Contribution à la modélisation et à la simulation numérique du soudage par friction et malaxage

Abstract : The friction stir welding is a process for assembling a semisolid phase parts. The weld seam is achieved by a revolution tool consists of the shoulder and the pin. This process converts the mechanical energy into heat energy by friction of the tool with the parts to be joined.This thesis is a contribution to the experimental modeling and numerical simulation of this process in order to provide models to assist in understanding the thermal and mechanical phenomena and interactions between the welding parameters. Experimental studies are used for the characterization of the material flow with markers and to optimize the process parameters. The effect of tool geometry (cylindrical pin or tool with flats) on the material flow during welding is studied. To represent the flow geometry and predict the thermal and mechanical fields in the steady state, CFD models are adopted in this thesis. Two thermomechanical models are developed: (1) first numerical model is used to study the thermomechanical behavior and flow during FSW. FLUENT is employed to solve the coupled thermal and fluid flow equations. A behavior law depending on temperature and strain rate is used and a discussion on the contact conditions between the tool and the workpieces is presented. The results of the flow are compared with those obtained experimentally in the followed case of trajectories copper particles. (2) A second original model based on iterative procedure is implemented to welding large plates. To take account the correctly thermal boundary conditions, a thermomechanical model built around the welding tool and coupled with a thermal model for the rest of the area studied. This model allows taking into account the transfer of heat in the tool and in the backing-bar. Thermal cycles and the viscosity range for two aluminum alloys (AA7020-T6 and AA6061-T3) are successfully analyzed and compared with experimental results. The loads and torque welding are calculated numerically and validated in the literature.
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Ammar Guedoiri. Contribution à la modélisation et à la simulation numérique du soudage par friction et malaxage. Autre. Ecole nationale supérieure d'arts et métiers - ENSAM, 2012. Français. ⟨NNT : 2012ENAM0060⟩. ⟨pastel-00842393⟩

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