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Letteratura scientifica selezionata sul tema "Structural mistuning"

Autore: Grafiati

Pubblicato: 7 settembre 2024

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Articoli di riviste sul tema "Structural mistuning"

Wei, S. T., e C. Pierre. "Localization Phenomena in Mistuned Assemblies with Cyclic Symmetry Part I: Free Vibrations". Journal of Vibration and Acoustics 110, n. 4 (1 ottobre 1988): 429–38. http://dx.doi.org/10.1115/1.3269547.

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An investigation of the effects of small structural irregularities on the dynamics of nearly periodic structures with cyclic symmetry is presented. The system studied may be regarded as a simple model of a continuously shrouded blade assembly accounting for one structural mode per blade. A key aspect of the approach is the use of perturbation methods that lead to a physical insight into the effects of mistuning. The study shows that the sensitivity to mistuning depends primarily upon the ratio of mistuning strength to coupling strength. For a small mistuning to coupling ratio, the mistuned system behaves like a perturbation of the corresponding tuned system, in which case mistuning has a relatively small effect on both the free and forced responses. On the other hand, for a large mistuning to coupling ratio (i.e., weak coupling), the mistuned system behaves like a perturbation of the corresponding decoupled mistuned system, in which case small mistuning dramatically changes the dynamics of the system. This paper, Part I, investigates the effects of small mistuning on the free response of the system. Specifically, it is shown that strong mode localization and eigenvalue loci veering phenomena occur in the weakly coupled system when mistuning is introduced. The effects of mistuning on the forced response are studied in the companion paper, Part II (Wei and Pierre, 1987).

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Fu, Zhi Zhong, e Yan Rong Wang. "Mistuning and Structural Coupling Effects on Flutter of Turbomachinery Blades". Applied Mechanics and Materials 482 (dicembre 2013): 311–14. http://dx.doi.org/10.4028/www.scientific.net/amm.482.311.

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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.

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Kenyon, J. A., J. H. Griffin e D. M. Feiner. "Maximum Bladed Disk Forced Response From Distortion of a Structural Mode". Journal of Turbomachinery 125, n. 2 (1 aprile 2003): 352–63. http://dx.doi.org/10.1115/1.1540118.

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A method is presented for obtaining maximum bladed disk forced response from distortion of a structural mode. It is shown that maximum response from mode distortion in a bladed disk occurs when the harmonic components of a distorted mode superimpose in a certain manner, causing localization of the mode and strong response in a particular blade. In addition, it is shown that the response of an intentionally mistuned system with maximum response does not change significantly when small random mistuning is added to the system. A method is described for calculating the structural mistuning necessary to obtain the distorted mode that gives maximum response. The theory is validated numerically.

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Kenyon, J. A., e J. H. Griffin. "Forced Response of Turbine Engine Bladed Disks and Sensitivity to Harmonic Mistuning". Journal of Engineering for Gas Turbines and Power 125, n. 1 (27 dicembre 2002): 113–20. http://dx.doi.org/10.1115/1.1498269.

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The mistuned forced response of turbine engine bladed disks is treated using harmonic perturbations in the properties of a continuous ring. A continuous shear spring is attached to the ring in which the stiffness is allowed to vary along the ring annulus. The modes of such a structure with a single harmonic mistuning pattern are shown to obey the Mathieu equation, which is solved to obtain the natural frequencies and modes of the mistuned system. The forced response of the system is then examined to determine the sensitivity of the system to small mistuning. The model is extended to include multiple harmonics, allowing for the possibility of general mistuning. An expression for the maximum amplitude magnification due to small mistuning is developed by showing that high response is caused by distortion of the structural modes. A method to intentionally mistune systems for maximum forced response is demonstrated, and numerical results demonstrate the accuracy of the analytical prediction. The intentionally mistuned system response is shown to be robust with respect to small random mistuning. Such a result might be useful for designing a test rotor for screening new bladed disk designs or for establishing the root cause of fatigue problems.

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Mignolet, Marc P., Wei Hu e Ioan Jadic. "On the Forced Response of Harmonically and Partially Mistuned Bladed Disks. Part I: Harmonic Mistuning". International Journal of Rotating Machinery 6, n. 1 (2000): 29–41. http://dx.doi.org/10.1155/s1023621x0000004x.

