Mechanisms of wheel wear evolution and wheel-rail contact geometry variation in locomotives

Abnormal wheel-rail wear frequently leads to deteriorated dynamic behaviour in power-concentrated trainsets. These problems originate from changes in wheel-rail contact geometry, which can be effectively characterized by equivalent conicity. This study investigates wheel wear evolution mechanism and its influencing factors in terms of wear depth and nominal wear-peak migration. Two locomotive-type power heads used in power-concentrated trainsets are examined: an in-service B-type locomotive equipped with two-axle bogies and a C-type locomotive under testing equipped with three-axle bogies. Long-term field measurements were first used to define the nominal wear-peak position and classify wear types. A multibody dynamics model and a wheel wear prediction model were then established and validated using measured worn profiles. Simulation analyses identified rail profile, rail inclination, operating speed, and axle torque as the dominant factors. For C-type locomotives, the evolution of equivalent conicity is primarily affected by the lateral migration of the nominal wear peak position rather than wear depth; increasing the percentage of CN60 rail, increasing operating speed, and reducing axle torque effectively suppress conicity growth. Consequently, wheel reprofiling intervals for the C-type locomotive may be extended if equivalent conicity remains within allowable limits, thereby reducing maintenance frequency and improving wheel life. In contrast, the equivalent conicity of B-type locomotives shows limited sensitivity to wear-peak migration, suggesting that should focus mainly on target wear depth control. This study reveals the mechanisms by which wear depth and wear distribution jointly affect equivalent conicity evolution and translates these insights into operation-oriented, condition-based maintenance recommendations for power-concentrated trainsets.