Residual Stress in Wheels: Comparison of Neutron Diffraction and Ultrasonic Methods, with Trends in RCF
The critical damage mechanism on many GB passenger train wheels is Rolling Contact Fatigue (RCF) cracking in the rim. Evidence from field observations suggests that RCF damage occurs much more quickly as the wheelsets near the end of their life. Wheel manufacturing processes induce a compressive hoop stress in the wheel rim; variations in residual stress through the life of a wheel may influence the observed RCF damage rates. 
This paper describes experiments to measure residual stresses in new and used wheel rims to identify whether this could be a significant factor, and compares the findings from neutron diffraction and ultrasonic birefringence methods. The scope goes beyond previous applications of neutron diffraction to railway wheels and identifies key considerations for future testing. 
Assuming that the as-manufactured stress distribution was similar for all three wheels tested, it is found that the stresses are redistributed within the wheel rim during its life as material is removed and plastic flow occurs. However, the hoop stress near the running surface remains compressive and may not have a large influence on the RCF damage rates.
Wheel/rail rolling contact fatigue – Probe, predict, prevent
With the aim of putting prediction and prevention of rolling contact fatigue of wheels and rails in context, the paper sets out with a description of the phenomena. This is followed by a discussion on predictive models with emphasis on influencing factors needed to be accounted for and how these can be incorporated in a predictive model of surface and subsurface initiated rolling contact fatigue (RCF). The focus is on predictive models fast enough to be integrated with multibody dynamic simulations of train–track interaction. In particular an attempt is made to highlight how current predictive models of surface initiated RCF can be extended to incorporate all affecting phenomena. The discussion on influencing factors then forms the basis for a discussion on suitable and efficient measures to maintain RCF under control. Finally the paper provides a brief summary on similarities and differences between wheel and rail damage, and an outlook of expected future trends in terms of expected damage patterns and possibilities to meet these.
Influence of plastic deformations on growth of subsurface rolling contact fatigue cracks in railway wheels
Abstract A subsurface rolling contact fatigue crack in a railway wheel is studied. Stress and strain fields are evaluated by elasto-plastic finite-element simulations. The robustness and validity of the numerical model are investigated. A suitable measure to characterize crack propagation is then sought. Numerical results show that the effect of crack tip plasticity is small for cases studied, indicating that linear elastic fracture mechanics approaches are applicable. Further, the magnitudes of the stress intensity factor in mode I, KI, are negative implying crack closure. Motivated by these findings, the stress intensity factor range in mode II, ΔKII, is employed as a measure of crack propagation. Finally, studies are carried out to quantify the effects of altered contact load conditions and crack face friction.