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This series of two papers focuses on the determination and clarification of the characteristics of the forced response of bladed disks that exhibit a mistuning pattern that is either harmonic or partial. Harmonic mistuning refers to single wavelength variations in structural properties along the disk while partial mistuning is associated with blade characteristics that are random in a specific sector and tuned elsewhere. The results of this analysis demonstrate that many features of the response of these simple systems match not only qualitatively but also quantitatively their counterparts on randomly mistuned bladed disks. Relying on these similarities, simple and reliable approximations of the localization factor and of the mean response are easily derived that exemplify the usefulness of harmonic and partial mistuning patterns. Finally, it is demonstrated both theoretically and by comparison with simulation results that the maximum amplitude of response of a disk closely follows a Weibull-type distribution in all coupling situations, from very weak to very strong.

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Mignolet, Marc P., Wei Hu e Ioan Jadic. "On the Forced Response of Harmonically and Partially Mistuned Bladed Disks. Part II: Partial Mistuning and Applications". International Journal of Rotating Machinery 6, n. 1 (2000): 43–56. http://dx.doi.org/10.1155/s1023621x00000051.

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Kan, Xuanen, e Tuo Xing. "A novel mathematical model for the design of the resonance mechanism of an intentional mistuning bladed disk system". Mechanical Sciences 13, n. 2 (20 dicembre 2022): 1031–37. http://dx.doi.org/10.5194/ms-13-1031-2022.

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Abstract. Bladed disk systems with advanced functions are widely used in turbo-machineries. However, there are always deviations in physical dynamic properties between blades and blades due to the tolerance and wear in operation. The deviations will lead to vibration localization, which will result in high cycle fatigue and accelerate the damage of the bladed disk system. Therefore, many intentional mistuning patterns are proposed to overcome this larger local vibration. Previous studies show that intentional mistuning patterns can be used to reduce the vibration localization of the bladed disk. However, the determination of the resonance mechanism of the intentional mistuning bladed disk system is still an unsolved issue. In this paper, a novel mathematical model of resonance of an intentional mistuning bladed disk system is established. Mistuning of blades and energy resonance are included in this theoretical model. The method of the mechanical power of the rotating blade for one cycle is applied to obtain the resonance condition. By using this theoretical model, the resonance mechanism of an intentional mistuning bladed disk is demonstrated. The results suggest that the ideal results can be obtained by adjusting the intentional mistuning parameter. This paper will guide the design of the dynamic characteristics of the intentional mistuning bladed disk.

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Lalanne, Bernard. "Perturbations Methods in Structural Dynamics and Applications to Cyclic Symmetric Domains". Journal of Engineering for Gas Turbines and Power 127, n. 3 (13 dicembre 2004): 654–62. http://dx.doi.org/10.1115/1.1924430.

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The design of components must take into account the irregularities inherent to the manufacturing process. When the structures have close eigenvalues, small mass and stiffness variations or the damping generate strong variations of the eigenmodes: these structures are then not robust. Here, their dynamics has been analyzed by perturbation method, in the dissipative cases and with coupling within a light fluid. A new perturbation method allows first order developments whatever the spectral density may be. Applications to many different vibration problems are presented: aeroelasticity, mode veering problem, maximum amplitude of forced response in cyclic symmetric domains, with detuning and/or mistuning, i.e., the most important reliability problem in turbomachinery. The results of this study provide a new estimation of the amplification factor and damping due to mistuning and aerodynamic coupling.

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Kenyon, J. A., e J. H. Griffin. "Experimental Demonstration of Maximum Mistuned Bladed Disk Forced Response". Journal of Turbomachinery 125, n. 4 (1 ottobre 2003): 673–81. http://dx.doi.org/10.1115/1.1624847.

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A theory was previously developed for predicting robust maximum forced response in mistuned bladed disks from distortion of a structural mode. This paper describes an experiment to demonstrate the theory. A bladed disk is designed to be sufficiently sensitive to mistuning to obtain maximum response. The maximum amplitude magnification from mistuning is predicted using the theory, 1.918. The bladed disk is intentionally mistuned to obtain the maximum response, and the response to an engine order traveling wave excitation is measured. The measured amplitude magnification is in close agreement with the theory. The robustness of the maximum response is demonstrated.

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Liu, Zhanhe, Jinlou Quan, Jingyuan Yang, Dan Su e Weiwei Zhang. "A High Efficient Fluid-Structure Interaction Method for Flutter Analysis of Mistuned". Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 36, n. 5 (ottobre 2018): 856–64. http://dx.doi.org/10.1051/jnwpu/20183650856.

