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mechanically Driven Alloying and Structural Evolution of Nanocrystalline Fe_(60)Cu_(40) Powder

Journal of Materials science & technology 1997年第4期13卷 354-358页

作者： Yuanda DONG and Xueming MA(school of Materials science and {2., Shanghai University, Shanghai 2.0072. china)Yuanzheng YANG(Dept. of mechanical {2.(2., South china University of technology, Guangzhou 510641, china)Fangxin LIU and Genmiao WA school of Materials science and {2. Shanghai University Shanghai 200072 China Dept. of mechanical engineering(2. South China University of Technology Guangzhou 510641 China Lab. of Structure Analysis University of Science and Technology of China Hefei 230026 China

Highly supersaturated nanocrystalline fcc Fe60Cu40 alloy has been prepared by mechanical alloying of elemental powders. The phase transformation is monitored by X-ray diffraction (XRD),Mossbauer spectroscopy and extended X-ray absorption fine structure (EXAFS). The powder obtained after milling is of single fcc structure with grain size of nanometer order. The Mossbauer spectra of the milled powder can be fitted by two subspectra whose hyperfine magnetic fields are 16 MA/m and 2. MA/m while that of pure Fe disappeared. EXAFS results show that the radial structure function (RSF) of Fe K-edge changed drastically and finally became similar to that of reference Cu K-edge, while that of Cu K-edge nearly keeps unchanged in the process of milling. These imply that bcc Fe really transforms to fcc structure and alloying between Fe and Cu occurs truly on an atomic scale. EXAFS results indicate that iron atoms tend to segregate at the boundaries and Cu atoms are rich in the fcc lattice. Annealing experiments show that the Fe atoms at the interfaces are easy to cluster to α-Fe at a lower temperature, whereas the iron atoms in the lattice will form γ-Fe first at temperature above 350℃, and then transform to bcc Fe

关键词： mechanically Driven Alloying and Structural Evolution of Nanocrystalline Fe MA Cu Powder Figure

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Relationship between the Corrosion and Cr-Ni Content of Stainless Steel in Borax Bath

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Journal of Wuhan University of technology(Materials science) 2011年第6期26卷 1137-1139页

作者：王俊元 school of mechanical {2. and Automation North University of China

The corrosion of stainless steel was experimentally investigated and analyzed to improve the service-life of the crucible and fixture clamps. Through the experiment, stainless steel was found to satisfy the crucible and fixture clamps materials. As the chromium element mass percentage of the stainless steel increased, the corrosion decreased rapidly at first and then slowly increased. With the corrosion time prolonging, the corrosion growth rate is generally a downward trend. With Chromium 2.%, the corrosive were the least. With Nickel element mass percentage increased, the corrosion increased rapidly at first and then decreased rapidly, flatten at the last. It was special that the corrosion had little relationship with the Chromium and Nickel mass percentage when the Nickel percentage is more than 35%. The most remarkable corrosion is corresponding with the Nickel element 12., the least corrosion with Nickel element 80%. So Nickel element 35% is the most optional.

关键词： corrosion chromium nickel stainless steel borax bath

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Quasi-nano wear mechanism under repeated impact contact loading

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science china(Technological sciences) 2010年第6期53卷 1583-1589页

作者： ZHU JinHua1,REN XiangHong1,2.ZHANG JianJun1,3,XU YunHua1,3 & LU ZhengXin1,4 1 State Key Laboratory for mechanical Behavior of Materials,Xi’an Jiaotong University,Xi’an 710049,china 2.Xi’an Research Institute of High-tech,Xi’an 71002.,china 3 school of Materials science and engineering,Xi’an University of Architecture and technology,Xi’an 710055,china 4 school of Materials science and engineering,Xi’an University of technology,Xi’an 710049,china 1. State Key Laboratory for mechanical Behavior of Materials Xi’an Jiaotong University Xi’an 710049 China2. Xi’an Research Institute of High-tech Xi’an 710025 China3. School of Materials Science and Engineering Xi’an University of Architecture and Technology Xi’an 710055 China4. School of Materials Science and Engineering Xi’an University of Technology Xi’an 710049 China

