Started in 1985 Semimonthly
ISSN 1005-0302
CN 21-1315/TG
Impact factor:6.155

The journal has been awarded the excellent periodical in China, and its articles are covered by SCI, EI, CA, SA, JST, RJ, CSA, MA, EMA, AIA etc., PASCAL web. ISI web of Science,SCOPUS.

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      28 December 2003, Volume 19 Issue Supl. Previous Issue    Next Issue
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    Research Articles
    3D Modeling And Simulation of Dendritic Growth During Solidification
    Zuojian LIANG, Qingyan XU, Baicheng LIU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 1-4. 
    Abstract   HTML   PDF (1965KB)
    A mathematical model for the three dimensional simulation of free dendritic growth and microstructure evolution was developed based on the growth mechanism of crystal grains and basic transfer equations such as heat, mass and momentum transfer equations. Many factors including constitutional undercooling, curvature undercooling and anisotropy, which had vital influences on the microstructure evolution, were considered in the model. Simulated results showed that final microstructural patterns and free dendritic growth could be predicted reasonably and calculated results were coincident with experimental. The simulated results of free dendritic growth indicated that the strength of anisotropy has significant effects on free dendritic growth, dendrite profile, micro solute and temperature distribution. The dendritic grain profiles with fully-grown parallel secondary arm tend to be formed at the intensive anisotropy, while near octahedral grain profiles with small protuberances of surface at low strength of anisotropy. The simulated results of free dendritic growth also indicated that there are small molten pools left in interdendritic areas. This is helpful to understand the fundamental of the formation of microstructure related defects such as microsegregation and microporosity.
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    Parameter Optimisation of Stress-strain Constitutive Equations Using Genetic Algorithms
    Y.Y.Yang, M.Mahfouf, D.A.Linkens
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 5-8. 
    Abstract   HTML   PDF (814KB)
    The accuracy of numerical simulations and many other material design calculations, such as the rolling force, rolling torque, etc., depends on the description of stress-strain relationship of the deformed materials. One common method of describing the stress-strain relationship is using constitutive equations, with the unknown parameters fitted by experimental data obtained via plane strain compression (PSC). Due to the highly nonlinear behaviour of the constitutive equations and the noise included in the PSC data, determination of the model parameters is difficult. In this paper, genetic algorithms were exploited to optimise parameters for the constitutive equations based on the PSC data. The original PSC data were processed to generate the stress-strain data, and data pre-processing was carried out to remove the noise contained in the original PSC data. Several genetic optimisation schemes have been investigated, with different coding schemes and different genetic operators for selection, crossover and mutation. It was found that the real value coded genetic algorithms converged much faster and were more efficient for the parameter optimisation problem.
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    Study on Process Parameters Optimization of Sheet Metal Forming Based on PFEA/ANN/GA
    Juhua HUANG, Jinjun RAO, Xuefeng LI
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 9-12. 
    Abstract   HTML   PDF (2501KB)
    Sheet metal forming is widely applied to automobile, aviation, space flight, ship, instrument, and appliance industries. In this paper, based on analyzing the shortcoming of general finite element analysis (FEA), the conception of parametric finite element analysis (PFEA) is presented. The parametric finite element analysis, artificial neural networks (ANN) and genetic algorithm (GA) are combined to research thoroughly on the problems of process parameters optimization of sheet metal forming. The author programs the optimization scheme and applies it in a research of optimization problem of inside square hole flanging technological parameters. The optimization result coincides well with the result of experiment. The research shows that the optimization scheme offers a good new way in die design and sheet metal forming field.
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    Numerical Simulation of Microstructure Formation and Forecast of Mechanical Properties for Spheroidal Graphite Iron
    Weimin ZHAO, Shuping HOU, Haipeng LI, Aiwen HU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 13-16. 
    Abstract   HTML   PDF (2164KB)
    The numerical simulation can overcome the hardship of mathematical analysis and experimental research, explicate the mechanism of microstructure shaping, predict mechanical properties and operating life of castings and then optimize technology and control microstructure formation to obtain the qualified castings. The finite difference method (FDM) is applied to the simulation of temperature field based on all kinds of nucleation and growth models on all stages of solidification of spheroidal graphite cast iron. Visual C++ is used to program the numerical simulation software, QTstructure-1 to simulate the solidification process of spheroidal graphite cast iron and the formation of all phases in solidification process. Finally, the result of simulation is well agreed with the experimental result.
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    Atomic Scale Computer Simulation for Early Precipitation Process of Ni75Al6V19 Alloy
    Yuhong ZHAO, Hua HOU, Hong XU, Yongxin WANG, Zheng CHEN, Xiaodong SUN
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 17-19. 
    Abstract   HTML   PDF (1495KB)
    The atomic scale computer simulation for initial precipitation mechanism of Ni75Al6V19 alloy was carried out for the first time by employing the microscopic diffusion equation. The initial precipitation process was investigated through simulating the atomic pictures and calculating the order parameters of the two kinds of ordered phases. Simulation results show that the ordered phase precipitated earlier than θ ordered phase by congruent ordering+spinodal decomposition mechanism and thus produced a nonstoicheometric single ordered phase. Then, the nonstoichiometricθphase precipitated by a non-classical nucleation and growth mechanism at the APBS of phase.
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    Modeling Microstructural Evolution under the Influence of Thermosolutal Convection during Ingot Solidification Process
    Qiang Li, Chunli Mo, Dianzhong Li, Bainian Qian
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 20-22. 
    Abstract   HTML   PDF (1993KB)
    A model combined both macroscopic transport and microstructural evolution is applied to describe the influence of thermosolutal convection on microstructural evolution during the solidification process. Firstly, the volume average method and Simpler algorithm are used to solve the macroscopic transport equation. Then the calculated results are incorporated into the cellular automaton (CA) model to simulate the microstructural evolution. Using this model, a simple casting ingot is applied to simulate microstructural evolution. Through the simulation, it is found that the thermosolutal convection has a strong influence on the redistribution of temperature field and solute field, which influence the solidification microstructural evolution.
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    Numerical Analysis of Energy Effect in Laser-TIG Hybrid Welding
    Yanbin CHEN, Liqun LI, Junfei FANG, Xiaosong FENG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 23-26. 
    Abstract   HTML   PDF (1278KB)
    The hybrid source that combined CO2 laser with TIG arc to proceed welding was analyzed. Based on an energy model, the temperature field and weld shape were calculated numerically. The heat transfer characteristic of the hybrid heat source to workpiece and its effect to weld shape were also analyzed. Through analyzing the enhancement effect of the hybrid heat source, the absorption effect and defocusing effect of the hybrid arc to laser were calculated, and the regularity of the energy density to the current was obtained subsequently. At last, the critical energy matches to induce the enhancement effect of CO2 laser-TIG arc hybrid welding were obtained.
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    Bonding Strength of Ni/Ni3Al Interface with Different Lattice Misfit
    Ping PENG, Caixing ZHENG, Shaochang HAN, Zhaohui JIN, Rui YANG, Zhuangqi HU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 26-28. 
    Abstract   HTML   PDF (1278KB)
    The interfacial binding covalent bond density (CBD) and the local environmental total bond order (LTBO) of the Ni/Ni3Al interface with different lattice misfits (δ) were calculated by using first-principles discrete variation Xα method. It was found that the effects of lattice misfits on the electronic structures of incoherent Ni/Ni3Al interface were very obvious. On one hand, less than -0.6% negative lattice misfit can promote the binding strength of γ/ interface. On the other hand, the total bonding strength ofγ/ interface decreases with increasing δ. Therefore, the magnitude and sign of lattice misfit must be carefully controlled for balancing the high temperature creep strength of Ni-base single crystal superalloy and the structural stability ofγ/ interface when one designs a new Ni-base single crystal superalloy.
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    Molecular Dynamics Simulation of Gas Diffusion in B2O3 and SiC
    Yajing YE, Litong ZHANG, Laifei CHENG, Yongdong XU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 29-31. 
    Abstract   HTML   PDF (548KB)
    Molecular dynamics simulation using a universal force field has been employed to determine the diffusion coefficients of O2 and Na2SO4 vapor into B2O3 and SiC from 700 K to 1273 K, respectively. Einstein diffusion was observed in a 250~300 ps simulation. The diffusion coefficient for the O2 range from about 9.279×10-9 cm2/s for B2O3 to 2.275×10-10 cm2/s for SiC at a loading of 32 molecules per simulation box, that for the Na2SO4 vapor range from about 9.888×10-7 cm2/s for B2O3 to 1.837×10-10 cm2/s for SiC at a loading of 8 molecules per simulation box. Environment properties of C/SiC composite will be increased via the B2O3 preventing the diffusion of O2 and Na2SO4 vapor into the pyrolytic interphase and carbon fibers.
