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Apports à la compréhension du soudage FSW hétérogène d’alliages d’aluminium par une approche expérimentale et numérique

Abstract : The lightweight structures optimisation is one of the main topics in transportation industry. It can be achieved by optimisation of materials as well as induced assembly process. As a solid-state process, Friction Stir Welding (FSW) allows to produce dissimilar materials joining while avoiding fusion defects. This work focused on the dissimilar welding of aluminium alloys from 2xxx (Al-Cu-Mg-Ag) and 7xxx (Al-Zn-Mg) series in an industrial context. Joints characterizations were conducted at multiple scales to understand parameters impact on material flow, joint morphology, and performances. They have shown large heterogeneities in the microstructure as well as the global and local mechanical behaviour. Whatever the welding parameters used, good mechanical performance has been reached. A specific softened zone has been detected in the 7xxx alloy’s HAZ which caused fracture during transverse tensile test. Significant metallurgical evolution induced by thermal cycles mainly explains these phenomena.On the other hand, simulation works were also conducted to simulate the welding process in similar material configuration. The finite elements model integrates, for the first time, the real and complex tool design (thread, flats…). Complex geometry can be used by coupling with a specific moving mesh technique. This numerical development completely overcomes the consequent mesh distortion often encountered in FSW simulation. The current model presents good sensitivity and robustness for several welding conditions and materials. It also demonstrates an excellent correlation between experimental and numerical thermal fields while revealing the predictive aspect of the model.
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Hugo Robe. Apports à la compréhension du soudage FSW hétérogène d’alliages d’aluminium par une approche expérimentale et numérique. Autre. Université de Lyon, 2017. Français. ⟨NNT : 2017LYSEE005⟩. ⟨tel-01755099⟩

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