What steps were made towards the detection and monitoring of crack through the transient vibration analysis?
Few works have been reported on the detection and monitoring of crack through the transient vibration analysis while the rotor system is passing through the critical speed. However, these works were mainly focussed using speed response, time domain signals and/or the traditional signal processing technique such as FFT for the analyses to detect cracks during startup of the rotor system. Prabhakar et al., successfully used the wavelet transform to detect the shaft cracks during while the rotor-bearing system is passing through the critical speed during start-up. Sekhar extended the use of wavelet transform to detect crack during startup and shut down of the rotor system mounted on the fluid film bearings. The crack features such as the presence of subcritical speed may also present due to oil whirl in case of rotor system supported on fluid film bearings under certain conditions and hence in this work the rotor-bearing system mounted on rolling element bearings is considered to detect shaft crack during coast down.
In the present study, the transient analysis of the rotor-bearing system with transverse breathing crack has been studied by using finite element method (FEM) for flexural vibrations. Time responses and the corresponding wavelets transformed vibration signals have been analyzed for various parameters like depth and location of the crack and for different decelerations of a rotor system during shut-down.