On the parametric excitation of the wheel/track system

As a wheel moves along a discretely supported track, it can experience parametric excitation due to the varying dynamic stiffness of the track. In order to study this, an equivalent time-varying model is developed for the track, according to the space-varying receptance in a sleeper bay. Using this track model combined with a mass representing the wheel, the wheel/rail interaction and response to the parametric excitation are simulated. The results are compared with those from a moving irregularity model and the differences between the moving wheel and moving irregularity models are examined from various aspects of wheel/rail dynamics. The wheel/rail interaction force due to the parametric excitation may be significant compared with that due to the roughness excitation especially at low frequencies and increases in magnitude with the running speed of a train. Because of the parametric excitation the wheel/rail contact force spectra contain many harmonics with a basic component at the sleeper-passing frequency, and the components around the pinned–pinned resonance frequency show a higher level.