2A22 Influence of Surface Roughness and Temperature on the Adhesion of Wheel and Rail in Wet Conditions(Boundary)

Abstract

A series of experiments on the traction between wheel and rail were carried out for the purpose of obtaining the fundamental knowledge of how to prevent the occurrence of wheel slips in driving and wheel slides in braking. A twin disc rolling contact machine was used for the experiments by varying the surface roughness and the temperatures of wheel and rail discs, as well as the sprayed water. Adhesion coefficient acquired from the relationship between slip parameters and traction coefficients which can be obtained by experiments and film parameter which is the minimum EHL film thickness with smooth contact surfaces divided by the combined roughness were estimated. Relationship between the adhesion coefficients and combined roughness shows that the adhesion coefficients have a local maximum or almost constant values at 1〜3μm combined roughness and become large with an increase of the temperature of the wheel disc in the range where adhesion coefficients have a local maximum or almost constant values, however, the influence of temperature becomes smaller with the decrease of the combined roughness in the region of less than 1μm. Re-adhesion which is a phenomenon characterized by the dramatic increase of the traction coefficient occurs in some experimented conditions.