Short pitch corrugation on straight tracks—Theory and numerical simulation

Abstract

Simulation models (Frederick, Sinclair, Valdivia, Hempelmann) which have been developed during the last 20 years showed the formation of short pitch corrugation to be a frequency constant mechanism, where a track mode about 1000 Hz dominates the corrugation process. Based on this, however, it is difficult to explain the relatively small variation in wavelength with vehicle speed which is observed in practice. In this presentation a sophisticated linear wheel-rail model is introduced which could help in resolving this contradiction. The transient dynamics is described by a feedback loop: Fluctuations in the contact geometry and the creepages cause varying contact forces. This produces fluctuating relative displacements between wheel and rail which in turn change the contact geometry and the creepages again. The simulation of the long-term behavior shows how the rail surface is damaged after a high number of wheel passages. Based on numerical results it is demonstrated that, due to contact mechanical effects, short pitch corrugation is growing within a fixed wavelength band, which could explain why the wavelength varies only a little with vehicle speed. The presented model is therefore a good basis for future research on how short pitch corrugation can be suppressed.