Effect of Traffic on Crack Initiation in Rails

Abstract

This paper describes a method to predict wear rates and time until fatigue crack initiation. A computer simulation of ratcheting wear is used to model the accumulation of plastic shear deformation in the rail and predict the wear rate, based on wheel-rail contact conditions. Contact data for two types of high speed trains at two sites on the East Coast Mainline, U.K., have been obtained from multi-body simulations of train-track interaction. Material microstructure has been modeled as grains of pearlite and ferrite in order to represent the real rail steel. Results showed that the wear rate increases as the proportion of Class-91/Mark-4 vehicles increases. Conditions for crack initiation arise at Harringay within 10,000 wheel passes. At Sandy, conditions for crack initiation do not arise until after 100,000 wheel passes, and arise soonest when traffic consists of only Class-91/Mark-4 vehicles. Together with fracture mechanics models for larger cracks, these models provide guidelines for rail grinding in order to optimize rail life and safety.