Numerical Methodology for the Evaluation of High Speed Vehicle Stability in Curved Track

The calculation of the critical speed for a railway vehicle is a complex problem particularly affected by the non – linearities associated to the wheel/rail contact. Hence as far as the valuation of vehicle stable motion of a railway vehicle is concerned, different methodologies are adopted based both on linear and non linear techniques, but till now it is not defined a common approach to deal with the problem. Furthermore, experimental evidence coming from homologation campaigns, carried out on the Italian high speed line, shows that the same vehicle can present a stable behaviour in tangent track, while incipient hunting motion can be observed while negotiating large radius curves. Aim of this paper is to investigate this phenomenon theoretically, with the support of a numerical model of vehicle dynamics and train-track interaction along a curved track and of a methodology to define the critical speed of the vehicle, considering the non–linearities associated with wheel/rail contact. In particular, a relationship between the vehicle critical speed defined according to European standard EN14363 and curve radius is looked for to provide theoretical relevance to the experimental findings obtained in line tests and to provide practical solution to the problem