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The actual European regulations for the acceptance of railway vehicles prescribe the measurement of not only accelerations but also contact forces exchanged at wheel-rail interface, in order to assess the level of running safety, track loading and vibration behaviour. It is important to point out that the standards do not prescribe any specific method to measure forces, or define the measurement of forces. The aim of this paper is to investigate the metrological properties of a dynamometric wheelset in order to determine the associated measurement uncertainty and to verify its readiness in the range of frequencies where the force analysis must be performed. With reference to a specific instrumented wheelset, a method for increasing the accuracy of the measure when critical running conditions (i.e. large values of the derailment coefficient Y/Q) are detected is proposed. The proposed method can be applied to any instrumented wheelset, but it is particularly effective on non-conventional wheelsets, where only few measurements are available and the classical methods cause large estimation errors.

Modelling of elastomeric elements of railway components, able to represent stiffness and damping characteristics in a wide frequency range, is fundamental for simulating the train–track dynamic interaction, covering issues such as rail deflection as well as transmitted forces and higher frequency phenomena such as short pitch corrugation. In this paper, a modified non-linear Zener model is adopted to represent the dependences of stiffness and damping of the rail fastening, made of elastomeric material, of a reference Embedded Rail System (ERS) on the static preload and frequency of its deformation. In order to obtain a reliable model, a proper laboratory test set-up is built, considering sensitivity and frequency response issues. The equivalent stiffness and damping of the elastomeric element are experimentally characterised with force-controlled mono-harmonic tests at different frequencies and under various static preloads. The parameters of the non-linear Zener model are identified by the experimental equivalent stiffness and damping. The identified model correctly reproduces the frequency- and preload-dependent dynamic properties of the elastomeric material. The model is verified to be able to predict the dynamic behaviour of the elastomeric element through the comparison between the numerically simulated and the experimentally measured reaction force to a given deformation time history. Time domain simulations with the model of the reference ERS demonstrate that the modelled frequency- and preload-dependent stiffness and damping of the elastomeric material make a clear difference in the transient and steady-state response of the system when distant frequency contributions are involved.

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