Influence of temperature on adhesion coefficient and bonding strength of leaf films: a twin disc study

In the autumn, train operations in the UK are likely to be unstable due to the low adhesion coefficient between the wheel and rail, and fallen leaves on the line have been known as the main cause of this problem. In this study, the temperature effects on the adhesion coefficient as well as the bonding strength of the leaf film were investigated using a twin disc machine, to develop a potential prevention and mitigation method. The high surface temperature of the disc seemed to improve the adhesion when the leaf powder suspension was present, forming a linear relationship between the surface temperature. The surface temperature around 240 °C could be enough to attain the required level of traction. The high temperature could decrease the bonding energy between the leaf film and rail, possibly decelerating the chemical reaction for the leaf film formation. Continuous drag braking in the autumn was proposed as a countermeasure. Two effects can be expected for this method: prevention of leaf contamination by removing the leaf residue on the wheel surface and improvement of the adhesion level by braking heat.