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Dive into the research topics where Jin-Dong Zhu is active.

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Featured researches published by Jin-Dong Zhu.


International Journal of Cast Metals Research | 2005

Numerical simulation and X-ray direct observation of mould filling during vacuum suction casting

S. Kashiwai; Itsuo Ohnaka; A. Kimatsuka; T. Kaneyoshi; T. Ohmichi; Jin-Dong Zhu

Abstract The mould filling of the aluminium casting alloy AC4C was directly observed by X-ray radiography in order to evaluate the accuracy of simulated results for the mould filling behaviour of a vacuum suction casting process. A numerical method has been applied to simulate mould filling behaviour, in which evacuation of gas through the suction vent is taken into account and the backpressure of gas is coupled with the pressure field of the melt. Backpressure of gas in the empty mould cavity was also measured using a semiconductor pressure sensor. Experiments have been carried out at two different suction pressures (10 and 20 kPa) and three different decompression rates (1·2, 4·2 and 80 kPa s-1), controlled by the aperture of the valve between the gas pipe of the vacuum suction system. Experimental results showed that the effects of suction pressure and decompression rate on the mould filling behaviour were significant. The higher the suction pressure and decompression rate, the more turbulent the free surface of molten metal, resulting in earlier occurrence of gas entrapment, larger volumes of entrapped gas and higher risk of misrun. By comparing simulated results with experimental ones, it was found that good agreement could be obtained in terms of mould filling patterns, positions of gas entrapments and mould filling time. It was also found that results simulated by the conventional method, in which gas evacuation and the effects of backpressure on mould filling are not taken into account, showed poor agreement with experimental values.


International Journal of Cast Metals Research | 2011

Challenging issues in computer simulation of casting

Itsuo Ohnaka; Jin-Dong Zhu; N. Sako; Akira Sugiyama; C.-K. Ye

Abstract Although computer simulation has progressed rapidly and widely in the casting industry over the last decades, many problems still remain challenging. This paper overviews the problems being faced most frequently, including estimation of material properties and boundary conditions, simulation of mould filling and solidification, prediction of porosities and optimisation of casting. The authors emphasise, in particular, the importance of estimating the material properties of sand moulds and boundary conditions with consideration of the oxide film on the molten metal, and the comparison of simulation results with observations of real casting processes.


International Journal of Cast Metals Research | 2003

Modeling of mold filling in gating systems with filters

Jin-Dong Zhu; Itsuo Ohnaka; Akira Sugiyama; T. Ohmichi; Y. Ogino

A numerical method has been developed to simulate mold filling in gating systems with filters. The discretization method of flow and temperature fields is based on the DFDM (Direct-Finite-Difference-Method), which directly derives the discrete governing equations from physical phenomena. For the simulation of fluid flow through filters, in addition to the momentum convection, pressure and gravity terms, the Darcy force term is incorporated into the momentum-conservation equation to account for the filter flow resistance. Furthermore, for the simulation of heat transfer between the melt and the filter, both the melt- and the filter- temperatures were solved by applying the energy conservation law to each part of a mass region (element) individually. Simulated results showed the possibilities of the decrease of the melt front turbulence and less entrapments of gas in the downstream runner and cavity. Simulated results also showed that the permeability and the thickness of the filter significantly influence both the mold filling behavior and the temperature distribution. Simulated mold filling patterns were validated against the experimental ones observed directly by X-ray radiography, and good agreements were obtained.


International Journal of Cast Metals Research | 2003

Mold filling simulation with consideration of gas escape through sand mold

A. Kimatsuka; Itsuo Ohnaka; Jin-Dong Zhu; T. Ohmichi


International Journal of Cast Metals Research | 2003

Prediction of porosity defect in spheroidal graphite iron castings

Itsuo Ohnaka; Jun Iwane; Hideyuki Yasuda; Jin-Dong Zhu


Journal of Japan Foundry Engineering Society | 1996

Three Dimensional Computer Simulation of Mold Filling of Casting by Direct Finite Difference Method

Jin-Dong Zhu; Itsuo Ohnaka


Archive | 1995

Computer simulation of fluid flow and heat transfer in partially reinforced casting

Jin-Dong Zhu; Itsuo Ohnaka


Journal of Japan Foundry Engineering Society | 2000

Observations of Mold Filling Behavior of Aluminum Bar Castings Cast by Lost Foam Casting Process

Jin-Dong Zhu; Itsuo Ohnaka; Tetsutaro Ohmichi; Kentaro Mineshita; Yoshihiro Yoshioka


Materia Japan | 1999

Mechanism of Lift-off Phenomenon.

Katsuaki Suganuma; Itsuo Ohnaka; Hideyuki Yasuda; Jin-Dong Zhu


Journal of Japan Foundry Engineering Society | 2004

Direct Observation and Numerical Simulation of Mold Filling during Vacuum Suction Casting

Shigeo Kashiwai; Itsuo Ohnaka; Akihiko Kimatsuka; Takahiro Kaneyosi; Tetsutaro Ohomichi; Jin-Dong Zhu

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