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Micro-structural based acoustic modelling of anisotropic open cell materials
KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. AB Volvo, Volvo Construction Equipment.ORCID iD: 0000-0001-9948-249X
KTH, School of Engineering Sciences (SCI), Engineering Mechanics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.ORCID iD: 0000-0001-9980-0144
KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.ORCID iD: 0000-0003-1855-5437
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2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A method for the calculation of the acoustic performance of open-cell foammaterials is discussed. From a known micro-structural geometry and theconstituent material, the relevant acoustic properties are computed using apreviously published analytical method for the calculation of the dynamicdrag impedance and a previously published method for the calculation of theelastic moduli. These have been combined and are here used to generate thenecessary inputs to a fully anisotropic state space formulation of a TransferMatrix Method (TMM) based solution where only geometry and materialproperties need to be known. From the TMM solution, the sound absorptionand sound transmission loss of multilayer panels including anisotropic opencell materials is estimated. It is shown that the proposed method may beused in an optimization of sound absorption in multi-layer porous materials, where the different layers can have different degrees of anisotropy in theiracoustic and elastic properties. In the current work, the micro-geometry is based on the Kelvin cellwhich then is modified to achieve a controlled degree of anisotropy. The method has been validated by comparing the absorption and sound transmission loss for isotropic porous materials have been compared to equivalent structures computed with a commercial TMM mode, including a porous material which has been fully characterized with regard to previously published Johnson-Champoux-Allard parameters. In addition the calculated dynamic drag impedance has been compared to measurements conductedon a series of small samples with a defined 3D printed micro geometry forwhich the static flow resistivity has been measured. The method in general underestimates the dynamic drag impedance compared to the static flowresistivity due to not including the contributions to the losses from the constrictions between the struts close to the cell vertices. All verification showa good degree of agreement, confirming that for open-cell porous materials with reasonably high porosity the method may be used for design of novel acoustic treatments.

Abstract [sv]

En metod för beräkning av de akustiska egenskaperna hos skummaterialmed öppna celler diskuteras. Baserat på en känd mikrogeometri and de ingående materialen kan de relevanta akustiska egenskaperna beräknas. Metoden bygger på arbeten för dynamiskt flödesmotstånd och beräkning avelastiska egenskaper som publicerats tidigare. De egenskaperna ¨ar inkluderade i en fullt anisotrop formulering för lösning av en state space TransferMatrix Method (TMM) beräkning, där endast geometri och material krävs som indata. Från TMM-beräkningen kan ljudabsorption och ljudtransmission i konstruktioner med flera skikt uppskattas. Möjligheten att göra optimering av ljudabsorption av flera kombinerade skikt med olika grader avanisotropi i beräknade akustiska och styvhetsegenskaper har visats. I detta arbete baseras mikrogeometrin på en Kelvincell-geometri, som modifierats för att uppnå en definerad grad av anisotropi. Metoden har validerats genom att jämföra absorption och ljudtransmission av ekvivalenta strukturer beräknade med ett kommersiellt TMM-program på ett skum-material som karaktäriserats med avseende på publicerade Johnson-Champoux-Allard parametrar. Dessutom har de beräknade dynamiska flödesmotstånden jämförts medmätningar av statiskt flödesmotstånd på små prov tillverkade med 3D-printer. Metoden underskattar generellt flödesmotståndet jämfört med det uppmätta statiska flödesmotståndet eftersom inverkan av trånga sektioner mellan mikro-strävorna negligeras. All verifiering visar en god nivå av överensstämmelse och bekräftar att metoden skulle kunna användas för att göra nya typer av akustiska konstruktioner i flera lager med porösa material med öppna celler och relativt hög porositet .

