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Etude et modélisation du comportement mécanique de panneaux de structure soudés par friction-malaxage (FSW)

Abstract : The Friction Stir Welding (FSW) process generally induces a critical hardness decrease inside the welded joint. To design aeronautical structure welded by FSW in fatigue, it is then necessary to know the impact of this hardness drop on the constitutive behaviour of the junction. In this study, the hardening structural aluminium alloy 2198-T8 is considered.A fatigue lifetime assessment loop of a welded structure is implemented. It integrates a calculations and experiments coupling which is used to model the structure’s mechanical behaviour. The gradient mechanical behaviour of the weldment is initially studied.Monotonic and cyclic mechanical tests are carried out to room temperature. Digital Image Correlation (DIC) is used to measure local displacement fields around the junction. Based on this experimental data, mechanical parameters for a constitutive model are identified on a volume element, zone by zone across the welded joint. In parallel, a quantification of the T1 (Al2CuLi) strengthening precipitates is realized in different region of the joint with a Transmission Electron Microscope. A connection between the microstructure evolution and the mechanical parameters is researched. The gradient mechanical behaviour of the joint is assessed on a 3D structure by Finite Element Analysis. Furthermore, fatigue tests are carried out on uniaxial and multiaxial loadings welded specimen. Thanks to the mechanical behaviour model and the fatigue lifetime measured, a damage model is used to predict the fatigue lifetime and the crack initiation zone for a welded structure which is subjected to higher multiaxial loads.
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Submitted on : Tuesday, April 30, 2019 - 10:00:49 AM
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  • HAL Id : tel-02115123, version 1


Xavier Truant. Etude et modélisation du comportement mécanique de panneaux de structure soudés par friction-malaxage (FSW). Matériaux. Université Paris sciences et lettres, 2018. Français. ⟨NNT : 2018PSLEM043⟩. ⟨tel-02115123⟩



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