Influences of the vertical and the roll motions of frames on the hunting stability of trucks moving on curved tracks

Based on the heuristic nonlinear creep model, the nonlinear coupled differential equations of the motion for the truck modeled by a eight-degrees of freedom system moving on curved tracks, considering the lateral displacement and the yaw angle of the each wheelset and the lateral displacement, the vertical displacement, the roll angle and the yaw angle of the truck frame, are derived. The accuracy of the present analysis is verified by comparing the limiting case and the current numerical results with the findings available in published literature. The influences of the vertical and the roll motions of frames on the critical hunting speed of trucks are studied and evaluated via the linear and the nonlinear creep models. It is shown that the critical hunting speeds evaluated using the eight-degrees of freedom system differ significantly from those calculated using a system with six-degrees of freedom. In addition, the influences of the physical parameters, including those missing in the six-degrees of freedom system, on the critical hunting speed of trucks are also examined.