A new quasi-nano wear mechanism (QNWM) has been proposed in this paper based on the facts of wear curve turning under high energy impact contact *** characteristic is that the wear rate of QNWM is only 1/10-1/3 that of delamination mechanism at the same energy *** diameters of wear debris and pits on the worn surfaces fall into the quasi-nanometer scale (about 50-12. nm).The necessary and sufficient conditions,which bring about the QNWM,are:(i) the nano-structure (nano-crystalline + amorphous phase) in impact contact surface layer has formed by the intensive impact strain;(ii) the delamination wear cracking in sub-surface layer must be restrained;(iii) the microcracks of QNWM are produced in amorphous phase of surface nano-structure layer rather than in nano-crystalline.

关键词： impact wear quasi-nano wear mechanism delamination wear mechanism nano-structure

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Modeling and Assessment of Buoyancy-Driven Stratified Airflow in High-Space Industrial Hall

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湖南大学学报（自然科学版） 2009年第S1期36卷 19-22页

作者： WANG Han-qing1,2.CHEN Ke1,HU Jian-jun1,3,KOU Guang-xiao2.WANG Zhi-yong2.1.school of Energy science and {2.,Central South University,Changsha,Hunan 410083,china 2.Department of Civil {2.,Hunan University of technology,Zhuzhou,Hunan 412.08,china 3.school of mechanical {2.,Purdue University,West Lafayette,USA) school of Energy science and {2. Central South University Changsha 410083 China Department of Civil engineering Hunan University of Technology Zhuzhou 412008 China school of mechanical {2. Purdue University West Lafayette United States

In industrial environment,heat sources often are contaminant sources and health threatening contaminants are mainly passive,so a detailed understanding of airflow mode can assist in work environment hygiene measurement and *** paper presented a numerical investigation of stratified airflow scenario in a high-space industrial hall with validated commercial code and experimentally acquired boundary *** upon an actually undergoing engineering project,this study investigated the performance of the buoyancy-driven displacement ventilation in a large welding hall with big components *** results have demonstrated that stratified airflow sustained by thermal buoyancy provides zoning effect in terms of clean and polluted regions except minor stagnant eddy *** competition between negative buoyant jets from displacement radial diffusers and positive buoyant plume from bulk object constitutes the complex transport characteristics under and above stratification ***,downdraft and turbulent eddy motion complicate the upper mixing zone,but the exhaust outlet plays a less important role in the whole field *** the corresponding suggestions concerning computational stability and convergence,further improvements in modelling and measurements were given.

关键词： modelling buoyancy-driven large enclosure industrial ventilation

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HCWCI/Carbon Steel Bimetal Liner by Liquid-Liquid Compound Lost Foam Casting

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Journal of Iron and Steel Research International 2012年第10期19卷 13-19页

作者： XIAO Xiao-feng1,2. YE Sheng-ping2. YIN Wei-xin3, XUE Qiong4 (1. school of mechanical {2. and Automation, Wuhan Textile University, Wuhan 430073, Hubei, china 2. State Key Laboratory of Material Processing and Die and Mould technology, Huazhong University of science and technology, Wuhan 430074, Hubei, china 3. Wuhan Zhike Abrasive-Resistant Material science and technology Development Co Ltd, Wuhan 430073, Hubei, china 4. College of science, Wuhan University of technology, Wuhan 430079, Hubei, china) [a] school of mechanical {2. and Automation Wuhan Textile University Wuhan 430073 Hubei China [b] State Key Laboratory of Material Processing and Die and Mould technology Huazhong University of Science and Technology Wuhan 430074 Hubei China [c] Wuhan Zhike Abrasive-Resistant Material science and technology Development Co Ltd Wuhan 430073 Hubei China [d] College of science Wuhan University of Technology Wuhan 430079 Hubei China

