Vibration characteristics of systems with multiple blades

An interesting phenomenon can be observed when the state-space dynamic subs tructural method is applied to the eigenproblem of bladed disk-shaft system s: whether or not the shaft is flexible, each frequency of the single root- fixed blade appears as a frequency of the whole structure with a multiplici ty of at least (n - 3), where n is the number of repetitive blades. The pre sented result can be regarded as an extension of previous findings by the a uthors in the sense that the commonly interfaced repetitive substructures a re allowed to be treated as a rigid body in modal analysis. The defectivene ss issue of the multiple eigenvalues arising from the repetitive substructu res is also addressed. Examples of rotary wing models and a simplified turb ine model are presented for validation together with attempting their physi cal explanations. (C) 1999 Academic Press.