Effects of location and aspect ratio of a flexible disk on natural frequencies and critical speeds of a rotating shaft-disk system

Abstract

The effects of changes in the location and the aspect ratio of a flexible disk on natural frequencies and critical speeds of a rotating flexible shaft-disk system are studied. Free vibration analysis of the system is carried out using the assumed modes method. The disk is modeled by Kirchhoff plate theory. The Euler-Bernoulli shaft is supported by two rigid bearings. In modeling the system, gyroscopic moments and centrifugal stiffening effects are taken into account. The results show that the disk flexibility property has a significant influence on the natural frequencies and critical speeds. Moreover, the disk position along the shaft (α) and the aspect ratio of the disk (β) can increase, decrease, or eliminate the disk flexibility effect. Therefore, there are special ranges of α and β in which the effect of the disk flexibility is completely negligible, so, in this case, the disk can be considered as a rigid body. Two new diagrams are presented for the first time in this study, which show the behavior of the critical speeds versus α and β. The results emphasize that in order to present a more detailed comment about the disk flexibility effects these parameters must be considered.