Papers by Author: Itsuo Ohnaka

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Authors: Hideyuki Yasuda, Itsuo Ohnaka, B.K. Dhindaw, Shinji Fujimoto, N. Takezawa, T. Tamayama, A. Tsuchiyama, T. Nakano, Kentaro Uesugi
Abstract: Unidirectional solidification of Al-In, Cu-Pb and Cu-Pb-Al monotectic alloys was performed under static magnetic fields up to 10T for formation of the regularly aligned-rod structure. mThe imposition of static magnetic fields exceeding 4T suppressed movement of the In liquid droplets at the Al solidifying front and enhanced the engulfment of the In droplets into the front. As a result, the eutectic-like structure was obtained in the Al-10 and 15at%In hypermonotectic alloys. The micro X-ray tomography indicated that the continuous In rods with diameters of 10-20 µm were aligned parallel to each other. In the case of the Cu-Pb and the Cu-Pb-Al alloys, the imposition of static magnetic fields also enhanced the formation of the aligned Pb rods. The electrochemical etching by using a 10% HNO3 solution successfully removed the minor phase, and the porous aluminum and copper with deep pores were fabricated.
289
Authors: Hai Dong Zhao, Itsuo Ohnaka
Abstract: To describe the shape and location of free surfaces in the mold filling simulation, parameters including volume filled ratio, surface dimensionless distance, and surface filled ratio for the DFDM (Direct Finite Difference Method) elements were proposed. A model of mold filling process was established, considering the mass, momentum and heat transfer in the vicinity of free surface. It had been applied to an experimental Al casting. In-situ observation and record of actual mold filling process of the casting with special X-ray apparatus were carried out, and were used to validate the simulation results. The validation showed that the model could predict the mold filling process well. It was found that back pressure of gas in the mould cavity had minor effect on change of liquid flow when using pressurized feeding system and sand mould with good air permeability.
841
Authors: Hiroyuki Y. Yasuda, Itsuo Ohnaka, H. Kaziura, Toyohiko Yano
736
Authors: Hideyuki Yasuda, Itsuo Ohnaka, Akira Sugiyama, Yoshiki Mizutani, Takumi Sakimura, Asako Kawaguchi, Yoshiharu Waku
2709
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