Sensitivity of Tuned Bladed Disk Response to Frequency Veering

Abstract

A continuous method is presented for representing the mode interaction that occurs in frequency veering in terms of the nominal sector modes of a cyclic symmetric bladed disk model constrained at a reference interblade phase angle. Using this method, the effect of frequency veering on the mode shapes can be considered in the context of the generalized forces exciting the system and the modal response of the bladed disk. It is shown that in a blade-dominated family of modes, the transfer of modal energy to the disk in the veering results in a lower generalized force exciting the mode as well as reduced response amplitude in the blade. For the disk-dominated modes, the sharing of modal energy with the blades can lead to the disk being excited by aerodynamic loading. These effects can have important implications for predicting and interpreting forced response in bladed disks. Numerical examples are provided to illustrate these concepts.