The paper presents the vibration analysis and the evaluation of dynamic stresses in flexible multibody systems, and their parameter optimization using symbolic-numeric methods. Based on the fundamentals of multibody system modeling the force method and the deformation method are described and the latter one is extended to include the static and dynamic responses of the structure. Performance criteria are defined for optimization. The overall design process is supported by appropriate software for all steps of analysis and optimization. The application of the approach is devoted to railcar dynamics. For the analysis of the dynamic stresses in a railcar wheelset the extended deformation approach is used. The simulation results indicate that the durability of the design of the wheelset under consideration is satisfactory. The vertical vibrations of the passenger coach with rigid wheelsets and a flexible bogie frame results in acceleration amplitudes of the carbody which may cause a brumming or droning noise. The substitution of the rigid wheelsets by radialelastic ones reduces these amplitudes considerably. An optimization of spring and damper coefficients of the model with radialelastic wheels results in reduced droning noise of such a passenger coach and lower force level between wheel and rail. The symbolic approach is especially highlighted for the simulation at different vehicle speeds and the optimization of the suspension parameters.
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