Modeling & Analysis of Bladed Disk with Cracks and Mistuning PDF Download
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Author: Tianyi Hu
Publisher:
ISBN:
Category : Mechanical engineering
Languages : en
Pages : 43
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Book Description
In this thesis, efficient techniques are presented for analyzing the dynamics of mistuned bladed disks with cracks. The analysis of the influence of cracks coupled with the influence of mistuning on the dynamics of bladed disks is computationally challenging for several reasons: (i) complex geometry of modern turbines results in very high dimensional computational models; (ii) mistuning in these structures breaks the cyclic symmetry in these systems; and (iii) cracks further disrupt the symmetry property and introduce a piecewise-linear nonlinearity into these systems. Recently several approaches have been developed to handle these challenges individually. The component mode mistuning (CMM) approach was developed to efficiently model small mistuning in bladed disks. The X-Xr method was developed for generating reduced-order models of cyclically symmetric systems with cracks. More recently, the generalized bilinear amplitude approximation (BAA) technique was created to efficiently approximate the nonlinear vibrational response of a class of piecewise-linear nonlinear systems. This work modifies and combines these techniques, for the first time, to enable modeling and analysis of mistuned bladed disks with cracks in an efficient manner. The novel method can generate the reduced-order model of full disks using single-sector models only and approximate the nonlinear vibrational response of mistuned disks with significantly reduced computational effort. A mistuned bladed disk with a crack is parametrically studied using the proposed approach. The influence of different mistuning patterns and crack lengths on the dynamics of the system is discussed.
Author: Tianyi Hu
Publisher:
ISBN:
Category : Mechanical engineering
Languages : en
Pages : 43
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Book Description
In this thesis, efficient techniques are presented for analyzing the dynamics of mistuned bladed disks with cracks. The analysis of the influence of cracks coupled with the influence of mistuning on the dynamics of bladed disks is computationally challenging for several reasons: (i) complex geometry of modern turbines results in very high dimensional computational models; (ii) mistuning in these structures breaks the cyclic symmetry in these systems; and (iii) cracks further disrupt the symmetry property and introduce a piecewise-linear nonlinearity into these systems. Recently several approaches have been developed to handle these challenges individually. The component mode mistuning (CMM) approach was developed to efficiently model small mistuning in bladed disks. The X-Xr method was developed for generating reduced-order models of cyclically symmetric systems with cracks. More recently, the generalized bilinear amplitude approximation (BAA) technique was created to efficiently approximate the nonlinear vibrational response of a class of piecewise-linear nonlinear systems. This work modifies and combines these techniques, for the first time, to enable modeling and analysis of mistuned bladed disks with cracks in an efficient manner. The novel method can generate the reduced-order model of full disks using single-sector models only and approximate the nonlinear vibrational response of mistuned disks with significantly reduced computational effort. A mistuned bladed disk with a crack is parametrically studied using the proposed approach. The influence of different mistuning patterns and crack lengths on the dynamics of the system is discussed.
Author:
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ISBN:
Category :
Languages : en
Pages : 13
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 27
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Turbomachinery rotors, or bladed disks, are known to suffer from severe vibration problems due to small, random deviations (mistuning) of the blade properties. Mistuning can lead to dramatic increases in the maximum blade stress and cause high cycle fatigue (HCF), which is a major cost, readiness, and safety concern for the U.S. Air Force. The primary objective of this research was to provide significantly improved understanding, modeling, and prediction of the vibration response of mis-tuned bladed disk systems by including the effects of important phenomena that had been largely neglected in previous mistuning models. The models developed in this research program were used to investigate the interaction of blade mistuning with aerodynamic coupling, stage-to-stage connections for multistage rotors, blade damage, and nonlinearities. In addition, key mistuning phenomena were examined through vibration testing of blisks (single-piece bladed disks). New methods were developed for identifying blade mistuning parameters from test data and for running experimental Monte Carlo assessments of the effects of mistuning on the system forced response.
Author: Gísli Sigurbjörn Óttarsson
Publisher:
ISBN:
Category :
Languages : en
Pages : 442
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Author: Sang-Ho Lim
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ISBN:
Category :
Languages : en
Pages : 482
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Author: Vsevolod Kharyton
Publisher:
ISBN:
Category :
Languages : en
Pages : 206
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The general aim of the study is to offer mathematical model of the process, which can allow crack identification in the compressor or turbine blade of aircraft gas-turbine engine in operation. Within the frameworks of this goal cracked blade non-linear dynamic model was elaborated and introduced to the global model of the bladed disk. Crack induced non-linearity was taken into account applying contact analysis elements in conjunction with harmonic balance method. For system size reduction the sub-structuring methodology using fixed-interface method was applied. It supposes the crack location to be considered as interface between two dependent, in this case, substructures. Such approach was applied to the both uncoupled cracked blade and bladed disk models. Also considering uncoupled cracked blade the centrifugal forces effect was examined. It was concluded, that depending on crack properties (location and size), it will be enough to use the linear crack presence formulation supposing crack to be always open (initial gap). During simulation of the bladed disk forced response containing cracked blade the effect of blade mistuning was simulated. Simulation results shown that at certain level of mistuning it becomes impossible to separate cracked blade response. Furthermore such crack detectability decreases with absence of cracked blade frequency localization. The last one phenomenon is very important diagnostic sign, which simplifies cracked blade detection at almost all cases. The last phase of the work was devoted to simulation of blade tip-timing method application for cracked blade identification. It consisted in blade arriving time generation, blade tip amplitudes reconstruction and bladed disk frequency response calculation on the base of measured (simulated) time data. Such approach allowed us to identify cracked blade in the same way as in frequency response analysis. Generally speaking, blade tip-timing method can be used as the part of engine health monitoring system for compressor or turbine blades dynamic performances monitoring.
Author:
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ISBN:
Category : Aeronautics
Languages : en
Pages : 492
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Author: Marlin Jay Kruse
Publisher:
ISBN:
Category :
Languages : en
Pages : 330
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Author: Bereket Kiflu
Publisher:
ISBN:
Category : Disks, Rotating
Languages : en
Pages : 138
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Author:
Publisher:
ISBN:
Category : Engines
Languages : en
Pages : 232
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