Nonlinear Dynamics and Vibration Localization of Shrouded Blisk with Contact and Friction Effects

Abstract

Shrouds have been widely used to reduce the level of excessive vibration of blisks. However, complicated nonlinear motion can be induced by the contact and friction between shrouds. Even worse, harmful localization of vibration can be encountered due to nonsmooth behaviour at the shroud contact interfaces in the tuned disk. In this paper, the nonlinear dynamics and localization of vibration of a shrouded blisk are studied considering the spin softening. The continuous parametric model of a shrouded blisk is established, and the transition boundaries between different status (i.e., stick, slip and separation) of shrouds are determined based on the Coulomb friction model. The steady-state responses of the blisk are analysed using variable rotation speed, and the primary resonance, beat and quasi-periodic vibration are presented in connection with the non-smooth behaviour of contact. A particular type of vibration localization initiated by the contact and friction effect of the shrouds in the form of asymmetric vibration in the tuned blisk is discovered. It is found that the blades-disk coupling has strong influences on the level of the localization. The effects of the contact stiffness and localization on the blade vibration are demonstrated through the change in the powers of the blade motions.