Liquid-solid interaction at opening in rolling contact fatigue cracks

The purpose of analysis was to verify commonly taken assumption about the ability of liquid sucking in (for instance oil or water if present in the wheel/rail contact area) into the crack interior during one cycle of opening. The analysis was carried out for load, crack and contact geometry typical for rail/wheel contact. The results obtained from the analysis indicate on the existence of “limiting speed” of moving contact load (train speed) for which the phenomenon of continuous liquid sucking in into the crack is possible. For the RCF rail head crack of length a = 13.5 mm inclined at 15° to the horizontal, this speed is about 0.9 m/s. For higher speeds, the SFF model does not give the reasonable solution because pressure in the section of fluid film near the crack tip drops deeply below zero. These conditions indicate that cavitation can occur in the fluid film inside the crack or fluid flow can be broken or confined to fraction of crack length. Additionally, the lack or very insignificant influence of the existence of fluid film inside the crack on the kinematics of crack opening in the analysed phase of loading cycle was observed.