The potential of Fluid Dynamic Absorbers for railway vehicle suspensions

Sammanfattning: The main running objectives concerning the vertical dynamics of passenger rail vehicles are ride comfort and safety. The goal of this thesis is to employ the use of a Fluid Dynamic Absorber to minimize the vertical acceleration of the car body while minimizing the dy-namic force fluctuations in the wheel rail contact. The Fluid Dynamic Absorber is a device which employs a tube with a varying cross section containing oscillating fluid. The device is characterized by two effects: The inertia effect of the oscillating fluid in the varying cross section and the damping effect due to the pressure losses during the fluid flow. It is in-troduced as a potential damping device for automobiles and also for earthquake resistant buildings. The work encompasses the creation of a linearized approximation of the non-linear model for parameter selection. Then, a non-linear model is built with the help of the Modelica language for use in time simulation of quarter-car models in the Dymola interface. A generalized design methodology for the device is then developed with the help of design procedures used for common tuned mass dampers and liquid column dampers. Finally, the non-linear model built using the Dymola interface is also exported for use in the full-car model in Simpack using Functional Mock-up Interface. A reduction of about 4% to 5% in the magnitude of the root mean square of the carbody acceleration was observed while the wheel-rail dynamic forces remained the same. Further improvement possibilities and the parameters influencing the vertical dynamic behavior of the vehicle are discussed.