Progression of the stick / slip zones in a dry wheel-rail contact: Updating theories on the basis of tribological reality

摘要

At present, optimizing control of maximum wheel-rail adhesion, from the anti-skidding systems piloting" the sliding and the rolling speeds of locomotives, is done on the basis of the wheel-rail contact models available in the literature. Improved accuracy of power train control has highlighted the limits of this optimization technique since the contact conditions of the models, i.e. the stick / slip zones, do not take into account the physical phenomena involved, although they are hardly known. To attenuate this difficulty, the recent works presented in this paper, allow describing the tribological reality of a wheel-rail contact, i.e. the progression of the stick / slip zones. This reality is achieved thanks to monitoring the changes in the the characteristics of the third body present between wheel and rail. The results of tests under initial condition show that there is a correlation between the progressions of the third body flows and that of the adhesion for the various phases of the adhesion-sliding curve. Therefore activation of the internal flow of third body is in fact the physical manifestation of the theoretical condition of stick. On the other hand, the activation of the internal source and recirculation flows of the third body are the physical manifestation of the theoretical condition of slip. This tribological reality therefore allows us to update the theoretical stick / slip conditions and by consequence, anti-skidding systems.