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Microstructure and formation mechanism of twins of laths of austenite with high nitrogen

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Science china(Technological Sciences) 2007年第6期50卷 755-764页

作者： WU CuiLan1,2 & LUO ChengPing2 1 Center for High Resolution Electron Microscopy, college of Materials Science and engineering, Hunan university, Changsha 410082, china 2 college of mechanical engineering, South china university of technology, Guangzhou 510641, china 1. Center for High Resolution Electron Microscopy College of Materials Science and Engineering Hunan University Changsha 410082 China 2. college of mechanical engineering South China University of Technology Guangzhou 510641 China

The microstructure of composite diffusion layer of the nitrided and chromized 0.2% carbon steel is investigated using TEM and EDS. It is found that laths of austenite with high nitrogen (γ N) precipitate from α-ferrite matrix in the deeper zone of the diffusion layer. These γ N laths are all twins, with their {111} twinning planes parallel to the lath axis, thus forming a characteristic "back-to-back" morphology. There are two types of γN lath. The first is a genuinely {111} twin, and γ N and α keep the accurate K-S relationship, and each γ N and α form a sharp and smooth γ N/α inter- face of {335}γN//{341}α, namely habit plane {335}fcc. The second is a pseudo-twin, with micro-twins {111} or faults formed within the two twin components. Localized lattice deformation (relaxation) seems to have occurred at the interfaces of the second type of γ N due to the formation of micro-twins or faults within the twin components. These micro-twins or faults make the orientation relationship (OR) between each of the γN and the α-matrix deviate from the accurate K-S OR, and the OR between two γ N twin components deviate from the genuine {111} twin relation- ship. In addition, the γ N/α interface of the second type of γ N is not as sharp or smooth as that of the first one.

关键词： austenite containing nitrogen, twins, steel 20, nitriding, composite chromizing

Parameters Relevant to Bubble Detachment when Gas-injecting into Polymer Melt Flow Field

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Journal of Wuhan university of technology(Materials Science) 2005年第1期20卷 68-71页

作者：陈再良 college of mechanical and electrical engineering Soochow University Suz hou 215021 China

The bubble deformation processes were reported when gas was injected into polyme r melt flow field in another paper, the experiments showed that the deformation was severely affected by the volume of the bubble, and in turn, for the different bubbles, several different deformation processes were presented d uring their movement along the flow channel. In addition, we could find that the magnitude of the bubble volume was dependent upon the pressure difference of th e gas injection pressure and the melt pressure. In this paper, more experimental conditions were changed to investigate the parameters relevant to the detachmen t of bubbles from the injection nozzle. The experimental results show that the p ressure difference, the melt flow velocity as well as the melt pressure were all critical for the parameters, such as the bubble detachment time, the maximum bu bble diameters and the magnitude of the bubble volume. The morphology changes of bubble were very large when the flow field was abruptly changed, and the situat ions were more complicated.

关键词： bubble morphology detachment time geometry parameters flow field

Parameter identification theory of a complex model based on global optimization method

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Science china(Physics,Mechanics & Astronomy) 2008年第11期51卷 1722-1732页

作者： QU Jie1, JIN QuanLin2 & XU BingYe3 1 college of Automotive engineering, South china university of technology, Guangzhou 510640, china 2 Beijing Research Institute of mechanical and electrical technology, Beijing 100083, china 3 Department of engineering Mechanics, Tsinghua university, Beijing 100084, china 1. college of Automotive engineering South China University of Technology Guangzhou 510640 China 2. Beijing Research Institute of mechanical and electrical technology Beijing 100083 China 3. Department of engineering Mechanics Tsinghua University Beijing 100084 China

With the development of computer technology and numerical simulation technology, computer aided engineering (CAE) technology has been widely applied to many fields. One of the main obstacles, which hinder the further application of CAE technology, is how to successfully identify the parameters of the selected model. An elementary framework for parameter identification of a complex model is provided in this paper. The framework includes the construction of objective function, the design of the optimization method and the evaluation of the identified results, etc. The parameter identification process is described in this framework, taking the parameter identification of the superplastic constitutive model considering grain growth for Ti-6Al-4V at 927°C as an example. The objective function is the weighted quadratic sums of the difference between the experimental and computational data for the stress-strain relationship and the grain growth relationship; the designed optimization method is a hybrid global optimization method, which is based on the feature of the objective function and incorporates the strengths of genetic algorithm (GA), the Levenberg-Marquardt algorithm and the augmented Gauss-Newton algorithm. The reliability evaluation of parameter identification result is made through the comparison between the calculated and experimental results and between the theoretical values of the parameters and the identified ones.

