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Effective vibro-acoustical modelling of rubber isolators
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis, gathering four papers, concerns the enhancement in understanding and modelling of the audible dynamic stiffness of vibration rubber isolators including experimental measurements.

Paper A studies the performances of three different types of vibration isolator using an indirect measurement technique to estimate the blocked dynamic transfer stiffness of each specimen. The measurements are performed over a wide audible frequency range of 200 to 1000 Hz in a specially designed test rig enabling the investigation of arbitrary preload influences.

Paper B addresses the modelling of the audible-frequency stiffness of the rubber conical mount experimentally appraised in Paper A accounting for preload effects. The model is based on a simpliflied waveguide approach approximating the nonlinearities attributed to the predeformations by adopting shape factor considerations. The carbon black filled rubber is assumed incompressible, displaying a viscoelastic behavior based on a fractional derivative Kelvin-Voigt model efficiently reducing the number of required material parameters.

In Paper C the focus is on the axial dynamic stiffness modelling of an arbitrary long rubber bushing within the audible frequency range. The problems of simultaneously satisfying the locally non-mixed boundary conditions at the radial and end surfaces are solved by adopting a waveguide approach, using the dispersion relation for axially symmetric waves in thick-walled infinite plates, while fulfilling the radial boundary conditions by mode-matching. The results obtained are successfully compared with simpliflied models but display discrepancies when increasing the diameter-to-length ratios since the influence of higher order modes and dispersion augments.

Paper D develops an effective waveguide model for a pre-compressed cylindrical vibration isolator within the audible frequency domain at arbitrary compressions. The original, mathematically arduous problem of simultaneously modelling the preload and frequency dependence is solved by applying a novel transformation of the pre-strained isolator into a globally equivalent homogeneous and isotropic configuration enabling the straightforward application of a waveguide model to satisfy the boundary conditions. The results obtained present good agreement with the non-linear finite element results for a wide frequency range of 20 to 2000 Hz at different preloads.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , 25 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2005:25
Keyword [en]
Applied mechanics, Rubber isolator, Bush mounting, Dynamic stiffness, Waveguide, Fractional derivatives, Mode-matching, Pre-compressed, Prestrain, Preload, Predeformation, Viscoelasticity, Dispersion
Keyword [sv]
Teknisk mekanik
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-266ISBN: 91-7178-104-8 (print)OAI: oai:DiVA.org:kth-266DiVA: diva2:8332
Public defence
2005-06-16, D3, Lindstedtsvägen 5, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101001Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2010-10-01Bibliographically approved
List of papers
1. Rubber versus steel vibration isolators - The audible frequency contest
Open this publication in new window or tab >>Rubber versus steel vibration isolators - The audible frequency contest
2005 (English)In: KGK Kautschuk Gummi Kunststoffe, ISSN 0948-3276, Vol. 58, no 11, 564-569 p.Article in journal (Refereed) Published
Abstract [en]

The audible frequency axial dynamic stiffness of three vibration isolators plausibly used in the design of a ship main engine suspension system are examined and compared for different static preloads. An indirect measurement method is used to investigate the blocked dynamic transfer stiffness using a specially designed test rig displaying a strong frequency dependence where resonance and antiresonance phenomena appear in the form of troughs and peaks respectively. The significant influence of the preload effects is also assessed for each isolator. Clearly, the rubber isolator presents superior performances in comparison with the two others, steel and combined steel-rubber isolators, over the studied frequency range 200 to 1000 Hz for each preload 30, 40 and 50 kN.

Keyword
vibration isolator, dynamic stiffness, rubber, steel, audible frequency
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-5289 (URN)000233533200002 ()2-s2.0-27744541371 (Scopus ID)
Note

QC 20101001. Uppdaterad från submitted till published (20101001).

Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2014-12-01Bibliographically approved
2. A simple engineering audible-frequency stiffness model for a preloaded conical rubber isolator
Open this publication in new window or tab >>A simple engineering audible-frequency stiffness model for a preloaded conical rubber isolator
(English)Manuscript (preprint) (Other academic)
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-5290 (URN)
Note

QC 20101001 Ingår i avhandling

Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2016-05-18Bibliographically approved
3. Axial audio-frequency stiffness of a bush mounting: the waveguide solution
Open this publication in new window or tab >>Axial audio-frequency stiffness of a bush mounting: the waveguide solution
2007 (English)In: Applied Mathematical Modelling, ISSN 0307-904X, E-ISSN 1872-8480, Vol. 31, no 1, 38-53 p.Article in journal (Refereed) Published
Abstract [en]

An axial, dynamic stiffness model of an arbitrary wide and long rubber bush mounting is developed within the audible-frequency range, where influences of audible frequencies, material properties, bush mounting length and radius, are investigated. The problems of simultaneously satisfying the locally non-mixed boundary conditions at the radial and end surfaces are solved by adopting a waveguide approach, using the dispersion relation for axially symmetric waves in thick-walled infinite plates, while satisfying the radial boundary conditions by mode matching. The rubber is assumed nearly incompressible, displaying dilatation elasticity and deviatoric viscoelasticity based on a fractional derivative, standard linear solid embodying a Mittag-Leffler relaxation kernel, the main advantage being the minimum parameter number required to successfully model wide-frequency band material properties. The stiffness is found to depend strongly on frequency, displaying acoustical resonance phenomena; such as stiffness peaks and troughs. The presented model agrees fully with a simplified, long-bush model while diverging from it for increased diameter-to-length ratios. To a great extent, the increased influences of higher order modes and dispersion explain the discrepancies reported for the approximate approach.

Keyword
waveguide, non-mixed boundary condition, Mittag-Leffler, fractional derivative, audible frequency, bush mounting
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-5291 (URN)10.1016/j.apm.2005.08.008 (DOI)000242415200004 ()2-s2.0-33749665802 (Scopus ID)
Note

QC 20101001

Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2017-12-04Bibliographically approved
4. An effective waveguide model for pre-compressed vibration isolators
Open this publication in new window or tab >>An effective waveguide model for pre-compressed vibration isolators
(English)In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959Article in journal (Refereed) Submitted
Place, publisher, year, edition, pages
S. Hirzel Verlag
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-5292 (URN)
Note

QC 20101001 Ingår i avhandling

Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2017-12-04Bibliographically approved

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