Influence of creep forces on the risk of derailment of railway vehicles

Abstract

The derailment mechanism in a railway vehicle is a complex mechanical phenomenon which has been, and still is, the subject of intense research activity due to the serious consequences it can entail. Since Nadal deduced his well-known formula, many researchers have put forward alternative equations which all attempt to move closer to data obtained experimentally. This paper provides a summary of the best known, and draws up a new formulation based on the theoretical 3-D study of creep forces emerging in contact on the wheel likely to derail. It also provides an in-depth analysis of the role played by spin creepage, including its effect on obtaining theoretical derailment limits which are more realistic than those obtained using Nadal’s formula. Finally, a new derailment criteria is proposed. This new criteria leads to less conservative values than Nadal’s equation for zero yaw angles. When the yaw angle is high enough, the results obtained are coincident with those predicted by Nadal’s equation.