The influence of spatial variation of railroad track stiffness on the fatigue life

Abstract

Railroad transportation is very important for the economic growth. The effective maintenance of railroad transportation is a critical factor for its economic sustainability. The high repetitive forces from a moving railcar induce cyclic stresses that lead to bending and potential deterioration of rails due to the initiation and propagation of fatigue cracks. Previous research on the prediction of fatigue life has been done under the assumptions of a uniform track bed and a homogeneous rail. However, the spatial variation of track stiffness is expected to increase the maximum stresses in the rails and, therefore, accelerate the fatigue process. This study is focused on the variations of the track modulus and the impact on fatigue life. The computational procedure is based on several hundreds of finite element models of the rails across a set of crossties chosen from a random ensemble with representative statistical variations. The mean of the track moduli is estimated from the field track deflection dynamic measurement data in comparison with the deflection data from the FE models. A multiaxial fatigue model is used for the estimation of fatigue cycles to crack initiation. The results show that a non-uniform track bed can reduce the fatigue life by up to 100 times in comparison with the behavior expected for a uniform track bed. The results of this study are expected to improve the effective maintenance and scheduling of rail inspection.