Influence of the residual stresses in reshaping operations of large aeronautical parts

International audienceLarge aeronautical parts present important distortions at the end of its manufacturing process. To solve this problem, a reshaping operation is required. This step is highly manual and involves skilled workers. The traditional analysis of reshaping requires to simulate before all the manufacturing steps, in order to determine the residual stresses that generate distortion. Here, a new strategy to study reshaping is presented, which consist in using the initial distortion as a starting point considering the part free of residual stresses

Modélisation thermomécanique hybride en perçage pour la simulation du champ de temperature dans l'outil

10 pagesInternational audienceCet article s'attache à présenter une approche hybride permettant de prédire les chargements thermomécaniques sur l'outil au cours de l'opération de perçage. Une première étape analytique conduit à la détermination de la répartition des flux de chaleur aux interfaces à partir de la mesure des actions mécaniques en cours de perçage. Cette distribution des flux de chaleur constitue le point d'entrée de l'étape suivante de simulation par éléments finis des transferts thermiques. L'approche proposée est validée au travers d'essais de perçage sur un alliage de titane Ti6Al4V

Prediction of laser beam welding-induced distortions and residual stresses by numerical simulation for aeronautic application

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Experimental investigation and finite element simulation of laser beam welding induced residual stresses and distortions in thin sheets of aa 6056-t4

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Thermo-mechanical analysis of laser beam welding of thin plate with complex boundary conditions

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A simple Eulerian thermomechanical modeling of friction stir welding

International audienceA simple three-dimensional thermomechanical model for friction stir welding (FSW) is presented. It is developed from the model proposed by Heurtier et al. (2006) based on a combination of fluid mechanics numerical and analytical velocity fields. Those velocity fields are introduced in a steady state thermal calculation to compute the temperature field during welding. They allow partial sliding between the shoulder and the workpiece, the amount of which is provided as an additional result of the model. The thermal calculation accounts for conduction and convection effects by means of the particular derivative. The complete thermomechanical history of the material during the process can then be accessed by temperature and strain rate contours. The numerical results are compared with a set of experimental test cases carried out on an instrumented laboratory device. The choices for modeling assumptions, especially tribological aspects, are discussed according to agreements or deviations observed between experimental and numerical results. The amount of sliding appears to be significantly influenced by the welding conditions (welding and tool rotational velocities), and physical interpretations are proposed for its evolution

Testing locomotor hypothesis in early hominids: 3d odelling and simulation of bipedalisms using anatomical data

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New functionalities of the 3.0 version of TFEL, MFront and MTest

International audienceMFront is a tool which allows easy implementation of abritrary complex mechan- ical behaviours in an efficient way. Those implementations are portable between various finite element solvers and solvers based on FFT. MFront is part of the open-source TFEL project which also provide an useful point-wise solver called MTest

Heparin-Binding Hemagglutinin Adhesin (HBHA) Is Involved in Intracytosolic Lipid Inclusions Formation in Mycobacteria

The heparin-binding hemagglutinin adhesin (HBHA) is an important virulence factor of Mycobacterium tuberculosis. It is a surface-displayed protein that serves as an adhesin for non-phagocytic cells and is involved in extra-pulmonary dissemination of the tubercle bacillus. It is also an important latency antigen useful for the diagnosis of latently M. tuberculosis-infected individuals. Using fluorescence time-lapse microscopy on mycobacteria that produce HBHA-green fluorescent protein chimera, we show here that HBHA can be found at two different locations and dynamically alternates between the mycobacterial surface and the interior of the cell, where it participates in the formation of intracytosolic lipid inclusions (ILI). Compared to HBHA-producing mycobacteria, HBHA-deficient mutants contain significantly lower amounts of ILI when grown in vitro or within macrophages, and the sizes of their ILI are significantly smaller. Lipid-binding assays indicate that HBHA is able to specifically bind to phosphatidylinositol and in particular to 4,5 di-phosphorylated phosphatidylinositol, but not to neutral lipids, the main constituents of ILI. HBHA derivatives lacking the C-terminal methylated, lysine-rich repeat region fail to bind to these lipids and these derivatives also fail to complement the phenotype of HBHA-deficient mutants. These studies indicate that HBHA is a moonlighting protein that serves several functions depending on its location. When surface exposed, HBHA serves as an adhesin, and when intracellularly localized, it participates in the generation of ILI, possibly as a cargo to transport phospholipids from the plasma membrane to the ILI in the process of being formed