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International Journal of Rotating Machinery
Volume 2009, Article ID 265198, 8 pages
Research Article

Multiresolution Wavelet Analysis of the Dynamics of a Cracked Rotor

1Department of Mechanical Engineering, Cleveland State University, 2121 Euclid Ave., Cleveland, OH 44115-2214, USA
2Department of Mathematical Sciences, Indiana University, 402 N. Blackford Street, Indianapolis, IN 46202, USA
3Department of Mechanics, Technical University of Lublin, Nadbystrzycka 36, 20-618 Lublin, Poland

Received 17 December 2008; Revised 22 April 2009; Accepted 22 June 2009

Academic Editor: Agnes Muszynska

Copyright © 2009 Jerzy T. Sawicki et al. 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.


We examine the dynamics of a healthy rotor and a rotor with a transverse crack, which opens and closes due to its self weight. Using discrete wavelet transform, we perform a multiresolution analysis of the measured vibration signal from each of these rotors. In particular, the measured vibration signal is decomposed into eight frequency bands, and the rms amplitude values of the healthy and cracked rotors are compared in the three lowest-frequency bands. The results indicate that the rms vibration amplitudes for the cracked rotor are larger than those of the healthy rotor in each of these three frequency bands. In the case of externally applied harmonic force excitation to the rotor, the rms values of the vibration amplitude of the cracked rotor are also found to be larger than those of a healthy rotor in the three lowest-frequency bands. Furthermore, the difference in the rms values between the healthy and cracked rotors in each of the three lowest-frequency bands is more pronounced in the presence of external excitation than that with no excitation. The obtained results suggest that the present multiresolution approach can be used effectively to detect the presence of a crack in a rotor.