On the effects of interblade coupling on the statistics of maximum forced response amplitudes in mistuned bladed disks

Studies of mistuning effects on nearly cyclic systems have left one puzzling question unanswered. A free response analysis indicates that mistuning effects on the mode shapes increase monotonically as the coupling between the subsystems of the assembly is decreased, with the mode shapes becoming increasingly localized. Hence, very weakly coupled systems experience the most dramatic mistuning effects. Forced response analysis produces evidence to the contrary, namely that there is some threshold value of coupling that leads to maximum mistuning effects, and that these effects are even more dramatic than those that might be predicted by the free response analysis. This would indicate that there is a second, unknown, mechanism at play that enhances the well known mode localization phenomenon in the forced response case. In this paper a search for this unknown mechanism is conducted, and some answers are proposed.