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Design of Multifunctional Body Panels for Conflicting Structural and Acoustic Requirements in Automotive Applications
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
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: urn:nbn:se:kth:diva-31112ISBN: 978-91-7415-904-2OAI: oai:DiVA.org:kth-31112DiVA: diva2:402692
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
List of papers
1. Prediction of NVH behaviour of trimmed body components in the frequency range 100-500 Hz
Open this publication in new window or tab >>Prediction of NVH behaviour of trimmed body components in the frequency range 100-500 Hz
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.

Keyword
NVH prediction, Trimmed body components, Finite element method, STL, Biot modelling
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-25149 (URN)10.1016/j.apacoust.2010.03.002 (DOI)000279325600004 ()2-s2.0-77955266569 (ScopusID)
Note
QC 20101011Available from: 2010-10-11 Created: 2010-10-11 Last updated: 2011-03-11Bibliographically approved
2. Structural-acoustic Design of a Multi-functional Sandwich Panel in an Automotive Context
Open this publication in new window or tab >>Structural-acoustic Design of a Multi-functional Sandwich Panel in an Automotive Context
2010 (English)In: Journal of Sandwich Structures and Materials, ISSN 1099-6362, E-ISSN 1530-7972, Vol. 12, no 6, 684-708 p.Article in journal (Refereed) Published
Abstract [en]

This article deals with the design and weight optimization of a multi-functional vehicle body panel in an automotive context. An existing vehicle design has provided functional design requirements regarding static, dynamic, and acoustic behavior of the components of a car roof. A novel, multifunctional panel is proposed which integrates the component requirements present in a traditional roof system within a single module. The acoustic properties of two configurations of the novel panel are examined using numerical methods including advanced poro-elastic modeling tools compatible with Nastran, and compared with numerical results of a finite element model of the existing construction.

Keyword
sandwich structures, acoustic modeling, design optimization
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-25148 (URN)10.1177/1099636209359845 (DOI)000284691100002 ()2-s2.0-77954143529 (ScopusID)
External cooperation:
Note

QC 20101011

Available from: 2010-10-11 Created: 2010-10-11 Last updated: 2016-09-01Bibliographically approved
3. Proposal of a Methodology for Multidisciplinary Design of Multifunctional Vehicle Structures including an Acoustic Sensitivity Study
Open this publication in new window or tab >>Proposal of a Methodology for Multidisciplinary Design of Multifunctional Vehicle Structures including an Acoustic Sensitivity Study
2009 (English)In: International Journal of Vehicle Structures & Systems, ISSN 0975-3060, Vol. 1, no 1-3, 3-15 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, a design methodology is proposed, wherein tools and knowledge from the areas of structural design, numerical optimization, and noise, vibration and harshness (NVH) engineering are combined into a single toolbox for vehicle design. The methodology attempts to address the topic of sustainable development from both economic and environmental perspectives within the vehicle industry. A brief review of the topics of NVH and numerical optimization is given for the purposes of disseminating knowledge. Finite element codes for predicting structural and acoustic response are implemented within the iterative design methodology, which is explained for generic problems. Specific focus is placed on the need for understanding functional requirements of the entire system rather than its components. The methodology is implemented in an automotive case study. The results in terms of design solution and development framework are evaluated and discussed. As part of this evaluation, and integral to the design process, an acoustic sensitivity analysis of the final solution is performed and the results are presented.

 

 

Keyword
Multifunctional, Sandwich structures, Sustainable, Optimization, Acoustics, Vehicle NVH
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-31109 (URN)10.4273/ijvss.1.1-3.01 (DOI)2-s2.0-84857772404 (ScopusID)
Note
QC 20110311Available from: 2011-03-09 Created: 2011-03-09 Last updated: 2011-03-11Bibliographically approved
4. Material Property Steered Structural and Acoustic Optimization of a Multifunctional Vehcile Body Panel
Open this publication in new window or tab >>Material Property Steered Structural and Acoustic Optimization of a Multifunctional Vehcile Body Panel
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Conventional vehicle passenger compartments often achieve functional requirements using a complex assembly of components. As each component is optimized for a single task, the assembly as a whole is often suboptimal in achieving the system performance requirements. In this paper, a novel iterative design approach based on using a multi-layered load bearing sandwich panel with integrated acoustic capabilitiesis developed focusing on material properties and their effecton the systems behavior. The proposed panel is meant to fulfilmultiple system functionalities simultaneously, thus simplifying the assembly and reducing mass. Open cell acoustic foams are used to achieve acoustic performance, and the effect of altering the stacking sequence as well as introducing an air gap within the acoustic treatment is studied in detail to determine effects on the acoustic and structural performance of the panel as a whole.

National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-31110 (URN)
Note
QC 20110311Available from: 2011-03-09 Created: 2011-03-09 Last updated: 2012-08-15Bibliographically approved
5. A Design Method using Toplogy, Property, and Size Optimization to Balance Structural and Acoustic Performance of Sandwich Panels for Vehicle Applications
Open this publication in new window or tab >>A Design Method using Toplogy, Property, and Size Optimization to Balance Structural and Acoustic Performance of Sandwich Panels for Vehicle Applications
(English)Manuscript (preprint) (Other academic)
Keyword
Vehicle Design, Topology Optimization, NVH, FEM, Sandwich Structures, Acoustic Optimizatio, Porous Foam
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-31111 (URN)
Note
QS 2012Available from: 2011-03-09 Created: 2011-03-09 Last updated: 2012-08-16Bibliographically approved

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