Měření a numerické modelování hluku a vibrací železničního kola

Abstract

The presented PhD. project deals with an extensive study of the dynamic properties of railway wheel. The paper describes a series of experiments that led to the detection of modal and acoustic properties of railway wheel and its behavior during a harmonic signal excitation. The compilation of a mathematical model of the railway wheel and the application of a number of computational tasks on this model was an integral part of the work. Natural frequencies, undamped mode shapes and the damping parameter for each mode shape of the vibration were determined. The measurement was performed using an impact hammer with force transducer and uniaxial vibration sensor. 35 mode shapes were detected, classified and analyzed in detail. Besides these, was also set up the mathematical model of railway wheel for solving modal analysis using FEM. It managed the model has been set to a very good agreement with the experiment data. A series of experiments continues with the harmonic analysis of railway wheel. Harmonic analysis was performed for individual harmonic force excitation, in several specific ways - radial, axial and combined. In this part of project the echo method was derived. This method significantly assimilated the measured natural frequency to the actual value. In harmonic analysis the frequencies for following acoustic measurement were selected. Considerable attention has been paid to the issue of splitting the mode shapes of the vibration. Acoustic measurements were initiated by measurement of the acoustic holography using Beamforming method. Measurements prove that the excitation effect was sufficient and acoustic response well measurable for the entire investigated frequency range. It was found that the similarity of noise maps and visualized eigen mode shapes is very high. Then an experiment allowing the determination of levels of acoustic power emitted by the railway wheel was designed. During this procedure several SW applications were prepared for processing of measured data. Results of acoustics measurements are compiled noise maps of the area around the railway wheel and efficiency of fitted noise damper for selected mode shape vibration. The whole work was developed in cooperation with the producer of railway wheels. The proposed procedures and methods described in the project reflect the needs of engineering practice. The results obtained in this work were used in the proposal of arrangements contributing to reduce the noise of railway wheelsets.