Characterization of Blisk Mistuning Induced by Bonded Piezoelectric Elements

Adaptive structures enable enhanced structural properties and performance, such as vibration reduction in turbomachinery blisk components and mistuning characterization. Although the fundamental concepts and ideas of these vibration reduction approaches have been developed, further research is needed to understand how incorporating adaptive elements alters the dynamics of the structure. In this paper, we analyze the bonding of piezoelectric patches to cyclically symmetric components, which tend to be highly sensitive to any changes in the structure’s geometry or material properties. This problem is generally known as mistuning and is an active area of research for turbomachinery structures like fan, compressor, and turbine blades. This paper focuses on possible methods that minimize final mistuning as a result of bonding piezoelectric patches to an academic blisk and enables further characterization of their capability for vibration reduction approaches that may be sensitive to mistuning. We are interested primarily in tuned system dynamics where engine-order excitation excites a single mode with a nodal diameter matching the engine order of the excitation. In this paper, we investigate two tuned blisks—one acrylic and one aluminum—and generate a baseline dynamics analysis of the tuned system. Each blisk has surface-mounted piezoelectric patches. We characterize the mistuning of each blisk post-bonding through statistical properties of the FRFs, along with the interplay of additional modes whose nodal diameters do not match the engine-order excitation. The application of piezoelectric patches induces mistuning and couples multiple modes in the response, and we propose a metric to aid in quantifying the associated amount of mistuning.