• Sciences de l'ingénieur/Matériaux
  
• Sciences de l'ingénieur/Mécanique/Génie mécanique
  
• Sciences de l'ingénieur/Mécanique/Mécanique des fluides
  
• Sciences de l'ingénieur/Mécanique/Thermique
  
• Sciences de l'ingénieur/Mécanique/Mécanique des solides
  
• Sciences de l'ingénieur/ Robotique
  
• Sciences de l'ingénieur/Mécanique/Mécanique des matériaux
  
• Sciences de l'ingénieur/Génie des procédés
  
• Sciences de l'ingénieur/Mécanique/Matériaux et structures en mécanique
  
• Sciences de l'ingénieur/Traitement du signal et de l'image
  
• Physique/Physique/Instrumentations et Détecteurs
  
• Sciences de l'ingénieur/Mécanique
  
• Physique/Mécanique/Génie mécanique
  
• Physique/Mécanique/Mécanique des fluides
  
• Physique/Mécanique/Mécanique des matériaux
  
• Physique/Mécanique/Matériaux et structures en mécanique
  

Welding processes imply rapid solidification, in presence of high thermal gradient and strong fluid flows in the weld pool. This work presents, in the case of welding, an analysis of the coupling between solidification mechanisms and fluid flows at the macroscale and the microscale. An experimental setup was designed in order to observe in situ a fully penetrated weld pool generated on a Cu30Ni plate with a GTAW torch. At the macroscale, observations are carried out by three cameras: two cameras recording in visible light the top and the back side of the whole weld pool, and one infrared camera catching the thermal field on solid part at the back side. At the microscale, a high-speed camera, mounted with a microscope lens, is used to observe dendritic growth and fluid flows at the back side trailing edge of the weld pool. The observations provide a lot of data allowing analyses and discussions on the correlations between solidification mechanisms and fluid flows, with respect to welding parameters. Then, the experimental results are compared to theoretical results obtained from analytical modelling, in order to discuss the possible limitations of models and try to better understand the coupling between physical phenomena.

The purpose of this article is to investigate the influence of growth kinetic models and nucleation models on the grain structure predicted by cellular automata (CA) during bead on Cu30Ni thin plate. Temperature field is obtained with the computation of two-dimensional finite element model (FE). Based on these temperatures, a CA model simulates the evolution of the envelope of grains along the solidification front. It is shown that for the same temperature field, the grains structure is modified if the growth model changes. The influence of the nucleation law parameters is also discussed from a modelling point of view. Experimental size of the weld pool are compared with thermal results and EBSD maps are compared with grain structure prediction obtained with the CA algorithm.

Wire Arc Addtive Manufacturing (WAAM) is a promising direct energy de-position technology to produce high-value material components with a low buy-to-fly ratio. WAAM is able to produce thin-walled structures of large scale and also truss structures without any support. To manufacture complex parts, process reliability and repeatability are still a necessity and this often leads to long developing times. In this paper, a method is proposed to automatically manufacture complex truss structures with point by point arc additive manufacturing and a six axis robot. Computer aided manufacturing (CAM) software is designed to manage (i) material deposition at intersections and (ii) collisions between the part under construction and the torch. Because it is difficult to model the deposition process, the bead geometry is monitored using video imaging. Image treatment program detects the contour of the deposit and computes its current position. With this position, the CAM software corrects the geometry of the part for future deposition. Simple case studies are tested to validate the algorithm. Two solid free form geometries designed by topology optimization are manufactured with this skeleton arc additive manufacturing process.

The purpose of this paper is to show a modelling scheme to predict rapidly three dimensionnal grain structure. The modelling is based on a plane thermal finite element for the process coupled with a monte carlo simulation for grain structure. To demonstrate the interest of this type of modelling the simulations are done for a squared pulse mode and results are compared with experimental results (EBSD) done during the work of A.Chiocca. The originality of the paper is that predictions of grain structure are investigated with current and arc voltage evolving with time. Results show the interest of using monte carlo simulation.

WAAM (Wire+Arc Additive Manufacturing) allows manufacturing mechanical components by adding successive layers of molten metallic wire using electrical arc. The WAAM process, compared to other processes using metallic powders, presents some advantages such as: high deposition rate (2-4kg/hour), manufacturing of large scales components and cheaper industrial installations. WAAM is then an interesting candidate for manufacturing components often CNC machined. However, the main disadvantages of this process are: high surface roughness requiring a post machining, strains and stresses states generated during the deposition process [1]. A better understanding of the relation between the welding parameters and the state of stresses can contribute to minimize residual stresses, eventually in relation with a deposition strategy [2]. As a first approach, the effects of the first deposition of molten metal on the base plate is investigated. This work focuses on finite element method, based on Code Aster solver, with a nonlinear thermo-mechanical model. Concerning the thermal aspects, the GMAW heat input is modeled by a Gaussian distribution [3]. The temperature fields are used to solve the mechanical problem. The material behavior laws are assumed to be elastoplastic with different hardening configurations: no hardening, linear isotropic or kinematic hardening and non-linear isotropic hardening. Based on the results from these elastoplastic models, the influence of the hardening is presented.