A parametric study on the effect of ring damper on wheel damping

Ring dampers have been widely applied to control vibration of, and noise from, train wheels due to the simple structure, negligible impact on operational safety and potential in vibration and noise reduction. Yet, parameters affecting the vibro-acoustic performance of a ring-damped wheel are not adequately studied. In this paper, the apparent modal damping ratios of a ring-damped wheel are studied numerically using a finite element model allowing for frictional nonlinearity. Studied parameters include the impact force used to excite the wheel, the preload in the ring, the friction coefficient of the interface between the ring and the wheel, and the number of rings installed. Several findings can be drawn from the study. Installation of one or two rings to the wheel does not change the resonance frequencies (they are also termed the modal frequencies of the ring-damped wheel) but reduces the resonance responses by generating extra damping to the modes. The ring is more effective for radial excitation than for axial excitation. At most modal frequencies, damping with double rings is higher than with a single ring. Although there are few modal frequencies at which the modal damping ratios are reduced by installing the second ring, the average damping ratio with two rings is much higher, by a factor of 2.37 for axial excitation and 1.73 for radial excitation, than that with a single ring. The apparent damping of the ring-damped wheel increases with the level of the impact force, especially for radial excitation. There is an optimal combination of the preload in the ring and the frictional coefficient with which damping induced by the ring is the highest. Besides, the average damping ratios of the modes above 2000 Hz are proposed to be an indicator of the effectiveness of the performance of a ring-damped wheel in noise reduction.