Smart-GFEM for welding simulation

In this paper, a new and efficient method for welding simulation is proposed. This method, known as Smart-GFEM introduces in a GFEM framework an enrichment function which is capable of adapting the approximation space optimally. The enrichment function can be seen as a computational vademecum which depends on technological and material parameters of the process and it is completely computed off-line. In this work we present how to perform the thermal analysis of the welding and a general strategy to address the mechanical analysis

Etablissement de la texture au cours du soudage TIG d’alliages austénitiques : soudures réelles et numériques

The structure prediction of metallic alloys during a welding or additive manufacturing process is the key point for the joining’s properties. In addition to the welding parameters (or additive manufacturing), the base metal microstructure, chemical homogeneity and crystallographic structure are numerous factors playing an important role on the final microstructure and texture development. Few studies are available in this way. This work purposes a focus on the microstructure establishment during the welded zone solidification during Gas Tungsten Arc Welding. The materials investigated are nickel – chromium – iron austenitic alloys. The grain selection is tracked in a real weld and a texturation criteria is proposed. The following data’s are compared to the properties of the numerical weld experience. The conclusion suggests that is necessary to improve the knowledges in the grain selection mechanism in order to produce numerical welding microstructure in good accordance with real microstructure welding.La prédiction de la structure des alliages métalliques durant une étape de soudage ou de fabrication additive est un point clef du développement de ces procédés et des propriétés des assemblages. En plus des paramètres de soudage (ou de fabrication additive), la microstructure du métal de base, son homogénéité chimique et sa nature cristallographique sont autant de facteur jouant un rôle sur l’établissement final des microstructures et des textures pour lesquels peu d’études détaillées sont disponibles. Une description précise de l’établissement des microstructures de solidification lors du soudage TIG d’alliage austénitique nickel-chrome-fer est réalisée dans ce travail. La sélection des grains dans la soudure est suivie dans une soudure réelle. Un critère de texturation est proposé et les données sont comparées aux textures simulées d’où il ressort l’importance d’augmenter la connaissance des mécanismes de sélection de grains pour espérer modéliser encore plus fidèlement les propriétés microstructurales et de texture générées par le soudage

Evaluation of distortions in laser welded shipbuilding parts using local-global finite element approach

In recognition of the differences of scale between the welding pool and the heat affected zone along the welding line on one hand, and the overall size of the components being welded on the other, a local-global finite element approach was developed for the evaluation of distortions in laser welded shipbuilding parts. The approach involves the tandem use of a 'local' and a 'global' step. The local step involves a three-dimensional finite element model for the simulation of the laser welding process using the Sysweld finite element code, which takes into account thermal, metallurgical, and mechanical aspects. The simulation of the laser welding process was performed using a non-linear heat transfer analysis, based on a keyhole formation model, and a coupled transient thermomechanical analysis, which takes into account metallurgical transformations using the temperature dependent material properties and the continuous cooling transformation diagram. The size and shape of the keyhole used in the local finite element analysis was evaluated using a keyhole formation model and the Physica finite volume code. The global step involves the transfer of residual plastic strains and the stiffness of the weld obtained from the local model to the global analysis, which then provides the predicted distortions for the whole part. This newly developed methodology was applied to the evaluation of global distortions due to laser welding of stiffeners on a shipbuilding part. The approach has been proved reliable in comparison with experiments and of practical industrial use in terms of computing time and storage

Presentation du projet MUSICAS - Premiers résultats du projet collaboratif FUI - MUSICAS

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