| Summary: | 博士 === 國立中山大學 === 機械工程學系 === 87 === Cracks frequently appear in the rotating machinery, for
as much as manufacturing flaws or cyclic fatigue during operation. Especially for the turbo-disk, numerous cracks
were observed after severe operation. In this dissertation,
the effect of blade crack on the mode localization and
dynamic stability of a rotating turbo-blade-disk is
studied.
Mode localization phenomenon and dynamic stability of
a mistuned system should be worthy of attention, because
the structural or material irregularities and non-constant rotating speed in blade-disks system are unavoidable.
However, only few investigations have dealt with this
mode localization and dynamic stability in those mistuned systems, with cracked blades. In this article, an
investigation of the effect of blade crack on the
stability and mode localization in a rotating blade-
disk is studied. Blades of a blade-disk are simulated respectively by the uniform and pretwisted taper beams.
The crack on the blade can be regarded as a local
disorder of this periodically coupled blades system.
Galerkin''s method and Hamilton''s principle are used to formulate the unperturbation equations of motion of the mistuned system. An application of the perturbation
multiple scales method is employed to derive the
approximate solution for the boundary of instability of
the mistuned system.
The effects of pretwisted angle, rotating speed and
crack size of the blade on the mode localization and
stability in a rotating system are studied. Numerical
results indicate that the increase of pretwisted angle, rotating speed and crack depth could affect the mode localization phenomenon and stability of this mistuned
system significantly.
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