Etude numérique de l'amorçage et de la propagation de fissures de fretting

Abstract : The blade-disc fixings of an aircraft engine are subjected to complex loadings composed by a high pressure and oscillatory relative motions during operation. This corresponds to a loading type called fretting. The appearance of fretting phenomenon reduces the fatigue resistance of structuresand generates damage which, in various forms (wear, rupture), can lead to a loss of functionality. In order to ensure the reliability of turbo-engines, the improvement of the models for estimating life prediction is then needed.This thesis is devoted to the study of crack initiation and crack micro-propagation, in the so called "short crack domain", where they are still in interaction with the microstructure. At first, a multiaxial fatigue model is proposed. It predicts the location and the number of cycles to initiation, taken into account the possible surface treatments. Then, a numerical study of the direction and the kinetics of crack propagation is performed with consideration to the influence of the material microstructure. A crystal plasticity model is used, that takes into account all the relevant families of crystallographic slip systems. The crack plane is assumed to be one of the crystallographic plane where the plastic slip is the most intense. The crack propagation rate decreases when approaching grain boundaries, that is qualitatively consistent with the experimental observations.
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Lingtao Sun. Etude numérique de l'amorçage et de la propagation de fissures de fretting. Autre. Ecole Nationale Supérieure des Mines de Paris, 2012. Français. ⟨NNT : 2012ENMP0033⟩. ⟨pastel-00755695⟩

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