Abstract
There have been numerous attempts and investigations carried out with the objective to reduce the noise generated by railway freight wagons because noise is one of ever-present negative environmental pollution phenomena. This resulted in strong legislation requirements on noise reduction in railway transport, in the case of freight wagons, only exterior noise is a problem. However, the extremely hard metal structures of the wagons running on hard rails naturally generate high magnitudes of acoustic energy. One big initiative, especially in Germany, seeks a solution in replacement of the cast iron brake pads with the composite one which should result in so-called “silent trains”. But braking is used only during a minor part of the train run, leaving most of the acoustic phenomena of the train run unaffected. In our research, we focused on freight bogies type Y25Ls(s)e-K that are used, including in Slovakia. We simulated the structural natural frequencies to predict vibrations and consequent sound generated by these vibrations. The idea was to localize the vibrations and propose possibilities of noise attenuation. The more realistic view about sound fields was obtained by practical measurements on a moving bogie. Measurements on the test track at a maintenance workshop were done by using a digital acoustic camera Soundcam. For attenuation of noise radiated by the bogie frame, acoustic silencers made from recycled porous fiber material have been applied to the bogie frame. To determine the acoustic difference, the material was applied only on half of the bogie, and then the measurements were carried out. The results showed a promising improvement in reduced noise radiation, which gives support for further research in this area with more precise simulations and more precise coating of the bogie frame as well as the proposal and measurement of noise-attenuating coatings of other structural parts of the freight wagons.
Highlights
Introduction published maps and institutional affilThe objective of the study was to investigate the noise sources on railway freight wagons and to propose measures for its mitigation
The focus was given to freight bogies type of Y25Ls(s)e-K that are widely used, including in Slovakia, as the extremely hard metal structures of the wagons running on hard rails generate high magnitudes of acoustic energy, so the primary noise source on railway vehicles is from wheel–rail contact
We focused on noise reduction directly at the noise source
Summary
The objective of the study was to investigate the noise sources on railway freight wagons and to propose measures for its mitigation. The focus was given to freight bogies type of Y25Ls(s)e-K that are widely used, including in Slovakia, as the extremely hard metal structures of the wagons running on hard rails generate high magnitudes of acoustic energy, so the primary noise source on railway vehicles is from wheel–rail contact. The noise analysis is based on preliminary numerical simulations of bogie-frame vibrations and by localization of the vibration modes. This would be used for the proposal of placement of silencing pads made from porous fiber material that is expected to attenuate noise radiation from the surface. If the efficiency of the noise attenuation showed promising results, further iations
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