Morgan Dal

Ecole Nationale Supérieure d'Arts et Métiers | ENSAM · Laboratoire Procédés et Ingénierie en Mécanique et Matériaux (PIMM)

Thermo-hydrodynamic phenomena which take place during laser welding or additive manufacturing processes as laser powder bed fusion, have been investigated for years, but recent advances in X-ray images and in situ analysis have highlighted new findings that are still under debate. Conduction-to-keyhole transition, and more broadly, keyhole dynamics...

Laser welding of pure copper and its alloys is a challenging process with a growing industrial interest due to the latest development in the field of electric mobility. The difficulties are mainly related to the material’s high thermal conductivity and a poor absorptivity of few percent at the classical IR laser (YAG). It is also well known that su...

A 1 kW CW green laser source operating at 515 nm was used to investigate the absorptivity of pure copper powder beds and pure copper substrates. Various interaction regimes were considered, ranging from the solid and/or powder layers, to the liquid state and up to the deep penetration keyhole regime. Reflectance measurements were carried out using...

Directed energy deposition (DED) with laser and powder allows the manufacturing of multi-metallic near net shape structures, with control over the feedstock composition and intense liquid mixing of elements. To better understand the multi-physical aspects of the melt pool and strive toward local composition prediction, a 3D finite element model of...

Purpose : During thermal laser processes, heat transfer and fluid flow in the melt pool are primary driven by complex physical phenomena that take place at liquid/vapor interface. Hence, the choice and setting of front description methods must be done carefully. Therefore, the purpose of this paper is to investigate to what extent front description...

A Finite element model is developed with a commercial code to investigate the keyhole dynamics and stability at keyhole threshold, a fusion regime characteristic to laser microwelding or to Laser Powder Bed Fusion. The model includes relevant physics to treat the hydrodynamic problems—surface tension, Marangoni stress, and recoil pressure—as well a...

The Laser Metal Deposition (LMD) process is an additive manufacturing method, which generates 3D structures through the interaction of a laser beam and a gas/powder stream. The stream diameter, surface density and focal plan position affect the size, efficiency and regularity of the deposit tracks. Therefore, a precise knowledge of the gas/powder s...

Although metal vaporisation has been observed in several laser processes such as drilling or welding, vapour plume expansion and its induced side effects are not fully understood. Especially, this phenomenon is garnering scientific and industrial interest since recent investigations in laser powder bed fusion (LPBF) have designated metal vaporisati...

Laser Beam Melting (LBM) is currently garnering industrial attention and many numerical researches have been carried out in order to understand the physics behind the process. However, due to the gap between the grain scale (micrometres) and the bead scale (millimetres), current state-of-the-art multi-physical models are computationally expensive a...

As the layer additive manufacturing processes exhibit currently a huge growth in industrial applications, more and more simulation researches have been carried out recently. Nevertheless, the scale factor between the grains sizes (several tens of micrometers) and the piece sizes (couple of centimeters at least) leads to the use of too large numeric...

Interest has recently emerged for the manufacture of aeronautical parts by Laser Beam Melting (LBM) additive process. This energy efficient process can for instance be used to build complex geometries, which cannot be made with traditional processes. However, complex phenomena occur during powder melting and track development : vaporisation phenome...

The presence of defects like gas bubble in fabricated parts is inherent in the selective laser sintering process and the prediction of bubble shrinkage dynamics is crucial. In this paper, two artificial intelligence (AI) models based on Decision Trees algorithm were constructed in order to predict bubble dissolution time, namely the Ensemble Bagged...

Un modèle numérique de vaporisation de l'Inconel 718® sous faisceau laser est proposé afin d'étudier l'effet de la nature de l'atmosphère ambiante - argon ou hélium - sur les écoulements de gaz induits en fabrication additive par fusion de lits de poudres (LBM). Ce modèle développé sous COMSOL Multiphysics® montre que si sous hélium l'aspiration gé...

The increase of process simulations in industry leads to the need of accurate knowledge of material thermal properties. As the determination of liquid metal properties is quite difficult, this article presents an experimental setup and a technique to estimate the surface tension and the density of several refractory metals (Nb, Ta, and W) and their...

As the Layer Beam Melting (LBM) technology - also referred to as Selective Laser Melting (SLM) - is garnering industrial interest, understanding of the associated physical phenomena is necessary to control the process. Particularly, metal vaporisation generates melt pool instabilities and collateral effects - powder bed denudation or ejection of me...

The authors propose an analysis of the effect of various operating parameters on the keyhole depth during laser welding. The authors have developed a model that uses the analysis of the thermal field obtained in 2D geometry, which is mainly defined by the characteristic Peclet number. This allows us to show that the dependence of the aspect ratio R...

Selective Laser Sintering process is one of the additive manufacturing techniques in which parts are manufactured layer by layer. During such process, gas bubbles are formed in the melted polymer due to faster polymer grains coalescence at surface than deeper in the powder bed. Although gas diffusion is possible through the polymer melt, it’s usual...

Laser Metal Deposition (LMD) is an additive manufacturing process able to produce, repair and add coatings or functions to 3D metallic parts. During the process, a filler material-such as powder particles-is injected through a design nozzle into a melt pool generated by the interaction of a laser beam on a metallic substrate surface. The powder str...

We propose an analysis of the effect of various operating parameters on the keyhole depth during laser welding. We have developed a model that uses the analysis of the thermal field obtained in 2D geometry, which is mainly defined by the characteristic Peclet number. This allow us to show that the dependence of the aspect ratio R of the keyhole wit...