关键词： constitutive model parameter identification theory inverse analysis global optimization

Boundary conditions for the bending of a piezoelectric beam

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Science china(Physics,Mechanics & Astronomy) 2008年第7期51卷 847-856页

作者： GAO Yang1, XU SiPeng2 & ZHAO BaoSheng3 1 college of Science, china Agricultural university, Beijing 100083, china 2 college of engineering, Ocean university of china, Qingdao 266071, china 3 School of mechanical engineering, university of Science and technology Liaoning, Anshan 114044, china 1. college of Science China Agricultural University Beijing 100083 China 2. college of engineering Ocean University of China Qingdao 266071 China 3. School of mechanical engineering University of Science and Technology Liaoning Anshan 114044 China

For beam bending in transversely isotropic piezoelectric media, the reciprocal theorem and the general solution of piezoelasticity are applied in a novel way to obtain the appropriate stress and mixed boundary conditions accurate to all orders for the beam of general edge geometry and loadings. By generalizing the method developed by Gregory and Wan, a set of necessary conditions on the edge-data for the existence of a rapidly decaying solution is established. The prescribed edge-data of the beam must satisfy these conditions in order that they could generate a decaying state within the beam. When stress and mixed conditions are imposed on the beam edge, these decaying state conditions for the case of bending deformation of piezoelectric beam are derived explicitly. They are then used for the correct formulation of boundary conditions for the beam theory solution (or the interior solution). Besides, an analytical solution of elastic beam is formulated to verify validity of our boundary conditions. For the stress data, our boundary conditions coincide with those obtained in conventional forms of beam theories. More importantly, the appropriate boundary conditions with two sets of mixed edge-data are obtained for the first time.

关键词： boundary conditions beam bending piezoelectric media decaying states regular states

Mixed boundary conditions for piezoelectric plates

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Science china(Physics,Mechanics & Astronomy) 2009年第5期52卷 755-761页

作者： GAO Yang 1 ,XU SiPeng 2 &ZHAO BaoSheng 3 1college of Science,china Agricultural university,Beijing 100083,china 2college of engineering,Ocean university of china,Qingdao 266071,china 3 School of mechanical engineering,university of Science and technology of Liaoning,Anshan 114044,china college of Science China Agricultural University Beijing 100083 China college of engineering Ocean University of China Qingdao 266071 China School of mechanical engineering University of Science and Technology of Liaoning Anshan 114044 China

For plate bending and stretching problems in piezoelectric materials,the reciprocal theorem and the general solution of piezoelasticity are applied in a novel way to obtain the appropriate mixed boundary conditions accurate to all order.A decay analysis technique is used to establish necessary conditions that the prescribed data on the edge of the plate must satisfy in order that it should generate a decaying state within the *** the case of axisymmetric bending and stretching of a circular plate,these decaying state conditions are obtained explicitly for the first time when the mixed conditions are imposed on the plate *** are then used for the correct formulation of boundary conditions for the interior solution.

关键词： boundary conditions piezoelectric plates mixed data bending problems stretching problems

Cutting Performance and Mechanism of RE Carbide Tools

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Rare Metals 2001年第3期20卷 197-201页

作者： Jianbing Cheng, Yufang Wu, Qixun Yu 1) Department of mechanical engineering, Beijing technology and Business university, Beijing 100037, china 2) college of mechanical engineering and Automation, Beijing Institute of technology Beijing 100081, china Beijing Technol & Business Univ Dept Mech Engn Beijing 100037 Peoples R China Beijing Inst Technol Coll Mech Engn & Automat Beijing 100081 Peoples R China

The research of rare earth elements (RE), added into cemented carbide tools, is one of the recent developments of new types of tool materials in china. Systematic experiments about RE carbides YG8R. (K30), YT14R (P20) and, YW1R (M10) were made to study on the cutting performance in comparison with non-RE carbides YG8, YT14 and YW1. The cutting experiments were as follows: tool life, cutting force, tool-chip friction coefficient and interrupted machining. The action of RE on the carbide materials and the cutting mechanism of the RE carbide tools in the cutting process were verified with the aid of SEM and energy spectrum analysis. Experimental results show that the RE carbide tools have a good overall performance.

