A study is presented of the mode localization phenomenon in imperfect blade-disk and blade-shroud-disk assemblies. This surprising phenomenon, first discovered in solid state physics, occurs in a number of periodic structures when the periodicity is broken by disorder or imperfections. Localization is signalled by the amplitude of a global blade-disk mode becoming confined to one or more local regions consisting of just a few blades, and could have serious implications for blade fatigue life. The results of this investigation indicate that unshrouded blades mounted on stiff disks are especially susceptible, and even small blade imperfections within manufacturing tolerances are likely to trigger mode localization. Increasing the interblade coupling by adding shrouds or reducing the disk stiffness greatly reduces the localization susceptibility, although certain modes may still become localized if the shrouds are free to slip.

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