Response Behavior of Damp-Warm Air to Adhesion and Damage of Wheel-Rail Interface at Different Ambient Temperatures

As an open and complex tribological system, the friction force (i.e. wheel-rail adhesion) and damage failure on the wheel-rail rolling contact interface are strongly interfered by the external environment, and the complex operating environment will seriously affect the service performance of the wheel-rail system. In order to study the effect of high-humidity warm and humid airflows on the adhesion and damage of wheel materials under different service temperatures, and provide theoretical reference for safe and reliable service of wheels and rails. In this paper, a wheel-rail rolling contact wear/fatigue testing machine was used to simulate the response behavior of intermittent warm and humid airflows to high-speed wheel-rail interface adhesion and wheel surface damage in a wide temperature range (−55~60 ℃). The results indicated that, under the same conditions of warm and humid airflows (99% RH), the ambient temperature had a remarkable impact on the adhesion and damage of the wheel–rail rolling contact interfaces. Under the condition of low temperature, the adhesion coefficient between the wheel and rail decreased rapidly, by contrast, there was a slight increase in the high temperature environment. The wheel damages (such as plastic deformation and surface fatigue cracks) induced by warm and humid airflows under low temperature condition was significantly higher than that in high temperature condition. At low temperature, the material was brittle, the pits on the wear surface were significant, and the abrasive particles formed by fatigue spalling provided the possibility for the ploughing effect. In addition, the wheel-rail interface was easy to be congealed into water film after the warm and humid air flow, and the oxidation was slight and the area was wide. However, at high temperature, water vapor was easy to cause debris accumulation and local oxidation was obvious. Thus, the wear mechanism also changed significantly, from fatigue wear and abrasive wear under low temperature condition to oxidation wear, adhesion wear and fatigue wear under high temperature condition. Therefore, the behavior of train wheel-rail low adhesion induced by warm and humid airflows should be paid more attention, to ensure the safe and reliable operation of trains passing through instantaneous humid and hot environments such as tunnels in alpine regions.