Modélisation Numérique de la tenue mécanique des soudures laser avec aciers THR

L'allègement en masse des véhicules, reste un enjeu majeur pour les constructeurs automobiles. Une des solutions à ce problème est l'utilisation d'aciers THR (Très Haute Resistance), d'épaisseurs de nuances et de caractéristiques mécaniques souvent différentes. L'assemblage est fait par soudage. Le problème dans l'utilisation de ces aciers THR et la soudabilité et la tenue de soudure. Dans cette étude, nous nous intéresserons à la modélisation numérique de la Zone Fondue et la Zone Affectée Thermiquement , Nous allons décrire un modèle numérique qui prend en compte la micro duret

Modélisation théorique et numérique de la formabilité des flans aciers raboutés laser - Validation expérimentale

COMPIEGNE-BU (601592101) / SudocSudocFranceF

A complete heat and fluid flow modeling of keyhole formation and collapse during spot laser welding

International audienc

A new approach to compute multi-reflections of laser beam in a keyhole for heat transfer and fluid flow modelling in laser welding

International audienceIt is widely accepted that laser reflections can play a critical role during keyhole laser welding. The energy concentration, the mask effects and the laser polarization can directly affect the molten pool dynamic. In this paper a new approach to compute laser reflections is proposed which consists of treating laser under its wave form by solving Maxwell's equations. The method has the advantage to be easily coupled with heat transfer and fluid flow equations and can be immediately transposable in any 2D, 2D axi or 3D configurations. The reliability and limits of this approach are discussed through different numerical examples. The complete model takes into account the three phases of the matter: the vaporized metal, the liquid phase and the solid base. To predict the evolution of these three phases, coupled equations of energy, continuity, momentum and Maxwell are solved. The liquid/vapour interface is tracked using the level-set method. All these physics are solved simultaneously with the commercial code COMSOL Multiphysics®. The calculated temperatures, velocities and free surface deformation are analysed. Examples of simulations leading to the formation of porosity are also presented. Finally, melt pool shapes evolution are compared to experimental macrographs

A complete heat and fluid flow modeling of keyhole formation and collapse during spot laser welding

International audienc

A complete model of keyhole and melt pool dynamics to analyze instabilities and collapse during laser welding

International audienceA complete modeling of heat and fluid flow applied to laser welding regimes is proposed. This model has been developed using only a graphical user interface of a finite element commercial code and can be easily usable in industrial R&D environments. The model takes into account the three phases of the matter: the vaporized metal, the liquid phase, and the solid base. The liquid/vapor interface is tracked using the Level-Set method. To model the energy deposition, a new approach is proposed which consists of treating laser under its wave form by solving Maxwell's equations. All these physics are coupled and solved simultaneously in Comsol Multyphysics®. The simulations show keyhole oscillations and the formation of porosity. A comparison of melt pool shapes evolution calculated from the simulations and experimental macrographs shows good correlation. Finally, the results of a three-dimensional simulation of a laser welding process are presented. The well-known phenomenon of humping is clearly shown by the model

Guidelines in the experimental validation of a 3D heat and fluid flow model of keyhole laser welding

During the past few years, numerous sophisticated models have been proposed to predict in a self-consistent way the dynamics of the keyhole, together with the melt pool and vapor jet. However, these models are only partially compared to experimental data, so the reliability of these models is questionable. The present paper aims to propose a more complete experimental set-up in order to validate the most relevant results calculated by these models. A complete heat transfer and fluid flow three-dimensional (3D) model is first proposed in order to describe laser welding in keyhole regimes. The interface is tracked with a level set method and fluid flows are calculated in liquid and gas. The mechanisms of recoil pressure and keyhole creation are highlighted in a fusion line configuration chosen as a reference. Moreover, a complete validation of the model is proposed with guidelines on the variables to observe. Numerous comparisons with dedicated experiments (thermocouples, pyrometry, highspeed camera) are proposed to estimate the validity of the model. In addition to traditional geometric measurements, the main variables calculated, temperatures, and velocities in the melt pool are at the center of this work. The goal is to propose a reference validation for complex 3D models proposed over the last few years