Rapid Investigation of Blisk Mistuning Via Piezoelectric-Induced Stiffness Perturbations

Abstract

Manufacturing tolerances and engine wear produce slight variations in the nominally identical blades of a bladed disk, or blisk. In theory, the vibrational energy of a tuned blisk is evenly distributed among the identical blades. Mistuning arises when blades are not exactly identical, producing vibration localization at one or more blades that can lead to premature failure via high-cycle fatigue. Blisk designers must consider how expected manufacturing variations and potential engine wear affect blade vibration and lifetime. However, a single experimental blisk can only capture a single mistuned configuration, making experimental assessment of mistuning both cost- and time-prohibitive. This paper investigates piezoelectric-induced stiffness perturbations as a potential approach that enables rapid testing of a wide range of mistuned configurations in a lab environment. Integrating piezoelectric material onto the blisk produces a continuous range of effective blade stiffness values. Piezoelectric stiffness perturbations alter the relative stiffnesses of all blades, changing the mistuned configuration. Simulations of a lumped blisk model characterize piezoelectric mistuning to motivate use in experimental preliminary testing of blisks. Optimization of the piezoelectric stiffness perturbation enables testing of desired mistuned amplitude distributions. Finally, benchtop testing of an academic blisk validates the ability of piezoelectric stiffness perturbations to change the mistuned configuration without any mechanical adjustments. Overall, piezoelectric mistuning enables rapid investigation of a theoretically infinite number of mistuned configurations with only one experimental blisk.