Papers by Keyword: Mistuning

Abstract: Abstract. The objective of this paper is to probabilistically evaluate the effects of mistuned sectors on the dynamic characteristics of an integrally bladed disk (blisk). Small blade to blade physical variation in a disk is termed as mistuning. In this study, the dynamic characteristics of the perfectly tuned blisk were firstly analysed as a baseline. Secondly, a probabilistic approach is used for the mistuning analysis of a blisk. A reduced-order method named as the subset of nominal modes (SNM) was used to generate modes for a mistuned blisk from a cyclic perfectly tuned FE model without creating the full model. Furthermore, as only the modes with natural frequencies close to the modes of interest were considered, a relatively shorter computational time and a much smaller model size than a full blisk model is used. Therefore, the dynamic characteristics of the forced response for random mistuned blisks were obtained.

Abstract: A fast numerical method based on aeroelastic eigenvalue analysis is applied to study the effects of mistuning on the aeroelastic stability of turbomachinery blades in which the structural coupling is included by a simplified method and an influence coefficient method is employed to deal with the unsteady aerodynamic effects. Results show that there exists an optimal mistuning amount at which the system has the best aeroelastic stability. Structural coupling almost has no effects on aeroelastic stability of a tuned system. But the benefit of alternate frequency mistuning to aeroelastic stability is inhibited drastically when structural coupling is introduced into the bladed disk system.

Abstract: The mode localization phenomenon in mistuned cyclically periodic structures has been a hot spot in the past few decades. According to numbers of documents, the fundamental concepts, mechanism, main research methods, and the main results of mode localization are introduced; the current research status of the mode localization is summarized. The possiblity of mode localization in a telescope reflector model has been analyzed by using Finite Element Method. We also illustrate the problems for further studies, including: the unified modeling and analysis theory with more extensive applicability and better analytical accuracy; determining how to properly introduce mistuning parameters that can reflect the true state of the structure; constructing mode localization factor which can sensitively and effectively reflect the effect of mode localization; developing new damage identification method considering the influence of mode localization; how to make use of the localization characteristic to control the vibration level of the important sub-structure and improve the sensitivity of the periodic structure to the random detuning.

Abstract: The finite element models of bladed disks with different lashing wire locations were established. The natural characteristics and mode shapes of bladed disks with different lashing wire locations were compared, and the effect of lashing wire location on the natural characteristics and mode localization of bladed disks were analyzed. These results show that different lashing wire locations could carry different natural frequencies to bladed disk, and there must be one lashing wire location with the highest frequencies. Lashing wire location has a significant influence on the mode localization of the mistuned bladed disks, and the mode localization of the bladed disks is less sensitive to mistuning when the lashing wire is in the middle of blades.

Abstract: In this paper, by adopting the continuous ring model and the perturbation analysis for free vibration, the authors showed the reason and the importance for the modes split phenomena and provided the qualitative relation between modes split and perturbation for the harmonic number of stiffness perturbation. Also through the modal analysis for forced vibration the authors showed possible ways to predict and prevent the worst case when blade will crack. That is, the harmonic number for stiffness distribution should be avoided to be twice the engine order.