关键词： rare earth elements cemented carbide tool cutting performance cutting mechanism

Theoretical analysis of alloy multiplying factor by the empirical electron theory of solids and molecules

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Science china(Technological Sciences) 2007年第6期50卷 807-814页

作者： SONG YuePeng1,2, LIU GuoQuan2, LI ZhiLin3, FENG ChengMing1 1 mechanical and Electronic engineering college, Shandong Agricultural university, Tai’an 2.1.1., china 2 college of Materials Science and engineering, university of Science and technology, Beijing 100083, china 3 college of Material Science and engineering, Beijing university of Chemical technology, Beijing 100029, china mechanical Electronic engineering college Shandong Agricultural University Tai’an 271018 China college of Materials Science engineering University of Science technology Beijing 100083 China college of Material Science engineering Beijing University of Chemical Technology Beijing 100029 China

By introducing the distribution probability of structural units in austenite contain- ing alloying elements and considering its effects on phase transformation, this paper establishes a calculation model of distribution probability of structural units. A new valence electron structure (VES) parameter-transformation effect coefficient of alloying elements (HL), is defined and then studied both theoretically and ex- perimentally. The relationship between the parameter HL and the multiplying factor (the quenching capability factor) of alloying elements is studied. The results indi- cate that the two parameters (HL and the quenching capability factor) have the same variation characteristic and substance feature. Therefore, the multiplying factor virtually expresses the relative quantity of structural units in the alloying elements-containing austenite.

关键词： multiplying factor (the quenching capability factor), empirical electron theory of solids and molecules, transformation effect coefficient of alloying elements, structural units in austenite containing alloying elements

Effects of MoS_2 on mechanical and tribological properties of NiCr-based alloys

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中国有色金属学会会刊：英文版 2000年第3期10卷 328-327,329-331页

作者： XIONG Dang sheng(熊党生) 1, PENG Chao qun(彭超群) 2, LIU Jin long(刘金龙) 1 1. college of mechanical engineering, china university of mining and technology, xuzhou 221008, P.R.china 2. State Key Lab for Powder Metallurgy, Central South Unive china Univ Min & Technol Coll Mech Engn Xuzhou 221008 Peoples R China Cent S Univ Technol State Key Lab Powder Met Changsha 410083 Peoples R China

Ni Cr based alloys with a wide temperature range self lubrication were made by hot pressing the mixture powder of alloyed Ni Cr powder, elemental Mo, Al, Ti and B powders and MoS 2 powder. The mechanical and tribological properties of these alloys when rubbing with Al 2O 3 ceramics and W18Cr4V high speed steel were measured in the temperature range of 20～700 ℃, and the mechanisms of self lubrication and wear resistance were studied. The results showed that the alloy containing 10% MoS 2 has the best combination of mechanical properties, antifriction and wear resistance. Over a wide temperature range from 20 ℃ to 700 ℃, when rubbing with Al 2O 3, its friction coefficient and wear rate are 0.19～0.3 and (1.1～1.5)10 -14 m 3/(N·m), respectively; when rubbing with the high speed steel, those values are 0.18 ～ 0.26 and (0.6～3.2)×10 -15 m 3/(N·m), respectively.

关键词： Ni Cr based alloys molybdenum disulfide self lubrication tribological properties

The Influence of Some Key Parameters on Fatigue Life of Common Metallic Components

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Journal of Central South university 2000年第3期12卷 159-161页

作者： LIU Yi lun (college of mechanical and electrical engineering, Central South university, Changsha 410083, china) 1. college of mechanical and electrical engineering Central South University 410083 Changsha China

The effect of key parameters on fatigue life of common metallic components, e.g. steel, aluminium alloy, has been analysed quantitatively. The influential coverage and degree of these parameters have been investigated systematically, some phenomena which can′t be discovered with qualitative analysis method have been revealed, a series of valuable conclusions has been obtained, which would be very beneficial to fatigue resistant design and improvement of anti fatigue ability of metallic components.

关键词： metallic material component fatigue life key parameter effect