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Feng Y.,Tianjin University of Technology | Wang R.,Tianjin University of Technology | Zhang H.,Tianjin University of Technology | Wen X.,Tianjin University of Technology | And 2 more authors.
Journal of Computational Information Systems | Year: 2012

A terrain data organization method was proposed in this article in order to solve large scale data realtime rendering problem, which combines wavelet transform and quadtree to organize the terrain data, to further build a multi-resolution lunar terrain model. The experiment result shows that this method can achieve real-time visualization and interaction of massive terrain data of the whole surface of lunar. © 2011 by Binary Information Press.


Mei J.,Shanghai JiaoTong University | Liu W.,Shanghai JiaoTong University | Liu W.,Shanghai Light Alloy Net Forming National Engineering Research Center Co. | Wu G.,Shanghai JiaoTong University | And 2 more authors.
Journal of Materials Research | Year: 2014

A continuous nonflux inclusion-removal method, rotating gas bubble stirring, is used to purify Mg-10Gd-3Y-0.5Zr melt. The effects of rotating gas bubble stirring process parameters (Ar flow rate, time, and rotating speed) on purifying effectiveness, mechanical properties, and fracture behavior of sand-cast Mg-10Gd-3Y-0.5Zr alloy are studied. The results show that too high or too low Ar flow rate is unfavorable for inclusion-removal. The results also indicate that the high rotary speed of spraying gas is helpful to improve the inclusion-removal and mechanical properties. But when the melt is subjected to overtime gas bubbling treatment, the mechanical properties became poor again. Nonflux purification does not change the microstructure of Mg-10Gd-3Y-0.5Zr alloy. However, rotating gas bubble stirring has a certain effect on the fracture pattern of the alloy. In addition, the melt purifying mechanism of the gas bubble stirring treatment for the sand-cast alloy was discussed systematically. © 2015 Materials Research Society.


Cao L.,Shanghai JiaoTong University | Liu W.-C.,Shanghai JiaoTong University | Li Z.-Q.,Shanghai Aviation Precision Machinery Research Institute | Wu G.-H.,Shanghai JiaoTong University | And 3 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2014

The microstructure, mechanical properties and fracture behavior of sand-cast Mg-10Gd-3Y-0.5Zr alloy (mass fraction, %) under T6 condition (air cooling after solid solution and then aging heat treatment) were investigated. The optimum T6 heat treatments for sand-cast Mg-10Gd-3Y-0.5Zr alloy are (525 °C, 12 h + 225 °C, 14 h) and (525 °C, 12 h + 250 °C, 12 h) according to age hardening curve and mechanical properties, respectively. The ultimate tensile strength, yield strength and elongation of the Mg-10Gd-3Y-0.5Zr alloy treated by the two optimum T6 processes are 339.9 MPa, 251.6 MPa, 1.5% and 359.6 MPa, 247.3 MPa, 2.7%, respectively. The tensile fracture mode of peak-aged Mg-10Gd-3Y-0.5Zr alloy is transgranular quasi-cleavage fracture. © 2014 The Nonferrous Metals Society of China.


Mei J.,Shanghai JiaoTong University | Liu W.-C.,Shanghai JiaoTong University | Liu W.-C.,Shanghai Light Alloy Net Forming National Engineering Research Center Co. | Wu G.-H.,Shanghai JiaoTong University | And 6 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2015

The effect of complex melt-refining treatment (melt flux incorporating with rotating gas bubble stirring) on microstructure and mechanical behavior of the sand-cast Mg-10Gd-3Y-0.5Zr alloy was investigated. In addition, the melt purifying mechanism of the complex melt-refining treatment for the sand-cast alloy was discussed systematically. The results show that the new melt-refining method can significantly improve melt quality and mechanical behavior of the tested alloy, i.e., compared to the reference unpurified alloy, the volume fraction of inclusions decreased from 0.47% to 0.28%, the ultimate tensile strength and elongation for T6-treated alloy increased from 245 MPa and 0.7% to 312 MPa and 4.5%, respectively. Especially, combining 1% flux with rotating gas bubble stirring can get even better purifying effectiveness than conventional sole 2% flux purification; the use of melt flux decreased by 50% and significantly reduced environmental pollution. © 2015 The Nonferrous Metals Society of China.


Liu W.,Shanghai JiaoTong University | Jiang L.,Shanghai JiaoTong University | Cao L.,Shanghai JiaoTong University | Mei J.,Shanghai JiaoTong University | And 5 more authors.
Materials and Design | Year: 2014

In this study, the tensile properties, high cycle fatigue behavior and plane-strain fracture toughness of the sand-cast Mg-10Gd-3Y-0.5Zr magnesium alloy were investigated, comparison to that of sand-cast plus T6 heat treated magnesium alloy which named after sand-cast-T6. The results showed that the tensile properties of the sand-cast alloy are greatly improved after T6 heat treatment, and the fatigue strength (at 107cycles) of the sand-cast Mg-10Gd-3Y-0.5Zr magnesium alloy increases from 95 to 120MPa after T6 heat treatment, i.e. the improvement of 26% in fatigue strength has been achieved. The plane-strain fracture toughnesses KIC of the sand-cast and sand-cast-T6 alloys are about 12.1 and 16.3MPam1/2, respectively. In addition, crack initiation, crack propagation and fracture behavior of the studied alloys after tensile test, high cycle fatigue test and plane-strain fracture toughness test were also investigated systematically. © 2014 Elsevier Ltd.

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