Analysis of Physical Phenomena in Electrode Region of Arc Plasma

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In order to clarify electrode phenomena in the materials processing with arc plasma, the plasma diagnosis of gas tungsten arc (GTA) during welding was carried out by using a planar laser induced fluorescence (PLIF) analysis and a spectroscopic analysis.Change in distributions of metal vapor from the anode, namely, the weld pool to the arc plasma strongly affects the anode arc root owing to drastic change in electrical conductivity in the plasma. The difference between a diffuse mode and a constricted mode in the anode arc roots gives different forces such as the drag force of arc plasma, the electromagnetic force, etc.to the weld pool. These different forces would also lead to different vector of a fluid flow velocity in the weld pool, and then the penetration geometry of the weld should be changed.Experimental and theoretical results in the present research project give new knowledge of the interaction between the arc plasma and the electrodes to the materials processing with arc plasma, and also suggest a future direction of this research work.