Place, publisher, year, edition, pages
Stockholm, Sweden: KTH Royal Institute of Technology, 2022. , p. 43
Series
TRITA-SCI-FOU ; 2022:40
Keywords [en]
sound absorption, vehicle, anisotropic, foam, micro-structure, resource efficient, transfer matrix method
Keywords [sv]
ljudabsorption, anisotrop, skum, mikrostruktur, TMM, fordon, resurseffektiv
National Category
Vehicle Engineering Fluid Mechanics and Acoustics
Research subject
Vehicle and Maritime Engineering
Identifiers
URN: urn:nbn:se:kth:diva-317221ISBN: 978-91-8040-328-3 (print)OAI: oai:DiVA.org:kth-317221DiVA, id: diva2:1693709
Public defence
2022-09-30, Kollegiesalen, Brinellvägen 8, KTH Campus, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
VinnExcellence Center for ECO2 Vehicle design, VinnExcellence Center for ECO2 Vehicle design
Funder
Vinnova, 2016-05195
Note

QC 220905

Available from: 2022-09-08 Created: 2022-09-07 Last updated: 2022-09-08Bibliographically approved
List of papers
1. Acoustics modelling of open-cell foam materials from microstructure and constitutive properties
Open this publication in new window or tab >>Acoustics modelling of open-cell foam materials from microstructure and constitutive properties
2021 (English)In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 149, no 3, p. 2016-2026Article in journal (Refereed) Published
Abstract [en]

The dynamic relations for highly porous fibrous materials, having analytical expressions for dynamic viscous drag forces and oscillatory solid-to-fluid heat transfer, are now extended towards open-cell foam materials where the struts of the foam are considered to be primarily cylindrical except in the region of the joints. By also including analytical expressions for the stiffness of the foam cell, an entirely analytically-based model is presented for the acoustics of highly-porous, open-celled foam materials. This approach is extremely efficient, requiring only the mean cell size, mean strut diameter, and constitutive properties of the solid foam material and the surrounding viscous fluid as input. The acoustic performance prediction of not only isotropic foam cell designs, but also anisotropic ones may be performed rapidly and virtually, without the need for the determination of poroelastic material properties from existing material samples. The steps required for the development of the analytical foam-cell model are presented, along with the acoustic performance prediction of a typical Melamine foam cell, yielding very promising results in comparison against measurements. In order to understand the suitability of the cylindrical foam strut assumption, a viscous drag force comparison with foam struts having square and triangular cross-sectional profiles is also presented.

Place, publisher, year, edition, pages
Acoustical Society of America (ASA), 2021
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-292602 (URN)10.1121/10.0003824 (DOI)000632890100003 ()33765808 (PubMedID)2-s2.0-85103384820 (Scopus ID)
Note

QC 20210412

Available from: 2021-04-12 Created: 2021-04-12 Last updated: 2022-09-07Bibliographically approved
2. Tunable absorption of micro-structure based anisotropic opencell materials
Open this publication in new window or tab >>Tunable absorption of micro-structure based anisotropic opencell materials
(English)Manuscript (preprint) (Other academic)
Abstract [en]

A simplified analytical model based on the Kelvin cell micro geometry has been developed for estimating the dynamic drag impedance of a periodic open cell material based on a Kelvincell based micro structure. The calculated dynamic drag impedance estimates similar properties as the static flow resistivity, but is based on dynamic micro scale estimates of the viscous losses neglecting interactions between struts. The Kelvin cell model can have a controlled degree ofanisotropy. Implementing the micro model in a state space transfer matrix method allows for absorption calculations of anisotropic micro material including stiffness to be calculated with limited input information. In addition to the solid constituent material parameters only cell height,strut thickness and twist angle, determining the degree of anisotropy, are required. The modelling allows for fast computations making optimization feasible, which is demonstrated by optimizing a two-layer porous material with the degree of anistropy as a design variable. An optimized design with enhanced absorption at lower frequencies, where the two layers have different anisotropic cell geoemetry, is discussed.

