Chaos and bifurcation analysis of a flexible rotor supported by short journal bearings with non-linear suspension

The bifurcation and chaos of the unbalanced response of a bearing-rotor system with non-linear suspension are investigated on the basis of the assumption of an incompressible lubricant together with short bearing approximation. Numerical results show that, owing to the non-linear factors, the trajectory of the journal centre demonstrates steady state symmetric motion even when the trajectory of the bearing centre is in a state of disorder. Poincare maps, bifurcation diagrams and power spectra are used to analyse the behaviour of the bearing centre in the horizontal and vertical directions under different operating conditions. A unidirectional bifurcation phenomenon is detected ill the bearing-rotor system in this study. The fractal dimension concept is used to determine whether the system is in a state of chaotic motion. Numerical results show that the dimension of the bearing centre trajectory is fractal and greater than 2 in some operating conditions. This indicates that the bearing centre is in the state of chaotic motion at these operating conditions.