Effect of bearing dynamic properties on the lateral vibration of a flexible rotor

Analytic study of rotor vibration plays an important role in design, and fault detection and diagnosis of rotating machines. In this paper, vibration characteristics of a flexible rotor due to a central mass unbalance were analysed numerically under two cases. In Case I, bearings have symmetric, isotropic stiffness and damping matrices, while in Case II they have asymmetric, nonisotropic stiffness and damping matrices. It was found in Case I that critical speed occurs at 1690 rpm and the orbital trajectories of rotor mass stations are circular and corotational. In Case II, response orbit of either the bearing or the disk is elliptic and the size, shape, and orientation of the elliptical orbit changes with shaft speed, and also from the bearing to the disk.