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The time cost is very high by direct fluid-structure interaction method for mistuned bladed disk structures, so aerodynamic loads generally are ignored or treated as small perturbations in traditional flutter analysis. In order to analyze the flutter characteristics of mistuned blade rapidly and accurately, this paper presents an efficient fluid-structure interaction method based on aerodynamic reduced order model. system identification technology and two basic assumptions are used to build the unsteady aerodynamic reduced order model. Coupled the structural equations and the aerodynamic model in the state space, the flutter stability of mistuned bladed disk can be obtained by changing the structural parameters. For the STCF 4 example, the response calculated by this method agrees well with the results obtained by the direct CFD, but the computational efficiency is improved by nearly two orders of magnitude. This method is used to study the stiffness mistuned cascade system, and the stability characteristics of the system are obtained by calculating the eigenvalues of the aeroelastic matrix. The results show that the stiffness mistuning can significantly improve the flutter stability of the system, and also lead to the localization of the mode. The mistuning mode, mistuning amplitude and fluid structure interaction can influence the flutter stability obviously.

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Più fonti

Tesi sul tema "Structural mistuning"

POURKIAEE, SEYYEDMEHRDAD. "Modelli ed esperimenti per la dinamica non lineare di dischi palettati con mistuning e contatti con attrito". Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2861352.

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Sternchüss, Arnaud. "Multi-level parametric reduced models of rotating bladed disk assemblies". Phd thesis, Ecole Centrale Paris, 2009. http://tel.archives-ouvertes.fr/tel-00366252.

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Les disques aubagés, que l'on trouve dans les turbomachines, sont des structures complexes dont le comportement vibratoire est généralement déterminé par l'exploitation de conditions de symétrie dans leur configuration nominale. Cette symétrie disparaît lorsque l'on assemble plusieurs de ces disques pour former un rotor ou que l'on introduit une variabilité spatiale des paramètres mécaniques (on parle de désaccordage intentionnel ou non). Le raffinement des maillages, nécessaire à une évaluation correcte de la répartition des contraintes, conduirait à des modèles de rotor complet de taille prohibitive (plusieurs dizaines de millions de degrés de liberté). L'objectif de cette thèse est donc l'introduction de méthodologies de réduction qui par combinaison de calculs acceptables permettent d'étudier de façon fine la dynamique d'ensemble sur des modèles 3D fins multi-étages et potentiellement désaccordés. L'étude des transformations de Fourier séparées des réponses de chaque étage permet, dans un premier temps, de bien comprendre les effets de couplage inter-harmonique liés au couplage inter-disque et au désaccordage. A partir de ce constat, une première méthode utilise les résultats de calculs en symétrie cyclique et à secteur encastré pour construire un modèle de secteur exact pour certains modes dits cibles et de très bonne qualité pour les autres modes. Cette méthode est ensuite étendue au cas multi-étage en construisant des bases de réduction de secteur par combinaison de solutions mono-harmoniques. Les illustrations montrent que la méthodologie proposée permet le traitement de modèles de très grande taille, tout en restant compatible avec une grande richesse de post-traitements (calculs de modes, calculs de réponses forcées, analyses de leur contenu harmonique spatial, répartition d'énergie et effets de localisation...). La méthodologie est enfin étendue à la gestion de modèles paramétrés en vitesse de rotation. L'enrichissement des ensembles de modes cibles par des calculs à trois vitesses permet ainsi une reconstruction rapide de l'évolution des fréquences pour l'ensemble d'un intervalle.

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Schneider, Alexandra Patrizia. "Aerodynamic and aeroelastic investigation of a composite fan for ultra-high-bypass-ratio aircraft engines". Electronic Thesis or Diss., Ecully, Ecole centrale de Lyon, 2024. http://www.theses.fr/2024ECDL0018.