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    Numerical Simulation and Shrinkage Defects Prediction of a Turbine Blade Investment Casting
    Jing TIAN, Xiang XUE, Yuebing ZHANG, Yalong GAO, Luzhi LIU, Qin SUN, Shiyou YUAN
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 32-34. 
    Abstract   HTML   PDF (1897KB)
    By adopting the solid modeling software SoldEdge and the enmeshment software SRIFCast as the pre-processing platform, a Ni based alloy turbine blade was three-dimensionally modeled and automatically enmeshed. A software code for numerical simulation of fluid flow and heat transfer was developed. The Xue criterion and Niyama criterion were used to predict the position of the shrinkage defects occurring in the solidification processes of the turbine blade. The results showed that both Xue and Niyama criteria could precisely predict the shrinkage defects in the Ni based alloy turbine blade. This indicates that numerical simulation is a significant tool in improving casting quality.
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    Numerical Simulation and Experiments of Hydroforming of Rectangular-section Tubular Component
    Shijian YUAN, Gang LIU, Xianwei TIAN, Z.R.WANG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 35-37. 
    Abstract   HTML   PDF (2067KB)
    In order to reduce high calibration pressure in hydroforming of components with too small radii, a method was proposed to manufacture automotive hollow components with rectangular shape by relatively lower pressure. The process is simulated and analyzed. It is thought that the friction force between the die surface and tube is a main reason that high pressure is needed to form small radii. Using the method proposed in this paper, a petal-like section shape is first preformed so that the central zones of the four sides of the preform section do not contact with the die sides, thus the tube metal is easy to flow into the transition radii area in calibration stage. Moreover, a positive force along the sides is produced by the internal pressure, which is beneficial to overcome the friction force and push the material into the radii. Therefore, the pressure for forming the transition radii is greatly reduced and the components with small radii can be formed with relatively lower pressure. For the experimental case conducted in this paper, the forming pressure is reduced by about 28.6% than the estimated forming pressure.
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    3D Rigid-Plastic Finite Element Analysis for Skew Rolling Process of the Stepped Part
    Gang FANG, Pan ZENG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 38-40. 
    Abstract   HTML   PDF (2272KB)
    Based on rigid-plastic finite element method, a skew rolling process of stepped part is simulated. Considering nodesaving and effective remeshing, the tetrahedron solid elements are used to discrete workpiece. The workpiece material adopts rigid-plastic model, where the flow stress is function of effective strain, effective strain rate and temperature. The thermomechanical coupling is considered in the simulation. To model the spinning workpiece undergoing plastic deformation, a novel solution is presented and applied in this paper. The stress state in the workpiece and forming characteristic of skew rolling are analyzed. The forming load, including roller torque and forces in three directions are predicted. The above analyses are helpful to understanding of forming mechanisms and improving of process and die design.
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    Finite-Element Simulation and Experimental Research of the Hot-Press Sintering of Nano-Sized Ceramic Powders
    Guoqing CHEN, Kaifeng ZHANG, Guofeng WANG, Y, ong YU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 40-42. 
    Abstract   HTML   PDF (2272KB)
    Numerical simulation of hot-press sintering of nano-sized ceramic powders was introduced by the commercial finite element code MSC.MARC. The powder plastic model and the thermo-mechanical coupled quadrilateral element were developed and adopted in the simulation. The mechanical and thermal properties of the nano-sized alumina based powders were determined. In addition, the experimental research and numerical simulation of the sintering process of different initial densities were carried out. The stress state in sintering of green compacts with different initial densities was analyzed by the densification theory. The reason for the density fluctuations of as-sintered ceramic bulks was found out.
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    Finite Element Analysis of the Steel Reinforced Plastic Pipe
    Hongyi SUN, Wenqi MA, Dachang KANG, Keding ZHAO
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 43-45. 
    Abstract   HTML   PDF (2528KB)
    The steel reinforced plastic pipe is a kind of green environmental protection pipelines with double-sides corrosionresisting and better withstanding to medium working pressure. The structure and technical process of this pipe are described briefly in this paper, and the finite element analysis has been done for the sake of understanding the distributions of stress and displacement inside this pipe under hydrostatic pressure. The analysis results are very important for safety application of the steel reinforced plastic pipe.
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    Numerical Simulation of Superplastic Forming and Diffusion Bonding of Ti Alloys
    Kaifeng ZHANG, Wenbo HAN, Wei WU, Guofeng WANG, Dezhong WU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 46-48. 
    Abstract   HTML   PDF (1057KB)
    The research on numerical simulation for combinative process of SPF/DB is carried out in this paper. The contacting problem of sheets is analyzed by using the penalty method. In order to solve the contact problem of different parts of the sheet, a new algorithm for contacting judgment is proposed. According to the relation of the distance vector and the vector of contacting element area, and the condition of contact, it can be judged whether or not a node on the slave surface and the corresponding master surface are in the state of SPF/DB. The Mindlin shell element is employed to simulate SPF/DB process of an asymmetry double-cell cup of Ti-6Al-4V to examine the efficiency of the new algorithm using ARVIP-3D. The results of the numerical simulation are in good agreement with experimental results.
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    Melting, Oxidation, Evaporation of Particle in-Flight in Plasma Spray Processes
    H.B.Xiong, L.L.Zheng
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 49-52. 
    Abstract   HTML   PDF (2041KB)
    A comprehensive numerical model has been developed to investigate the transient behaviors of particle characteristics, such as temperature, melting, evaporation, and oxidation status during argon-hydrogen DC plasma spraying. This model includes heat, momentum and mass transfer of carrier gas, and particle heating, melting, evaporation and oxidation. Special attentions have been paid to the evaporation-induced mass transfer and oxidation-induced evaporation as well as variable non-continuum phenomena.
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    Generalized Mathematical Model for Hot Rolling Process of Plate
    Zhenshan CUI, Bingye XU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 53-55. 
    Abstract   HTML   PDF (809KB)
    A generalized mathematical model is developed to predict the changes of temperature, rolling pressure, strain, strain rate, and austenite grain size for plate hot rolling and cooling processes. The model is established mainly by incorporating analytical and numerical method for differential equations under complicated boundary conditions. An industrial rolling and cooling process of plate is simulated by the model, in which the thickness of steel Q235B plate is rolled from initial 200 mm to final 12 mm by 13-passes in a two-high mill. The calculated results are in good agreement with measured data. Different from FEM simulation, the model takes very short time in calculation and makes the influence of rolling passes on precision to be very slight.
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    Study on Polyurethane/(vinyl ester resin) IPN Damping Materials
    Chuanli QIN, Dongyan TANG, Jun CAI, Jusheng.ZHANG, Weimin CAI, Xiaodong SUN
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 56-58. 
    Abstract   HTML   PDF (2186KB)
    Polyurethane/(vinyl ester resin) interpenetrating polymer network (PU/VER IPN) materials with broad temperature ranges and excellent damping properties from low temperature to room temperature were prepared. The influence of comonomers and component ratios on the compatibility and damping properties of IPN materials was studied by DMA which indicates that such properties are improved by introducing acrylic esters instead of polystyrene (PSt) into VER comonomer system. The detected results of microstructure by AFM show that the phase ranges of the dual-phase continuous IPN materials obtained are both in nanometer scale. The results of mechanical properties show that IPN materials show the regulation from elastic deformation to brittle deformation with the increase of VER proportion.
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    Three-dimensional Numerical Study on Temperature Field of Laser Bending of Sheet Metal
    Shunhong LIU, Xiong FANG, Pengteng WAN, Jing YAN
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 59-61. 
    Abstract   HTML   PDF (2348KB)
    Laser bending of sheet metal is a flexible forming technique by using laser scanning. Based of temperature grads mechanism, the temperature field of sheet metal bending process by using single laser scanning is studied with the ANSYS soft. A finite element model of temperature field is built. The dynamic variation process and distribution of temperature field of laser bending at given parameters are analyzed. Furthermore, the influence parameter on the peak temperature and temperature grads are also studied.
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    A Finite-Element Analysis on the Rheorolling Process of Semi-Solid Spring Steel
    Hongbo DONG, Yonglin KANG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 62-64. 
    Abstract   HTML   PDF (2170KB)
    With a geometrical model of porous material, a 3D finite-element analysis on the rolling process of spring steel- 60Si2Mn in the semi-solid state is carried out using software MARC. In terms of flat and groove rolling conditions, stress field and strain field are studied. The simulation results show that the rigid-viscoplastic model can accurately describe the semi-solid metal rolling process. Semi-solid slurry has the characteristics of low flow stress and good fluidity. During groove rolling, distribution of stress and strain on the cross-section of deformation zone is more uniform than that during flat rolling. The results of simulation are in good agreement with the experiment data, and show that semi-solid material fits for groove rolling.
