Keywords: wheel-rail macro-sliding, martensite formation, friction braking, temperature distribution, finite element simulation.

Better understanding of the thermal and thermo-elastic phenomena in a railway wheel is of great importance because thermal fatigue cracks of wheel rows can be prevented and the risk of serious accidents can be significantly reduced, possibly avoided. This paper investigates the thermal processes that might lead to martensite formation on railway wheel treads - either in case of block-braked wheels or in case of disc-braked ones. Transient finite element simulations are performed to model the thermal processes evolving in the wheel row in details. Temperature-dependent material properties together with a transient and position dependent nonlinear heat partitioning model are taken into consideration. The combination of block braking-induced temperature field spreading all around the wheel and the more intensive - and rather local - temperature peaks occurring in the wheel/rail contact strip for the case of macroscopic wheel sliding are simulated. The simulated thermal processes are evaluated with special regard to the maximum temperature and cooling rate occurred in the close neighbourhood of the wheel/rail contact strip. Some thoughts are included concerning the role of normal or abnormal operation of the anti-slip device.

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