Abstract
In this paper, we examine an effective vibration control method for rotor-bearing system in an operation condition in which an oil whip occurs by using adjustable quasi-circular bearing with changeable configuration of cross section. This bearing can arbitrarily change the bearing clearance distribution in circumferential direction by using a piezoelectric actuator installed between bearing casing and metal. We confirmed from numerical studies that the threshold speed rose when the metal cross section was deformed the position of 30 to 40 degrees in the direction of shaft rotation from gravity from the metal center.