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Les fans modernes à faible vitesse de rotation à très haut taux de dilution (Ultra-High Bypass Ratio, UHBR) opèrent principalement sur la partie plate de la caractéristique de compression, ont des lon-gueurs de l'entrée d'air plus courtes et sont constitués d'aubes en composites flexibles et légères. Ces changements favorisent l'évolution de différents types d'instabilités avec des interactions multi-physiques telles que les vibrations non-synchrones convectives (NSV). Pour permettre de nouvelles avancées technologiques, des données de référence expérimentales sur des géométries représenta-tives sont nécessaires. Dans ce contexte, le projet européen CATANA a été initié à l'Ecole Centrale de Lyon. Le fan ECL5 a été conçu comme une configuration ouverte selon les directives industrielles et testé expérimentalement sur le banc d'essai ECL-B3. Cette thèse présente les résultats expérimen-taux du projet CATANA. L'investigation expérimentale de la configuration de référence ECL5 montre que les objectifs de conception ont été atteints. La machine est opérationnelle sur une large plage de fonctionnement et les performances aérodynamiques au point de design coïncident exactement avec les prédictions numériques. En revanche, les mécanismes d'instabilité sont plus complexes que ceux prédits. Par l'application d'une instrumentation multi-physique synchronisée, l'interaction fluide-structure complexe impliquée est résolue. L'analyse de l'influence des conditions d'entrée et de la symétrie géométrique et structurel du système permet d'identifier la sensibilité des caractéristiques aérodynamiques et structurelles ainsi que du comportement près de la limite de stabilité. L'investiga-tion d'une deuxième configuration de rotor présentant un désaccordage structurel met en lumière l'importance des variations géométriques d'aube à aube. Elles provoquent une asymétrie du champ aérodynamique en tête d'aube et suppriment des perturbations aérodynamiques se propageant de manière cohérente, retardant le NSV. Les résultats présentés dans cette thèse offrent une caractéri-sation complète du fan ECL5 et servent de jeu de données de référence pour la validation des simula-tions numériques
Modern low-speed Ultra-High Bypass Ratio (UHBR) fans operate predominantly on the flat part of the compression characteristic, have shorter intake lengths, and employ flexible, lightweight, composite blades. These changes promote the evolution of different types of instabilities with multi-physical interactions such as convective non-synchronous vibration (NSV). To enable further technological ad-vancements, experimental benchmark data on representative geometries required. Within this con-text, the European project CATANA was initiated at Ecole Centrale de Lyon. The open-test-case fan stage ECL5 was designed, following industrial guidelines, and tested experimentally on the facility ECL-B3. This thesis presents the experimental results of the CATANA project. The experimental investiga-tion of the ECL5 reference configuration shows that all design goals have been reached. The machine is operational in a wide range and aerodynamic performance at design condition is exactly coincident with the numerical prediction. In contrast, instability mechanisms are more complex than predicted by the employed numerical methods. Through application of synchronized multi-physical instrumenta-tion, the involved complex fluid-structure interaction is resolved. The analysis of the influence of in-flow conditions and geometrical and structural system symmetry allows to identify the sensitivity of aerodynamic and structural characteristics and the behavior close to the stability limit. The investiga-tion of a second rotor configuration featuring structural mistuning highlights the importance of geo-metrical blade-to-blade variations. They cause an asymmetry of the aerodynamic field at the blade tip and suppress coherently propagating aerodynamic disturbances resulting in a delayed onset of NSV. The results presented in this thesis provide a comprehensive multi-physical characterization of the ECL5 fan stage and serve as a benchmark data set for the validation of numerical simula-tions

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Mayorca, María Angélica. "Development and Validation of a Numerical Tool for theAeromechanical Design of Turbomachinery". Licentiate thesis, KTH, Energy Technology, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11992.

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The present work presents the development and validation of a numerical tool for aeromechanical design. The tool aims to integrate in a standard and simple manner regular aeromechanical analysis such as forced response analysis and aerodynamic damping analysis of bladed disks.

Mistuning influence on forced response and aerodynamic damping is assessed by implementing existing model order reduction techniques in order to decrease the computational effort and assess results in an industrially applicable time frame. The synthesis program solves the interaction of structure and fluid from existing Finite Element Modeling (FEM) and Computational Fluid Dynamics (CFD) solvers inputs by including a mapping program which establishes the fluid and structure mesh compatibility. Blade row interaction harmonic forces and/or blade motion aerodynamic damping forces are inputs from unsteady fluid dynamic solvers whereas the geometry, mass and stiffness matrices of a blade alone or bladed disk sector are inputs from finite element solvers. Structural and aerodynamic damping is also considered.

