Identification of Mistuning and Model Updating of an Academic Blisk Based on Geometry and Vibration Measurements

In this work, an experimental modal analysis is performed on an academic bladed disk using a base excitation to identify the mistuning of each blade. Optical measurement is used to obtain the exact geometry of the structure and to be able to associate geometrical mistuning to each blade. Differences are observed between the experimentally identified mistuning and the geometrical mistuning. Since the bladed disk is a one-piece structure, there are no welded connections between the blades and the disk and the material properties can be assumed to be uniform. It can be shown that these differences come from nonuniform clamping conditions, and that this mistuning is of the same order of magnitude than the variations in the geometry of the structure. It follows that the precise characterisation of mistuning for industrial structures is in practice illusory because of the numerous factors introducing mistuning, such as the clamping conditions, aerodynamic damping, wear in service, etc.