Predictive Modelling of Curve Squeal Occurrence in Tramways: Influence of Wheel/Rail Double Contact Points

The prediction of curve squeal is one of the most challenging problems especially in tramway applications, where the negotiation of very sharp curves often involves the presence of multiple contact points at wheel/rail interface. Curve squeal is generally attributed to the self-excited vibration of the wheel/rail system, which may occur due to the negative slope of the friction coefficient or due to the mode-coupling mechanism. The frequencies involved are usually the ones corresponding to the wheel modes of vibration, resulting in a strong, tonal and very annoying noise emission. Its occurrence is strictly related to the wheel/rail contact conditions, such as creepages, contact angle and friction coefficient. The purpose of this paper is to assess the role of the presence of double contact points at wheel/rail interface. The investigation is performed through a multibody simulation in time-domain and a frequency-domain predictive model capable to reproduce the linearized wheel/rail dynamics including the presence of multiple contact points between the wheel and the rail. It is shown how the presence of flange contact can alter the overall wheel/rail coupled system mobility, modifying the curve squeal occurrence as well as the wheel modes involved in the phenomenon.