Structural mistuning is assessed by importing different sectors and any combinations of the full disk model can be achieved by using Reduced Order Model (ROM) techniques. Aerodynamic mistuning data can also be imported and its effects on the forced response and stability assessed. The tool is developed in such a way to allow iterative analysis in a simple manner, being possible to realize aerodynamically and structurally coupled analyses of industrial bladed disks. A new method for performing aerodynamic coupled forced response and stability analyses considering the interaction of different mode families has also been implemented. The method is based on the determination of the aerodynamic matrices by means of least square approximations and is here referred as the Multimode Least Square (MLS) method.

The present work includes the program description and its applicability is assessed on a high pressure ratio transonic compressor blade and on a simple blisk.

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Mayorca, María Angélica. "Development and Validation of a Numerical Tool for the Aeromechanical Design of Turbomachinery". Licentiate thesis, KTH, Kraft- och värmeteknologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11992.

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In aeromechanical design one of the major rules is to operate under High Cyclic Fatigue (HCF) margins and away from flutter. The level of dynamic excitations and risk of HCF can be estimated by performing forced response analyses from blade row interaction forces or Low Engine Order (LEO) excitation mechanisms. On the other hand, flutter stability prediction can be assessed by calculation of aerodynamic damping forces due to blade motion. In order to include these analyses as regular practices in an industrial aeromechanical design process, interaction between the fields of fluid and structural dynamics must be established in a rather simple yet accurate manner. Effects such as aerodynamic and structural mistuning should also be taken into account where parametric and probabilistic studies take an important role. The present work presents the development and validation of a numerical tool for aeromechanical design. The tool aims to integrate in a standard and simple manner regular aeromechanical analysis such as forced response analysis and aerodynamic damping analysis of bladed disks. Mistuning influence on forced response and aerodynamic damping is assessed by implementing existing model order reduction techniques in order to decrease the computational effort and assess results in an industrially applicable time frame. The synthesis program solves the interaction of structure and fluid from existing Finite Element Modeling (FEM) and Computational Fluid Dynamics (CFD) solvers inputs by including a mapping program which establishes the fluid and structure mesh compatibility. Blade row interaction harmonic forces and/or blade motion aerodynamic damping forces are inputs from unsteady fluid dynamic solvers whereas the geometry, mass and stiffness matrices of a blade alone or bladed disk sector are inputs from finite element solvers. Structural and aerodynamic damping is also considered. Structural mistuning is assessed by importing different sectors and any combinations of the full disk model can be achieved by using Reduced Order Model (ROM) techniques. Aerodynamic mistuning data can also be imported and its effects on the forced response and stability assessed. The tool is developed in such a way to allow iterative analysis in a simple manner, being possible to realize aerodynamically and structurally coupled analyses of industrial bladed disks. A new method for performing aerodynamic coupled forced response and stability analyses considering the interaction of different mode families has also been implemented. The method is based on the determination of the aerodynamic matrices by means of least square approximations and is here referred as the Multimode Least Square (MLS) method. The present work includes the program description and its applicability is assessed on a high pressure ratio transonic compressor blade and on a simple blisk.
QC 20110324
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Libri sul tema "Structural mistuning"

Afolabi, Dare. Effects of mistuning and matrix structure on the topology of frequency response curves. Cleveland, Ohio: Lewis Research Center, 1989.

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Center, Lewis Research, a cura di. Effects of mistuning and matrix structure on the topology of frequency response curves. Cleveland, Ohio: Lewis Research Center, 1989.

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Capitoli di libri sul tema "Structural mistuning"

Kahl, G. "Structural Mistuning and Aerodynamic Coupling in Turbomachinery Bladings". In Unsteady Aerodynamics and Aeroelasticity of Turbomachines, 335–46. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5040-8_22.

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Chan, Y. J., e D. J. Ewins. "The application of robust design strategies on managing the uncertainty and variability issues of the blade mistuning vibration problem". In IUTAM Symposium on the Vibration Analysis of Structures with Uncertainties, 443–56. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-0289-9_32.

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Chen, G., e J. Hou. "Effects of mistuning patterns on forced response for an integrally bladed disk". In Recent Advances in Structural Integrity Analysis - Proceedings of the International Congress (APCF/SIF-2014), 193–97. Elsevier, 2014. http://dx.doi.org/10.1533/9780081002254.193.

