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Diagnostics of adhesion of the tram wheel using Acoustic emission method
Skoupý, Martin ; Dočkal, Aleš (referee) ; Klapka, Milan (advisor)
The aim of the thesis is to develop a method of adhesion diagnostics of a tram wheel by monitoring the acoustic emission originating from the wheel-rail contact. Application on a twin-disk test rigs is expected. The possibilities of using both contact and contactless sensors are examined. The thesis is focused on describing the response to varying speeds, angles of attack and the change of adhesion due to the application of water into the contact. RMS and energy of the acoustic emission, kurtosis or Shannon’s entropy were evaluated. It was discovered, that form the low values of the angle of attack (10 mrad) the acoustic emission RMS rises in linear manner with further increase of the angle or speed. After the application of water, the drop of the acoustic emission corresponding to the drop of adhesion coefficient was detected. The transitional states associated with unequal distribution of water were observed following its application and during the contact starvation. This can lead to an undesirable squeal noise. Another transient phenomenon manifested by the increase of acoustic emission activity was observed preceding the contact starvation, its timing corresponds to the removal of oxide layer described in the literature. Acoustic emission therefore proved to be suitable for its study and possibly for the contact starvation prediction.
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Noise form rolling stock in Brno
Dolíhal, František ; Dočkal, Aleš (referee) ; Klapka, Milan (advisor)
This study is focused on the analysis of data from long-term noise measurements of trams at the turning loop in Brno-Komín, and at the Technological Park turning loop in Brno. Automated field measurement based on sound pressure level and frequency evaluated tram passages to determine if there was the occurrence of squealing noise while traversing tightly curved track segments. Concurrent with noise measurements, meteorological conditions (temperature, relative humidity, and rain) were recorded. Alongside data from the preceding switch memory, including vehicle identification numbers and inspection data provided by the Brno Public Transit Company, an analysis of influencing factors on the occurrence and parameters of squealing noise was conducted. A weak dependence on air humidity (and consequently temperature) was found. This revealed varied noise behavior among tramcars of the same construction. Influence of water in contact of wheel was described during process of drying tracks. Manual field measurements also suggest the influence of vehicle speed. Observations also indicate the need for future assessment of the driver's influence and overall driving dynamics (especially acceleration), which this study does not address.
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Effect of operating conditions on tram noise in real traffic
Lounek, Kryštof ; Galas, Radovan (referee) ; Valena, Martin (advisor)
The bachelor's thesis investigates the influence of weather conditions on the squeal noise produced by the contact of the wheel with the top of the rail. Weather conditions are defined here as humidity, air temperature and the presence of rain. The thesis also compares specific trams in terms of their propensity to produce squeal noise and the parameters of the noise produced. The data sets used in the analysis come from a one-month period from a stationary module located near the track curve in the Brno-Komín tram loop. The graphical dependencies, which are the result of the work, describe a decreasing tendency of the average noise level depending on the humidity and an increasing tendency of the average noise level depending on the temperature. They also show a significant reduction in the occurrence of squeal noise during rain. As far as the tram comparisons are concerned, tram no. 1713 produces the most squeal noise, in fact in 86% of the cases. It also has one of the highest values of all noise parameters. The results of this work can help to explain the variable behaviour of squeal noise and can also be used to identify specific noisy trams.
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