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Publications: Articles

Toutes :: 2013
Tous :: A, B, C, D, F, G, H, J, K, L, M, N, S, T 
Tous :: Malik, Migot-Choux 
References par page: Mots clefs Voir les resumes



Jardy, Alain, Chapelle, Pierre, Malik, Ashish, Bellot, Jean-Pierre, Combeau, Herve and Dussoubs, Bernard
ISSN: 0915-1559

Resume: The present study aims to understand the melting of the consumable electrode in the VAR process and gain some insight into the influence of an ensemble arc motion on the melting behaviour. In a previous study, a 2D axisymmetric model of the heat transfer in the cathode had been developed. Using the operating parameters as model inputs, it enabled prediction of the melt rate and the evolution of the melting area. Model results were successfully compared to melt rate measurements in an industrial VAR furnace. In recent years, it has been claimed that the electric arc may not be considered as steady and axisymmetric. Our experimental investigation of the luminosity recorded during an actual VAR heat confirms that a transient 3D behaviour may take place. Therefore, a 3D version of the previous model was set up to predict the heat transfer and melting of the electrode, using the unknown ensemble arc motion as an input. The arc is assimilated to a transient distribution of energy flux density. Results evidence that the influence of the arc motion on the shape of the electrode tip can be very important. In industrial practice, the cathode tip usually remains relatively flat during melting. The shapes of the computed electrode tips enable us to propose some arc parameters which remain compatible with both the periodic behaviour of the light emitted and the flatness of the electrode.

Equipe: Centre de Compétences : ERMIONE informatique et calcul

Hamdan, Ahmad, Audinot, Jean-Nicolas, Migot-Choux, Sylvie, Noel, Cedric, Kosior, Francis, Henrion, Gerard and Belmonte, Thierry
ADVANCED ENGINEERING MATERIALS, 15(10):885-892 Hamdan, A (Reprint Author), Univ Lorraine, Inst Jean Lamour, CNRS, UMR 7198, F-54042 Nancy, France. Hamdan, Ahmad; Migot-Choux, Sylvie; Noel, Cedric; Kosior, Francis; Henrion, Gerard; Belmonte, Thierry, Univ Lorraine, Inst Jean Lamour, CNRS, UMR 7198, F-54042 Nancy, France. Audinot, Jean-Nicolas, Ctr Rech Publ Gabriel Lippmann, SAM Dept, L-4422 Belvaux, Luxembourg.
ISSN: 1438-1656

Resume: Discharges in heptane in pin-to-plate configuration are produced between a platinum wire and a (100)-oriented silicon wafer coated by a carbon nanotube (CNT) carpet. This carpet is used to simulate the behavior of a nanostructured surface in electro-discharge machining (EDM) where small protrusions on the surface could play a similar role. CNTs behave like simple electrical conductors between the discharge and the silicon wafer. They act as if they would focus the current on smaller areas. The average diameter of impacts is about five times smaller if the silicon wafer is coated by a CNT carpet. The underlying silicon surface is heated by the plasma and melts, forming a central spot surrounded by a serrated trailing edge. The current density being about one order of magnitude larger when a CNT carpet is present, the induced magnetic field stirs the molten silicon, creating serrations all around the impact. Hot nanoparticles of carbon coming from the plasma fall and roll randomly on the silicon surface where they create wavy micro-channels. Nanowires that are detached from the surface are covered by nanoparticles of platinum in the plasma and embedded within an amorphous carbon layer deposited on the nanotube. However, these effects can only be observed if the current density is high enough (>approximate to 10A mu m(-2) depending on the material) like in micro-EDM but not in nano-EDM.

Equipe: Centre de Compétences : ERMIONE informatique et calcul

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