UBC Theses and Dissertations

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UBC Theses and Dissertations

An experimental study of nonlinear oscillations in railroad friction control systems Talebi Bidhendi, Mohammad Reza


Friction control at the wheel-rail interface has been an outstanding challenge in front of the rail road engineers throughout the world. On-board solid stick friction modifier system, simply named stick-applicator assembly, has proved to be one of the simple and efficient ways to tackle the excessive wear and rail corrugation. Interlocking solid sticks are applied to the wheel flange and tread by means of a mechanical applicator mounted on a bracket, which is connected to the bogie. Relative sliding motion in the stick-wheel interface provokes gradual transfer of solid lubricant film to the wheel-rail interface through the wheel’s motion. Consequently, friction control at wheel-rail interface could be achieved. Instability and failure of stick-applicator assembly due to stick-wheel interaction destabilize its performance. The present study uses a lab-scale setup to produce consistent instability, which helps examine the behavior of the stick-applicator assembly during instability. The lab-scale setup incorporates a mock-wheel connected to the stick-applicator assembly. Mock-wheel is used to simulate up - down and transverse motion based on the concept of parametric excitation in the presence of internal resonance. Dynamics of each substructure is investigated to gain better understanding of the behavior of the coupled system. Having known the characteristics of each substructure, the dynamics of the coupled system is studied. It is found that period doubling bifurcation occurs consistently in certain ranges of excitation frequencies and voltages. Lateral stiffness is identified as one of the design parameters of the lab-scale setup that governs the vibration level. Clearances in the stick-applicator assembly and looseness between each interlocking sticks are found to be parameters which weaken the lateral stiffness of the coupled system. Some modifications in the design of the main contributing parts to eliminate instability and suppress the vibration of the coupled system in the lab-scale setup are also addressed in this thesis. Furthermore, full-wheel rig experiments are carried out to check the practicality of the design modifications.

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