The formation of short pitch corrugation is studied by using an approach combining wheel/track dynamics, contact mechanics and wear. Multiple wheel/rail interactions are taken into account in the wheel/track dynamics in the frequency domain. The active wheel/rail contact forces are assumed to be responsible for the rail corrugation. In the contact mechanics, a quasi-static method is used to determine the contact patch and the boundary between the stick and slip zones due to unsteady rolling contact where the normal contact force and the surface curvature vary. The total wear on the railhead is calculated by accumulating the wear in the slip zone in each time step as the wheel rolls over the track for a given wavelength. The corrugation growth rate has been calculated at different wavelengths and at two train speeds using parameters corresponding to tracks with three pad stiffnesses. The dynamic contact force under multiple wheel/rail interactions has many peaks at different frequencies due to the wave reflections between the wheels when using softer rail pads. lt is therefore expected that the wavelengths of short pitch corrugation are associated with several frequencies rather than only one frequency as in the case of a single wheel/rail interaction. Since the normal contact force and the contact geometry are functions of time or distance, the rolling contact becomes unsteady, so that in the contact patch, the boundary of the stick and slip zones and the slip velocity between the wheel and rail also vary with time or distance. In addition, wear only occurs in the slip zone and corrugation results from an accumulation process of wear. As a result of a combination of all these factors, it has been found that the corrugation growth rate becomes largest when the phase of the normal dynamic contact force lags about 135 rather than 180 degree with respect to the roughness, that is when the force peaks just before the roughness crest. lt is also found that wear is heavier at shorter wavelengths and increases with the amplitude of the dynamic contact force. Moreover, corrugation develops more quickly using stiffer pads than using softer pads.
An investigation into rail corrugation due to micro-slip under multiple wheel/rail interactions
2003
9 Seiten, 12 Bilder, 10 Quellen
Conference paper
English
An investigation into rail corrugation due to micro-slip under multiple wheel/rail interactions
British Library Conference Proceedings | 2003
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