Coupling effect of parameters on critical speed and hunting frequency of the linearized railway bogie system

Critical speed and hunting frequency are critical metrics for assessing running stability, with a significant impact on railway vehicle dynamic performance. Evaluating effects of vehicle parameters on these two metrics is important for the optimization of vehicle design. This study focuses on a rigid bogie with secondary suspension, for which a lateral dynamic model accounting for lateral displacement and yaw motion is developed. Analytical formulas for critical speed and hunting frequency were derived by using perturbation procedures, Newton method and some simplified treatments. Employing the analytical formulas, a comprehensive analysis of multi-parametric influences was carried out, yielding global sensitivity indices for critical speed and hunting frequency against various parameters. The results indicate that the derived analytical formulas align well with numerical calculations, providing a basis for preliminary vehicle design optimization. There exists a coupling interaction between different parameters for their effects on critical speed and hunting frequency, which indicates the necessity of total-order global sensitivity analysis. The equivalent wheel–rail contact conicity is identified as the most sensitive factor on both critical speed and hunting frequency, while the damping of yaw damper also significantly affects the hunting frequency.