Experimental Modal Identification of Mistuning in an Academic Blisk and Comparison With the Blades Geometry Variations

In the field of turbomachinery, the assumption of cyclic symmetry of rotor stages is usually made to lower the required computational resources. However, in reality, small random blade-to-blade variations, known as mistuning, appear due to manufacturing tolerances, etc. and disturb the dynamic behavior of bladed disks. In this work, an experimental modal analysis is performed on a mono-stage and monobloc academic bladed structure. The frequency response function (FRF) is measured using a base excitation with an electrodynamic shaker and one measurement point per blade. The mistuning of the structure is identified. Then, an optical geometry measurement system is used to obtain the exact geometry of each blade. Based on these optical data, a finite element model of the structure is constructed and the FRF of this model is compared to the experimental FRF. The accurate measurement of the geometry allows to compare the level of geometry mistuning of the academic structure with the identified frequency mistuning.