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Semi-solid Processing of Al-7Graghite Composite

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Journal of university.of Science and Technology beijing 2001年第3期8卷 203-206页

作者： peng zhang, yunhui du, daben zeng department of mechanical engineering, tsinghua university. beijing 100084, china department of mechanical engineering Tsinghua University Beijing 100084 China

Al-7graphite composite was processed using Al-7graphite mushy prepared by electromagnetic-mechanical stirring method, and the influence of solid fraction on the distributing of graphite particles in ingot was studied. The results shows that the relationship between solid fraction and stirring temperature of mushy is: f(s) = 591.5-0.897 t (where f(s) is the solid fraction, t is the stirring temperature). For Al-7graphite composite, with the increasing of solid fraction, the aggregation extent of graphite particles reduced gradually, and when solid fraction was larger than 30%, graphite particles could distribute evenly in ingot.

关键词： Al-7graphite composite electromagnetic-mechanical stirring method distributing of graphite particles solid fraction stirring temperature

Study on Steel-Mushy Al-20Sn Alloy Bonding

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Journal of Materials Science & Technology 2001年第2期17卷 224-228页

作者： peng zhang, yunhui du and daben zeng department of mechanical engineering, tsinghua university. beijing 100084, china Jianzhong CUI Metal Forming department, NEU, Shenyang 110006, china Limin BA Anshan Automobile Fittings Factory, Anshan 114014, china Dept. of Mech. Eng. Tsinghua Univ. Beijing 100084 China

Steel-mushy Al-20Sn alloy bonding was studied for the first time. The relationship model about preheat temperature of steel plate, solid fraction of Al-20Sn alloy mushy, rolling speed and interfacial shear strength of bonding plate could be established by artificial neural networks perfectly. This model could be optimized with a genetic algorithm. The optimum bonding parameters were: 505 degreesC for preheat temperature of steel plate, 34.3% for solid fraction of Al-20Sn alloy mushy and 10 mm/s for rolling speed, and the largest interfacial shear strength of bonding plate was 71.2 MPa.

关键词： Al Sn Study on Steel-Mushy Al-20Sn Alloy Bonding

MESHLESS METHOD FOR 2D MIXED-MODE CRACK PROPAGATION BASED ON VORONOI CELL

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Acta Mechanica Solida Sinica 2003年第3期16卷 231-239页

作者： Lou Luliang zeng Pan (department of mechanical engineering,tsinghua university.beijing 100084,china) department of mechanical engineering Tsinghua University Beijing 100084 China

A meshless method integrated with linear elastic fracture mechanics(LEFM)is presented for 2D mixed-mode crack propagation *** domain is divided automatically into sub-domains based on Voronoi cells,which are used for quadrature for the potential energy. The continuous crack propagation is simulated with an incremental crack-extension method which assumes a piecewise linear discretization of the unknown crack *** each increment of the crack extension,the meshless method is applied to carry out a stress analysis of the cracked *** J-integral,which can be decomposed into mode Ⅰ and mode Ⅱ for mixed-mode crack,is used for the evaluation of the stress intensity factors(SIFs).The crack-propagation direction,predicted on an incremental basis, is computed by a criterion defined in terms of the SIFs. The flowchart of the proposed procedure is presented and two numerical problems are analyzed with this *** meshless results agree well with the experimental ones,which validates the accuracy and efficiency of the method.

关键词： meshless method crack propagation mixed-mode crack Voronoi cell

The Influence of Preheat Temperature of Steel Plate on Steel-mushy Cu-graphite Bonding

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Journal of Wuhan university.of Technology(Materials Science) 2006年第3期21卷 12-14页

作者：张鹏 department of mechanical engineering Beijing Jiaotong UniversityBeijing 100044China

The pressing bonding of steel plate to QTi3.5-3.5 graphite slurry was conducted. Under the conditions of 530 ℃ for the preheat temperature of dies, 45% for the solid fraction of QTi3.5- 3.5 graphite slurry, 50 MPa for the pressure and 2 min for the pressing time, the relationship between the preheat temperature of steel plate and interfacial mechanical property of bonding plate was studied. The results show that when the preheat temperature of steel plate is lower titan 618 ℃ , the interfacial shear strength of bonding plate increases with the increasing of the preheat temperature of steel plate. When the preheat temperature of steel plate is higher than 618 ℃ , the interfacial shear strength decreases with the increasing of the preheat temperature of steel plate. When the preheat temperature of steel plate is 618 ℃ , the highest interfacial shear strength of bonding plate of 127.8 MPa can be got.

关键词： steel-mushy QTi3.5-3.5 graphite pressing bonding interfacial shear strength preheat temperature of steel plate

Evaluation of Surface Cracks Using Magnetic Flux LeakageTesting

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Journal of Materials Science & Technology 2002年第4期18卷 319-321页

作者： Luming LI, Songling HUANG, peng ZHENG and Keren SHINUT Center, mechanical engineering department, tsinghua university. beijing 100084, china NDT Cent. Mech. Eng. Dept. Tsinghua Univ. Beijing 100084 China

The magnetic field distribution characteristics of surface cracks with various widths are discussed based on finite element (FEM) results. The crack depth was 0.20 mm, the width range was from 0.02 to 1.00 mm. The results showed that crack width and lift-off (the distance between surface and sensor) will influence signals. Discussed in this paper is the influence of various lift-off parameters on the peak to peak values of the normal component in magnetic flux leakage testing. The effects can be applied to evaluate surface breaking cracks of different widths and depths. An idea is presented to smooth narrow, sharp crack tips using alternating current (AC) field magnetization.