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    A Method of Obtaining Deformation Information by Tracing Deformation from Sections for 3D FE Simulation
    Mei ZHAN, He YANG, Yuli LIU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 65-68. 
    Abstract   HTML   PDF (3661KB)
    With the development of computer technology and finite element method, the priority research area of plastic forming has focused on 3D FE simulation of forming processes for components with complicated geometrical shape. These processes have complex deforming mechanism, and different sections have different deforming characteristics. Therefore, for making a simple, convenient, and practical analysis of its deforming law, how to obtain deformation information of key sections from the results of 3D FE simulation has become one of problems urgently to be solved. So, a method of obtaining deformation information by tracing deformation from sections for 3D FE simulation has been proposed. From the deformation information got by this method, the deformation law of key locations and the whole deforming body can be obtained. This method can also help to compare the result from FE simulation with that from physical modeling. Key procedures of this method have been presented in detail, and it has been tested by applying to 3D FE simulation of precision forging of the blade with a damper platform. The result shows that the method is practicable and reliable, and it can also be applied to 3D FE simulation of plastic forming processes of other components.
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    Numerical Simulation of the Stress and Distortion of the Fiberglass-Reinforced Plastics Crust-Stainless Steel Liner Compound Conduit
    Hongyuan FANG, Chenglei FAN, Jianguo YANG, Ming LI, Zhen LUO, Xianzhong HOU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 69-70. 
    Abstract   HTML   PDF (2564KB)
    A new type of compound conduit is designed and the finite element method (FEM) is applied to analyze the mechanical performance of a typical compound conduit. The results of the numerical simulation confirm that the distributions of the strain, stress and the flexure distortion of the conduit are reasonable under the working conditions, and the stress and strain are continuous at the interface of the crust and the pipe liner. The conduit can endure 7.4 times of the working load before break, which fits well with that of the experiment and means that the conduit has good ability to bear overload. The peak value of the flexure distortion of the conduit (6 m) is about 3 mm in the middle bottom of the pipeline, which also accords well with that of the experiment.
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    Simulation on Thermal Integrity of the Fin/Tube Brazed Joint of Heat Exchangers
    Yiyu QIAN, Feng GAO, Fengjiang WANG, Hui ZHAO
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 71-72. 
    Abstract   HTML   PDF (1788KB)
    In the applications of heat exchangers, the fin efficiency of heat transfer is the key issue. Thermal distribution within the brazed joints in heat exchanger under loading conditions is investigated in this paper. Simulated results showed that the thermal distribution at the brazed joint zone is related to not only the geometry of the fin and tube, but also the brazed joint topology. A poor brazed joint will result in very poor heat transfer. Thermal contact resistance is adopted to analyze the fin heat efficiency.
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    An Electronic Approach to Materials Design
    Masahiko MORINAGA, Yoshinori MURATA, Hiroshi YUKAWA
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 73-76. 
    Abstract   HTML   PDF (878KB)
    A molecular orbital approach to materials design has recently made great progress. This approach is based on the electronic structure calculations by the DV-Xα cluster method. In this paper recent progress in this approach is reviewed. In particular, it is stressed that New PHACOMP approach is useful for predicting the formation of topologically close-packed (TCP) phases (e.g., σ phase and μphase ) in nickel based superalloys. Compared to the current PHACOMP, New PHACOMP provides a better tool for designing those alloys which are free from such TCP precipitates at service temperatures. In addition, the d-electrons concept is shown for alloy design and development.
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    Environmental Simulation Experiments of 3D-C/SiC Composites with Different PyC Interfacial Layers
    Ning DONG, Yongdong XU, Laifei CHENG, Litong ZHANG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 77-80. 
    Abstract   HTML   PDF (1007KB)
    A series of 3D-C/SiC composites with different pyrolytic carbon (PyC) interfacial layers (about 20~300 nm thick) were prepared by chemical vapor infiltration. Simulation experiments at different temperatures were performed by exposing C/SiC specimens in single and coupling gases partial pressure atmospheres, namely, O2, H2O vapor and molten salt (Na+) vapor. It suggested that at intermediate temperature range (about 600~800℃) a dramatic effect of PyC thickness on the weight and strength change of C/SiC was shown, which was mainly influenced by O2 partial pressure, at high temperature range (about 1200~1300℃) the effect was not obvious relatively, which might be influenced by H2O vapor partial pressure, and finally at very high temperature range (>1500℃) the molten salt vapor was the factor of most possibility affecting the weight change of C/SiC.
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    Numerical Simulation of Residual Stress during Microlayer Composite Material Processing by EBPVD Technique
    Liping SHI, Yao LI, Xiaodong HE
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 80-82. 
    Abstract   HTML   PDF (1007KB)
    The preparation technology of microlayer composite material by the electron beam physical vapor deposition (EBPVD) technique was briefly introduced. Taking the advantage of the large-scale commercial software of finite element analysis, a reasonable physical model was built up during the deposition processing and the distribution of residual stress was analyzed between substrate and deposition layer or among deposition layers. The results show that: with the increasing substrate preheating temperature, the interlaminar shear stress increases but the axial residual stress decreases. The probability of curling up after de-bonding tends to enhance as the thickness of deposition film increases.
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    Evaluation of the Fatigue Characteristics of Laser-processed Hot Work Tool Steel Based on Reliability
    Satoshi HANAK, Yahong SUI, Masato YAMASHITA, Hitoshi UCHIDA, Hironobu TSUJII
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 83-85. 
    Abstract   HTML   PDF (903KB)
    It is reported that laser-processing is effective to repair the heat checks, which are fine shallow cracks on a surface of die-casting dies. In this study, the rotating bending fatigue tests have been carried out to evaluate the fatigue characteristics of laser-processed hot working tool steel. Because test results are scattered, S-N curves are decided based on the evaluation of fatigue strength distribution. As a result, the fatigue strength of the laser-processed specimens decreases remarkably in comparison with that of base metal. However, it can be recovered to almost initial value by heat treatment at secondary hardening temperature. This procedure is also effective to decrease the scatter of fatigue strength. The laser-processing can be carried out at low cost and this method is effective for the extension of the work life of dies.
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    Electron Structure of γ/α2 Phase Boundaries in TiAl Based Alloys
    Fantao KONG, Ziyong CHEN, Yuyong CHEN, Jing TIAN, Yufeng SI
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 85-87. 
    Abstract   HTML   PDF (903KB)
    The valence electron structure ofγ/α2 phase boundaries in lamellar colonies in Ti-47Al-2M (M=Nb, Cr, V) (at. pct) was investigated by empirical electron theory of solid and molecules (EET) and its bond-length-difference (BLD) method. On this basis, the boundary condition of electron movement was employed in the improved Thomas-Fermi-Dirac (TFD) theory to decide the continuity of the electron density of the lamellar colonies interface and it is found that ofγ/α2 interface is continuous. Furthermore, it is found that adding alloying elements (including Nb, Cr, and V) can improve the electron density ( ρ ) ofγ/α2 interface, decrease △ρ ofγ/α2 interface. With the electron structure analysis together with properties analysis, the effect mechanism of alloying elements (Nb, Cr, V) improving mechanical properties was explained.
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    Study on Non-interlayer Liquid Phase Diffusion Bonding for SiCp/ZL101 Aluminum Matrix Composite
    Wei GUO, Jitai NIU, Jinfan ZHAI, Changli WANG, Jie YU, Guangtao ZHOU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 88-90. 
    Abstract   HTML   PDF (1041KB)
    Through the vacuum diffusion bonding for SiCp/ZL101 aluminum matrix composite, the influence of bonding parameters on the joint properties was reported, with the aim to obtain optimal bonding parameters. The microstructure of joints was analyzed by means of optical microscope and scanning electron microscope in order to study the relationship between the macro-properties of joints and the microstructures. It was found that diffusion bonding could be used for bonding aluminum matrix composites successfully. Meanwhile, the properties of the matrix and the joint were all affected by some defects such as the reinforcement aggregation in aluminum matrix composites made by stirring casting.
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    Repair Effect of Hot Work Tool Steel by Laser-Melting Process
    Yahong SUN, Satoshi HANAKI, Hitoshi UCHIDA, Hisakichi SUNADA, Nobuhiro TSUJII
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 91-93. 
    Abstract   HTML   PDF (548KB)
    Both wear and crack due to heat checking in hot work tool steel are major failure modes. It is desirable to find a method to lengthen the tool life while reducing manufacturing cost. This paper suggests a method to improve tool life for hot work tool steel (SKD6) with crack by laser-melting process. The method has been evaluated using the impact and fatigue test results. It is demonstrated that a repair of the crack by a laser-melting process is effective for life extension of the damaged tool.
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    Spatial Potential Distribution around Trench Target during Plasma Immersion Ion Implantation
    Xiubo Tian, Chunbei Wei, Shiqin Yang, Paul K.Chu, Ricky K.Y.Fu
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 94-96. 
