Papers by Keyword: Torsional Vibrations

Abstract: The use of high power railway vehicles requires enhanced control of wheel-rail adherence. When setting the train in motion, driving axles can exhibit torsional vibrations resulting in poor adherence and even axle damage. A significant number of railway authorities safety warnings and accident reports were issued related to the above phenomena. Adhesion saturation and negative slope are the characteristics which lead to self-sustained axial vibration. The aim of the present work is to prove the appropriateness of non-smooth models in the study of the axle torsional stick-slip vibrations which may occur when traction vehicles are set into motion. The model is simple, observes the main friction characteristics and provides the basis for efficient dynamics simulation. An experimental setup comprising a reduced scale wheel set is analyzed in order to validate the model proposed. The friction parameters are then identified using the proposed force-creepage relationship. Validation and verification is further carried out in frequency domain using both steady state and transient manoeuvres. Specific phenomena like discontinuities in the time-history friction force values occur. Validation and verification is carried out in frequency domain using both steady state and transient manoeuvres. From the comparison between the numerical and experimental results, it can be concluded that the setup is modeled accurately. Related problems may be solved using the present method, as it is pointed out in the article.

Abstract: In the paper dynamic electromechanical coupling between the structural model of the rotating machine drive system and the circuit model of the asynchronous motor has been investigated. By means of the computer model of the rotating machine drive system the results of experimental testing have been confirmed. From the obtained results of computations and measurements it follows that the coupling between the considered rotating system and the installed rotary dampers with the magneto-rheological fluid (MRF) results in effective energy dissipation leading to significant reduction of undesired torsional vibrations.

Abstract: To investigate the aerodynamic method for reducing motion induced vortex excitation as well as the galloping and torsional flutter of a tall building, We conducted wind tunnel tests on a tall building having a rectangular cross-section with a side ratio, D/B of 4.0 and aspect ratio of 10.0. Three aeroelastic building models were constructed to assess the effect of modified building shapes on the reduction of these vibrations. One is a plain model and the others are the shape-modified versions of the plain model, in which one has chamfered corners and the other has two openings at the top level. Experimental results showed that the chamfered model was more effective than model with the opening in reducing the above-mentioned types of vibrations, especially in motion induced vortex excitation, but not in reducing torsional vibration when the reduced velocity is high. Increasing the damping ratio might not be effective in reducing the bending and torsional vibrations of both the chamfered model and the model with openings when the reduced velocity is high.