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Interface Damping: Characterization and Implementation
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Material damping in a structure is well defined and documented. However, dissipation due to mechanical contact (surface contact) in a complex built-up structure is not as well represented, in particular in large scale noise and vibration simulations. The present work is dealing with the understanding of the physical behaviour of losses that take place at such complex interfaces. The objective is to investigate, if, these mechanical loss phenomena can be modelled using linear response simulation techniques and implemented using commercially available finite element software. In a first step, the losses at the interfaces were experimentally investigated using an experimental setup capable of in-vacuo conditions. Following this, the second step was aimed at different ways of representing the proposed boundary conditions in a linear response simulation of a built-up structure. Two different approaches were studied, one using a continuous surface approach and one using a discrete element method.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , v, 25 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2012:13
National Category
Vehicle Engineering Fluid Mechanics and Acoustics
Research subject
Järnvägsgruppen - Ljud och vibrationer
Identifiers
URN: urn:nbn:se:kth:diva-93413ISBN: 978-91-7501-289-6 (print)OAI: oai:DiVA.org:kth-93413DiVA: diva2:515793
Presentation
2012-04-20, D41, Lindstedtsvägen 17, KTH, Stockholm, 13:15 (English)
Opponent
Supervisors
Funder
TrenOp, Transport Research Environment with Novel Perspectives
Note

QC 20120424

Available from: 2012-04-24 Created: 2012-04-16 Last updated: 2013-04-11Bibliographically approved
List of papers
1. Damping Modelling in Complex Built-up Structures
Open this publication in new window or tab >>Damping Modelling in Complex Built-up Structures
(English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568Article in journal (Other academic) Submitted
Abstract [en]

Damping in a given structure can be characterized and attributed to mechanisms like internal material dissipation and non material damping. While material damping is well understood and rather straightforward to model, the losses occurring at interfaces are less accessible and representable in simulations of realistic built-up body structures. Here, an approach based on linear modelling is discussed. The main objective of the work is to investigate the modelling of interface damping in a spot-welded structure by numerical simulations. Damping due to surface contact and movement of air through unsealed gaps is included. The results are promising in terms of the losses predicted for a realistic structure.

Keyword
Interface damping, Surface contact damping, Structural damping, Air damping, Air pumping, Loss factor, Built-up structures, Finite element modelling.
National Category
Other Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-93779 (URN)
Note
QS 2012Available from: 2012-04-26 Created: 2012-04-26 Last updated: 2017-12-07Bibliographically approved
2. Implementing Linear Modelling of Interface Damping in a Finite Element Software
Open this publication in new window or tab >>Implementing Linear Modelling of Interface Damping in a Finite Element Software
(English)In: Finite elements in analysis and design (Print), ISSN 0168-874X, E-ISSN 1872-6925Article in journal (Other academic) Submitted
Abstract [en]

In the automotive industry virtual modelling of losses in a built-up structure is still a challenge. A body-in-white car structure consists of many spot-welded parts and the modelling of their associated losses is highly interesting. For this purpose, the dissipation of mechanical energy is here modelled in the frame of large scale computations using linear techniques with commercially available finite element software. Mechanical, vibration damping is introduced through external forces which are pairwise applied such that they oppose the relative motion at the contact interfaces between two parts. Two aspects are investigated, first if the proposed modelling captures the main mechanisms of the damping on a system level. Second, if the predicted local vibration responses at different locations correlate well between predicted and previously measured (in vacuo) spectra. Initial simulations show promising results and the level of damping observed in the predictions are similar to the measured spectra, fo rvibration shapes which involve significant relative motion along the spot-welded surfaces. An advantage with this technique is that it helps in understanding of different sources of total system damping, i.e. due to material and other sources of damping. It is verified that non-material damping due to mechanical contact is a significant contributor to the losses in a built-up structure which may be simulated with the proposed technique. In the paper the overall approach is discussed together with the specific aspects of the finite element implementation technique proposed.

Keyword
Interface damping, Mechanical contact damping, Air damping, Air pumping, Material damping, Vibration reduction, Loss factor, Finite element method.
National Category
Other Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-93781 (URN)
Note
QS 2012Available from: 2012-04-26 Created: 2012-04-26 Last updated: 2017-12-07Bibliographically approved

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