A mechanical behavior law for the numerical simulation of the mushy zone in welding

The aim of this work is to propose a mechanical behavior law dedicated to the mushy zone located between the solid phase and the weld pool in welding. The objective is to take into account of the influence of the mushy zone in the simulation of welding in order to improve the computation of induced effects such as residual stresses

Simulation of material consequences induced by fsw for a trigonal pin

The numerical simulation of Friction Stir Welding processes involves the coupling of a solid mechanics approach under large strains and large strain rates and heat transfer. The eulerian formalism leads to specially efficient finite element simulations of the matter flow under steady conditions. But with such a formulation, the calculation of the consequences induced by the stirring on the material (stirred state, microstructure, etc.) requires the coupling of advection equations for integrating the associated state variables. In this paper, a moving mesh strategy is proposed for the numerical simulation of Friction Stir Welding and material consequences, for complex pin’s geometries. The numerical processing is detailed and the efficiency of the proposed method is discussed on a Friction Stir Welding simulation of 7075 series aluminum alloy

Vademecum-based GFEM (V-GFEM): optimal enrichment for transient problems

This paper proposes a generalized finite element method based on the use of parametric solutions as enrichment functions. These parametric solutions are precomputed off-line and stored in memory in the form of a computational vademecum so that they can be used on-line with negligible cost. This renders a more efficient computational method than traditional finite element methods at performing simulations of processes. One key issue of the proposed method is the efficient computation of the parametric enrichments. These are computed and efficiently stored in memory by employing proper generalized decompositions. Although the presented method can be broadly applied, it is particularly well suited in manufacturing processes involving localized physics that depend on many parameters, such as welding. After introducing the vademecum-generalized finite element method formulation, we present some numerical examples related to the simulation of thermal models encountered in welding processes

Étude de l'austénisation de l'acier martensitique 15-5PH lors de cinétiques thermiques rapides caractéristiques de l'usinage

En usinage, la simulation nécessite des modèles métallurgiques adaptés à des cinétiques thermiques très rapides. Les cinétiques d'austénisation du 15-5PH sont donc mesurer pour des chauffes de 6°C.s-1 à 11000°C.s-1 à partir d'essais de dilatométrie. Puis, les paramètres du modèle de Leblond ont été identifiés pour tester diverses combinaisons (vitesse de chauffe, de refroidissement et température maximale). Finalement, la prise en compte des changements de phase en usinage ne se résume pas à la prévision d'une température maximale atteinte comparée à une température de début de transformation

In-plane/out-of-plane separated representations of updated Lagrangian descriptions of viscoplastic flow models in plate domains

A new efficient updated Lagrangian strategy for numerical simulations of material forming processes is presented. The basic ingredient is the tensorial decomposition of the velocity field into a finite sum of in-plane and an out-of-plane components, giving rise to an equivalent computational complexity of some two-dimensional problems and some one-dimensional ones (therefore, much less than the true three-dimensional complexity of the original problem). This is efficiently achieved by using Proper Generalized Decomposition (PGD) techniques, which are here employed in an updated Lagrangian framework for the very first time. This updated Lagrangian nature of the method needs the use of a robust numerical integration technique (in this case, the Stabilized Conforming Nodal Integration has been chosen) for addressing the highly distorted projected meshes. The resulting strategy is of general purpose, although it is especially well suited for addressing models defined in plate or shell (in general, parallelepipedic) domains. The basics of the just-developed method are shown, together with some numerical examples to show the potential of the technique

Numerical Simulation of the Molten Pool of a Powder Bed

In this study, a numerical approach is developed to simulate the molten pool formation during the melting of a powder bed. It is based on a fluid formulation that allows taking into account the dynamics in the molten pool through the two effects of surface tension (including both 'curvature effect' and the 'Marangoni effect') and buoyancy. Additionally, the free surface is considered using an ALE method. The shrinkage of the powder layer after its melting and the change of the thermo-physical properties depending on the material state (powder or compact) are also modeled. As an application, a 3D thermo-fluid simulation of the powder bed melting is carried out. It is found that the powder layer porosity has a great effect on the molten pool morphology