Influence of Pad Support Length on the Vibration of Wheel-track

A transfer matrix method for analyzing the vibration of wheel-track system with finite support length of rail fastening system is proposed,due to the chain characteristic of track structure. The research on the natural frequencies of track system and wheel-track coupling system, as well as the influence of pad support length, indicate that the first two natural frequencies of the track system correspond to the same-phase and anti-phase vibration of rail and sleepers. The frequencies and responses of these two resonances depend on the bending stiffness and mass distribution of rail, mass of sleeper, as well as the stiffness and damping of fastening system and track bed. The support length of pad has no effect on these resonances. However, the pinned-pinned resonance and anti-resonance of rail are affected obviously by the support length of pad. With the increase of pad support length, the effects of pinned-pinned resonance and anti-resonance weaken dramatically. With the coupling of unspring mass and track system, the vibration of wheel-track system is mainly the P2 resonance, of which the frequency is much lower than the first natural frequency of track system. The response of rail near the pinned-pinned frequency is influenced by the support length of pad. The analysis of wheel rail impact response indicates that the dominated frequency of the vibration of wheel and rail is P2 resonance frequency as well as several high frequency fluctuations of P1 force during the initial stage. Severe wheel rail impact invokes high order harmonic vibrations with fundamental frequency of P2 resonance. The increase of pad support length reduces the responses of wheel and rail near the pinned-pinned frequency dramatically, nevertheless its influence on the wheel and sleeper displacement is negligible.