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On the use of viscoelastic materials for railroad vibration and noise reduction

Rolling noise is the dominant source of noise and vibration in railroad transport. Currently, used polymeric damping elements for rolling noise do not and cannot utilize the full damping potential of viscoelastic materials. Within this thesis, patented Granular Damping Elements (GDE) are introduced, consisting of woven fiber tube and filled with granular polymeric materials. Their properties can be adjusted using hydrostatic pressure to which granular materials are exposed and enable tuning of their damping characteristics.

Testing the concept of patented GDE, showed that dissipated energy of such elements at higher pressures can increase for up to 10 times, while stiffness increases for up to 20 times. For further improvement of damping behavior, Granular Friction Analyzer (GFA) apparatus was developed, that enables studying the inherent friction of granular materials, exposed to pressure loading and conditions at which granular material will start to flow. In addition, the effects of pressure (expressed by the position of mechanical spectrum) and viscoelastic material functions (expressed with spectrum width) on the characteristics of vibration damping elements were studied. The effects of both were analyzed through transmissibility.

It was shown that developed GFA can predict and measure the effects of size and size distribution of particles, shape of particle, etc., on the friction and flowability of granular materials which is essential for the manufacturing of GDE, as well as for creating hydrostatic pressure inside GDE. It was also found that shifting spectrum to the left, along the logarithmic time-scale, caused by a decrease of pressure, will move the resonance peak to smaller frequencies and at the same time, transmissibility will be significantly enlarged. On the other hand, when materials are exposed to higher pressures, which shifts their spectrum to the right along the logarithmic time-scale, their resonance peak will be shifted towards higher frequencies and the transmissibility will be diminished towards T = 1.

Lesen Sie die deutsche Zusammenfassung auf Kunststoffe.de
Author
 Marko Bek

Marko Bek
Center for Experimental Mechanics
University of Ljubljana

Information

Free keywords: railroad noise, rolling noise, granular damping elements, granular friction analyzer,viscoelastic material functions, viscoelastic retardation spectra, hydro-static pressure, damping, stiffness, transmissibility
Institute / chair: Faculty of Mechanical Engineering, University of Ljubljana
Language: English
Technical consultant for expert services: Prof. Dr.-Ing. Igor Emri (Mentor), Prof. Dr. Miha Boltezar, Assoc. Prof. Dr. Jurij Prezelj, Prof. Dr. Polhronis-Thomas D. Spanos, Prof. Dr. Arkady Voloshin
Publication year: 2017
Provider: Wissenschaftlicher Arbeitskreis Kunststofftechnik (WAK) / Kunststoffe.de

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