Abstract
Many rotors are supported by an oil film bearing which has high stiffness. Since the gap of an oil bearing is very small, we must suppress vibration as much as possible to prevent metal contact by an oil membrane break. Therefore the damping ratio is an important index to use when evaluating the rotor system stability. However it is difficult to identify the damping ratio under various conditions. In this paper, we introduce a new method using the modal open loop transfer function. This method provides a more accurate Q-value and can help to identify the damping ratio by considering only the mode which we want to measure. We evaluate the damping ratio of the oil film bearing with a dynamic damper which is developed for suppression of oil whip instability.
