Influence factors on critical speed hysteresis in railway vehicles

This research has been performed to estimate the hunting motion hysteresis of railway passenger cars. An old and a new car with almost the same structure are chosen for analysis models. To solve a set of simultaneous equations of motion that are strongly coupled with creep relations effectively, a shooting algorithm in which the nonlinear relations are regarded as a two-point boundary value problem is adopted. The bifurcation theory is applied to the dynamic analysis to distinguish the differences between linear and nonlinear critical speeds by variation of parameters. It is found that there are some factors and their operation area to make nonlinear critical speed respond to them more sensitively than linear critical speed. Full-scale roller rig tests are carried out for the validation of the numerical results. Finally, it is concluded that the wear of wheel profile and the stiffness discontinuities of wheelset suspension caused by deterioration have to be considered in the analysis to predict the hysteresis of critical speed precisely.