Impact load due to railway wheels with multiple flats predicted using an adaptive contact model

Abstract

Although numerous investigations have been undertaken to study the impact load between railway wheel and rail in the presence of a single wheel flat, little attention was devoted to the case of multiple flats. In practice, it is not uncommon that one wheel develops more than one flat or each wheel on the same axle has a single flat. In this study an adaptive contact model, a two-dimensional roll-plane vehicle model, and a three-dimensional track model are developed to investigate the wheel-rail impact load due to multiple flats. Unlike the commonly used Hertzian contact model, the adaptive contact model takes into account the asymmetry of the contact patch as the wheel flat enters and leaves the contact patch. Two scenarios of multiple flats are considered in this investigation. One deals with two flats on the same wheel defined by their size and relative position, and the other deals with a single flat on each wheel of the same axle. In each case, the induced impact loads are compared with those due to a single flat. The results suggest that the magnitude of impact force attributed to the second flat entering the contact region is strongly affected by the responses due to the preceding flat, depending upon the flat geometry, relative co-ordinates of the flats and the operating speed. The results further suggest that the length of a flat alone, which is commonly regarded as wheel removal criteria, may not be adequate when multiple flats are present.

Modelling traffic action in high-speed railway bridges

“…An alternative method proposed to calculate the normal force is the Adaptive Wheel Rail Contact Model. It is argued that the non-linear Hertzian normal force model overestimates the forces during impact loadings and underestimates them at low speeds (Zhu et al, 2007(Zhu et al, , 2009.…”

Development of a vehicle–track model assembly and numerical method for simulation of wheel–rail dynamic interaction due to unsupported sleepers

“…In this study, an adaptive wheel-rail contact model, which can adapt the contact length and depth, is developed for predicting the vertical wheel-rail contact forces. This adaptive contact model has been described in detail in [10,11]. As shown in Figure 3, the wheel-rail vertical interaction is represented by a set of continuous radially distributed springs that takes into account the elasticity of the wheel and the rail.…”

“…However, for this investigation, it is established based on an equivalency with the well established Hertzian nonlinear point contact model for a perfect wheel in the static state. The detailed procedure to determine instantaneous wheel radiusR i , contact patch (α f and α r ) and to establish radial spring constant K w are presented in references [11]. For perfect wheel-rail profile contact in which the rear contact angle equals to the front, the normal contact force can be expressed as…”

“…This paper presents the proposed approach and its application to a coupled vehicle-track system. In this study, a roll plane vehicle model is formulated and coupled with a continuous three-dimensional track model through an adaptive contact model [9][10][11] for the investigation of the dynamic behaviour in both sides of a track system in the presence of unsupported sleepers.…”

Influences of track and rolling stock parameters on the railway load amplification factor

“…Johansson and Nielsen 12 investigated the effect of out-of-round wheels on the vertical dynamic wheel–rail contact force and track response, using field tests and numerical simulations. Zhuet al 13 used a wheel–rail contact model to conduct a theoretical study on the calculation of impact loads caused by multiple flats on a single wheel or single flats on two wheels sharing the same axle. They concluded that using the length of the wheel flat as a criterion for wheel removal might not be sufficient, suggesting further investigations.…”