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International Journal of Rotating Machinery
Volume 6, Issue 1, Pages 11-18

Experimental Modal Analysis – A Tool for Unbalance Identification of Rotating Machines

Institute of Mechanics, University of Kassel, Moenchebergstr. 7, Kassel 34109, Germany

Received 12 May 1998; Revised 17 July 1998

Copyright © 2000 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


In this paper a method is proposed for unbalance identification ofelastic rotors. The method is essentially based on the rotordynamic theory combined with experimental modal analysis and allows to identify the unbalance distribution on the complete rotor. A rotor test rig designed for rotordynamic experiments, modal analysis and especially for the unbalance identification has been developed. It allows an arbitrary excitation with a particularly developed noncontact magnetic exciter, as well as measuring vibrations in radial direction with non-contact laser sensors and eddy currents. Special effects of rotordynamic like anisotropic journal bearings and gyroscopic forces can be simulated. Experimental and theoretical results like mode shapes and unbalance parameters for the laboratory model are presented in detail.