Papers by Author: Tashiro Shinichi

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Authors: Manabu Tanaka, Tashiro Shinichi, Takayuki Kashima, John J. Lowke, Anthony B. Murphy
Authors: Anh Nguyen Van, Tashiro Shinichi, Huu Manh Ngo, Akihisa Murata, Tadasuke Murata, Manabu Tanaka
Abstract: The purpose of this investigation is to clarify the behavior of exit keyhole diameter during switch off (cutting arc) period in case of Plasma keyhole arc welding (PKAW). During switch off period, the keyhole and weld pool are visualized from backside via a high speed video camera (HSVC). The result showed that keyhole diameter on the backside is unstable. The keyhole size is much changed in X-axis. Firstly, it is increased and then it is decreased to a stationary value at t = 0.05 s after cutting arc. Meanwhile, the size in Y-axis is not changed approximately from t = 0.01 s after cutting arc. The results can be considered to control this process more efficiency.
Authors: Tashiro Shinichi, Toru Iwao, Tuginori Inaba, Manabu Tanaka
Abstract: We have developed non-equilibrium simulation model of GTA. In this paper, simulation results of plasma property of argon GTA at atmospheric pressure are presented and, furthermore, the reliability of the simulation model is evaluated. As a result, it was revealed that non-equilibrium characteristic appears in regions close to both electrodes and the fringe of the arc column where the temperatures decrease below approximately 10000K. It was also found that non-equilibrium region near the anode surface has thickness of 0.3mm. This result agrees with the simulation result predicted with one-dimensional electrical sheath model.
Authors: Kentaro Yamamoto, Manabu Tanaka, Tashiro Shinichi, Kazuhiro Nakata, Keiichi Suzuki, Kei Yamazaki
Abstract: It is important to consider the interaction between arc plasma and electrodes because melting of electrodes strongly affects arc plasma. Therefore, a GMA model will be developed, based on the unified model of TIG arc. As a first step, a TIG arc model with a calculation for molten cathode shape has been proposed. This model is calculated in two cases; molten W cathode and Calculation result of W cathode. In the case of W cathode, cathode shape change was found to affect the arc plasma property strongly. Calculated results of radial temperature distributions on electrode surface and arc pressure distributions at the anode surface are very similar to the experimental results.
Authors: Manabu Tanaka, Kentaro Yamamoto, Tashiro Shinichi, John J. Lowke
Abstract: Study of current attachment at thermionic cathode for TIG arc at atmospheric pressure is attempted from numerical calculations of arc-electrodes unified model. The calculations show that the maximum temperature of arc plasma close to the cathode tip for W-2% ThO2 reaches 19,000 K and it is the highest value in comparison with the other temperatures for W-2% La2O3 and W-2% CeO2, because the current attachment at the cathode tip is constricted by a centralized limitation of liquid area of ThO2 due to its higher melting point. The calculations also show that, in cases of W- 2% La2O3 and W-2% CeO2, the liquid areas of La2O3 and Ce2O3 are widely expanded at the cathode tip due to their lower melting points and then produce uniform current attachments at the cathode. It is concluded that the current attachment at thermionic cathode is strongly dependent on work function, melting point and Richardson constant of emitter materials.
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