Abstract
This paper investigates the stability and the stability degree of a flexible cracked rotor supported on different kinds of journal bearings. It is found that no matter what kind of bearings is used, the unstable zones caused by rotor crack locate always within the speed ratio when gravity parameter Wg > 1.0; and locate always within the speed ratio when Wg < 0.1, where ΔKξ is the crack stiffness ratio, N = 1, 2, 3, 4, 5 … and . When 0.1 < Wg < 1.0, there is a region, where no unstable zones caused by rotor crack exist.
Outside the crack ridge zones, the rotor crack has almost no influence on system’s stability and stability degree; while within the crack ridge zones, the stability and stability degree depend both on the crack and system’s parameters. In some cases, the system may still be stable even the crack is very large. For small gravity parameter (Wg < 0.1), the mass ratio α has large influence on the position of unstable region, but its influence on the stability degree is small. The influence of fixed Sommerfeld number So on the crack stability degree is small although So has large influence on the stability degree of uncracked rotor.