Abstract
The article presents the results of friction and vibroacoustic tests of a railway disc brake carried out on a brake stand. The vibration signal generated by the friction linings provides information on their wear and offers evaluation of the braking process, i.e., changes in the average friction coefficient. The algorithm presents simple regression linear and non-linear models for the thickness of the friction linings and the average coefficient of friction based on the effective value of vibration acceleration. The vibration acceleration signals were analyzed in the amplitude and frequency domains. In both cases, satisfactory values of the dynamics of changes above 6 dB were obtained. In the case of spectral analysis using a mid-band filter, more accurate models of the friction lining thickness and the average coefficient of friction were obtained. However, the spectral analysis does not allow the estimation of the lining thickness and the friction coefficient at low braking speeds, i.e., 50 and 80 km/h. The analysis of amplitudes leads to the determination of models in the entire braking speed range from 50 to 200 km/h, despite the lower accuracy compared to the model, based on the spectral analysis. The vibroacoustic literature presents methods of diagnosis of the wear of various machine elements such as bearings or friction linings, based on amplitude or frequency analysis of vibrations. These signal analysis methods have their limitations with regard to their scope of use and the accuracy of diagnosis. There are no cases of simultaneous use of different methods of analysis. This article presents the simultaneous application of the amplitude and frequency methods in the analysis of vibroacoustic signals generated by brake linings. Moreover, algorithms for assessing the wear of friction linings and the average coefficient of friction were presented. The algorithm enables determination of the time at which the friction linings should be replaced with new ones. The final algorithm analyzes the vibration acceleration signals using both amplitude analysis for low braking speeds, as well as spectral analysis for medium and high braking speeds.
Highlights
Changes in the construction of disc brakes are related to the increase in train speed.The braking system absorbs and dissipates the vehicle’s energy to the environment as heat during the braking process
Attention was paid to the influence of the condition of the braking system understood as the wear of friction linings on the frictional characteristics and vibroacoustic characteristics
Besides the assessment of the technical object condition, the changes in the average coefficient of friction as a function of the braking speed can be determined. This is due to the strong dependence of the diagnostic parameter on wear expressed by the dynamics of changes, exceeding 6 dB, as well as the dependence of the average coefficient of friction on the speed and friction linings wear
Summary
Changes in the construction of disc brakes are related to the increase in train speed. The braking system absorbs and dissipates the vehicle’s energy to the environment as heat during the braking process. The unfavorable processes during the braking of rail vehicles include vibroacoustic processes in the brake system (vibrations, noise), thermal processes occurring in the friction pair, and wear of the brake components. The above processes affect the deterioration of the acoustic environment, especially the comfort of passengers and the operating costs of rail vehicles. Vibroacoustic phenomena emitted by brake systems are considered very undesirable. The problem of vibrations in the brakes of railway and car vehicles has been recognised since the 1930s [1,2]
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