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Atti di convegni sul tema "Structural mistuning"

KAZA, KRISHNA, ORAL MEHMED, MARC WILLIAMS e LARRY MOSS. "Analytical and experimental investigation of mistuning in propfan flutter". In 28th Structures, Structural Dynamics and Materials Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1987. http://dx.doi.org/10.2514/6.1987-739.

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SHAH, ASHWIN, V. NAGPAL e C. CHAMIS. "Probabilistic analysis of bladed turbine disks and the effect of mistuning". In 31st Structures, Structural Dynamics and Materials Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1990. http://dx.doi.org/10.2514/6.1990-1097.

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Phan, Hien, e Li He. "Phasing Structural and Aerodynamic Mistuning For Leveraging Aeroelastic Performance". In ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-82168.

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Abstract Although modern turbomachinery design relies on the tuned blades assumption, mistuning (blade-to-blade variations within each blade row) is known to affect significantly the aeroelastic performance. The structural (frequency) mistuning has been studied extensively in the past, while the aerodynamic mistuning starts to attract more attention recently. The question of the present interest is: if/how may the structural and the aerodynamic mistuning interact? The present work uses the fully-coupled fluid-structure simulation method to analyse and elucidate the physical vibration mechanisms of the concurrent structural-aerodynamic mistuned cascade. Three variation patterns, namely alternating, sinusoidal, and random, are used to ensure the generality of the observations. Both the self-excited (flutter) and the forced response vibrations of the mistuned cascade are investigated. The results show that the aerodynamic mistuning has considerable effects on the blade aeroelasticity. More remarkably, it is revealed for the first time that the intentional phasing between the structural and the aerodynamic mistuning may result in significantly different aeroelastic performances. This distinctive behaviour is consistently observed for all studied mistuning patterns of both the flutter and the forced response vibrations. Consequently, the structural-aerodynamic mistuning phasing may be potentially exploited as an extra design variable to leverage the blade aeroelastic performance. In addition, whilst the interaction between the structural and the aerodynamic mistuning exhibits some nonlinearities, a further comparative study also demonstrates that a simple linear superposition can still provide qualitatively consistent results in capturing the trend of mistuned vibratory amplitudes at all possible phase angles. Thus, a simple postprocessing by superimposing two separate aerodynamic and structural mistuned solutions can be very effectively utilized as a starting point for determining the optimum phasing.

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Phan, H. M., e L. He. "ANALYSIS OF STRUCTURALLY AND AERODYNAMICALLY MISTUNED OSCILLATING BLADEROW USING FULLY-COUPLED METHOD". In GPPS Xi'an21. GPPS, 2022. http://dx.doi.org/10.33737/gpps21-tc-330.

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Turbomachinery blades are normally designed based on the tuned idealization. However, blade-to-blade variations will inevitably occur due to manufacturing and assembly processes as well as wearing and tearing during the operation. These variations are denoted as mistuning and it is known that mistuning can affect blade aeroelasticity performances. Although there have been various studies on mistuned cases, they typically are based on reduced methods with corresponding modeling assumptions. Direct fluid-structure coupled solutions of mistuned bladerows are rather limited, thus there is lack of clear and systematic understanding of physical behaviours and mechanisms of mistuned bladerows. The main objectives of the present work are two-folds. First, elucidate the basic vibration kinematics of a mistuned bladerow for both a structural mistuning and an aerodynamic mistuning. Second, examine the effects of mistuning on flutter susceptibility for a specific alternating arrangement. The present results show that firstly a mistuned configuration tends to vibrate with the same frequency and inter-blade phase angle. Vibration amplitudes of the blades however vary with a strong mode localization effect for a structural mistuning. For the concurrent structural-aerodynamic mistuning, the localization is stronger than the standalone structural mistuning case. Secondly, a monotonic increase of the aeroelastic stability with structural mistuning is observed. On the other hand, the aerodynamically mistuned cascade shows a stabilizing effect at a small amount of mistuning but exhibits a destabilizing effect at a large mistuning. At a low reduced frequency condition, there is a striking difference between the aerodynamically tuned and mistuned bladerows. Although the tuned cascade is stable, the aero-mistuned cascade can experience flutter. More remarkably, an additional structural mistuning seems to enhance the localization effect, leading to a larger vibration amplitude of the most unstable blade.

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Stapelfeldt, Sina, e Christoph Brandstetter. "Suppression of Non-Synchronous-Vibration Through Intentional Aerodynamic and Structural Mistuning". In ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-59659.

