中文摘要：

综合采用升．降速法和“合成分岔图”法对复杂非线性轮轨接触关系下转向架系统的对称／不对称分岔行为和混沌运动进行分析。发现系统有可能因发生亚临界Hopf分岔而存在定常运动与周期运动并存的现象，同时在其他的一些速度区间也存在多解并存的非线性动力学现象，这些多解并存的特性会使系统在接近失稳点时由于扰动的不同而使摆振幅值急剧变化，因此应该尽量避免。此外，对转向架系统对称／不对称混沌运动和对称性破坏规律的研究则表明，对称的非线性轮轨接触关系下转向架系统会存在不对称的运动状态，但存在对称／不对称混沌运动的速度范围很小，而系统的对称性刚开始实际是通过音叉分岔而破坏的。

英文摘要：

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.