    Abstract   HTML   PDF (480KB)
    Plasma ion implantation, an alternative to conventional beam-line ion implantation, is a sheath-acceleration ion bombardment technique and the initial sheath is crucial to the process efficacy and surface properties. The initial spatial potential distribution in the plasma sheath around a trench-shaped target is simulated using a two-dimensional model in this work. The results demonstrate that the sheath structure depends very much on the trench width. The potential drop in the trench may be quite small and the sheath expands outward if the width is small. This leads to a smaller incident ion dose into the sidewalls of the trench. In contrast, the initial potential distribution in the central region is quite similar to that without a trench if the trench width is larger than twice the ion-matrix sheath thickness for an infinite plane. Consequently, a higher ion dose into the sidewalls is possible.
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    Simplification of the Plasma Load of Negative-Pulse-Bias Source Used in Arc Ion Plating
    Dong QI, Ninghui WANG, Guoqiang LIN, Zhenfeng DING
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 97-98. 
    Abstract   HTML   PDF (355KB)
    Based on the voltage and current fluctuating phenomenon in the arc plasma load under the negative-pulse-bias, using the plasma physics theory and analysis of computer simulation expatiates that the nature of plasma load in vacuum arc plasma is a capacitance load caused by plasma sheath and can be simplified as a parallel unit composed of a capacitor and a resistor, which have exact and quantitative description in the plasma physics theory. It concludes the values of capacitance and resistance are thousand PF and hundred ohm from the result of simulation and experiment. As a result, this has solved the key theoretical issues for the design of negative-pulse-bias source specifically used for vacuum arc ion plating.
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    A Theoretical Model of Arc Light Radiation Based on GTA Spectral Diagnosis
    Chenming XU, Hongming GAO, Guangjun ZHANG, Lin WU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 99-100. 
    Abstract   HTML   PDF (327KB)
    An arc light radiation phenomenon in TIG welding process was studied through experiments and theoretical analysis. The arc spectra were acquired under a variety of welding parameters from 200 nm to 1000 nm wavelength range in TIG. The influence of welding parameters on the arc radiation was discussed. The radiation energy from lines emission mechanisms was calculated and the comparison was made with the one from the continuum emission mechanisms. The result shows that the radiation energy from the line emission mechanisms is equal to the one from the background. Based on the experiments and analysis, a physical model of arc light radiation has been developed. In this model, the arc plasma was presumed to be in local thermal equilibrium (LTE) with light thinness property. The Bolzmann distribution and Saha equation were applied to establish the arc light radiation model. This helps lay the foundation for further mathematical modeling of the arc light radiation.
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    Microstructure of in-situ Synthesized (TiB+TiC)/Ti Composites Prepared by Hot-pressing
    Zhenzhu ZHENG, Lin GENG, Honglin WANG, Weimin ZHOU, Hongyu XU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 101-102. 
    Abstract   HTML   PDF (519KB)
    In-situ 5 vol.pct TiB whiskers and TiC particulates reinforced Ti composites were fabricated by blending Ti powder and B4C particulates followed by reactive hot-pressing. The microstructure of the composites was investigated by using differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). The results showed that the reactive temperature between Ti and B4C is above 570°. Two kinds of reinforcements with different shapes were formed during hot-pressing: TiB short-fiber and equiaxed TiC particles. The interfacial bonding between the reinforcements and Ti matrix is perfect. No interfacial reaction between reinforcements and Ti matrix was found.
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    Simulation on Magnetostriction Strain of Polymer-bonded Terfenol-D Composites
    Jiuchun YAN, Shixiong LU, Shiqin YANG, Shiyu HE
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 103-104. 
    Abstract   HTML   PDF (389KB)
    A model of magnetostrictive strain for polymer-bonded Terfenol-D composite is presented, which is composed of a submodel for the average strain of Terfenol-D composite and a magnetostriction submodel for Terfenol-D particles. Simulated results show that the saturation magnetostriction ¸λs is very closely with experimental results, although there exists some difference between the calculated and the experimental results under low applied magnetic field. The saturation magnetostriction of the composites increases with the particle fraction (vI=72.5~90 vol. pct) in the simulated and experimental results, but the simulation result is not ideal when the particle fraction is higher than 85%.
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    Physical Simulation of Thermally Induced Martensite Formation from Retained Austenite in TRIP Steels
    Lie ZHAO, Fred J. VERMOLEN, Jilt SIETSMA, Sybr, van der ZWAAG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 105-108. 
    Abstract   HTML   PDF (709KB)
    The present work analyses the total free energy of the material during the martensitic transformation. A general expression for the martensite fraction as a function of temperature is derived, assuming that the nonchemical free energy is proportional to the volume of martensite. This expression indicates that the temperature-dependent martensite fraction can be predicted once the characteristic transformation temperatures and the relation between the chemical free energy and temperature of the martensite and austenite are known. An advantage of this development is that the proposed equation is valid for all types of relations between the chemical free energy and temperature. This simulation is successfully applied to the martensitic transformation upon further cooling of retained austenite in a low-alloyed TRIP steel, in which the relation between chemical free energy and temperature is quadratic and the fraction is determined from a thermo-magnetic measurement.
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    Effect of Substrate Bias on Microstructure and Properties of Tetrahedral Amorphous Carbon Films
    Jiaqi ZHU, Jiecai HAN, Songhe MENG, Qiang LI, Manlin TAN
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 109-111. 
    Abstract   HTML   PDF (499KB)
    The microstructure and properties of tetrahedral amorphous carbon (ta-C) films deposited by the filtered cathodic vacuum arc technology has been investigated by visible Raman spectroscopy, AFM and Nano-indentor. The Raman spectra have been fitted with a single skewed Lorentzian lineshape described by BWF function defining coupling coefficient, which characterizes the degree of asymmetry and is correlated with the sp3 content. When the substrate bias is -80 V, the sp3 content is the most and simultaneously the coupling coefficient is the least, following with the minimum root mean square surface roughness (Rq=0.23 nm) and the highest hardness (51.49 GPa), Young’s modulus (512.39 GPa), and critical scratching load (11.72 mN). As the substrate bias is increased or decreased, the sp3 content and other properties lower correspondingly.
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    Observations on the Formation of Ultrafine Ferrite Grain Size in Steels by Physical Simulation Routes
    L.X.Pan, L.P.Karjalainen, M.C.Somani
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 112-114. 
    Abstract   HTML   PDF (929KB)
    Some observations are reported on the simulation of two thermomechanical routes to produce ultrafine ferrite grain size in steels. One C-Mn grade and Nb, Nb-Ti and Nb-high Ti bearing steels were used in the tests performed on a Gleeble simulator and a laboratory rolling mill. The routes included severe hot deformation of prior grain-refined austenite at the temperature close to Ar3 (DIF) and static recrystallization of fine-grained cold-rolled martensite (SRM). It was observed that the hot deformation induces the formation of ferrite above the Ar3 temperature of the steel, but severe reductions are required for the complete transformation. Strain of 1.2 can result in about 70% of ferrite with the grain size of about 1.4~2 μm in all the studied steels. Similarly, in short annealing of cold-worked martensite, the static recrystallization can also lead to a grain size of about 1.5 μm. The distribution of carbon varies in the microstructures, carbon being in the second phase in the DIF route and in carbide particles in the SRM route, which may have a significant influence on the mechanical properties and the thermal stability of ultrafine grain structure.
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    Measurement and Simulation of Grain Size in Strong Textured and Coarse-Grained Metal Sheets
    Leng CHEN, Weimin MAO, Yongning YU, Huiping FENG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 115-116. 
    Abstract   HTML   PDF (382KB)
    An X-ray diffractometer that equipped with a two-dimensional detector is used for developing the technique of grain size measurement for strong textured and coarse-grained Si steel sheet. The method is based on the concept that the position of diffraction spots depends on the orientation of individual grains. The two-dimensional detector has the ability to collect abundant diffraction information in seconds, thus it can be determined rapidly and accurately whether a series of diffraction spots come from the same grain. The experimental results show that this method can be used for measuring grain size and its distribution in strong textured and coarse-grained metal sheets.
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    Static Recrystallization Behavior of Hot Deformed Austenite for Micro-Alloyed Steel
    Jie HUANG, Zhou XU, Xin XING
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 117-118. 
    Abstract   HTML   PDF (403KB)
    Static recrystallization behavior of austenite for micro-alloyed steel during hot rolling was studied and the influence (т-εdiagram) of holding time and deformation at different deformations and isothermal temperatures on microstructural state of austenite were discussed. Corresponding to parameter Z in the dynamic recrystallization diagram, parameter Y was then introduced to simplify static recrystallization diagrams.
