Abstract
This paper deals with the motion of an unsymmetrical rotor possessing nonlinear spring characteristics, due to the angular clearance of a singlerow deep groove ball bearing, in the vicinity of the major critical speed. When this system is operated near the major critical speed, no unstable vibration occurs, but we obtain peculiar resonance curves of hard spring type which have three stable amplitudes at most against the rotating speed. The resonance curves are classified into two types. They are the cases where the jump phenomenon appears once or twice during deceleration of the rotating speed. It is clarified that the type of the resonance curve depends on the angular position of rotor unbalance.
