Research For Some Dynamic Problems In The Vehicle System

The main contents of the thesis are composed of three parts.The first part is about some research of the linear random dynamic of the vehicle system,and also of the simulation method used to calculate the Stress Power Spectral Density(SPSD)of the dynamic systems by the random excitement and fatigue prediction method.Besides,the load response method and the SPSD is founded and the formula is derived.Thus a new method for the simulated calculating of the SPSD is founded.Simulation computation of SPSD and the reliability fatigue life prediction of the RD3 axle、209HS and CW-200 type vehicle truck are made using random rail excitement spectrum.Those contents can be found in chapter two and chapter three.The computational method in this thesis can not only apply to the running dynamic systems,but also has more significance in the SPSD computation and fatigue life prediction of newly designed dynamic structures.In the second part,first of all the periodic motion and the stability in the dry friction vehicle system with one degree of freedom are researched by numerical computation.The results show that the vertical vibration of vehicle is stable periodic motion under the condition of originality design parameters and normal running and has no bifurcation and chaos.Those contents can be found in chapter five.In chapter six,the bifurcation and chaos of the impact damper with two degree of freedom are researched by four-dimensional poincaremap.The results show that the dynamic system have complex dynamic behaviors.With some parameters the system will appear period doubling bifurcation and HOPF bifurcation and breaking of quasi-periodic torus.They will lead to chaos.Based on the above research the numerical results can be used to recognize the nonlinear appearance and essence of the system and direct the design of the dynamic system with the nonlinear damper.In the last part,General kinetostatics and analytical methods are presented for solving the impact problem.Examples of the impact problem from existing mechanics are solved to illustrate the merits of the methods.It is shown that the methods presented in this paper in solving the impact problem are simple and convenient,especially for complex with multi-freedom.Those contents can be found in chapter seven.