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Caractérisation expérimentale et numérique du comportement d'assemblages soudés soumis à des sollicitations quasi-statiques et dynamiques

Abstract : When subjecting a metallic structure to an impact or a crash, two kinds of fracture can be seen to appear jointly: rupture initiated in the sheet and rupture located on the joint areas. Depending on the type of transportation mean and materials used for the design of the vehicles, structures can be assembled either by rivets, spotwelds or weld beads. To prevent the failure of these joints, which can lead to a complete and particularly brutal structural disarticulation, their behaviour must be studied. The aims of this work are to measure the response of a spotwelded joint under quasi-static and dynamic loadings, to determine the load velocity influence on its behaviour, to understand how and where the failure starts and propagates in the assembly. Original tests, which make it possible to mix loading directions and to control the boundary conditions around the spotweld and the deformation of the metal sheet, were developed and performed under quasi-static and dynamic loadings on an hydraulic jack in a range of velocities from 5mm/mn to 1m/s. A new device was also developed to test spotwelds in pure tensile direction on SHB. This device uses SHB in a no-direct tensile testing configuration and a velocity of 13 m/s is reached. Load-displacement responses, failure mechanisms and topographies were obtained. To complete experiments, a fine numerical model of the spotweld was performed. The elastoplastic properties of the HAZ were experimentaly identified using some materials having undergone heat treatments. This model allows us to understand where the deformations are located
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Pierre Mahelle. Caractérisation expérimentale et numérique du comportement d'assemblages soudés soumis à des sollicitations quasi-statiques et dynamiques. Mécanique [physics.med-ph]. Université de Valenciennes et du Hainaut-Cambrésis, UVHC, (France), 2007. Français. ⟨NNT : 2007VALE0037⟩. ⟨tel-02998211⟩

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