Experimental observation of temperature and surface roughness effects on wheel/rail adhesion in wet conditions

In this study, the relationship between the adhesion coefficient in the wheel and rail contact zone and the temperature under wet conditions was evaluated by means of a twin-disc rolling contact machine while varying the surface roughness of two rolling discs. The experimental results show that the adhesion coefficient is increased by raising the temperature. The surface roughness has a significant influence on the adhesion coefficient, but no trend of increasing the adhesion coefficient proportionally at low temperature was observed. Also, the adhesion coefficient has local maximum or nearly constant value at a threshold of surface roughness. On the other hand, re-adhesion phenomenon, which is characterized by a dramatic increase of the traction coefficient followed by a reduction in slip ratio, was found generally occurs in low temperature.