Nonlinear optimal specification of a locomotive axle-box hydraulic damper for vibration reduction and track-friendliness

As speeds and loads continue to increase in modern railway transportation, it becomes more and more important to be able to model the exact characteristics of all elements of the vehicle suspension. In this paper, the issue of symmetric and asymmetric damping characteristics for hydraulic dampers used in railway applications is discussed and a comparison of three different damper models and their effects on the Chinese SS₉ locomotive system dynamics has been carried out. The three damper models included are a simple linear damper model, the Maxwell damper model and a fully nonlinear ‘in-service’ damper model. An optimization has been carried out using the nonlinear ‘in-service’damper model and the Design of Experiments (DoE) approach to optimise the SS₉ locomotive axle-box hydraulic dampers. Global optimal nonlinear damping characteristics of the axle-box dampers were obtained and the locomotive dynamic responses show that both the vibrations of the bogie frame and the dynamic wheel-rail interaction forces can be significantly reduced, compared to the results when conventional linear damper models were employed. The locomotive stability and track-friendliness is also improved. The nonlinear model and the approach introduced in this study can also be applied to the engineering specification of other kinds of hydraulic dampers where nonlinearities are significant.