Wheel-rail dynamics with closely conformal contact Part 2: Forced response, results and conclusions

Abstract

Observations on the Vancouver mass transit system suggest that noise, vibration and corrugation of the rail appear to be associated with close conformity between the transverse profiles of the wheel and rail. To investigate this, a dynamic model of the wheel and rail under conditions of close conformity has been developed. Previous work has suggested that motion of the wheel could be neglected, so the model comprises two subsystems: (a) the rail and its supports, and (b) the contact between wheel and rail. A dynamic model of a continuously supported rail is presented, which is consistent with similar models in the literature. Conformal contact has been represented in two ways: (a) as a single highly eccentric elliptical contact, and (b) as a two-point contact. Novel`rolling contact mechanics' have been incorporated in both these models. The complete system is closed: oscillations of the rail give rise to fluctuating contact forces, which in turn excite the rail. A linear stability analysis of the system shows it to be stable under all conditions examined, thus precluding the possibility of self-excited oscillations occurring on a perfectly smooth rail. The model can then be used to investigate the forced response to existing roughness on the railhead, which is the subject of a companion paper (1).

Rail corrugation: advances in measurement, understanding and treatment

“…[20,31]. However, it has not been possible to date to demonstrate analytically that the contact conditions, particularly high spin creep, associated with close conformity do indeed give rise to an oscillation that could cause corrugation [31].…”

“…[20,31]. However, it has not been possible to date to demonstrate analytically that the contact conditions, particularly high spin creep, associated with close conformity do indeed give rise to an oscillation that could cause corrugation [31]. A fundamental difficulty that has been evident for some time is that the track provides extremely high damping at frequencies that are typical of short pitch corrugation [27], except in a few narrow frequency ranges.…”

Corrugation models and the roaring rails enigma: a simple analytical contact mechanics model based on a perturbation of Carter’s solution

“…The mathematical description of the beam model is obtained from the case of load moving with speed V given in the Appendix, although it has certainly been obtained elsewhere previously. For validation and comparison, we shall use the more sophisticated model of Bhaskar et al [1997a;1997b], where the rail is continuously supported by uniformly distributed rail pads, sleeper mass and ballast. The effect of discrete sleepers in that work was neglected, because the SkyTrain system has mostly a continuous support.…”

“…the high lateral rail receptance between 1600 and 1800 Hz and the low vertical rail receptance near 300 Hz. Bhaskar et al [1997a;1997b] looked at the Vancouver SkyTrain tramway system where no traction or braking is done at the wheels, yet longitudinal creepage "can arise from curving, hunting motion or misaligned axles", and indeed their reference case has three comparable components of steady creepage. However, the fluctuating parts of creepage are only caused by conformity ("principal cause of fluctuating longitudinal creepage was found to be the fluctuation in rolling radius due to the movement of the contact point [see equation (27) in [Bhaskar et al 1997a], which is almost in phase with the angular ripple at most frequencies"), whereas rotational inertia of the wheelset is not included in the model, nor its complete receptance.…”

Effect of rail pad stiffness on the wheel/rail force intensity in a railway slab track with short-wave irregularity

“…In this regard, several numerical and experimental researches have been carried out to investigate the effect of rail pad stiffness on the wheel/rail force and track behavior in the ballasted railway track. [10][11][12][13][14][15] Nowadays, slab track superstructure is used widely compared to the ballasted one by dint of its advantages. 16 Although a review of the literature related to the ballasted tracks indicates that rail irregularity and rail pad stiffness have the most effects on the wheel/ rail force, very few works have been carried out on the effect of rail pad stiffness on the wheel/rail force in slab track.…”