Study on vibration response characteristics of mistuned bladed disk (Mistuning phenomena evaluated by vibratory stress)

Abstract

Although bladed disks of turbomachinery are nominally designed to be cyclically symmetric (tuned system), the vibration characteristics of all blades on a disk are slightly different due to the manufacturing tolerance, the deviation of the material property, the wear during operation, and so on. These small variations break the cyclic symmetry, and split the eigenvalue pares. The actual bladed disks with the small variations are referred to a mistuned system. In the forced response of a mistuned bladed disk, the responses of all blades become different, and the response of a certain blade may become extremely large due to the split of the duplicated eigenvalues, the distortion of the vibration modes, and so on. On the other hand, many researchers suggest that the mistuning suppresses the blade flutter, because the complete travelling wave mode is not formed in a disk. In other words, the main conclusions of researches on mistuning are that while mistuning has an undesirable effect on the forced response, it has a beneficial (stabilizing) effect on the blade flutter (the self-excited vibration). Although such mistuning phenomena of bladed disks have been studied extensively since 1980s, almost all studies focused on the mistuning effect of the displacement response, and few studies researched the mistuning effect of the vibratory stress response. In this study, the frequency response analysis of the mistuned simple bladed disk is carried out. Comparing the mistuning effect of the displacement response with that of the vibratory stress response, the mistuning effect evaluated by the vibratory stress is studied in detail.