Impact, friction and corrosion from the grinding balls and the grinding medium during the mineral processing result in liner breakage. Liner, made from Hadfield steel or alloyed steel, could not have served in wet grinding environment for more than ten months. Composite liner, made from HCWCI (high Cr white cast iron) and carbon steel, has been developed successfully with liquid-liquid composing process based on LFC (lost foam casting). The microstructure of composite was analyzed with optical microscope, SEM (scanning electron microscope)/EDX energy-dispersive X-ray and XRD (X-ray diffraction). According to micrograph, the combination region of two metals was staggered like dogtooth, no mixtures occurred between two liquid metals, and its interface presented excellent metallurgical bonding state. The results of mechanical property test show that, the hardness of HRC, the fracture toughness, and the bending strength are more than 61, 16.5 J/cm2.and 1 600 MPa, respectively. Comparison between liners made from bimetal composite and alloyed steel has also been investigated in industrial hematite ball mill. The results of eight months test in wet grinding environment prove that the service life of bimetal composite liner is three times as long as that of one made from alloyed steel.

关键词： composite liner bimetal liquid-liquid compound composite interface lost foam casting high Cr white cast iron

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Second-order consensus in networks of dynamic agents with communication time-delays

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Journal of Systems engineering and Electronics 2010年第1期21卷 88-94页

作者： Bo Yang1,2. Huajing Fang3, and Hua Wang4 1. school of Navigation, Wuhan University of technology, Wuhan 430063, P. R. {2. 2. Wuhan Second Ship Design and Research Institute, Wuhan 430064, P. R. {2. 3. Department of Control science and engineering, Huazhong University of science and technology, Wuhan 430074, P. R. {2. 4. Department of Aerospace and mechanical engineering, Boston University, Boston MA02.15, USA school of Navigation Wuhan University of Technology Wuhan 430063 P. R. China Wuhan Second Ship Design and Research Institute Wuhan 430064 E R. China Department of Control science and engineering Huazhong University of Science and Technology Wuhan 430074 P. R. China Department of Aerospace and mechanical engineering Boston University Boston MA02215 USA

This paper proposes second-order consensus protocols with time-delays and gives the measure of the robustness of the protocols to the time-delay existing in the network of agents with second-order dynamics. By employing a frequency domain method, it is proven that the information states and their time derivatives of all the agents in the network achieve consensus asymptotically, respectively, for appropriate communication timedelay if the topology of weighted network is connected. Particularly, a tight upper bound on the communication time-delay that can be tolerated in the dynamic network is found. The consensus protocols are distributed in the sense that each agent only needs information from its neighboring agents, which reduces the complexity of connections between neighboring agents significantly. Numerical simulation results are provided to demonstrate the effectiveness and the sharpness of the theoretical results for second-order consensus in networks in the presence of communication time-delays.

关键词： second-order consensus protocols dynamic networks algebraic graph theory frequency domain analysis com-munication constraints.

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Mechanism of Breakdown in Laminar-Turbulent Transition of Incompressible Boundary Layer on a Flat Plate

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Transactions of Tianjin University 2007年第2期13卷 79-87页

作者：唐洪涛罗纪生周恒 school of mechanical {2. Tianjin University

Temporal mode direct numerical simulation was done for the process of laminar-turbulent transition in an incompressible boundary layer on a flat plate. The analysis of the results showed that during the breakdown process of laminar-turbulent transition, the modification of the mean flow profile by the disturbances led to a remarkable change in its stability characteristics, manifested in the significant enlargement of the linear unstable zone and the maximum amplification rate, and led to that many more disturbances were excited and enhanced rapidly, correspondingly the turbulent energy also increased rapidly, and the mean flow profiles evolved swiftly from laminar to turbulent. It was also found that if the oblique waves in the initial disturbances did not form symmetrical pairs, the subsequent span-wise mean velocities would, in general, be nonzero due to nonlinear interaction, which would have a great effect on the stability characteristics and also implied that the turbulence obtained by direct numerical simulation might not be fully a random process.