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    Recrystallization and Grain Growth in Austenitic Stainless Steels: a Statistical Approach
    A.Di Schino, G.Abbruzzese, J.M.Kenny
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 119-121. 
    Abstract   HTML   PDF (510KB)
    A mathematical model, able to describe the recrystallization and grain growth in metals, has been developed. Taking into account the classical constitutive equations of the Taylor’s theory, the model involves only two free parameters (the dislocation density and the initial number of nuclei). Results from the model are here discussed in comparison with measurements performed on an AISI 304 stainless steel. The predictions of the model are in good agreement with experimental results. As cross check of the model prediction, the independent parameter “dislocation density” was found to properly correlate to the mechanical properties of the steel and to X-ray diffraction measurements, according to Taylor’s and Debye’s relations respectively.
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    Study on Thermal Simulation of Solidification in Heavy Section Ductile Iron
    Zhenhua LI, Yanxiang LI, Huiyuan GENG, Jianjun CHEN, Chunyan ZHOU, Junfa CHEN
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 122-124. 
    Abstract   HTML   PDF (611KB)
    Using an artificial intelligent instrument and a computer feedback control method, a new thermal simulation system is studied. Based on numerical simulation of casting solidification, a sample in the new system successfully simulated the solidification of heavy section ductile iron. The results show that the new thermal simulation system is accurate and reliable. Not only cooling curve but also graphite in the center of the thermal sample and the heavy section ductile iron is identical. Realization of accurate thermal simulation of solidification in heavy section ductile iron will be helpful for studying formation mechanism and controlling graphite degeneration in heavy section ductile iron.
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    Simulation of Ultrasonic Propagation Based on Raying Model in Typical Structure
    Tie GANG, Weizhi ZHANG, Liwei GUO
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 125-128. 
    Abstract   HTML   PDF (609KB)
    The convenient and useful raying mode was selected to develop the analysis module of ultrasonic parameters, and the simulation of ultrasonic propagation in typical plane structure was carried out. Using this model, the ultrasonic propagation in the water immersion testing was analyzed. For the complex plate structure, the intelligent analysis and simulation module was developed.
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    Numerical Simulation of Magnetic Pressure in Tube-electromagnetic Bulging with Die
    Hongwei JIANG, Chunfeng LI, Haiping YU, Zhiheng ZHAO
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 129-132. 
    Abstract   HTML   PDF (1011KB)
    Calculation of magnetic pressure is the basis of application of electromagnetic forming (EMF). This paper carries out a numerical simulation of magnetic pressure under the influence of die by means of finite element method. The analysis model of electromagnetic bulging with die is created by using ANSYS, and the distribution of magnetic pressure acting on the tube and the die is obtained. The differences between EMF and other technologies and the effect of die on tube formability are analyzed. The die has important influence upon the calculation accuracy. The simulating conclusions with different discharge energy and current frequency are verified through the technologic tests. The distribution of magnetic pressure acting on the tube agrees well with the measurements of the deformed tube.
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    Microstructure of Co-Ni-Al2O3 Composite Coatings by Electroforming
    Gang WU, Ning LI, Derui ZHOU, Kurachi Mitsuo
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 133-134. 
    Abstract   HTML   PDF (854KB)
    The metal matrix composite coatings of Co-Ni- Al2O3 were studied by electrolytic codeposition of Co-Ni alloys and Al2O3 on a Cu substrate from a sulfamate electrolyte containing Al2O3 particles. It was illustrated from the examined results of SEM, AFM and XRD that surface morphology and microstructure of Co-Ni- Al2O3 coatings appear to be mainly influenced by variations in Co content. The high Co content coatings with hcp lattice structure have a more uniform and fine structure than that of low Co content coatings with fcc lattice structure. The codeposition of Al2O3 particles in Co-Ni alloys can not change the phase structure of solid solution, only affects the growth and orientation of crystal planes and mostly increase the d value of lattice.
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    Cure of a New Type Composite on Noise Control and Effect of Filler Modification
    Jun CAI, Fei XU, Weimin CAI
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 135-136. 
    Abstract   HTML   PDF (703KB)
    A new type composite of high efficiency sound attenuation was cured. The superfine tungsten powder, plasticizer and stabilizer are added into the PVC resin and blended in the mixing chamber of a HAAKE rheometer. The effect of the filler modification is considered in the composite cure. The properties of modified composite and unmodified one are studied by SEM morphology viewing, acoustic and mechanical measurement. The test results indicate that the reason of the better soundproof and mechanical properties is the particle uniform dispersion and stronger adhesion.
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    Numerical and Experimental Studies of Substrate Melting and Resolidification during Thermal Spraying
    H.Zhang, G.Wei, L.Zheng, L.Li, X.Y.Wang, A.Vaidya
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 137-140. 
    Abstract   HTML   PDF (1285KB)
    A good understanding of melting and resolidification of the substrate will help us to achieve better bonding. A numerical model is developed to investigate the solidification of the droplet, and melting and resolidification of the substrate. The molybdenum powder spraying onto three different substrates: a stainless steel, brass (70%Cu) and aluminum by atmospheric plasma spraying has been investigated. The maximum melting depth of the substrate has been measured and compared with the numerical prediction. Experimental results show that the material properties of the splat and substrate and melting temperature of the substrate play the important roles on substrate melting. A dimensionless parameter, temperature factor, has been proposed and served as an indicator for substrate melting.
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    Numerical Simulation of Upsetting a Cubic Sintered Iron Powder Compact
    Wei XIA, Puqing CHEN, Zhaoyao ZHOU, Weibin ZHAO, Yuanyuan LI
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 141-143. 
    Abstract   HTML   PDF (548KB)
    This paper establishes a mechanical model for sintered powder metal material and simulates the material behavior. Powder metal specimens were compacted, sintered and upset. Relative density and contour of the specimen were measured. The force displacement relationship during upsetting was recorded. The same upsetting process was simulated with 3-dimensional finite element method. In simulation, the cubic specimen was treated as a piece of metal embedded with pores. Its overall relative density was controlled via adjusting the concentration of the pores. In the virtual upsetting process, when the pores are compressed, material around the pores will be in touch with each other. This kind of self-contact effect was dealt with direct contact detecting method. Classical V.Mises principle and isotropic hardening rule were applied on the material. Simulation results agree with experimental.
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    Numerical Simulation of Powder Injection Molding Filling Process Based on ANSYS
    Zhoushun ZHENG, Xuanhui QU, Yunping LI, Jianfeng GUO
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 144-146. 
    Abstract   HTML   PDF (3436KB)
    A mathematical model of two-dimensional flows of PIM derived from the momentum, continuity equations and the heat transfer equation is obtained. The formula of calculating the flow conductance and the pressure equation are deduced when the no slip boundary condition is employed at the wall, and the pressure equation is a non-linear elliptic partial differential equation. The flow front locations, distribution of velocities, temperature and pressure are simulated by the finite element analysis software ANSYS. Simulation results indicate that it is in the final filled part that defects appear easily. The region in which the defects may occur during the PIM process can be predicted.
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    Numerical Simulation for Three-Dimensional (3D) Unsteady State Temperature Field in Circumferential Laser Oxygen Cutting of Pipes
    Kaijin HUANG, Dawen ZENG, Changsheng XIE, Desheng XU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 147-150. 
    Abstract   HTML   PDF (614KB)
    A 3D unsteady state numerical model of heat transfer in the circumferential laser oxygen cutting of pipes was developed. In order to minimize the computing time required for solving the finite difference equations as much as possible, the alternating direction implicit (ADI) method was adopted. Based on the characteristics of the pipe cutting process, the periodic boundary condition was applied to calculate the temperature distribution in the θ direction and the self-adaptive grid technology was also used. The mathematical model takes account of the temperature-dependent thermal properties of the pipe. The calculated kerfs width and the heat-affected zone (HAZ) were compared with the experimental results.
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    New Finite Elements in Shear Stress Analysis of Saint Venant’s Torsional Loaded Beam Structures
    J.Brnic´, G.Turkalj
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 151-153. 
    Abstract   HTML   PDF (987KB)
    Recent engineering design as well as material processing on the optimization procedure are based and computer oriented. Finite element stress and sensitivity analysis are the most important things in such modern determination of optimal solution. According to high computer capacity finite element continuum discretization and load application independent of the coming fields become unlimited. This paper deals with the development of a new finite elements generation used in shear stress analysis caused by S.Venant’s torsional load and bending with shear. Their stiffness matrices and load vectors on the basis of their geometrical properties are derived. For justification of new finite elements application some examples are presented.
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    Numerical Simulation of Thermal Stress Fields in the Magnetic Quenching Process of 45 Steel
    Ziliang LI, Junruo CHEN, Miao ZHANG, Yihong GUAN
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 153-155. 
