Physical processes in wheel–rail contact and its implications on vehicle–track interaction

Wheel-rail creep force model for predicting water induced low adhesion phenomena

“…Linear regression models have been implemented for the (internal) calculation of the Polach parameters in the WILAC model because the observed change of the adhesion characteristic as a function of vehicle speed and normal force does not agree well with available experimental data from locomotive tests [Six 2015] when fixed values are used for the Polach parameters in the calculation. Experimental data from the tram wheel test rig were not available for the whole range of operating conditions with respect to normal force and rolling speed for the WILAC model development.…”

“…Experimental data from the tram wheel test rig were not available for the whole range of operating conditions with respect to normal force and rolling speed for the WILAC model development. Thus, extrapolation of data to a wider range of normal forces and rolling speeds was necessary, which was done with the Extended Creep Force (ECF) model [Meierhofer 2015, Six 2015]. The ECF model explicitly considers third-body layers and the effects of plastic deformation, material hardening, and temperature-related softening of this layer on the adhesion level.…”

“…Each of these experimental data (at fixed water flow rate w) were recorded at a normal force of 4.2 kN and a rolling speed of 5 m/s. These data were extrapolated to a wider range of operating conditions with the ECF model [Meierhofer 2015, Six 2015, which was parameterised based on locomotive test data previously. The experimental data and the extrapolated data then served as the basis for the determination of the linear regression models for the (internal) calculation of the Polach parameters in the WILAC model (see Section 5.2).…”

Design and optimisation of wheel–rail profiles for adhesion improvement

“…The research in [15] on the influence of geometric characteristics on static friction coefficient for elastic non-saturated in case of disk brake contact shows that while increasing contact area 1.5 times it becomes possible to increase the friction coefficient by 2.2%. Moreover, the results shown in [16] suggest that the relationship between the rail head radius and traction coefficient is nearly linear, while increasing the head radius of the rail by 2 times, the traction coefficient increases roughly by 20%, and obviously the contact area formed in the contact interface is a nonlinear function of the radius for the twindisc contact. The authors concluded that decreasing the contact area by reducing the rail head radius decreases the traction level significantly.…”

“…The investigations made for disc brake in paper [15] show that friction coefficient increase with the increase in the contact area of contact pair. Moreover, Six et al [16] recently proposed a so-called ECF model which is able to take into account all observed effects from measurement regarding the adhesion coefficient including contact geometry.…”