关键词： boundary layer transition direct numerical simulation breakdown

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Optimization of a serpentine flow field with variable channel heights and widths for PEM fuel cells

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science china(Technological sciences) 2010年第2期53卷 453-460页

作者： LIN Lin, ZHANG XinXin, FENG HuTing & WANG XiaoDong Department of Thermal engineering, school of {2. engineering, University of science and technology Beijing, Bejing 100083, china 1. Department of Thermal engineering School of Mechanical Engineering University of Science and Technology Beijing Bejing 100083 China

The present study proposes a modified serpentine flow field design in which the channel heights vary along each straight flow path to enhance reactant transport and liquid water removal. An optimization approach, combining a simplified conjugate-gradient method (inverse solver) and a three-dimensional, two-phase, non-isothermal fuel cell model (direct solver), has been developed to optimize the key geometric parameters. The optimal design has tapered channels for channels 1, 3 and 4 and increasing heights for channels 2.and 5 with the flow widths first increasing and then decreasing. The optimal channel heights and widths enhance the efficiency by 2..51% compared with the basic design having all heights and widths of 1 mm. The diverging channels have a greater impact on cell performance than fine adjustments of the channel widths for the present simulation conditions. The channel heights have more effect on the sub-rib convection, while the channel widths affect the uniformity of the fuel delivery more. The reduced channel heights of channels 2.4 significantly enhance the sub-rib convection to effectively transport oxygen to and liquid water out of the diffusion layer. The final diverging channel prevents significant leakage of fuel to the outlet via sub-rib convection.

关键词： PEM fuel cell simplified conjugate-gradient method optimization sub-rib convection

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Improvement on strip flatness of cold temper mills by modifying roll contour shape

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Journal of University of science and technology Beijing 2004年第3期11卷 251-255页

作者： Xiaoyan Li Jie Zhang Xianlin Chen Jianguo Cao Haixia Li mechanical engineering {2., University of science and technology Beijing, Beijing 100083, china Mech. Eng. Sch. Univ. of Sci. and Technol. Beijing Beijing 100083 China

A study on roll gap profile (strip profile) control was accomplished in a1700 mm single-stand temper mill. Some critical problems such as the deviation of work roll contourcaused by grinding and wear, the effectiveness of work roll bending were discussed. Using a finiteelement model, the effects of roll contours (ground and wear) on strip profile were *** roll bending effect on strip thickness was also analyzed. It is pointed out that there are somespecial features of flatness control in the temper mill: during temper rolling, roll deformation isslight due to small rolling load, and the loaded roll gap profile mainly depends on work rollcontour, while the backup roll has a little effect on gap crown; the effect of bending force ongauge can not be ignored due to the coupling between flatness control and gauge control. A new rollcontour arrangement adaptable to the mill was presented and has been put into practical *** application of the new set of rolls showed some good results: larger crown control range of workroll bender, higher rolling stability, better strip profile and flatness quality.

关键词： cold rolling temper mill strip shape control roll contour arrangement bending

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Temperature distribution in the tool-chip-workpiece system during the orthogonal cutting process

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International Journal of Minerals,Metallurgy and Materials 1997年第3期11卷 30-34页

作者： ZHENG Chun GU Tong (Department of mechanical engineering, McMaster University, Canada) (Applied {2. school, University of {2. and technology Beijing, Beijing 100083, china) McMaster Univ Canada

The temperature distribution in the tool, chip and workpiece was studied during the orthogonal cuttingprocess Under several different cutting conditions. The temperature distribution is calculated by the finite differencemethod. and the variation of the material properties with temperature was taken was taken into account The results obtained arecoincident with both previous published results and experimental measurements.

关键词： temperature distribution orthogonal cutting FDM tool-chip-workpiece system

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