ESTIMATION OF STRAIN RATES FOR WHEEL-RAIL SURFACE MATERIALS UNDER HIGH-SPEED ROLLING-SLIDING CONTACT

A 3D wheel-rail transient rolling contact model has been developed using the explicit finite element method to calculate the average strain rates of rail surface material of 0.25 mm~0.5 mm deep at 300 km/h, for which smooth rail, rail corrugation (wavelength of 30 mm~170 mm) and macro-roughness (wavelength of 4 mm~30 mm) are considered. Obtained results have shown:1) the highest strain rate occurs on the surface layer spatially, and during the loading or unloading processes of a material particle passing the contact patch; the rate of the normal strain is the largest among all strain components, being 1.50~1.86 times of Von Mises (V-M) strain rate; 2) element size and time step have important effects on strain rate results; 3) the V-M strain rate of smooth surfaces reaches the maximum of 64.1 s^-1 when the element size is 0.5 mm and the time step is 0.32 μs, the material elasto-plasticity has no effects, the rail corrugation and macro-roughness result in the maximum V-M strain rate of 92.5 s^-1 and 79.4 s^-1 in elasticity respectively; the results are 1.65~1.88 times higher when an element size of 0.25 mm and a time step of 0.042 μs are used; 4) the maximum strain rate increases linearly with speed, monotonically with increasing friction coefficient, while the influence of traction coefficient is negligible.