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H. Ecker, H. Springer:
"Suppression of self-excited vibrations in drive trains";
in: "Ninth International Conference on Vibrations in Rotating Machinery", issued by: IMechE - Institution of Mechanical Engineers; Chandos Publishing Ltd., Oxford, 2008, ISBN: 978-1-84334-458-2, 371 - 382.

Self-excited vibrations may be encountered in drive train systems when friction loads decrease with an increasing sliding velocity present in the system. Such non-linear phenomena are known as stick-slip effects in drive trains. Furthermore, there are certain types of machines used in process plants that generate self-exciting frictional torques and may cause violent torsional vibrations. Mixers, separators and conveyor drums are among these equipments where such friction-induced vibrations may occur.

This contribution deals with mechanical systems that can be reduced to a minimal torsional vibration model of three degrees of freedom. A self-excitation mechanism is acting between the two dominant masses of the system and can be represented by a linear viscous damping element with negative coefficient. The third mass is attached to the system in order to provide positive damping for the system and stabilize the otherwise unstable system.

To investigate the system, a suitable linearized model is established and a damped eigenvalue analysis is carried out to decide on the stability of the torsional vibration behavior. This numerical approach is extended and stability maps are calculated for ranges of various system parameters. Different configurations are investigated to study the effectiveness of measures to prevent the system from becoming unstable.