The Dynamics Of Vibration Impact System And Its Application In Railway Vehicle

In this thesis, a two-degree-of-freedom system subjected to harmonic excitation isconsidered. The piecewise smooth dynamic factors, such as clearance, constraints and friction,make the dynamic performance of the system becomes more complex. The correlativerelationship and matching law between dynamic performance and system parameters arestudied by numerical simulation analysis. Two key parameters of the system, the excitingfrequency ω and clearance δ, are first considered to reveal the influence on dynamicperformance of the system. Diversity and evolution of periodic impact motions are analyzed.The occurrence mechanism of chattering-impact vibration of the system is studied. In thesystem, the motions can be divided into pure sliding motion and sliding–sticking motionbecause of the existence of friction. As the clearance δ is small enough, the transitionfrom1p q(q≥1)motion to1p+1q+1motion (or1p q+1motion) basically goesthrough the processes as follows: pitchfork bifurcation, sliding bifurcation, quasi-periodicmotion or chaotic motion caused by a succession period-doubling bifurcations,1p+1q+1motion (or1p q+1motion) generated by a degeneration of chaos. As forslightly large clearance, a series of grazing bifurcations of periodic impact motions occur withdecreasing the exciting frequency so that the number of impacts of the fundamental group ofmotion increases progressively. As the number becomes big enough, the system exhibitsincomplete chattering-impact characteristics and impact velocities successively attenuate anexcitation period. Finally, complete chattering-impact motions with sticking will appear withdecreasing the frequencyω up to the sliding bifurcation boundary. As the clearance δ is bigenough, the types of periodic motions are relatively simple in the system, and most of them arepure sliding motions. Based on sampling ranges of parameters, the influence of dynamicparameters on impact velocities, existence regions and correlative distribution of differenttypes of periodic-impact motions of the system is emphatically analyzed. In the next study,the modern of railway passenger vehicles was established by the vehicles-orbit couplingdynamics theory. The effects of parameters on the vehicles hunting stability and bifurcationbehavior are studied. These parameters include the vehicle velocityv, wheel tread equivalenttaper λ, the transverse stiffness of primary suspensionK1y, the longitudinal stiffness ofprimary suspensionK1x, and the coulomb friction coefficient between wheel and rail μ. Themodel consists of a car-body, two bogies and four wheel sets, so the system has more degreesof freedom. Vibration types, distribution, and bifurcation features of the system are obtainedby numerical study in a given parameter range. The smaller the wheel tread equivalent taper is,the higher the critical speed of wheel-rail collision is, the longer the periodic motion area is. For the vehicle systems with new wheels, the smallerK1yandK1x, and the bigger μ resultthe higher critical speed of wheel-rail collision and longer periodic motion area. For thevehicle systems with wearing wheels, the biggerK1yand smallerK1xresult the higher criticalspeed of wheel-rail collision and longer periodic motion area.