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Prediction of NVH behaviour of trimmed body components in the frequency range 100-500 Hz
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.ORCID iD: 0000-0003-0198-6660
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.ORCID iD: 0000-0003-1855-5437
2010 (English)In: Applied Acoustics, ISSN 0003-682x, Vol. 71, no 8, 708-721 p.Article in journal (Refereed) Published
Abstract [en]

The work within this paper focuses on the application and validation of numerical methods for predicting the acoustic and structural NVH behaviour of trimmed body components in an automotive context. In particular, the level of modelling refinement and accuracy necessary to establish a reliable finite element analysis model for comparative purposes in the development of alternative designs is investigated. Specifically, the roof structure of a passenger car was investigated from various performance aspects, using both structural and acoustic excitation. The roof was initially tested in situ, with and without interior lining, to provide a reference for subsequent component tests. It was then detached from the car, mounted in a stiff frame and tested in a transmission window using both acoustic and structural excitation. A finite element model of the detached component was developed using shell and solid elements for the structure and solid elements for the interior lining. Predictions were carried out to evaluate the STL as well as the vibrational frequency response due to a force applied to the structure. Special attention was given to the modelling of the headliner as well as the air gap separating the headliner from the outer sheet metal. A sensitivity study of various headliner properties was performed in addition to a comparison between solutions calculated using standard Nastran elements and augmented poro-elastic elements via the software package CDH/EXEL. The main objective of the current work has been to establish a datum reference for alternative designs. From this aspect, the validation of the numerical modelling methodology, in particular the level of detail and accuracy used, was a crucial step. It was found that the predictions agreed very well with the measured data. As an additional, very interesting result, it was also found that the in situ testing correlated well with the transmission suite testing.

