Influence of ambient humidity on the adhesion and damage behavior of wheel–rail interface under hot weather condition

Abstract

A wheel/rail system is an open system, where the operating environment factors, such as atmospheric humidity, temperature, and oxidation behavior, are subject to change. This study conducts experiments on a twin-disc test rig with a climate chamber to examine the effect of ambient humidity on adhesion and damage between the wheel and rail interface under hot weather conditions. Results indicate that humidity has a remarkable effect on the adhesion behavior of a wheel–rail rolling contact interface. Under low humidity levels, fatigue wear is predominant, abrasive wear becomes increasingly serious with an increase in humidity, oxide wear debris acts as abrasive particles and accelerates the wear process. Under high humidity levels, a friction-reducing layer is formed, and the rollers are protected from excessive wear. Adhesive wear is the main damage mechanism in addition to oxidative wear. Raising the humidity level helps the rollers to avoid excessive wear. However, high humidity level is unconducive to the safe operation of trains because high humidity and a high heat environment promotes the formation of tribochemical products which are a mixture of iron oxide and water molecules and lead to a great decrease in the adhesion between wheel and rail.