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Comportement dynamique d'un redresseur de turbomachine aéronautique : effets du désaccordage

Abstract : The fatigue design of aircraft engines components such as bladed disks passes necessarily by their dynamic analysis. In order to be more predictive, the geometric and material dispersions due to the manufacturing tolerances, sources of mistuning, are taken into account and make the assumptions of cyclic symmetry be not applicable anymore. The mistuning has a non-negligible effect on the vibratory behavior of the bladed disks by localizing an important part of the energy on a reduced number of blades which can lead to a premature vibratory fatigue of the component. This phenomenon of modal localization is conditioned on the one hand, by the coupling stiffness between the blade sand the disk and on the other hand, by the rate of the mistuning. The stator vanes are located in the various stator stages of the aircraft engines. Their role is to straighten the air flow from the rotors located upstream to obtain the maximum thrust at the engine output. A new technology consists in considering a stator vane as an assembly of many independant monoblock multi-blades sectors. So, the cyclic symmetry conditions cannot be employed anymore even in the tuned case. The vibratory behaviour of a tuned stator vane sector is characterized by a high modal density in some frequency ranges, which corresponds to the blade bending and torsion modes. This phenomenon results in a high sensitivity of these modes to the mistuning within the stator vane. The main objective of this thesis is to develop a strategy allowing to predict the vibratory behavior of monoblock sectored mistuned stator vanes in a robust way. Indeed, by determining the most sensitive areas of a given sector with the maximum accuracy, the engineering departments will be able to optimize the strain gauges positioning on the prototypes stator vanes. In order to reach this objective, several sensitivity to mistuning numerical studies and some component tests were performed. They allowed to have first results about the relative predictable errors that could be done, depending on the mistuning. Then, the spectral stochastic finite element method has been implemented on a simplified model in order to determine its random eigen modes projected on a basis composed by orthogonal polynomials and to deduce the random forced response by modal superposition. The polynomial chaos basis has been chosen thanks mainly to the low computation time in comparison to Monte Carlo simulations and to the accuracy of the obtained results. At last, the stochastic methodology has been validated on an industrial finite element model of a sectored stator vane provided by SNECMA by means of model reduction methods such as Craig-Bampton. An optimum gauge positioning strategy has been proposed ;it represented the main industrial deliverable expected at the end of the thesis.
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Submitted on : Wednesday, November 21, 2012 - 10:42:34 AM
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  • HAL Id : tel-00755391, version 1



Amadou Ciré Sall. Comportement dynamique d'un redresseur de turbomachine aéronautique : effets du désaccordage. Autre. Ecole Centrale de Lyon, 2011. Français. ⟨NNT : 2011ECDL0045⟩. ⟨tel-00755391⟩



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