Modélisation du fluage des superalliages monocristallins : effets d'anisotropie et de microstructure

Abstract : The creep of high pressure turbine blades is a critical issue for the certification of a helicopter turboshaftengine. Due to their excellent mechanical properties at high temperatures, nickel-based single crystalsuperalloys are widely used for the manufacturing of these blades. For these components, certificationrequirements include non-isothermal conditions based on the mixing of different operating conditions (cruise,take-off …), conditions much more damaging than standard isothermal conditions used conventionally inlaboratories.The aim of this thesis is to get a better prediction of the mechanical behavior and creep life of thesematerials during certification procedure of helicopter turboshaft engines under which creep is the main lifelimiting factor. For this, a new constitutive modeling approach has been used for the creep behavior and damageevolution. This model includes the impact of microstructure evolutions and the impact of the crystal anisotropyon the mechanical behavior and creep life.The first objective was to study the impact of crystalline anisotropy on the isothermal creep propertiesand its impact in terms of non-isothermal creep at high temperatures.The second objective was to propose a mechanical modeling of the creep behavior under complex loads pathsusing POLYSTAR model, a crystal plasticity model including a coupling between creep behavior and creepdamage and new internal variables explicitly representing rapid changes in the precipitation state.
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Julien Ghighi. Modélisation du fluage des superalliages monocristallins : effets d'anisotropie et de microstructure. Autre. ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2013. Français. ⟨NNT : 2013ESMA0005⟩. ⟨tel-00823045⟩

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