The dynamic design of bladed disks consists in making sure that structural modes are not excited by the harmonics caused by engine speed (coincidences predicted after a Campbell diagram analysis). In practice, it is impossible to avoid every single coincidence over the whole operating range. An engine test is carried out at the end of the design cycle, in order to determine vibration levels. By means of this test and the validated FE model, the designer verifies frequency margins, and from this, is able to determine whether or not the bladed disk is likely to be at risk from vibration fatigue, otherwise known as High Cycle Fatigue (HCF). This analysis needs several FE calculations whose models have been updated in relation to component tests to measure stress distribution (use of strain gauges). One of the drawbacks of this type of measurement lies in the intrusive character of instrumentation used, which upsets the dynamic behavior of the blades in particular for high level modes. This document puts forward the application of non-intrusive, optical measurements, and highlights the accuracy that can be obtained by measuring mode shapes. Furthermore, this paper highlights the importance of defining levels of accuracy for measurements obtained, for example, in characterizing frequency scatterings for each blade individually, scatterings which are translated by an amplification of the structure aeroelastic response.

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