Detecting Cracked Rotors using Auxiliary Harmonic Excitation
JT Sawicki (Cleveland State University, USA), MI Friswell (Swansea University), Z Kulesza (Bialystok University of Technology, Bialystok, Poland), A Wroblewski & JD Lekki (NASA Glenn Research Center, USA)
Journal of Sound and Vibration, Vol. 330, No. 7, March 2011, pp. 1365-1381
Cracked rotors are not only important from a practical and economic viewpoint, they also exhibit interesting dynamics. This paper investigates the modelling and analysis of machines with breathing cracks, which open and close due to the self-weight of the rotor, producing a parametric excitation. After reviewing the modelling of cracked rotors, the paper analyses the use of auxiliary excitation of the shaft, often implemented using active magnetic bearings, to detect cracks. Applying a sinusoidal excitation generates response frequencies that are combinations of the rotor spin speed and excitation frequency. Previously this system was analysed using multiple scales analysis; this paper suggests an alternative approach based on the harmonic balance method, and validates this approach using simulated and experimental results. Consideration is also given to some issues to enable this approach to become a robust condition monitoring technique for cracked shafts.
This material has been published in the Journal of Sound and Vibration, Vol. 330, No. 7, March 2011, pp. 1365-1381. Unfortunately the copyright agreement with Elsevier does not allow for the PDF file of the paper to be available on this website. However the paper is available from ScienceDirect - see the link below.
Link to paper using doi: 10.1016/j.jsv.2010.10.006
Journal of Sound and Vibration on ScienceDirect