The static stiffness of rubber springs is affected by temperature and prepressure. In this thesis, the relationship between Young’s modulus and temperature of rubber was studied, and the quantitative relationship between them was determined. The approximate formula for calculating the static stiffness of rubber pads was further modified, and the ellipse approximation method and convexity coefficient correction method were proposed. In addition, the influence of temperature on geometric nonlinearity was considered. The formula for calculating nonlinear stiffness includes two variables: temperature and prepressure. The results of tests and theoretical calculations demonstrate that the nonlinear formula can be a good approximation and that it can meet the requirements of engineering applications.
Low-frequency carbody swaying phenomenon often occurs to railway vehicles due to hunting instability, which seriously deteriorates the ride comfort of passengers. This paper investigates low-frequency carbody swaying through experimental analysis and numerical simulation. In the tests, the carbody acceleration, the wheel–rail profiles, and the dynamic characteristics of dampers were measured to understand the characteristics of the abnormal carbody vibration and to find out its primary contributor. Linear and nonlinear numerical simulations on the mechanism and optimization measures were carried out to solve this carbody swaying issue. The results showed that the carbody swaying is the manifest of carbody hunting instability. The low equivalent conicity and the decrease of dynamic damping of the yaw damper are probably the cause of this phenomenon. The optimization measures to increase the equivalent conicity and dynamic damping of the yaw damper were put forward and verified by on-track tests. The results of this study could enrich the knowledge of carbody hunting and provide a reference for solving abnormal carbody vibrations.
Cross-line operation that can improve the utilization of railway equipment and transportation efficiency is expected to be the development of the future, and the key to realizing this is to guarantee the dynamics performance of high-speed trains operating on different railway lines. To this end, this study focuses on determining the parameters of a suspension system for a high-speed train equipped with semi-active dampers. Multi-body dynamics method is used to establish a mathematical model of a high-speed vehicle, and a numerical integration method is applied to calculate the system response. An improved genetic algorithm adopting the dynamic Hamming distance, dynamic crossover, and mutation coefficients is integrated into the numerical simulation process to determine the parameters. Based on the numerical analysis, the optimized damping values for various hydraulic dampers in their passive modes are obtained. Finally, an experimental validation based on roller-rig and field loop-line tests is performed, and the test results verify the effectiveness of the optimized parameters. Thus, the study findings can serve as a reference to enhance the realization of cross-line operation.
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