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ISIJ INTERNATIONAL,
53(2):213-220
2013
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 |
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JOURNAL OF APPLIED PHYSICS,
114
2013
ISSN: 0021-8979
DOI: 10.1063/1.4821884
Equipe: Centre de Compétences : X-Gamma rayons X et spectroscopie |
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New Journal of Physics,
15
2013
Equipe: Département P2M : Nanomagnétisme et Electronique de Spin |
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PHYSICAL REVIEW B,
88(12)
2013
ISSN: 1098-0121
Equipe: Département P2M : Surfaces et Spectroscopies |
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ISIJ International,
53:1215-1223
2013
Equipe: Département SI2M : Microstructures et Contraintes |
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8626
2013
ISSN: 0277-786X
DOI: 10.1117/12.2010105
Equipe: Centre de Compétences : X-Gamma rayons X et spectroscopie |
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SYMMETRY-BASEL,
5(4):344-354
2013
ISSN: 2073-8994
DOI: 10.3390/sym5040344
Equipe: Département P2M : Surfaces et Spectroscopies |
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Surface and Coatings Technology,
221:70
2013
Resume: The plasma electrolytic oxidation (PEO) of aluminium alloys is investigated for different electrical working conditions using a pulsed bipolar current supply. A particular attention is paid to the effect of the anodic current density (from 10 to 90 A dm-2) and current pulse frequency (from 100 to 900 Hz) on the resulting oxide layer. Micro-discharges are characterized during the process by means of fast video imaging with a time and a space resolution of 8 μs and 0.017 mm2, respectively. Correlations are established between themicro-discharge characteristics (surface density, lifetime and size) and the elaborated oxide layers (morphology, growth rate and surface roughness). The highest coating growth rate measured (2.1 μm min-1) is achieved with the combination of the highest current density (75.7 A dm-2) and the highest current pulse frequency (900 Hz). Within these specific current conditions it is concluded that the detrimental effects of numerous micro-discharges are minimized. The results also show that the surface roughness may be largely affected by the presence of long-lived and large micro-discharges which develop over the processed surface. The strongest micro-discharges (live duration up to 0.3 ms and cross-sectional area up to 1 mm2) are mainly observed with the combination of the highest current density (75.7 A dm-2) and the lowest current pulse frequency (100 Hz). Equipe: Département CP2S : Expériences et Simulations des Plasmas Réactifs - Interaction plasma-surface et Traitement des Surfaces ESPRITS |
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PHYSICAL REVIEW B,
87(7)
2013
ISSN: 1098-0121
Equipe: Département P2M : Surfaces et Spectroscopies |
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Journal of Physics Condensed Matter,
25(29)
2013
Equipe: Département P2M : Nanomagnétisme et Electronique de Spin |