Study Of An Electric Locomotive Secondary Vertical Hydraulic Damper With Shim Stacks

With the high-speed and high-load operation of rail vehicles in China, rail vehicles become more sensitive to parameter and characteristics variations of their components. Due to research works concerning high-speed railway hydraulic damper with shim stacks are insufficient, this paper has carried out the following research with a secondary vertical hydraulic damper with shim stacks used on the Chinese main type electric locomotive SS9.(1) A macro ‘nonlinear in-service parametric model’ which is more suitable for modern high-speed and heavy-load rail vehicles was suggested in this work. By using this concept, a concrete parametric nonlinear in-service model was established for an electric locomotive secondary vertical hydraulic damper with shim stacks, the model includes equations of damper motions and forces, equations of variable oil properties, equations of fluid losses and equations of pressure-flow(P-Q) characteristics of the damping valves. In modeling the P-Q characteristics of the damping valves, an engineering model for shim stack deflection estimation based on Finite Element Analysis(FEA) was suggested and applied.(2) Damping characteristics of comparison of simulation results and test results of the secondary vertical hydraulic damper with shim stacks show that: simulation results agree well with test results both at the nominal velocity and at the maximum velocity, relative errors concerning key nominal damping indices of simulation results and test results are all small. Thus, the nonlinear in-service damper model and the FEA-based shim stack deflection engineering estimation model are validated.(3) By using the validated nonlinear in-service parametric model and Multi-body Dynamics Simulation(MBS) approach, a research of key in-service parameter variations, such as variations of the damping coefficient, the saturation speed, the effective series stiffness and the small series clearance on the secondary suspension dynamics of an electric locomotive, was conducted.The obtained nonlinear in-service parametric model of secondary vertical hydraulic damper with shim stacks and the secondary suspension dynamic response, could be applied to optimal specification of damper characteristics, vehicle dynamics simulation and damper product optimization for modern high-speed rail vehicles.