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Simulation numérique des procédés thermomécaniques dans une approche couplant les écoulements du fluide avec les déformations du solide : application au soudage laser et à la fusion d'un lit de poudre

Abstract : In the current study, numerical methods are developed to simulate the laser welding and the melting of a powder bed while taking into account their complexity. These methods are based on a new strategy of fluid/solid coupling. They allow to simulate the formation of the melted zone by taking into account the fluid flows through the two effects of the surface tension ("curvature effect" and "Marangoni effect") and the buoyancy. An ALE approach is used to follow the evolution of the free surface. The interaction between the fluid flows in the molten pool and the deformations in the solid part is ensured by imposing the velocities of the solid nodes during the fluid computation. Several analytical and numerical tests are used to validate the formulation of the fluid problem and the new strategy of fluid/solid coupling. The results confirm the efficiency and the robustness of the numerical methods developed.As first application, a thermal-fluid-mechanical simulation of laser welding is carried out. The results obtained show a good correlation with the literature results. The second application consists of simulating the melting of a powder bed. It allows to take into account the shrinkage of the powder layer after melting, and the change of the thermalphysical properties depending on the material state (powder or compact).Although the study consisted mainly in developing numerical methods, it also includes an experimental part. Specific set-up has been done using different instrumentation tools. These tools allow to better understand the physical phenomena involved during the two processes. In a second step, a database (morphology of molten pool, temperature and residual stresses) on welded parts is constituted. This database will allow in a subsequent work to carry out a global validation process of the proposed numerical methods.
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Yassine Saadlaoui. Simulation numérique des procédés thermomécaniques dans une approche couplant les écoulements du fluide avec les déformations du solide : application au soudage laser et à la fusion d'un lit de poudre. Mécanique des fluides [physics.class-ph]. Université de Lyon, 2019. Français. ⟨NNT : 2019LYSES005⟩. ⟨tel-02467818⟩

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