    Abstract   HTML   PDF (987KB)
    Based on a transient temperature distribution of a 45 steel cylinder workpiece during magnetic quenching, which was obtained by solving the governing equations with nonlinear boundary on the condition of coupling effects of heat-magnetism. According to the theory of thermal non-elasticity, computational mechanics, ferromagnetism and phase transformation, a new constitutive equation considering effects of phase transformation is proposed and solved by means of finite element method. The transient thermal stress and residual stress are obtained and the influencing factors on the thermal stress of magnetic field are analyzed and discussed.
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    Prediction of grain size for blade precision forging process under thermo-mechanical coupling
    He YANG, Yuli LIU, Wang CAI, Mei ZHAN
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 156-158. 
    Abstract   HTML   PDF (848KB)
    Blade precision forging is a high temperature and large plastic deformation process. Interact of deformation and heat conduction results in producing large temperature unevenness inside the billet. The unevenness has a great effect on the mechanical property and microstructure of the forged blade. However, internal quality of the blade is decided by its microstructure, it is necessary to conduct a research on the microstructure of the blade forging process. Taking a blade with a tenon as an object, its precision forging process is simulated and analyzed using a 3D coupled thermo-mechanical FEM code. And based on the prediction model of Ti-6Al-4V presented by the predecessor, a study of the evolution of grain size in the forging process is made. The distribution characteristics of grain size in typical sections are obtained under various deformation degrees. This study may provide a base for designing the blade forging process and working out its parameters.
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    Modelling of Level Fluctuation in Continuous Casting
    Xiao LIU, Huanxin ZHANG, Rongjun XU, Yongquan LI, Houfa SHEN, Baicheng LIU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 158-160. 
    Abstract   HTML   PDF (848KB)
    The free surface profile and fluid flow in the mold of continuous casting have been calculated by the VOF method coupling the SIMPLER algorithm. The SIMPLER-VOF model developed is validated by solving a classical experiment, broken dam problem. The calculated surface profile is consistent with water modelling. It is found that the free surface profile is coherently related to the position of circumfluence in the mold of continuous casting. With the increase of nozzle port inclination, the positive vortex above the jet is near to the meniscus and the level fluctuation becomes prominent.
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    Prediction and Simulation of Microstructure of Ti-15-3 Alloy
    Ping LI, Kemin XUE, Yan LU, Jianrong TAN
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 161-163. 
    Abstract   HTML   PDF (521KB)
    Ti-15-3 alloy is a new metastable β- type titanium. The influence of hot deformation parameters on the microstructure of Ti-15-3 alloy after solution treatment has been studied by isothermal compression tests as well as quantitative metallographic analysis. On the basis of the data obtained from the tests, predicting models for equivalent grain size and recrystallization volume fraction have been established with an artificial neural network method. An FE numerical simulation system has been developed to simulate the distribution of microstructure in Ti-15-3 alloy after hot back extrusion and solution treatment by combining the neural network model with thermal-mechanical coupled rigid-viscoplastic FE model. Corresponding experimental research is performed. The agreement of the simulated results with measured ones shows that the simulation system is reliable.
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    Mathematical Models and Computer Simulation of Nitrogen Concentration Profiles in Pulse Plasma Nitrided Layers
    Mufu YAN, Qingchang MENG, Jihong YAN
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 164-166. 
    Abstract   HTML   PDF (417KB)
    Two materials, pure Fe and pure Al, were nitrided in a pulse plasma nitriding facility. The nitrogen profiles in surface layers and the surface phase structures of specimens nitrided at 500℃ for 8 h for Fe and for 6 h for Al were measured using the glow discharge spectrometry and an X-ray diffractometer, respectively. XRD results indicate that the compound layer with hcp crystal structure (AlN) was formed on the top of Al substrate. During nitriding of Fe, the compound layer growth conforms to parabolic law and the surface nitrogen concentration change little with increasing the nitriding time. The surface nitrogen content of nitrided Al specimens is less than theoretical value 34.17 wt pct of AlN. The mathematical models of nitrogen concentration profiles in the surface layer of nitrided Al specimen have been established based on the research of the kinetics of pulse plasma nitriding of Fe and the nitrogen concentration profiles were also simulated. Results show that the predicted curves agree basically with the experimental data.
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    Laser-assisted Grinding Wheel Dressing (II) –Experimental Researches
    Ming CHEN, Fanghong SUN, Youngmoon LEE, Seunghan YANG, Jongchan LEE
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 167-168. 
    Abstract   HTML   PDF (512KB)
    Most of the mechanical dressing technologies for resin bonded superabrasive grinding wheels are time consuming and costly. Based on the outcomes of the simulations in the previous study, this paper demonstrates the comprehensive researches on the laser-assisted dressing process control, grinding wheel topography reconfiguration by 3D laser scanning technology and analyses of grinding temperature. The synthesized parameter incorporates the laser dressing process parameters and can be used to the process control. In order to evaluate the laser-assisted dressing effectiveness, the newly developed non-contact laser measuring system based on the principle of the triangulation was used. Grain protrusion height and intergrain spacing can characterize the grinding wheel surface. A series of grinding tests with the laser-assisted dressed grinding wheel and mechanically dressed grinding wheel were conducted for comparison. The results proved the feasibility of laser-assisted dressing for resin bonded superabrasive grinding wheels and revealed the importance of choosing appropriate laser dressing parameters.
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    Sprayformed Hot Work Steels for Rapid Tooling
    Yunfeng Yang, Simo-Pekka Hannula
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 169-172. 
    Abstract   HTML   PDF (1994KB)
    The present work compares microstructures of hot work steels made by different processes, that is, by sprayforming, by casting, and a commercially supplied H13 steel. Material benefits are recognized by sprayforming hot working tools such as die inserts for hot forging. The sprayformed hot work steels present a fine and homogeneous microstructure, which implies that, at a similar toughness level, the sprayformed steel can be higher alloyed, so that the thermal fatigue and wear resistance at elevated temperatures can be improved. A series of steels with higher vanadium content than commercial hot work steels are developed. There are no segregation and carbide network problems usually encountered in conventional ingot/forging processed high-vanadium steels. Microstructure and hardness of the new sprayformed steels are studied under different heat treatment conditions. It is justified that these sprayformed steels can be directly used for tooling without high temperature hardening. Sprayforming the tool steels onto a precision ceramic mould is demonstrated to extend the technoeconomical benefits, so that a net shape production tool can be rapidly made. Features of the rapid tooling process are also discussed.
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    Indirect Measurement of Material Thermal and Mechanical Properties during Welding
    Dongqing LI, Jun TAO, Qingguo Meng, Hongyuan FANG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 173-175. 
    Abstract   HTML   PDF (533KB)
    By means of a newly developed non-contact detecting method, electronic speckle pattern interferometry (ESPI), a method of determining material property data during welding is studied. A TIG fixed-point welding process is modeled in which some achievements of simulation, such as the effect of welding pool on temperature field and nonlinear relation between convection coefficient and temperature, are all considered. In addition, by taking into account effect of heating rate, the workpiece is divided into near-weld zone and far-weld zone, which will be treated with different property values. When the displacement field computed with original property data is compared and matched with the experimental displacement field, which is measured by ESPI, these original data are adjusted properly. A group of raw properties are obtained and are corrected by statistical regression before they enter the simulation process again. By such a loop of “simulation-comparison-modification”, a set of property data that best satisfy the real condition are achieved finally. In such a way, a new method for measuring material properties during welding is found.
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    Effect of Filler Composition on the Brazing of Alumina to Copper Using Ultrasonic Wave
    Khalid M.HAFEZ, Masaaki NAKA
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 176-178. 
    Abstract   HTML   PDF (1123KB)
    An ultrasonic wave was applied during brazing of alumina to Cu. First alumina was metallized by applying ultrasonic wave in braze bath. Then the metallized alumina was brazed with Cu using the same filler alloy. The filler used were Zn-Al alloys and Zn-Sn Alloys. The weight percent of Al in filler was ranging between 0, 5%, 10%, respectively. The weight percent of tin in filler was ranging between 0, 30%, 60% and 91%, respectively. The joining mechanism was investigated by measuring the joining strength, hardness and analyzing the microstructure at interface of the joint. The shear strength and microstructure of the joint strongly depend on the filler composition. The effect of ultrasound was derived primarily from acoustic cavitations, impact and friction of the filler against alumina ceramic. This improved the wetting between alumina and the filler, and reflected to improve the joint strength. Another ultrasonic advantage as to reduce of the joining temperature, that reduced the thermal stress in the braze joint.
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    Liquid-Phase-Impacting Diffusion Welding Mechanism and Microstructure of Welded joint of Al Matrix Composite SiCp/101A
    Jitai NIU, Wei GUO, Qingchang MENG, Xinmei ZHANG, Xingqiu LIU, Guangtao ZHOU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 179-181. 