关键词： Magnetic flux leakage testing (MFL) Slot width Finite element method (FKM)

Effect of Interface on mechanical Property of Steel-mushy Al-20Sn Bonding Plate

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Journal of Wuhan university.of Technology(Materials Science) 2006年第1期21卷 60-62页

作者：张鹏 department of mechanical engineering Beijing Jiaotong University Beijing 100044 China

The ratio of Fe-Al compound at interace, which could determine the quarttity of Fe-Al compound at the interace of steel-mushy Al- 20 Sn bonding plate, was used to characterize the interfacial structure of steel-mushy Al-20 Sn bonding plate quantitatively. The effect of ratio of Fe-Al compound at interface on interacial shear strength was investigated perfectly. The results show that the relationship between ratio of Fe-Al compound at interace and interfacial shear strength is S = 3.3 ＋ 1.91 t - 0.0135t^2 （ where t is ratio of Fe-Al compound at in- terface and S is interfacial shear strength ）. When the ratio of Fe-Al compound at interface is 71%, the largest interfacial shear strength 70.9 MPa is got. This reasonable ratio of Fe-Al compound at interface is a quarttitative criterion of interfacial embrittlement. When the ratio of Fe-Al compound at interface is higher than 71% , interfacial embrittlement will occur.

关键词： interfacial structure ratio of Fe-Al compound at interface interfacial shear strength

A TWO-SCALE SECOND-ORDER MOMENT PARTICLE TURBULENCE MODEL FOR GAS-PARTICLE FLOW

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Journal of Hydrodynamics 2006年第6期18卷 659-665页

作者： zeng Zhuo-xiong ZHOU Li-xing department of engineering Mechanics Tsinghua University Beijing 100084 China department of mechanical engineering Nanchang Institute of Aeronautical Technology Nanchang 330034China

A two-scale second-order moment two-phase turbulence model was developed and used to simulate gas-particle flow in a sudden-expansion chamber and a channel. The simulation results were in agreement with the experimental results, and the results were compared with those of the single-scale second-order moment two-phase turbulence model. Several improved features show that the two-scale model is to a certain extent better than the single-scale model, which may be attributed to the fact that particle turbulence is well characterized by the two-scale turbulence model.

关键词： gas-particle flow second-order moment model,two-scale fluctuation

Preparation of QTi4.3-4Graghite Composite by Semi-solid Casting Technology

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Journal of Wuhan university.of Technology(Materials Science) 2005年第4期20卷 69-72页

作者：张鹏 department of mechanical engineering Beijing Jiaotong University Beijing 100044 China

The electromagnetic-mechanical stirring technology was employed for preparing QTi4.3-4 graghite composite slurry,and QTi4.3-4 graghite composite with uniform distribution of graphite particles was prepared uring the semi-solid casting technology *** structure of this QTi4.3-4graphite composite was studied and the condition for uniform distribution of graphite particles was *** experimental results show that there exists a linear relationship between the solid fraction and the stirring temperature of QTi4.3-4graphite *** the decreasing of stirring temperature,the solid fraction of QTi4.3-4 graghite slurry increases *** casting,with the increasing of solid fraction of QTi4.3-4 graphite *** agglomeration of graphite particles is removed *** the solid fraction is higher than 40%,graphite particles can distribute evenly in QTi4.3-4 graghite composite.

关键词： semi-solid casting technology distribution of graphite particles solid fraction

Preparation of nanoparticles with an environment-friendly approach

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Journal of Environmental Sciences 2009年第6期21卷 727-730页

作者： YAO Kefu,peng Zhen,FAN Xiaolin Key Laboratory of Advanced Materials Processing Technology,Ministry of Education of china,department of mechanical engineering,tsinghua university.beijing 100084,china. Key Laboratory of Advanced Materials Processing Technology Ministry of Education of China Department of Mechanical Engineering Tsinghua University Beijing 100084 China

Developing various approaches for preparing high performance materials has long been topics and tasks both for scientists and for engineers. Despite that many methods have been developed for preparing nanomaterials, developing simple and environment-friendly ways for preparing nanomaterials is very attractive. Here a simple approach of synthesizing Fe3O4 nanoparticles by arc-discharge submerging in water was reported. The results showed that by this method Fe3O4 nanoparticles can be synthesized at large scale. The as-prepared Fe3O4 nanoparticles exhibited uniform spherical shape and their diameters varied with arc-discharging parameters. The experimental results showed that the size of the synthesized Fe3O4 nanoparticles can be controlled through adjusting the processing parameters. Since no vacuum system has been used, the synthesizing process is greatly simplified. In addition, only cheap deionized water and industrial iron bar are used and no pollution or harmful byproducts are found in the synthesis process. It indicated that the present approach is a simple, low-cost and environment-friendly one for preparing nanoparticles.

关键词： nanoparticles preparation approach Fe3O4