Crack induced vibration localization in simplified bladed-disk structures

In this paper, we study the effect of a crack on the vibratory response of a simplified aero-engine bladed-disk model, which consists of cantilevered beams (blades) coupled with springs (inter-blade internal coupling). Our goal is to obtain qualitative understandings of the unique dynamic behavior of such structure with crack, i.e., the occurrence of vibration localization and its level. A fracture mechanics based approach is employed to evaluate the crack induced stiffness loss on a single beam. By taking advantage of the structural periodicity or near-periodicity, using the U-transformation approach we then develop analytical solutions to the free and forced vibrations of the bladed-disk with a single crack. It is identified that, while the stiffness loss on a single beam could be small and may not cause a significant frequency change, it could lead to the free and forced vibration localization in a periodic structure. The intrinsic relation between the response amplitudes and various system parameters such as internal coupling, crack severity, excitation patterns and number of blades is systematically investigated. (c) 2005 Elsevier Ltd. All rights reserved.