In this paper the stability of nonlinear misaligned rotor-bearing systems is investigated, using the Lyapunov direct method. A finite element formulation is used to determine the journal bearing pressure distribution. Then the linear and nonlinear stiffness, damping, and hybrid (depending on both displacement and velocity) coefficients are calculated. A general method of analysis based on Lyapunov's stability criteria is used to investigate the stability of nonlinear misaligned rotor bearingsystems. The equations of motion of the rigid rotor on the nonlinear bearings are used to find a Lyapunov function using some of these coefficients, which depend on L/D ratio and the misalignment anglesψ{sub}x 4,ψ{sub}y The analytical conditions for the stability or instability of some examined cases are given and some examples for the orbital stability are also demonstrated.
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