Keywords: wheel wear, freight wagons, two axle, friction damper.

Wheel reprofiling costs are very important for freight wagons in Sweden, and the causes can be divided mainly into three groups: wheel flats, shelling and uniform wear. In this paper the development of uniform wheel wear in a two-axle freight vehicle is studied. This wagon with Unitruck running gear had a major modification in the suspension elements in 2005 which highly reduced flange wear. The method developed at KTH for the uniform wear calculation is applied on both old and new simulation models. In this paper, the development of uniform wear in two axle freight vehicles with friction dampers is studied, including the influence of different friction damping elements and modifications in the running gear.

First, the two axle vehicle model with Unitruck running gear has been modelled and validated with experimental measurements from UIC tests. Some modifications were introduced in the running gear that allowed the reduction of 50% in flange wear. These modifications have also been modelled.

Uniform wear calculation has been carried out with the developed models. First, the behaviour of the real vehicle has been confirmed with the performed simulations: uniform wear volume of the old model is much greater than the one in the new model, as the steering considerably improved with the modified running gear. Second, the increase of the wheel-rail friction coefficient increases the value of the uniform wear, as reported in previous publications. Also, the increase of the friction coefficient in the friction dampers increases the value of the uniform wear, arising from the stiffening of the suspension system. Lastly, it has been observed that the reliability of uniform wear calculations is strongly dependant on the severe wear limit in combination with the behaviour of the wheel-rail contact. This effect has more influence for high axle loads, because the contact pressure of sliding areas can rise more easily over the severe wear limit.

Calculation of uniform wheel wear of freight vehicles is feasible, but specific details about vehicle behaviour must be taken into account. Especially the influence of freight vehicle uncertainties must be analysed in order to ensure good modelling of the wheel wear evolution.

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