The effect of contact load reduction on the fatigue life of pearlitic railsteel in lubricated rolling-sliding contact

Twin-disc contact simulation tests were carried out to investigate the infl uence of contact pressure variation on rail steel fatigue life. Both a coll oidal suspension of molybdenum disulphide in an oil carrier fluid (similar to a commercial flange lubrication product) and water were used as lubrican ts. It was found that the reduction from 1500 to 900 MPa of the maximum Her tzian contact pressure (at which a molybdenum-disulphide-lubricated and pre viously worn rail sample was tested) extended the fatigue life of the rail steel by over five times. For water lubrication a similar reduction in cont act pressure produced only a marginal increase in fatigue life. The results were found to be in qualitative agreement with the predictions of the newl y developed Three Mechanism (TM) model of rolling contact fatigue, which is introduced here. This model combines the mechanisms of ratcheting and the fracture mechanics-based mechanisms of both shear stress- and-tensile stres s-driven, fluid-assisted, crack growth.