Some Aspects about Driving Wheel/Rail Contact in Steady State Interaction
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The driving wheel/rail steady state interaction and the response to harmonic excitation were studied using a complex model for track. The starting point for numerical simulations is the Green matrix of the track. The wheel/rail displacements and the contact forces have been calculated having the aim of analysing the particularly case of driving wheel/rail interaction which is very interesting for corrugation wear issue. The driving wheel/rail interaction behaviour due to parametric excitation caused by the discretely support of the track is dominated by the first own frequency for wheel/rail system. When the passing frequency over the sleepers equals the first own resonance frequency, the wheel/rail contact forces (the normal force and the traction force) have the highest value and the wheel rolls over the rail at the critical speed. The numerical results show that the effective traction force can be 8.5% from the mean traction force. Consequently, the railway traffic at the critical speed must be avoided. Generally, the driving wheel/rail interaction is characterised by the superposition of the roughness and parametric excitation due to sleepers. The modulated oscillation phenomenon occurs – the carrier is the effect of the excitation due to roughness and the modulated is given by the parametric excitation. The spectral components of both the carrier and the modulated can be added in the pinned-pinned resonant/anti-resonant frequency range, especially. Due to this effect, the effective traction force is very sensitive to the roughness wavelength of the running surface and contributes to the rail corrugation. The effective traction force increases as the tractive power increases. This aspect explains why the heavy locomotives are more aggressive for rail.
- 2008 fascicula8