    Abstract   HTML   PDF (2598KB)
    The liquid-phase-impacting (LPI) diffusion welding mechanism and microstructure of welded joint of aluminum matrix composite SiCp/101A have been studied. It shows that by LPI diffusion welding, the interface state between SiC particle and matrix is prominent, the harmful microstructure or brittle phase can be restrained from the welded joint. Moreover, the density of dislocation in the matrix near the interface and in the matrix are all so higher than that of parent composite, the dislocation entwists each other intensively resulted in welding the composite successfully.
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    Microstructure and Strength of the TiB2 Cermet/TiAl Joint Diffusion Bonded with Ni Interlayer
    Zhuoran LI, Jicai FENG, Jian CAO, Yiyu QIAN
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 181-183. 
    Abstract   HTML   PDF (2598KB)
    Vacuum diffusion bonding of TiB2 cermet to TiAl -based alloys using Ni interlayer has been carried out at 1123~1323 K for 0.6~3.6 ks under 80 MPa. The effects of joining parameters on the microstructure of the joints and mechanical properties was investigated. The results showed that a TiAlNi2 intermetallic layer and two Ti, Al, Ni solid solution layers were formed at the interface of Ni/TiAl. The shear strength was 110 MPa with bonding temperature at 1223 K, bonding time for 1.8 ks and bonding pressure under 80 MPa.
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    Control of Titanium Alloy Thin Plate Welding Distortion by Trailing Peening
    Xuesong LIU, Hongyuan FANG, Shude JI, Zhibo DONG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 184-186. 
    Abstract   HTML   PDF (614KB)
    The technology of trailing peening is a kind of promisingly bran-new technology which can be used to control welding stress and distortion of Ti alloy thin plate. Control of TC4 Ti alloy thin plate welding stress and distortion under the condition of conventional welding and trailing peening is performed, respectively. The results show that the technology of trailing peening effectively reduces deflection and transverse shrinkage of thin plate weldment. The maximum deflection is decreased from 15 mm under the condition of conventional welding to 5 mm, while the weld transverse shrinkage is decreased from 0.5 mm to about 0.1 mm.
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    Evaluation of the Properties of Si3N4/Si3N4 Joint Brazed Using a Filler Alloy Containing Pd
    M.Naka, Jie ZHANG, Yu ZHOU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 187-188. 
    Abstract   HTML   PDF (402KB)
    Si3N4 ceramic was jointed to itself using a filler alloy of Cu76.5Pd8.5Ti15, and the mechanical properties of the joint were measured and analyzed. By using a filler alloy of Cu76.5Pd8.5Ti15, the Si3N4/ Si3N4 joints were obtained by brazing at 1373~1473 K for 0.9~5.4 ks under a pressure of 2×10-3 MPa. The effect of brazing parameters on the shear strength of the joint was investigated. When the brazing temperature and holding time is 1423 K and 5.4 ks respectively, the maximum shear strength of the Si3N4/Si3N4 joint is obtained to be 198 MPa.
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    Diffusion Bonding of Tungsten to Copper and Its Alloy with Ti Foil and Ti/Ni/Ti Multiple Interlayers
    Guisheng ZOU, Jun YANG, Aaiping WU, Genghua HUANG, Deku ZHANG, Jialie REN, Qing WANG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 189-192. 
    Abstract   HTML   PDF (1699KB)
    Ti foil and Ti/Ni/Ti multiple interlayers were selected for the bonding of tungsten to copper and CuCrZr alloy. The effects of processing conditions on the microstructures and shear strength of the joints were investigated. When Ti foil is used for bonding of tungsten to pure copper but not transformed into liquid solution during the holding time, the strength of the joints is relatively low because of the multiple compound layers with brittleness formed in the bonding zone. The strength of the joints increases significantly if the Ti foil is transformed into liquid solution and is mostly extruded out of the bonding zone. The same phenomena are found in the case when Ti/Ni/Ti multi-interlayers are used for bonding tungsten to CuCrZr alloy.
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    Influence of Slope and Slenderness Ratio on the Non-Column Volume in Skew Rolling
    Yongqiang KANG, Zhenghuan HU, Jinping LIU, Cuiping YANG, Huiping DU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 192-194. 
    Abstract   HTML   PDF (2121KB)
    A definition of non-column volume ratio (NCVR) is brought forward by the authors. It is influenced greatly by the slenderness ratio of the cylindrical billet and the slope of the wedge on the tool of skew rolling. Using the numerical simulation, the law of variation in NCVR during the forming process is found out. At the same time experiments have been carried out under different conditions, the result of which are found to be in good agreement with the theoretical predictions.
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    Effect of Welding Paramenter on Joint Property of Aluminum Matrix Composite in Liquid-Phase-Impacting Diffusion Welding
    Wei GUO, Qingchang MENG, Jitai NIU, Xinmei ZHANG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 195-198. 
    Abstract   HTML   PDF (1338KB)
    In this paper, a new method for welding SiCp/101A was put forward. It is LPI (liquid-phase-impacting) diffusion welding. Through LPI diffusion welding SiCp/101A aluminum, the effect of welding parameters on the welded joint property was investigated, and the optimal welding parameters were brought forward at the same time. The microstructure of joint was analyzed by means of optical-microscope, scanning electron microscope in order to study the relationship between the macro-properties of joint and the microstructure. The results show that LPI diffusion welding could be used for welding aluminum matrix composites SiCp/101A successfully.
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    Enhancement on Fatigue Property of Aluminum Alloy Welded Joint by Utilizing Trailing Peening
    Changli WANG, Zhimin WAN, Min ZHAO, Jitai NIU
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 198-201. 
    Abstract   HTML   PDF (1014KB)
    The fatigue properties of 2024T3 aluminum alloy welded joint treated by different peening methods were examined. The different effects on fatigue performance of high strength aluminum welded joints were compared with each other by carry out a series tests using two different peening treatment samples. Results show that by applying synchronized hammer peening to the weak part of joint when weld was going on, trailing peening, may refine the grains near weld line, hardening the surface of weld toe and amend the distribution of residual stress. Because of these results the position of fracture of joint was moved from weld toe to weld line. Compared to the joints treated by peening after welding, the fatigue strength of weld joint treated by trailing peening was enhanced by more than 102%.
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    Prediction Models on Distribution of Inherent Strains in T Type Welding Structure
    Peng HE, Jicai FENG, Jiecai HAN, Yiyu QIAN
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 202-204. 
    Abstract   HTML   PDF (336KB)
    A fundamental theory for the analysis of residual welding stresses and deformation based on the inherent strain distribution along the welded joint is introduced. The method of predicting maximum hardness Hv(y, z) and maximum inherent strain gmax is given. The model T.E.P-Tav-hardness calculation is proposed to predict distribution of inherent strains in T type welding structure. By T.E.P-Tav-hardness calculation, distribution of longitudinal inherent strains can be predicted in T type welding structure, and calculation and experimental results are consistent.
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    Thermal Stress Analysis of Welded Joint in 1420 Al-Li Alloy Induced by Thermal Cycling
    Hongbin GENG, Song HE, Dezhuang YANG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 205-208. 
    Abstract   HTML   PDF (884KB)
    A model of double grains under plane stress state has been established. According to the double grain model, thermal stress induced by thermal cycling in welding fusion zone is numerically simulated by finite element method, and the microstructures before and after thermal cycling are observed. The effect of thermal stress on weld microstructure is discussed. Experimental and analysis results show that the difference between the coefficients of thermal expansion and elastic modulus for grains along different crystal direction can produce alternate thermal misfit stress and strain near boundaries under thermal cycling. At the temperature of upper and lower limit, thermal stress nearby grain boundary reaches maxima. Thermal stress induced changes in microstructure, which expressed by the sending dislocations from boundaries to matrix, piling up against the boundaries and the increasing of dislocation density.
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    Effect of Gravity on Arc Shape in GTA Welding —for Low Electric Arc Current
    Hidetoshi FUJII, Yosuke SUMI, Manabu TANAKA, Kiyoshi NOGI
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 209-211. 
    Abstract   HTML   PDF (735KB)
    Gas tungsten arc (GTA) welding was performed both in a microgravity environment and in a terrestrial environment, and the arc shapes in both environments were compared. A microgravity condition was obtained using the free fall system at the Japan Microgravity Center. The system can maintain a 10 s microgravity of less than 10-5 g. A water-cooled Cu plate was used to simplify the arc phenomenon. The electric arc current was between 15 and 80 A, and the shielding and atmospheric gas was 99.9995% Ar and its flowing rate was 10 l/min. The polarity was a direct current electrode negative (DCEN). The arc gap was 3 mm and careful attention was also paid to the arc gap in both the terrestrial and microgravity environments being the same. As a result, it was found that no effect of gravity on the arc shape is observed under general welding conditions (over 60 A). When the electric arc current is lower than 25 A, the arc shape is determined by the initial position of the arc root and is constant with time. Accordingly, it can not be judged whether or not the arc shape is affected by gravity for this range. When the electric arc current is between 25 A and 60 A, it is estimated that the arc shape is not affected by gravity though it is occasionally affected by other minor effects.
