Evaluation of Wear of Disc Brake Friction Linings and the Variability of the Friction Coefficient on the Basis of Vibroacoustic Signals

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.

Mixtures of Lubricants and Ecological Refrigerants under Starved Lubrication Conditions

“…The moment of force was measured during the tests. Next, the coefficient of friction was calculated on the basis of the following formula based on brake system [ 51 ]: where μ is coefficient of friction (-), M is moment of force (Nm), P is load (pressure force) (N) and r is radius of the ring (m).…”

Investigating the Impact of Carbon Fiber as a Wheelchair Frame Material on Its Ability to Dissipate Kinetic Energy and Reduce Vibrations

“…Based on the direct measurement of vibration acceleration, it is possible to indirectly determine, for instance, the mechanical energy transferred to the human body. Similar acceleration calculations allowing the determination of mechanical and energy parameters are carried out in many fields of science [40][41][42][43].…”

Thermographic Fault Diagnosis of Ventilation in BLDC Motors

“…However, it is difficult to detect the localization of faults using vibration analysis. For this reason, methods based on a fusion of vibration and acoustic signals have been developed [7][8][9][10][11][12].…”

“…Techniques for detecting tool breakage using vibration signals were demonstrated in [11]. Vibro-acoustic analysis of a railway disc brake based on the amplitude and frequency domains was conducted in [12].…”