Wear

From the point of view of the railway opera­tor, two kinds of wear are to distinguish:

• The ordinary wear in lateral direction of the wheel and rail profiles, quite often addressed just as “wear”, mainly de­fines the maintenance intervals.
• The non-uniformity of the wear in longi­tudinal direction such as rail corrugation or wheel polygons, see figure below, is both the result and the cause of vibrations of the vehicle.

A lot of uncertain parameters influence the distribution of lateral wear of the wheel profiles, such as wheel and track profile, track irregularities, layout of the line, opera­tion conditions, train performance and con­tact conditions. Hence, a current project in cooperation with the Bayrische Oberland­bahn, a local train operator, deals with the determination of theses parameters. The wear at the wheels of their train sets is re­evaluated calculating the local distribution of the work of friction in the corresponding contact patch in multibody simulations.

Additionally, the consideration of the struc­tural dynamics of the wheel-sets and the rails and the refined contact description presented in Sec. of the Wheel/Rail Interface allows for a detailed analysis of non-uniform wear in longitudinal direction such as corrugation or out-of-round wheels since this type of wear is re­lated to higher frequency ranges.

Using such a model of a vehicle/track-sys­tem, it is possible to break down the inter­relations that lead to oscillations more de­tailed than in measurements and identify the main parameters of influence. The mechanism of friction induced oscillation with very high ampli­tudes of a light railway vehicles in narrow curves could be shown. The result of these vibrations is corrugation of the inner rail with a wavelength of typical 12 to 18cm.

Comprising, the key feature of the approach is the interplay of short time vehicle/track dynamics including the improved modelling of the wheel/rail interface and the long term behaviour of the vehicle and track compo­nents subjected to wear. In principle even rolling contact fatigue phenomena could be taken into account this way.