The experimental analysis of spatter formation was carried out on an instrumented SLM set-up allowing the quantification of spatter ejections and possible correlation with melt-pool behavior. Considering nearly similar SLM conditions than those carried out on SLM machines, an increase of large spatters (>80 μm) with volume energy density (VED) was...

The control of metal wettability is a key-factor in the field of brazing or welding-brazing. The present paper deals with the numerical simulation of the whole phenomena occurring during the assembly of dissimilar alloys. The study is realized in the frame of potential applications for the aircraft industry, considering the case of the welding-braz...

The laser powder bed fusion (LPBF) or powder-bed additive layer manufacturing process is now recognized as a high-potential manufacturing process for complex metallic parts. However, many technical issues are still to overcome for making LPBF a fully viable manufacturing process. This is the case of surface finish and the systematic occurrence of p...

The laser metal deposition (LMD) laser technique is a free-form metal deposition process, which allows generating near net-shape structures through the interaction of a powder stream and a laser beam. A simplified numerical model was carried out to predict layer heights together with temperature distributions induced by the (LMD) process on a titan...

The work presented in this paper deals with the laser welding simulation. Due to the rise of laser processing in industry, its simulation takes also more and more place. Nevertheless, the physical phenomena occurring are quite complex and, above all, very coupled. Thus, a state of art is necessary to summarize phenomena that have to be considered....

Series of experiments of high chromium steel (Fe-Cr- Ni-Mo-Mn) laser cladding over a 316L substrate have been carried out in both pulsed and continuous modes, using an Yb-YAG disk laser. The investigation focused on the effects of cladding parameters such as laser pulse energy, duration and travel speed, on cladding properties including dimensions,...

The nickel based alloy 690 is commonly used for steam generator as heat exchanger tubes in pressurized water reactors. Oxidation of this material in the primary circuit coolant leads to nickel release which is responsible for radioactive contamination in the reactor. It is known that a healing chromium high content layer can prevent the surface of...

Laser-induced reactive wetting and brazing of T40 titanium with A5754 aluminum alloy with 1.5 mm thickness was carried out in lap-joint configuration, with or without the use of Al5Si filler wire. A 2.4 mm diameter laser spot was positioned on the aluminum side to provoke spreading and wetting of the lower titanium sheet, with relatively low scanni...

The laser welding-brazing processes of dissimilar alloys are widely used in the aeronautical industry. The generation of heterogeneous assembly currently allows obtaining very efficient structures, combining satisfying mechanical properties and weight reduction. Nevertheless, on a large range of biomaterials (Fe/Ti, Fe/Al, Ti/Al) this kind of assem...

In this study, an heterogeneous Ti/Al assembly is proposed for the built of aircraft structures. This kind of structure combines advantages of both materials: the aluminum is light-weight and less expensive whereas the titanium offers superior mechanical properties. A welding - brazing assembly in overlap configuration is studied. The two selected...

In this study, an heterogeneous Ti/Al assembly is proposed for the built of aircraft structures. This kind of structure combines advantages of both materials: the aluminum is light-weight and less expensive whereas the titanium offers superior mechanical properties. A welding-brazing assembly in overlap configuration is studied. The two selected ma...

Résumé -Le travail, présenté dans cet article, traite de l'estimation de l'avancée d'un front de fusion résultant de l'application statique d'un procédé de soudage TIG à un acier inoxydable 316L. Suite à une précédente étude, purement théorique validant la méthode, une application expérimentale est effectuée. L'estimation est basée sur la méthode d...

With its uncommon presentation of instructional material regarding mathematical modeling, measurements, and solution of inverse problems, Thermal Measurements and Inverse Techniques is a one-stop reference for those dealing with various aspects of heat transfer. Progress in mathematical modeling of complex industrial and environmental systems has...

Résumé : Le travail présenté dans cet article traite de l'analyse thermique de l'avancée d'un front de fusion induite par une source de chaleur statique appliquée par le procédé de soudage TIG. Une méthode est développée afin d'estimer l'évolution de la limite de la zone fondue dans le cas d'une géométrie 2D axisymétrique. L'estimation est réalisée...

The paper deals with heat transfer analysis in a static welding process: a method is developed to estimate the evolution of the 2D axisymmetric shape of a forehead of fusion. The estimation is made from temperature measurements taken in the solid part. The estimation procedure is based on the conjugate gradient method coupled to the iterative regul...

METTI 2011, Eurotherm seminar n°94, 13-18 june 2011, Roscoff, France

Colloque Groupement de recherche Zéro Gravité, La Colle sur Loup, 17-20 octobre 2010.

préliminaire et mise en oeuvre d'une instrumentation thermique destinée à l'estimation de la position d'un front de fusion. Résumé : Le travail présenté dans cet article concerne l'étude de l'estimation de l'évolution d'un front de fusion dans le cadre de la modélisation de l'apport d'énergie lié à un procédé de soudage TIG (Tungsten Inert Gas) sta...

des erreurs de mesure lors d'une opération de soudage ; Définition d'une instrumentation optimale. Résumé -Le travail présenté dans cet article est lié à un projet sur la modélisation du soudage (le projet MUSICA). Dans le cadre de ce projet, des instrumentations fines en thermocouples de petites dimensions ont été réalisées. Des thermocouples de t...