This paper summaries the development of a damage model to predict the deterioration rates of the wheel tread in terms of wear and rolling contact fatigue (RCF) damage. The model uses a description of a fleet's route diagram to characterise the duty cycle of the vehicle in terms of curve radius, cant deficiency and traction/braking performance. Using this duty cycle a large number of vehicle dynamics simulations are automatically conducted to calculate wheel-rail contact forces and predict the formation of wear and RCF damage, using a combination of the Archard and frictional energy-based (Tγ) damage models.The damage models have been validated using observation data (wear rates and maximum observed RCF damage) acquired from a range of vehicle fleets in Great Britain (GB). Results from the validation of the model are presented along with a review of the wheel turning and observation data.A piece-wise linear regression is fitted to the wear and RCF parameters predicted from the model to determine the damage rates for each wheelset type on the vehicle. These damage rates are used within the recently developed Wheelset Management Model (WMM) to describe how the attributes of the wheel (i.e. wheel diameter, profile shape and tread damage) deteriorate over time and trigger a maintenance or renewal activity when the condition of the wheel matches a particular limiting value.This work formed part of the rail industry research programme managed by the Rail Safety and Standards Board (RSSB), and funded by the Department for Transport, to increase the rolling stock functionality of the Vehicle Track Interaction Strategic Model (VTISM) tool.

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The susceptibility of railway wheels to wear and rolling contact fatigue damage is influenced by the properties of the wheel material. These are influenced by the steel composition, wheel manufacturing process, and thermal and mechanical loading during operation. The in-service properties therefore vary with depth below the surface and with position across the wheel tread. This paper discusses the stress history at the wheel/rail contact (derived from dynamic simulations) and observed variations in hardness and microstructure. It is shown that the hardness of an “in-service” wheel rim varies significantly, with three distinct effects. The underlying hardness trend with depth can be related to microstructural changes during manufacturing (proeutectoid ferrite fraction and pearlite lamellae spacing). The near-surface layer exhibits plastic flow and microstructural shear, especially in regions which experience high tangential forces when curving, with consequentially higher hardness values. Between 1 mm and 7 mm depth, the wheel/rail contacts cause stresses exceeding the material yield stress, leading to work hardening, without a macroscopic change in microstructure. These changes in material properties through the depth of the wheel rim would tend to increase the likelihood of crack initiation on wheels toward the end of their life. This correlates with observations from several train fleets.

Background• Wheelset maintenance and renewal activities account for a large proportion of a fleets whole-life costs • Influenced by a large number of factors:• Optimisation of maintenance and renewal regimes will help to increase wheelset life and reduce costs • These enhancements go some way to determining the whole life costs for the complete system (vehicle-track)

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.