Effects of Rail Hardness on Rail Wear and Head Check Initiation

Abstract

In China, rail head check on heavy-haul railways is the main type of rolling contact fatigue defect, especially since the advent of rail with good wear resistance and high hardness. The influence of hardness on rail wear and head check was explored by use of a method to predict rail head check initiation by considering wear. The proposed method combined a profile wear model based on the Archard wear model and a prediction model for head check initiation life based on the critical plane theory, which used the worn profile iterations and the accumulation of fatigue damage as determined by the amount of wear. An analysis of the head check initiation characteristics of the as-rolled rail, U78CrV/U76CrRE, and the heat-treated rails, U71Mn, U75V, and U78CrV, was performed by considering wear. Results indicated that, when wear is taken into consideration, head check in all four kinds of rails started at the subsurface of the rail, at a depth of 1 to 2.5 mm (measured from the top of the rail) and at a lateral distance of 15 to 18 mm from the rail center; these results were more similar to field observations than results without consideration of wear. When all other conditions were identical, the rail with the highest hardness had a lower wear growth rate and a longer period before head check initiation. Therefore, it was determined that the rail with the highest hardness, U78CrV heat-treated rail, was more resistant to wear and head check initiation than were the other three rail grades.