Dynamics Research Of High-speed Locomotive Bogie Wheel/Rail Impact

In the thesis, firstly, a two-degree-of-freedom harmonically-force belt system with twoclearances shown by both elastic stops is considered. The correlative relationship andmatching law between dynamic performance and system parameters are analyzed. Two keyparameters of the system, the exciting frequency ω and clearance δ, are first considered toanalyze the influence of the main factors on dynamic performance of the system. In theparameters plane, the process of transformation between sliding motion and sliding-stickingmotion is analyzed, meanwhile, the existence of regional distribution and the size of differenttypes of impact motions are also studied. A series of grazing bifurcations of periodic impactmotions occur with decreasing the exciting frequency so that the number p and q of impactsof the fundamental group of motion increases one by one. As p and q becomes big enoughand in the low frequenct range, the system exhibits sliding-sticking characteristics and theimpact velocities successively attenuate in an excitation period. On the contrary, withdecreasing the exciting frequency in the small range, the number p and q of impacts of thefundamental group of motion decreases one by one. Finally, transition from1p qto1(p1) qor1p (q1)motion occurs with increasing ω up to the saddle-nodebifurcation boundarySN1p qof1p qmotion. The change of the system motion isnon-reversible. A series of singular points on the boundaries between existence regions of anyadjacent impact motions with fundamental period are found, i.e., saddle-node bifurcationboundary, period doubling bifurcation boundary, real-grazing and bare-grazing boundaries ofthe other mutually cross themselves at the point of intersection and create two types oftransition regions: narrow hysteresis and small tongues-shaped regions. In brief, based on thesampling ranges of parameters, the influence of dynamic parameters on impact velocities,existence regions and correlative distribution of different types of periodic-impact motions ofthe system is emphatically analyzed.Secondly, the dynamic model of the accelerated six-axis motorcycle bogie is built byconsidering the derivation of the existence of nonlinear factors between wheel and rail, thenbased on Poincaré projection and employing Runge-Kutta numerical method, the behavior ofthe system in the stage of new wheel set and the stable stage of wheel set wear is describedmainly by the detailed numerical results, such as the global bifurcation diagram, partialbifurcation diagram and phase diagram. In particular, the second and third wheel begin tocrash the orbit lagging behind for the primary wheel. At the same time, the correlativerelationship and matching law between dynamic performance of the system and someimportant structural parameters are analyzed, such as the lateral stiffness of primary suspensionK py, the longitudinal stiffness of primary suspensionK px, coulomb frictioncoefficient between the wheel and rail μ and equivalent slope of wheel tread λ. Thestudies show that the dynamic behavior of the system is relatively good by choosing largelateral stiffness of primary suspensionK py=8×106N m1, μ=0.2, λ=0.15, which canprovide reliable theory basis to optimize important structural parameters of the bogie andimprove the dynamics of the six-axis motorcycle bogie. Finally, consideding the influence ofthe speed on the dynamic characteristics of the system, the studies found that the impactvelocities of the system is gradually increased and the dynamic behavior became more andmore complex with increasing the locomotive speed.