The newly-revealed phenomenon of reduction of forced response levels in a mistuned bladed disc to levels significantly (e.g. by a factor of two and more) lower than that of its tuned counterpart is studied in detail on an example of a realistic bladed disc. Statistical properties of the amplification factor of the mistuned forced response calculated with aero-effects included have been studied for cases of random blade mistuning and for mistuned blade rearrangements. Optimization search for the best mistuning patterns providing maximum forced response reduction effect have been performed, and the robustness of the optimum mistuning patterns has been demonstrated. The combined effect of the aerodynamic and structural damping on the response reduction is assessed. It is shown that the new phenomenon is of major practical significance and has to be taken into account in analysis of the forced response and design decisions.

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