Effects of crack on modal parameters of mistuned blades

摘要

Mistuned blades are inevitable in compressor, and modal parameters of mistuned blades will change significantly compare with tuned blades. In this paper, mistuning stiffness is introduced and a lumped parameter model of coupled multi-blades is established. Mode localization of mistuned blades is analyzed by this model. When a crack appears in mistuned blades, local flexibility method is used to analyze lessened stiffness model of the cracked blade. A local parameter is introduced. It is used to quantitatively analyze that positions and depths of a crack affect modal parameter of blades. When depth of a crack is shallow or a crack locate near tip of a blade in mistuned blades system, these cannot change local parameter of modal amplitude in mistuned blades with a crack. In other words, this kind of the crack cannot change mistuned degree of blades. However, with depth of a crack increasing or a crack being close to root of a blade, local parameter of modal amplitude can increase sharply. The analytical results establish a based model for diagnosis of a crack in mistuned blades.