NUMERICAL-ANALYSIS FOR THE INFLUENCE OF WATER FILM ON ADHESION BETWEEN RAIL AND WHEEL

The adhesion force between rail and wheel is one of the important fact ors for proceeding towards the realization of high-speed railway. On t he other hand, it is supposed that the water film formed between the r ail and wheel has a remarkable influence on the adhesion force under r ainy condition at higher speeds. In this paper, taking Bett and Cappi' s viscosity values of water, which show quite a different behaviour fr om the viscosity of oil, the influence has been investigated of import ant factors such as rolling speed contact pressure and temperature on water film thickness for a smooth surface by applying elastohydrodynam ic lubrication theory. Based on the numerical solutions, an empirical equation has been developed for water film thickness relating to rolli ng speed, load and material parameter by using a linear regression met hod and comparing it with other authors' works on a lower material par ameter or elastic-isoviscous contact. Furthermore, in order to underst and the influence of the above factors and the surface roughness on th e adhesion force, adhesion coefficients have been calculated on a tria l basis in the case of rough surface contact under limited conditions, and the theoretical results have been compared with the measured valu es of the tests on Japanese Shinkansen vehicles in the field.