Finite Element Modeling and Analysis of Friction Wedge Damping During Suspension Bounce Modes

A two-dimensional finite element model (2D FEM) has been developed to improve the modeling and understanding of the friction damping characteristics of freight bogie suspensions. The specific suspension considered utilizes friction dampers with constant preload force as are widely used in three-piece bogie wagons in Australia. Unlike simpler models commonly used in rail vehicle dynamics, the FE model developed can accommodate distributed normal forces across the wedge surfaces. The model was tested in bounce modes and compared with the normal equations used to model wedge friction forces, which treat the forces on the wedge as a static problem. The simulation results using the 2D FEM model showed that the friction damping force is not constant and changes when the suspension is in motion. It was also shown that the force changes magnitude during the loading and unloading situations. The factors, which affect the change in friction force, are the friction characteristics on wedge contact surfaces, the direction and change in tangent force on wedge angular surface, the elastic deformation of the wedge, the wedge relative movement, and the wedge structure arrangement. The FE model assumptions are investigated and insights on wedge friction and creepage discussed.