Asymptotic description of damping mistuning effects on the forced response of turbomachinery bladed disks

Abstract

The effect of mistuning on the vibration of bladed disks has been extensively studied in the past 30 years. Most of these analyses typically cover the case of small variations of the elastic characteristics (mass and stiffness) of the blades. In this work we study the not so frequent case of the forced response of a bladed-disk with damping mistuning. A reduced order model, that provides a simplified description of the dynamics of the system, is derived from the full problem using a consistent asymptotic procedure. The resulting simplified model describes quantitatively the effect of blade to blade damping variation on the vibrational response of the system, and gives precise information on the underlying mechanisms involved in the action of damping mistuning. The reduced order model is applied to compute the forced response of an integrated bladed-disk with mistuning damping, and to locate the damping mistuning pattern that gives maximum amplification of the response. A detailed finite element model is also used to compute the forced response of the mistuned blisk, and the results show an excellent agreement with the predictions obtained from the reduced order model.