STABILITY AND BIFURCATION OF UNBALANCED RESPONSE OF A SQUEEZE FILM DAMPED FLEXIBLE ROTOR

The stability and bifurcation of the unbalance response of a squeeze f ilm damper-mounted flexible rotor are investigated based on the assump tion of an incompressible lubricant together with the short bearing ap proximation and the ''pi ''film cavitation model. The unbalanced rotor response is determined by the trigonometric collocation method and th e stability of these solutions is then investigated using the Floquet transition matrix method. Numerical examples are given for both concen tric and eccentric damper operations. Jump phenomenon, subharmonic, an d quasi-periodic vibrations are predicted for a range of bearing and u nbalance parameters. The predicted jump phenomenon, subharmonic and qu asi-periodic vibrations are further examined by using a numerical inte gration scheme to predict damper trajectories, calculate Poincare maps and power spectra. It is concluded that the introduction of unpressur ized squeeze film dampers may promote undesirable nonsynchronous vibra tions.