Nowadays there are many methods to control flexural vibrations on rotating systems including squeeze film and magnetic active bearings. The work of this paper shows how using widely known simple and inexpensive devices, called dynamic absorbers or neutralizers, the flexural unbalanced vibration response of rotating systems is held under control. Viscoelastic material is a low cost damping material widely recognized for its excellent shock and vibration isolation characteristics.

The viscoelastic dynamic vibration neutralizers (DVN) are simple devices that when optimally designed can reduce vibrations for a large frequency range. The viscoelastic material can be modeled using a four parameter fractional derivative model. The rotating system can be described using modal parameters obtained in the frequency domain space state model as in [1].

The goal of this work is to introduce the neutralizers directly in the mathematical model of the primary system and to use a non linear optimization algorithm to solve the compound system problem avoiding the need for long time consuming computational calculations.

To apply the proposed methodology it is necessary to use equivalent parameters on the dynamic neutralizers like shown in [2]. This concept allows the movement equations of the composite system (primary system plus neutralizers) to be expressed in terms of the generalized coordinates previously chosen to describe the primary system. Once the movement equations are stated in the space state, one can obtain the first principal coordinates and obtain a cost function to be optimized, using a non-linear algorithm. At the end of the optimization process the best natural frequencies of the neutralizers are known and they can be designed [3].

A set of DVN's were designed and applied to an experimental rotor rig. The results obtained out of the bump test and orbit measurements show a very good approximation to the numerical solution. The use of the designed dynamic vibration neutralizers allows the rotor rig to run stable and quit at the first critical speed. This is almost impossible without them.

1

M. Lalanne, G. Ferraris, "Rotordynamics prediction in engineering", 2nd. ed. New York, USA, John Wiley & Sons, Inc., 2001.

2

J.J. de Espíndola, H.P. Silva, "Modal reduction of vibrations by dynamic neutralizers: a generalized approach", IMAC-10, 1992, 10th International Modal Analysis Conference, New York, Society for Experimental Mechanics, INC, v. 2, p. 1367-1373, 1992.

3

C.A. Bavastri, J.J. de Espíndola, P.H. Teixeira, "A Hybrid Agorithm to Compute the Optimal Parameters of a System of Viscoelastic Vibration Neutralizers in a Frequency Range", MOVIC 98, v. 2, p. 577-582, Zurich, 1998.

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