NUMERICAL ASSESSMENT OF ROLLING CONTACT TESTING OF TREAD BRAKED WHEELS

Paper i proceeding, 2025

Railway wheel treads experience challenging loading conditions during rolling contact scenarios at normal conditions. If the wheel is also tread braked, a significant temperature increase occurs in the wheel rim for even moderate frictional braking loads, with temperature levels reaching several hundreds of degrees Celsius. The increase in damage to the tread material of the braked wheel during this combined thermomechanical and rolling contact loading is not well studied numerically due to the complexity and computational expense. The aim is to further increase knowledge on how the wheel steel behaves during combined braking and rolling contact loads accounting for the fact that the material itself weakens at high temperatures, which would increase the damage on the wheel rim.

In the present paper, full 3D finite element rolling contact simulations are performed on a wheel also exposed to idealised tread braked thermal loads. The material model used is a Chaboche-type viscoplastic model of ER7 wheel steel, calibrated for the typical temperature range experienced by tread braked wheels. Simulations are performed both for idealised stop braking and drag braking sequences.

It is found that the material model used behaves well during the simulations, with no convergence issues observed, although computational times are long. Expected behaviour such as elastic shakedown is observed for lower wheel tread temperatures, with only the first rolling contact cycle inducing significant plastic strain. The opposite is observed for high temperatures. ratcheting then occurs as there is no arrest in the generation of plastic strains with continued cycling, although the stress levels reduce slightly due to load redistribution. The results also show that the drag braking case with a comparatively higher axle load is worse than the stop braking case. Although calibration should be performed for higher strain rate testing, the material model shows promise for use in rolling contact simulations.