A time-domain finite element model is developed to study the transient rolling contact of a driving wheelset over a curved track with Low Adhesion Zones (LAZs) shorter than 1.0 m. LAZs on one rail, i.e., unilateral LAZs occurring more likely, is treated for a speed up to 500 km/h. Structural vibrations of wheelset are analyzed to explain the transient contact forces, creepages and the resulting irregular wear. LAZs on high rails are found more detrimental than those on low rails. The results explain the occurrence of flats and rolling contact fatigue in bad weather, although significant wheel idling is absent.

A methodology for the determination of a critical size of surface defects, above which RCF can initiate, has been developed and demonstrated with its application to the passive type of squats under typical Dutch railway loading conditions. Such a methodology is based on stress evaluation of transient rolling contact at the defects, for which a detailed 3D frictional rolling contact model is integrated in the vehicle–track interaction system. Through comparing the maximal von Mises stress at defects of different sizes with the tensile strength of the rail material, the critical size is derived for squats. Observations during a field monitoring test show a good validation of the determined critical size. In practice, the critical size can be used for distinguishing between light squats and trivial defects by visual inspection or by automatic image recognition, so that false statistics of squats can be reduced or prevented. With necessary modifications and improvements, the developed methodology may also be applied to RCF of other rolling contact pairs in general, such as bearings and gears.