Keywords
sound absorption, vehicle, anisotropic, foam, micro-structure, resource efficient, transfer matrix method
National Category
Vehicle Engineering Fluid Mechanics and Acoustics
Research subject
Vehicle and Maritime Engineering
Identifiers
urn:nbn:se:kth:diva-317048 (URN)
Funder
Vinnova, 2016-05195
Note

QC 20220908

Available from: 2022-09-05 Created: 2022-09-05 Last updated: 2022-09-08Bibliographically approved
3. Tuning sound transmission loss for multi-layer panels with anisotropic foams
Open this publication in new window or tab >>Tuning sound transmission loss for multi-layer panels with anisotropic foams
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2022 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Multilayer panels consisting of a load carrying structure, a porous material for thermal and acoustic insulation and an interior trim panel is a very common type of design for vehicles. Weight as well as total build height are usually limiting constraints on the design. The idea of using an anisotropic porous material instead of an isotropic one to improve the sound transmission loss without adding a lot of weight or thickness is explored in the paper. By using a state space formulation of the transfer matrix method transmission loss it is possible to include anisotropic material properties in the calculation. The anisotropic material is modelled by a combination of a simplified analytical model for the acoustic losses and inverse estimation of the 21 independent elastic constants of the Hooke’s tensor. The porous material, which has typical dimensions possible to 3D print, is based on a Kelvin cell micro model that has a controlled degree of anisotropy. 

Keywords
Transmission loss, anisotropic, foam, micro-structure, analytical, open-cell
National Category
Fluid Mechanics and Acoustics Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-317065 (URN)
Conference
ISMA 2022, International Conference on Noise and Vibration Engineering, Leuven, Belgium
Funder
Vinnova, 2016-05195
Note

Proceedings will be published after the conference taking part 12th-14th September 2022. The conference paper has been submitted.

QC 20220909

Available from: 2022-09-05 Created: 2022-09-05 Last updated: 2022-10-12Bibliographically approved
4. Simplified acoustic model of an anisotropic foam using a micro-macro approach
Open this publication in new window or tab >>Simplified acoustic model of an anisotropic foam using a micro-macro approach
2020 (English)In: Proceedings of ISMA 2020 - Internation Conference on Noise and Vibration Engineering and USD2020 - International Conference on Uncertainty in Structural Dynamics 2020: 7-9 September 2020 / [ed] W. Desmet, B. Pluymers, D. Moens, S. Vandemaele, Leuven, Belgium: KU Leuven, Departement Werktuigkunde, Heverlee, Belgium , 2020, p. 437-450Conference paper, Published paper (Refereed)
Abstract [en]

Porous foam materials with high porosity are used as part of multi-layer panels for sound insulation andabsorption in transportation vehicles. The acoustic properties of the foam are highly dependant on the microgeometryof the foam cells. In this work, simplified analytical models for calculating the viscous dynamicdrag forces, and oscillatory heat transfer within fibrous materials have been adapted towards foam materialshaving micro-cell geometries composed primarily of cylindrical struts. The analytical results are comparedto full visco-thermal numerical models of an isotropic unit foam cell, For both high porosity foam and lowporosity foam examples with typical dimensions for 3D printed materials, the agreement between analyticaland thermoviscous numerical models is shown to be very good. This approach model can easily be extendedto anisotropic materials as well.

Place, publisher, year, edition, pages
Leuven, Belgium: KU Leuven, Departement Werktuigkunde, Heverlee, Belgium, 2020
Keywords
acoustics, porous material, light-weight
National Category
Vehicle Engineering Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-290962 (URN)000652006000035 ()2-s2.0-85103420097 (Scopus ID)
Conference
ISMA 2020 - Internation Conference on Noise and Vibration Engineering and USD2020 - International Conference on Uncertainty in Structural Dynamics 2020
Funder
Vinnova, 2016-05195
Note

QC 20210614

Available from: 2021-02-27 Created: 2021-02-27 Last updated: 2022-09-07Bibliographically approved

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Eva_Lundberg_kappa(1300 kB)200 downloads
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File name FULLTEXT02.pdfFile size 1300 kBChecksum SHA-512
a17273ec8b61770abbc98cf334037acf7544e1b770dd89b5158fd70e324caf3d165a85609b788b17b8dc9f181979d7b8137b04437905fd2aadac0ff5a67edb3e
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Lundberg, EvaMao, HuinaSemeniuk, BradleyGöransson, PeterGaborit, MathieuRumpler, Romain

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Engineering MechanicsVinnExcellence Center for ECO2 Vehicle designFluid Mechanics and Engineering AcousticsVehicle Engineering and Solid Mechanics
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