Modal analysis of cracked rotor supported by the journal bearings

The detection of a growing transverse crack in a rotor is based on the vibrosignal analysis of the system consisting of the rotor and a flexible shaft supported by hydrodynamic bearings. The model of the flexible shaft and the flexible rotor has been developed using the finite element analysis. Such models give the rather accuracy description of the nonlinear dynamic of this system with or without crack. The three-dimensional finite-elemental model of the crack has been used for modelling. With help of the modal analysis the profiles of the vibrosignals have been obtained for different models of the crack. The model has been used for the quantitative estimation of the depth and location of the crack. Experimental results showed that when a crack occurs in the rotor, it can be detected by the experimental modal analysis at its early stage.