Mengwu WU
,
Shoumei XIONG
金属学报(英文版)
A numerical model based on the cellular automaton method for the three-dimensional simulation of dendritic growth of magnesium alloy was developed. The growth kinetics was calculated from the complete solution of the transport equations. By constructing a three-dimensional anisotropy model with the cubic CA cells, simulation of dendritic growth of magnesium alloy with six-fold symmetry in the basal plane was achieved. The model was applied to simulate the equiaxed dendritic growth and columnar dendritic growth under directional solidification, and its capability was addressed by comparing the simulated results to experimental results and those in the previously published works. Meanwhile, the three-dimensional simulated results were also compared with that of in two dimensions, offering a deep insight into the microstructure formation of magnesium alloy during solidification.
关键词:
Magnesium alloy
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Wenhui LIU
,
Yangai LIU
,
Shoumei XIONG
,
Baicheng LIU
,
Y.Matsumoto
,
M.Murakami
材料科学技术（英）
Casting pressure conditions have great influences on the casting defects, such as gas porosity, shrinkage porosity and gas holes. A Mg cylinder head cover die casting was used to experimentally study the influences of casting pressure, the loading time and the piston position of pressure intensification on the variation of pressure and the quality of casting. The results show that casting pressure, the loading time and the piston position of pressure intensification have great influences on the pressure variations in the mold, the quality and performance of casting. The external quality, the density and the tensile strength of casting were improved with the increase of casting pressure and the piston position of pressure intensification and the decrease of the loading time of pressure intensification.
关键词:
Magnesium alloy
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null
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Zhipeng GUO
,
Shoumei XIONG
,
Sang-Hyun Cho
,
Jeong-Kil Choi
材料科学技术（英）
A method based on die casting experiments and mathematic modeling is presented for the determination of the heat flow density (HFD) and interfacial heat transfer coefficient (IHTC) during the high pressure die casting (HPDC) process. Experiments were carried out using step shape casting and a commercial magnesium alloy, AM50. Temperature profiles were measured and recorded using thermocouples embedded inside the die. Based on these temperature readings, the HFD and IHTC were successfully determined and the calculation results show that the HFD and IHTC at the metal-die interface increases sharply right after the fast phase injection process until approaching their maximum values, after which their values decrease to a much lower level until the dies are opened. Different patterns of heat transfer behavior were found between the die and the casting at different thicknesses. The thinner the casting was, the more quickly the HFD and IHTC reached their steady states. Also, the values for both the HFD and IHTC values were different between die and casting at different thicknesses.
关键词:
Interfacial heat transfer coefficient
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Jinwu KANG
,
Baicheng LIU
,
Shoumei XIONG
材料科学技术（英）
In order to study the thermal stresses at the mushy zone, a three dimensional rheological model [H]-[H|N]-[N|S] including elastic, visco-elastic and visco-plastic elements was established, its algorithm and codes for finite element method were also developed. A FDM/FEM integrated analysis system of thermal stresses was built based on the integration of this procedure with thermal analysis by finite difference method. A steel sample casting with a hot spot was simulated in order to validate this system, and the calculated and experimental results were in good agreement.
关键词:
Liangrong JIA
,
Shoumei XIONG
,
Baicheng LIU
材料科学技术（英）
A 3-D mathematical model considering turbulence phenomena has been established based on a computational fluid dynamics technique, so called 3-D SOLA-VOF (Solution Algorithm-Volume of Fluid), to simulate the fluid flow of mold filling process of die casting. In addition, the mathematical model for simulating the heat transfer in die casting process has also been established. The computation program has been developed by the authors with the finite difference method (FDM) recently. As verification, the mold filling process of a S-shaped die casting has been simulated and the simulation results coincide with that of the benchmark test. Finally, as a practical application, the gating design of a motorcycle component was modified by the mold filling simulation and the dies design of another motorcycle component was optimized by the heat transfer simulation. All the optimized designs were verified by the production practice.
关键词:
Shuyong DONG
,
Shoumei XIONG
,
Baicheng LIU
材料科学技术（英）
A mathematical model to calculate the size and distribution of microporosities was studied and coupled with a stochastic microstructure evolution model. The model incorporates various solidification phenomena such as grain structure evolution, solidification shrinkage, interdendritic fluid flow and formation and growth of pores during solidification processes. The nucleation and growth of grains were modeled with a cellular automaton method that utilizes the results from a macro scale modeling of the solidification process. Experiments were made to validate the proposed models. The calculated results of aluminum alloy castings agreed with the experimental measurements.
关键词:
Numerical simulation
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