Keywords: wheelflat effect, train-track interaction, time-domain response, assumed mode analysis, finite element model, Winkler bedding, vehicle dynamic model, fault diagnosis.

A global method to investigate the wheel profile defects in railway transport is presented in this paper. The model, developed here, is destined for a fault diagnosis on an experimental platform. The main goal is to reduce the maintenance cost of railroad platforms. One of the most important problems facing the railway maintenance is the monitoring of the dynamic behaviour of tracks subjected to moving loads (freight and passenger trains). Higher speeds, increased traffic density and loading result in accelerated degradation. At the same time, interoperability, variety of different vehicles, induces a wider variety of potential degradation sources. The structures are therefore subjected to severe vibrations and dynamic stresses, which in turn are much more than the corresponding static stresses.

The dynamic forces of railway interaction are influenced by the geometrical characteristics of wheel and rail and the dynamic characteristics of the load. Here a major geometrical defect of wheel contour is considered, which is the wheelflat. Other research has been performed to study the effect of wheelflat on the dynamic interaction between rail and wheel. Despite the large volume of research on this subject, few works analyze comprehensively the problem for an experimental case. Above all, the algorithms of the model should quickly calculate the dynamic response of the track following the measured data.

Such models comprise three different sub-models for vehicle, contact force and track. To reduce the calculation time, a one dimensional vehicle model with two degrees of freedom is used. Previous work demonstrates that some non-Hertzian methods are convenient for the calculation of the interaction contact force. So a Winkler bedding contact is implemented and compared with the Hertzian model for a round wheel profile. The track is modeled as an ordinary Euler-Bernoulli beam with discretized supports. An analytical Lagrangian model with assumed modal number is proposed for the rail. Each support comprises the railpad, the sleeper and the ballast with linear characteristics. The parameters used for the rail and the sub-structure are obtained through different data acquisition stations from the experimental platform.

The results of time-domain response are evaluated and compared with a precise finite element model of the track. It is shown that the model provides good precision to predict the wheelflat while the computation is fast.

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