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Abstract Non-synchronous vibrations (NSV) arising near the stall boundary of compressors are a recurring and potentially safety-critical problem in modern axial compressors and fans. Recent research has improved predictive capabilities and physical understanding of NSV but prevention measures are still lacking. This paper addresses this by systematically studying the influence of aerodynamic and structural mistuning on NSV. This is achieved by incorporating mistuning effects in a validated linear model, in which individual blade modes are modelled as single-degree of freedom mass oscillators coupled by a convected aerodynamic disturbance term. The results demonstrate that both structural and aerodynamic mistuning are effective. While structural mistuning improves stability by preventing aero-structure lock-in, aerodynamic mistuning, which locally reduces the tip blockage, attenuates the aerodynamic disturbance causing NSV. In the latter case, the circumferentially-averaged conditions are shown to be most influential, while the pattern plays a minor role. A combination of moderate aerodynamic and structural mistuning (1%) was also found to be effective. These findings are relevant for design decisions, demonstrating that small blade-to-blade variations can suppress NSV.

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Madden, Andrew, Matthew Castanier e Bogdan Epureanu. "Mistuning Identification of Blisks at Higher Frequencies". In 50th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2009. http://dx.doi.org/10.2514/6.2009-2458.

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WHALEY, P., e J. MACBAIN. "Effects of mistuning on the forced vibration of bladed disks in subsonic flow". In 26th Structures, Structural Dynamics, and Materials Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1985. http://dx.doi.org/10.2514/6.1985-760.

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Lian, Bo, Xiaocheng Zhu e Zhaohui Du. "Mistuning Effects on Aero-Elastic Stability of Civil Transonic Fan Blades". In ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-80613.

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Abstract Flutter seriously affects the safety and reliability of aeroengine. The blade mistuning is inevitable due to machining error and service wear, which has a significant influence on flutter stability. In this paper, the eigenvalue method is used to calculate the aerodynamic damping of transonic fan blades of civil aviation engine at different nodal diameters (NDs) and structural modes. The results show that under the design condition, the first three structural modes of the blade are aero-elastic stable for each ND, and the aerodynamic damping gets the minimum at ND1 for the first bending mode. As the back pressure deviates from design condition towards stall, the aerodynamic damping obviously decrease and even negative aerodynamic damping occurs at normalized mass flow rate of 0.930. Six kinds of mistuning patterns are considered based on the eigenvalue method, divided into two categories: structural mistuning and aerodynamic mistuning, where structural mistuning includes alternate mistuning, sinusoidal mistuning and random mistuning. The alternate mistuning has better improvement on flutter suppression than the sinusoidal mistuning with the same frequency offset, though further increasing the amount of mistuning cannot provide extra aero-damping when the frequency offset reaches a critical value of 7%. For the aerodynamic mistuning, the improvement of aero-damping is limited in comparison with the structural mistuning, especially for the random mistuning through Monte Carlo simulations. Based on the analysis of eigenvectors, the single blade aerodynamic mistuning breaks the periodic pattern in travelling wave mode, which tends to make the aero-elastic systems stable. While the symmetry group mistuning maintains the periodicity and destabilizes the aero-elastic system.

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Gillaugh, Daniel, Alexander Kaszynski, Jeffrey M. Brown, David A. Johnston e Joseph C. Slater. "Accurate Strain Gage Limits Through Geometry Mistuning Modeling". In 58th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2017. http://dx.doi.org/10.2514/6.2017-0865.

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Sladojevic´, I., E. P. Petrov, M. Imregun e A. I. Sayma. "Forced Response Variation of Aerodynamically and Structurally Mistuned Turbo-Machinery Rotors". In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90948.

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The paper presents the results of a study looking into changes in the forced response levels of bladed disc assemblies subject to both structural and aerodynamic mistuning. A whole annulus FE model, representative of a civil aero-engine fan with 26 blades was used in the calculations. The forced response of all blades of 1000 random mistuned patterns was calculated. The aerodynamic parameters, frequency shifts and damping, were calculated using a three-dimensional Reynolds-averaged Navier-Stokes aero-elasticity code. They were randomly varied for each mistuning pattern, with the assumption that the system would remain stable, i.e. flutter would not occur due to aerodynamic mistuning. The results show the variation of the forced response with different types of mistuning, with structural mistuning only, with aerodynamic mistuning only and with both structural and aerodynamic mistuning.

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