Consulting support for wheelset torsional vibrations
Due to the development of power electronics over the past decades, propulsion systems in rail vehicle technology are becoming more and more powerful and efficient. This results in an increased utilization of the friction coefficient between wheel and rail, thereby achieving greater tractive power and traction capacity. The transient processes in the wheel-rail contact point lead to varying coefficients of adhesion, which result in a decreasing creepforce-slip function. Once slip velocities in the range of the instable, decreasing creepforce-slip function are reached during driving or braking, self-excitation occurs in the wheel-rail contact, which excites the first torsional eigenmode of the wheelset. This eigenmode describes a counter-phase rotational movement of the wheelbodies around the rotation axis and, due to the weak damping, leads very quickly to high torsional moments in the wheelset shaft, which can damage components of the drive train, wheelset shaft, interference fits and drive suspensions.
Due to this reason, for example in Germany, an additional proof of strength must be provided for the approval of wheelsets, which considers the maximum dynamic torsional moment. The maximum torque is determined metrologically, but analytical estimations and multi-body simulations are already used in the development phase for the design.
PROSE supports the whole or individual sections of the process chain, from the pre-dimensioning of the wheelset axle to the optimization of the mechanical components and the execution of the homologation measurements to determine the maximum dynamic torsional moment.
Using analytical and conceptual investigations, a fundamental evaluation of the wheelset torsional dynamics of the vehicle is carried out in advance, considering the dimensioning of the wheelset, the drive train configuration and drive systems. Based on the preliminary investigations, in-depth analyses are performed in consultation with the customer using multi-body simulation models. On the one hand, these investigations limit the expected maximum dynamic torsional moment, indicate the expected component stress and simultaneously describe further dynamic properties of the powertrain. Considering the existing powertrain configuration, its design properties are optimized in such a way that the modal damping of the first torsional eigenmode of the wheelset is increased and thus the maximum dynamic torsional moment is reduced. The results of the analyses provide relevant information for the system analysis, which describes the wheelset torsional dynamics of the vehicle and is required for the homologation. Furthermore, the analyses are used to determine the vehicle configurations that are critical for the planning and execution of the homologation measurements. Finally, the maximum dynamic torsional moment is determined with tests on the track.
The analyses help the customer to minimize risks during the homologation of the wheelsets. The preliminary investigations ensure realistic time and cost planning until the wheelsets are approved. The in-depth analyses and component optimizations reduce the stress caused by torsional vibrations and prevent damage to safety-relevant components during operation. Finally, the identification of critical operating conditions significantly reduces and secures the scope of homologation measurements.
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