Place, publisher, year, edition, pages
2010. Vol. 71, no 8, 708-721 p.
Keyword [en]
NVH prediction, Trimmed body components, Finite element method, STL, Biot modelling
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-25149DOI: 10.1016/j.apacoust.2010.03.002ISI: 000279325600004Scopus ID: 2-s2.0-77955266569OAI: oai:DiVA.org:kth-25149DiVA: diva2:356124
Note
QC 20101011Available from: 2010-10-11 Created: 2010-10-11 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Design of Multifunctional Body Panels in Automotive Applications: Reducing the Ecological and Economical footprint of the vehicle industry
Open this publication in new window or tab >>Design of Multifunctional Body Panels in Automotive Applications: Reducing the Ecological and Economical footprint of the vehicle industry
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Over the past century, the automobile has become an integral part of modern industrializedsociety. Consumer demands, regulatory legislation, and the corporate need togenerate a profit, have been the most influential factors in driving forward the evolutionof the automobile. As the comfort, safety, and reliability of the automobile haveincreased, so has its complexity, and most definitely its mass.The work within this thesis addresses the twofold problem of economy and ecologywith respect to sustainable development of automobiles. Specifically, the conflictingproblems of reducing weight, and maintaining or improving noise, vibration, andharshness behaviour are addressed. Potential solutions to these problems must also beexecutable at the same, or preferably lower production costs. The hypothesis is that byreplacing acoustic treatments, aesthetic details, and complex systems of structural componentsboth on the interior and exterior of the vehicle with a single multi-functionalbody panel, functionality can be retained at a reduced mass (i.e. reduced consumptionof raw materials) and reduced fiscal cost.A case study is performed focusing on the roof structure of a production vehicle. Fullvehicle and component level acoustic testing is performed to acquire acoustic functionalrequirements. Vibro-mechanical testing at the component level is performedto acquire structural functional requirements complimentary to those in the vehiclesdesign specifications. Finite element modelling and analysis is employed to createa model representative of the as-tested component and evaluate its acoustic and mechanicalbehaviour numerically. Results of numerical simulations are compared withthe measured results for both acoustic and mechanical response in order to verify themodel and firmly establish a set of acoustic and mechanical constraints for future work.A new, multi-layered, multi-functional sandwich panel concept is proposed which replacesthe outer sheet metal, damping treatments, transverse beams, and interior trimof the existing structure. The new panel is weight optimized to a set of structural constraintsand its acoustic properties are evaluated. Results show a significant reductionin mass compared to the existing system with no degradation of the acoustic environment.A discussion of the results is presented, as is a suggestion for future research.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. ix, 105 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2009:30
Keyword
Sandwich panels, mutifunctional, structural acoustic interaction, NVH, vehicle acoustics
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-10661 (URN)978-91-7415-362-0 (ISBN)
Presentation
2009-06-08, D3, KTH, Lindstedtsvägen 5, Stockholm, 13:00 (English)
Opponent
Supervisors
Available from: 2009-06-11 Created: 2009-06-10 Last updated: 2010-11-03Bibliographically approved
2. Design of Multifunctional Body Panels for Conflicting Structural and Acoustic Requirements in Automotive Applications
Open this publication in new window or tab >>Design of Multifunctional Body Panels for Conflicting Structural and Acoustic Requirements in Automotive Applications
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Over the past century, the automobile has become an integral part of society, with vastincreases in safety, refinement, and complexity, but most unfortunately in mass. Thetrend of increasing mass cannot be maintained in the face of increasingly stringentregulations on fuel consumption and emissions.The body of work within this thesis exists to help the vehicle industry to take a stepforward in producing vehicles for the future in a sustainable manner in terms of botheconomic and ecological costs. In particular, the fundamentally conflicting requirementsof low weight and high stiffness in a structure which should have good acousticperformance is addressed.An iterative five step design method based on the concepts of multifunctionality andmultidisciplinary engineering is proposed to address the problem, and explained witha case study.In the first step of the process, the necessary functional requirements of the systemare evaluated. Focus is placed on the overall system behavior and diverted from subproblems.For the case study presented, the functional requirements included: structuralstiffness for various loading scenarios, mass efficiency, acoustic absorption, vibrationaldamping, protecting from the elements, durability of the external surfaces,and elements of styling.In the second step of the process, the performance requirements of the system wereestablished. This involved a thorough literature survey to establish the state of theart, a rigorous testing program, and an assessment of numerical models and tools toevaluate the performance metrics.In the third step of the process, a concept to fulfil requirements is proposed. Here, amulti-layered, multi-functional panel using composite materials, and polymer foamswith varying structural and acoustic properties was proposed.In the fourth step of the process, a method of refinement of the concept is proposed.Numerical tools and parameterized models were used to optimize the three dimensionaltopology of the panel,material properties, and dimensions of the layers in a stepwisemanner to simultaneously address the structural and acoustic performance.In the fifth and final step of the process, the final result and effectiveness of the methodused to achieve it is examined. Both the tools used and the final result in itself shouldbe examined. In the case study the process is repeated several times with increasingdegrees of complexity and success in achieving the overall design objectives.In addition to the design method, the concept of a multifunctional body panel is definedand developed and a considerable body of knowledge and understanding is presented.Variations in core topology, materials used, stacking sequence of layers, effects ofperforations, and air gaps within the structure are examined and their effects on performanceare explored and discussed. The concept shows promise in reducing vehicleweight while maintaining the structural and acoustic performance necessary in the contextof sustainable vehicle development.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. ix, 61 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2011:16
National Category
Vehicle Engineering Reliability and Maintenance
Identifiers
urn:nbn:se:kth:diva-31112 (URN)978-91-7415-904-2 (ISBN)
Public defence
2011-03-31, F3, Lindstedtsvägen 26, Stockholm, 11:09 (English)
Opponent
Supervisors
Funder
TrenOp, Transport Research Environment with Novel Perspectives
Note
QC 20110311Available from: 2011-03-11 Created: 2011-03-09 Last updated: 2012-06-12Bibliographically approved

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Wennhage, PerGöransson, Peter

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