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Étude de l'amorçage et de la propagation de fissures de fatigue internes courtes en régime gigacyclique dans un alliage d'aluminium de fonderie

Abstract : Casting allows the mass production of parts with complex geometry at a low cost. However, defectsinherent to the manufacturing process (pores, shrinkages, etc.) are natural stress concentrators and act as amajor cause of fatigue crack initiation. The defect position from the part surface influences its harmfulnessand the fatigue strength of the component. Initiation and propagation mechanisms of internal fatiguecracks are currently less studied than those emanating from surface defects. The purpose of this work is tocharacterize short internal fatigue crack initiation and propagation mechanisms and kinetics in the A357-T6 cast aluminium alloy. An experimental testing device allowing the observation of internal fatigue crackinitiation and propagation by in-situ synchrotron tomography and infrared thermography was developed.The propagation kinetics of internal cracks were quantif ied through tomographic data processing. Stressintensity factor ranges were calculated by f inite element analysis along the crack fronts assuminghomogeneous material. In addition, the microstructure of the specimens was characterized by diffractioncontrast tomography (DCT) which allowed polycrystalline aggregates simulation in order to betterunderstand the interactions between cracks and microstructure. Finally, thanks to f inite elementthermomechanical simulations, the surface temperature increases of the specimens, measured by infraredthermography, were correlated to the 3D evolution of the crack fronts observed by tomography.
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https://pastel.archives-ouvertes.fr/tel-03076371
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Submitted on : Wednesday, December 16, 2020 - 2:12:11 PM
Last modification on : Thursday, December 17, 2020 - 3:35:20 AM

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  • HAL Id : tel-03076371, version 1

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Alexandre Messager. Étude de l'amorçage et de la propagation de fissures de fatigue internes courtes en régime gigacyclique dans un alliage d'aluminium de fonderie. Science des matériaux [cond-mat.mtrl-sci]. HESAM Université, 2020. Français. ⟨NNT : 2020HESAE032⟩. ⟨tel-03076371⟩

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