Wavelet analysis of vibration signals of an overhang rotor with a propagating transverse crack

This paper presents an experimental study of the dynamic response of an overhang rotor with a propagating transverse crack using the discrete wavelet transform (DWT)-a joint time frequency analysis technique. Start-up and steady state vibration signatures are analyzed using Daubechies (Db6) mother wavelet and the results are presented in the form of scalograms and space-scale energy distribution graphs. The start-up results showed that crack reduces the critical speed of the rotor system. The steady state results showed that propagating crack produces changes in vibration amplitudes of frequency scale levels corresponding to 1X, 2X and 4X harmonics. The vibration amplitude of frequency scale level corresponding to 1X may increase or decrease depending on the location of the crack and side load. However, the amplitude of frequency scale level corresponding to 2X increases continuously as the crack propagates. (C) 2001 Academic Press.