Research On Rubber Spring Dynamic Stiffness And Its Influence On Subway Vehicle Dynamics

When the addictives like carbon black are added to nature rubber, it becomes more flexible when it bears shearing or pressure, besides its special viscoelasticity can absorb energy。Because of all the unique superelasticity properties, rubber spring is widely used in the industry, such as locomotives, vehicles, ship, cars, meter, aviation, bridge and so on. In recent years, rubber spring is widely used on primary suspension system of bogie on metro vehicles and high-speed motor train unit. There are some differences between the dynamic stiffness and static stiffness of rubber spring, when the frequency of the component is low, the component can be seen as a component with integrated parameter of stiffness and damp, and the main function of the rubber spring is damping, taken as one component of spring and damper, and the rubber takes the main effect, while the rubber component works at high frequency, the stiffness of component will increase markedly, which means that the stiffness of the rubber spring is influenced by the frequency of vibration.So far, when consider the nonlinear characteristics of the suspension system, people mainly consider the nonlinear characteristics between the suspension force and the displacement or speed, such as nonlinear spring force and nonlinear damping force, but the nonlinear characteristics of the stiffness for rubber spring relating the vibration frequency. Little attention was paid to the effects of nonlinear frequency on the stiffness of primary suspension system in the past. Based on subway vehicle dynamics, in this paper the influence of the rubber spring nonlinear characteristics on the stiffness of the spring on the primary suspension system was analysed, and its effects on subway vehicle was also studied. And this paper will discuss this problem by the following sections.Discuss the development of the subway and the technical requirement of subway vehicles, and list some normal styles of primary suspension. Also discuss the actuality and direction to the study of nonlinear characteristics of rubber spring in the world. Study the basic mechanic characteristics and the popular constitutive equations of rubber and analyze the nonlinear characteristics of rubber spring used on the locomotives and vehicles.With the parameter of a actual conical rubber spring used on certain subway vehicle, get the nonlinear characteristics of the component stiffness under different displacements. Two different working condition 20mm displacement and 50mm displacement were considered, and the curve for the nonlinear characteristics of spring stiffness was fitted.Discuss the influence of frequency nonlinear characteristic of spring on the common mechanical vibration system. During the analysis process assume the stiffness of spring in vibration system has linear frequency varying characteristics. Based on this dynamic stiffness, this paper studied the influence of the frequency varying stiffness on single degree of freedom forced vibration system first and then studied that of double degree of freedom forced vibration system and its effects on amplitude-frequency characteristics, and verify the results by calculation.With the above results about the frequency nonlinear characteristic of rubber spring, establish the whole subway vehicle dynamic system model, and study the its influence on subway vehicle dynamics. Integrate the results got from chapter 3 into the subway dynamic model and compare results of the conventional model and the new model which consider the frequency varying stiffness.After comparison, reach the conclusion that the frequency varying stiffness characteristics has certain degree of influence on vehicle dynamics, which cannot be eliminated.