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Détermination rapide des propriétés en fatigue à grand nombre de cycles à partir de mesures d’auto-échauffement sous sollicitations cycliques : application aux alliages métalliques pour turboréacteurs aéronautiques

Abstract : In the context of fatigue design of aircraft engine parts, the fatigue properties of materials must be correctly determined at different conditions of temperature and loading ratio. However, the fatigue characterisation could be difficult using standard methods, particularly because of the fatigue scatter, and requires a lot of specimens. In order to reduce the time and cost of fatigue characterization (especially for high temperature testing), the purpose of this study is to adapt the self-heating method for high temperature tests. This method has been developed on a wide range of steels at room temperature and used on several materials. The challenge of this study is to be able to measure a low rise of the specimen temperature, the self-heating under cyclic loadings, in a high temperature environment. In this study, the self-heating method is applied at different temperatures on two aeronautical alloys for engines applications: up to 350°C on a titanium alloy, Ti-6Al-AV (TA6V), widely used in aircraft industry, and up to 950°C on a nickel-based single crystal, AM1, used for turbine blade applications. The fatigue properties of the Ti-6Al-4V are determined from the self-heating curves using a two-scale probabilistic model. It describes the activation of dissipative phenomena under cyclic loadings, which allow the fatigue properties determination. Indeed, the fatigue limit and the fatigue scatter are directly identified on the self-heating curve, so using only one specimen per condition. These results are really promising in order to reduce the time and cost of fatigue characterization at high temperature. Moreover, simulated based investigations are performed in this study in order to evaluate the fatigue scatter identification. Classical fatigue tests (Staircase procedures) are simulated and analysed to quantify the identification uncertainties. The results are compared to the two-scale probabilistic model. The self-heating behaviour of the single crystal superalloy is different from other tested materials. Thus, the two-scale probabilistic model is not suitable to analyse the experimental observations. Thus, additional studies are presented in order to provide elements of understandings, knowing the particularities of this class of material. However, the selfheating is well detected at high temperature (up to 950°C), which means dissipative phenomena are well activated. Thus, interesting perspectives exist in order to study the fatigue properties of single crystal superalloy using self-heating measurements.
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Submitted on : Monday, October 4, 2021 - 4:52:11 PM
Last modification on : Tuesday, December 7, 2021 - 11:42:02 AM

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  • HAL Id : tel-03364460, version 2

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Vincent Roué. Détermination rapide des propriétés en fatigue à grand nombre de cycles à partir de mesures d’auto-échauffement sous sollicitations cycliques : application aux alliages métalliques pour turboréacteurs aéronautiques. Matériaux et structures en mécanique [physics.class-ph]. ENSTA Bretagne - École nationale supérieure de techniques avancées Bretagne, 2020. Français. ⟨NNT : 2020ENTA0004⟩. ⟨tel-03364460v2⟩

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