Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Final Activity Report Summary - VERA (Vehicle-Rail Interaction Modelling)

The possibility to perform a correct simulation of the dynamical behaviour of a railway vehicle enables to understand the connections between the behaviour of the vehicle and the damages induced on the railway track. Modern simulation techniques allow us to obtain realistic indications on the behaviour of a railway vehicle when irregularities on the track are present. The mathematical model has to be very complex because it has to study either the dynamic of the vehicle or the rail. To have a correct model of simulation enables to plan the operation of the lines and to lead, on a rational base, to common rules at an European level in order to establish the correct "mix" of train, with different characteristics which can be accepted on the various tracks. The results of the project are illustrated in the following, describing the two research main phases.

Phase one concerned with the study of the dynamic performance of vehicles and tracks and their interactions through the wheel-rail interface. To assess the vertical dynamic behaviour of railway track due to moving railway vehicles, an integrated model was developed. The model was built up of two structures, namely the moving train and the railway track. The coaches were schematised by rigid bodies, pivoted at the bogies by springs and dampers. Bogies and wheelsets were also modelled as rigid masses connected with springs and dampers. Only vertical forces and displacements etc. are considered. Rail and track irregularities are one of the most important sources of dynamic loads generated by a moving train, in the model the loads were introduced by means of Hertzian springs travelling along a sine-shaped or irregularly shaped rail and track surface. The investigated structures consist of a train which travels al different speeds on either a classic ballast track or an embedded rail structure (ERS). The ERS track is supported either by a rigid slab or a flexible slab which is itself discretely supported by a rigid pile foundation. The loads between track and vehicle are introduced by a sine-shaped surface deformation of the rail. Different wavelengths are investigated for their impact on the results. Three subjects are investigated: the elastic displacement of the rail head under the wheels, the contact forces between wheel and rail, and, finally, the vertical accelerations of the body, referring to the passenger coach or the locomotive.

In the second phase an automatic procedure to calculate, from the measurement in real time of the rail and wheel profiles, the equivalent conicity parameter, as defined in the UIC 518 and UIC 519 Standards has been defined. The automatic procedure is based on optical units acquiring raw measurements of the rail head profile and of the wheel profile, of a pre-processing stage which smooth's the data via a polynomial fitting to reduce the effect of noise, and of a final processing stage (UIC 519-compliant) which executes necessary coordinate transformations and computes the equivalent conicity. The simplicity of the employed algorithms is the key to obtain actual real-time measurements; however, this simplicity did not affect the uncertainty performance, since the measurement uncertainty of the system has been experimentally evaluated, and demonstrated to be below the maximum measurement error, as imposed by UIC 519. The good accuracy allows us to follow the evolution of the wheel-rail interaction for long time periods. Furthermore in this phase, an automatic procedure for the calculations of the most common comfort indexes has been developed. This is helpful to plan on-condition maintenance works, i.e. executing a specific work only when the track status requires it, thus obtaining maintenance savings and improving the running safety.

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