关键词: 非线性轮轨接触关系　转向架系统　对称/不对称　分岔　并存

Abstract: The symmetric/asymmetric bifurcation behaviors and chaotic motions of a railway bogie system under complex nonlinear wheel-rail contact relation are investigated in great detail by a combination of the increasing-decreasing speed method and the ‘resultant bifurcation diagram’ method. It is indicated that the stationary equilibrium solutions and the periodic motions coexist for the possible sub-critical Hopf bifurcation in the railway bogie system. It is also found that the nonlinear dynamical behaviors of the coexistence of multiple solutions exist in many speed ranges. When the speed is close to the bifurcation point, the coexistence of multiple solutions may cause the jump and hysteresis of the oscillating amplitude for the different kinds of disturbances. So it should be avoided in the everyday operation. Furthermore, the studies on the symmetric/asymmetric chaotic motions and the rule of symmetry-breaking of the system indicate that the asymmetric motions exist in the railway bogie system. But the speed ranges of symmetric/asymmetric chaotic motions are very small. In addition, the rule of symmetry breaking in the railway bogie system is in fact through pitchfork bifurcation in the beginning.

Key words: Bifurcation, Coexistence, Nonlinear wheel-rail contact relation, Railway bogie system, Symmetry/Asymmetry