av effekten av ett antal geometri- och materialegenskaper på den beräknande ljudreduktionen. (Less)
Abstract
This thesis investigates structure-acoustic systems by use of finite element analysis. The systems studied here are limited to those that consist of an enclosed acoustic fluid cavity, which is coupled to a flexible structure and/or a porous sound absorbing material domain.



This type of analysis is applicable to a wide range of engineering problems, for example, studying the interior noise in a vehicle or the sound transmission loss in a wall between two dwellings. The geometrical properties of the studied system and the frequency limit of interest for the analysis determine the size of the system of equations to be solved. This size often becomes very large and the solution time becomes long.



To... (More)
This thesis investigates structure-acoustic systems by use of finite element analysis. The systems studied here are limited to those that consist of an enclosed acoustic fluid cavity, which is coupled to a flexible structure and/or a porous sound absorbing material domain.



This type of analysis is applicable to a wide range of engineering problems, for example, studying the interior noise in a vehicle or the sound transmission loss in a wall between two dwellings. The geometrical properties of the studied system and the frequency limit of interest for the analysis determine the size of the system of equations to be solved. This size often becomes very large and the solution time becomes long.



To decrease the size of the system, and thereby speeding up the analysis, methods are investigated and developed, using substructuring and modal reduction, for the analysis of structure-acoustic problems. The geometric problem domain is divided into a number of subdomains and a reduced set of basis vectors is derived for each of these subdomains. The set of basis vectors for each domain is derived to include information about both the internal behaviour of the subdomain and the coupling to the other subdomains. The reduced description enables efficient solution of the total system.



An important feature is to include the description of porous sound absorbing materials in the reduction process of the structure-acoustic problems.



The derived procedures are employed in engineering applications; particularly in the study of the sound transmission loss of lightweight double-leaf walls in the low-frequency range. The objective is to include a detailed geometric description of the problem enabling a structured evaluation of the influence of various geometrical and material properties of the studied wall on the predicted sound transmission loss. (Less)
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author
opponent
  • Ohayon, Roger, Professor, CNAM-Paris, France
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Mechanical engineering, hydraulics, vacuum technology, vibration and acoustic engineering, Maskinteknik, hydraulik, vakuumteknik, vibrationer, akustik, low frequency range, building acoustics, lightweight structures, porous materials, modal reduction, substructuring, finite element analysis, structural acoustics, vibroacoustics, Structural dynamics
in
Report TVSM
volume
TVSM-1018
pages
180 pages
publisher
Division of Structural Mechanics, Box 118; 221 00 Lund,
defense location
V:B, V-building, Lund Institute of Technology, John Ericssons väg 1, Lund
defense date
2004-09-20 13:15
ISSN
0281-6679
ISBN
91-628-6176-X
language
English
LU publication?
yes
id
bdffc3e3-1b12-4b27-8483-01848d7d9fa5 (old id 467245)
date added to LUP
2007-09-06 13:58:40
date last changed
2016-09-19 08:44:57
@phdthesis{bdffc3e3-1b12-4b27-8483-01848d7d9fa5,
  abstract     = {This thesis investigates structure-acoustic systems by use of finite element analysis. The systems studied here are limited to those that consist of an enclosed acoustic fluid cavity, which is coupled to a flexible structure and/or a porous sound absorbing material domain.<br/><br>
<br/><br>
This type of analysis is applicable to a wide range of engineering problems, for example, studying the interior noise in a vehicle or the sound transmission loss in a wall between two dwellings. The geometrical properties of the studied system and the frequency limit of interest for the analysis determine the size of the system of equations to be solved. This size often becomes very large and the solution time becomes long.<br/><br>
<br/><br>
To decrease the size of the system, and thereby speeding up the analysis, methods are investigated and developed, using substructuring and modal reduction, for the analysis of structure-acoustic problems. The geometric problem domain is divided into a number of subdomains and a reduced set of basis vectors is derived for each of these subdomains. The set of basis vectors for each domain is derived to include information about both the internal behaviour of the subdomain and the coupling to the other subdomains. The reduced description enables efficient solution of the total system.<br/><br>
<br/><br>
An important feature is to include the description of porous sound absorbing materials in the reduction process of the structure-acoustic problems.<br/><br>
<br/><br>
The derived procedures are employed in engineering applications; particularly in the study of the sound transmission loss of lightweight double-leaf walls in the low-frequency range. The objective is to include a detailed geometric description of the problem enabling a structured evaluation of the influence of various geometrical and material properties of the studied wall on the predicted sound transmission loss.},
  author       = {Davidsson, Peter},
  isbn         = {91-628-6176-X},
  issn         = {0281-6679},
  keyword      = {Mechanical engineering,hydraulics,vacuum technology,vibration and acoustic engineering,Maskinteknik,hydraulik,vakuumteknik,vibrationer,akustik,low frequency range,building acoustics,lightweight structures,porous materials,modal reduction,substructuring,finite element analysis,structural acoustics,vibroacoustics,Structural dynamics},
  language     = {eng},
  pages        = {180},
  publisher    = {Division of Structural Mechanics, Box 118; 221 00 Lund,},
  school       = {Lund University},
  series       = {Report TVSM},
  title        = {Structure-acoustic analysis; finite element modelling and reduction methods},
  volume       = {TVSM-1018},
  year         = {2004},
}