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    Numerical Simulation of Welding Deformation for Hull Superstructure Steel Based on the Finite Element Analysis
    Liming LIU, Guoli LIANG, Yujun LIU, Zheng ZHAN
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 212-214. 
    Abstract   HTML   PDF (575KB)
    Using finite analysis element software, the transient displacement field of automatic submerged arc welding is established. It was also considered that the thermal physical properties changes were depended on the temperature and the heat loss on the surface. At the same time, it analyzed the influence of the deformation and stress, which generated in the plate butt-welding process, to the superstructure steel welding deformation. The result showed that the deformation and stress generated in the steel plate butt-welding process are considered to be the main factors to influence the welding deformation of superstructure steel. It found the effective ways to reduce the welding deformation of the hull superstructure steel is to relieve the butt-welding deformation and release butt-welding stress before welding the hull superstructure steel.
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    A New Ductile Fracture Criterion and Its Application to the Prediction of Forming Limit in Deep Drawing
    Yuying YANG, Zhongqi YU, Xuechun LI, Zhenzhong SUN
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 217-219. 
    Abstract   HTML   PDF (538KB)
    With considering the influence of equivalent plastic strain on void-damage and taking Lemaitre damage equivalent stress as plastic potential, based on continuous damage mechanics theory, a new criterion for ductile fracture is derived. The two key material constants in the criterion are determined by the combination of tension tests with FE (finite element) simulation. On the basis of the values of stress and strain calculated from commercial finite element software, the forming limit in cylindrical deep drawing of annealed aluminum alloy LY12(M) is predicted by means of the new ductile fracture criterion. Experiments verify that the predicted results are in agreement with the experimental ones. Hence, it is reliable to predict the forming limit in deep drawing by means of the new ductile fracture criterion.
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    An Experimental Study on Constraint Cooling Process of Hot-rolled Coils
    Lijuan WANG, Chunli ZHANG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 220-222. 
    Abstract   HTML   PDF (733KB)
    In order to master mechanical property, surface quality and microstructure of constraint cooling (CC) coils under various water cooling parameters, more than 100 coils cooling experiments were done with real production process, of which is designed a cooling experimental instrument in the end. The experiments show that high initial cooling temperature, discontinuous cooling style, and long cooling time can improve mechanical property of cooling coils and shorten cooling time. The CC coils experiments cover the different steel grades, so that CC process effects on hot-rolled coils may be predicted and controlled actively.
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    Numerical Simulation of Electromagnetic Force in Double-Sided Arc Welding Process
    Hongming GAO, Lin WU, Honggang DONG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 223-224. 
    Abstract   HTML   PDF (329KB)
    Up till now, most of the researchers believe that there are four kinds of forces in the weld pool convection, they are surface tension, electromagnetic force, buoyancy and gas shear stress. So electromagnetic force is very important, especially when large current is applied. In most of previous models, the electromagnetic force is calculated analytically, in which only the axial component of current is considered. Actually the radial component of current has the same effect, and may be advanced in some locations. In double-sided arc welding process, instead of the earth clamp, another torch is placed on the opposite side, the current will go from one torch, through the weld zone, to another torch. In this case, the current is more concentrated in the weld zone, the electromagnetic force will have significant effect compared with conventional welding process. In this paper, a new method of numerical calculation for electromagnetic force is developed, in which both axial and radial components are considered. And as an example, the distribution of electromagnetic force in double-sided arc welding is calculated. It demonstrates that this new method could give more accurate simulation of electromagnetic force, and is close to the actual process.
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    Research on the Mechanism of Penetration Increase by Flux in A-TIG Welding
    Chunli YANG, Sanbao LIN, Fengyao LIU, Lin WU, Qingtao ZHANG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 225-227. 
    Abstract   HTML   PDF (808KB)
    The mechanism of penetration depth increased by activating flux in activating tungsten inert gas (A-TIG) welding was studied by measuring the distribution of trace element Bi in the weld and monitoring the change of arc voltage during A-TIG welding of stainless steel 0Cr18Ni9 with fluxes SiO2 and TiO2. The results show that the mechanism of penetration depth in A-TIG welding depends on the sort of flux used. The weld pool convection after coating the flux SiO2 and flux TiO2 is changed inversely compared with convectional TIG welding without flux. The arc voltage is increased by flux SiO2 whilst flux TiO2 does not have effect on the arc voltage. The reason of penetration depth increase for SiO2 is due to the constriction of arc plasma and the change of surface tension gradient. The increase of weld penetration depth with TiO2 only ascribes to the change of surface tension gradient.
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    Three-Dimensional Thermo-mechanical Coupled FEM Simulation for Hot Continuous Rolling of Large-Diameter Mandrel Bar
    Huiping HONG, Yonglin KANG, Changtao FENG, Xiqiang CHEN
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 228-230. 
    Abstract   HTML   PDF (553KB)
    Based on the important boundary conditions of rolling simulation including friction, heat conduction and interactions of the workpiece and rolls, the hot continuous rolling processes of large-diameter mandrel round bar (200 mm in diameter) in 6VH-stand hot tandem mill are successfully simulated by three-dimensional coupled thermomechanical elastoplastic finite element method (FEM). The distributions of stress, strain, temperature and the rolling force and torque for the two-pass and four-pass continuous rolling are calculated respectively. Thus, the two and four-pass roll schedules are verified, respectively. The simulation results show that it is safe to produce 200 mm round bar by the two-pass (oval pass and round pass) continuous rolling on the existing equipment compared to the four-pass continuous rolling. There are concave surfaces and increased widths occurring at the end of rolled billet due to uneven deformations between the outside and inside of the workpiece as well as the free spreading close to the roll gap of the final pass.
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    Experimental Simulation of Hot Rolling of Aluminium Alloy Al-5Mg
    Xigang FAN, Daming JIANG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 231-233. 
    Abstract   HTML   PDF (1111KB)
    Multipass hot-rolling process of a newly developed aluminum alloy was simulated by nonisothermal axisymmetric compression test. High temperature compression behavior and the microstructures of the alloy after deformation were investigated. The flow stress increases with the decreasing of deformation temperature or the increasing of pass times. Dynamic recovery was the operative deformation mechanism during hot deformation. Dense dislocations had been pinned by Al3Zr dispersoids during hot deformation, the Al3Zr dispersoids inhibited recrystallization and grain growth.
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    FEM Analysis of Effect of Die Angle on Tube Inversion Forming Process under Conical Die
    Zhichao SUN, He YANG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 234-236. 
    Abstract   HTML   PDF (461KB)
    Tube inversion including free deformation under conical die is an advanced forming process for manufacturing complicated thin-walled parts with high strength/weight ratio, high efficiency, and good flexibility for size changing. However, the successful reality of forming process, the change of deforming mode and shape and size of part formed are mainly on the die angle. Based on the analysis of the forming process, the model of rigid-plastic FEM (finite element method) is established and a numerical simulation system is developed. The effect of die angle on the tube inversion forming process is investigated with the code developed. The results of the effect of half die angle on shape of free deformation zone and on deforming load are obtained. There is an optimal die angle (about 75 deg), which makes the forming load minimum.
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    Analysis of Shear and Friction Behaviors in End Milling Process
    Seunghan YANG, Seungil CHANG, Youngmoon LEE, Heesool KIM, Taejo KO
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 237-238. 
    Abstract   HTML   PDF (418KB)
    As a new approach to analyze shear behaviors in the shear plane and chip-tool friction behaviors in the chip-tool contact region during an end milling process, this paper introduces a method to transform an up-end milling process to an equivalent oblique cutting process. In this approach, varying undeformed chip thicknesses and cutting forces in the up-end milling process are replaced with the equivalent of oblique cutting ones. Experimental investigations for Inconel 718 were performed to verify the presented model.
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    Study on the Deformation Characteristics of the Sheet Hydroforming with a Movable Die
    Linxin ZHOU, Yi XU, Zhongtang WANG, Shihong ZHANG
    J. Mater. Sci. Technol., 2003, 19 (Supl.): 239-240. 
    Abstract   HTML   PDF (632KB)
    An improved sheet hydroforming process with a movable die is proposed and investigated by elastoplastic FEM. The effects of varied process parameters on the deformation of the sheet blanks were investigated. The effects of the movable die on the FLD were also analyzed. Using a movable die may increase the forming limit of the blank and improve the forming performance. Moreover, the drawing ratio of the blank may be increased by changing the process conditions such as blank holder force and the counterforce of the movable die on the blank.
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ISSN: 1005-0302
CN: 21-1315/TG
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