Abstract: The effect of web-mounted braking disc on the sound radiation characteristics of a Metro wheel excited by different types of wheel-rail combined roughness is investigated. In the analysis procedure, a three-dimensional finite element model for the wheel is developed. The nature frequencies of the wheel are calculated based on the block Lanczos method and the frequency responses of the two kinds of wheels (with and without web-mounted braking disc) are calculated based on the modal summation method under four typical wheel-rail combined roughness excitations at the nominal contact point. Then the velocity boundary conditions for the acoustic model are generated by using the vibration results of the structure and the sound radiation characteristics are calculated based on the acoustic boundary element method. At the strong resonance peaks of the wheel, the efficiency of the wheel vibration and noise control is discussed by using the web-mounted braking disc under different wheel-rail combined roughness excitations. Through the comparison of the sound pressure contours of the field points and the directivity diagrams, the influence of this type of disc is discussed on the sound radiation directivity of the wheel, especially in the axial direction. From the results above, it can be concluded that the sound radiation of the wheel is mainly due to the axial vibration of the wheel web. The web-mounted braking disc can effectively reduce the axial vibration of the wheel web and act as a web-fitted noise screen which can mitigate the noise radiated from the wheel web. As a result, the web-mounted braking disc can effectively reduce the rolling noise (the wheel contribution).

Key words: Metro wheel, Sound radiation characteristics, Web-mounted braking disc, Wheel-rail combined roughness