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EVOLUTION OF SINGLE ELLIPTIC VORTEX RINGS

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Acta Mechanica Sinica 1997年第1期13卷 17-25页

作者： Zhao, y Shi, XG Department of Mechanics and Engineering Science Peking University The State Key Laboratory for Turbulence Research Beijing China

The evolution of single elliptic vortex rings for initial aspect ratio (AR) = 2,4,6 has been studied. The incompressible Navier-Stokes equations are solved by a dealiased pseudo-spectral method with 64(3) grid points in a periodic cube. We find that there are three kinds of vortex motion as AR increases and bifurcation occurs at certain AR. The processes of advection, interaction and decay of vortex ring are discussed. Numerical results coincide with experiments and other authors' numerical simulation.

关键词： elliptic vortex ring pseudo-spectral method bifurcation vortex reconnection

QUASI-INTERPOLATING OPERATORS AND THEIR APPLICATIONS IN HyPERSINGULAR INTEGRALS

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Journal of Computational Mathematics 1998年第4期16卷 337-344页

作者： Wong, RH Lu, y Dalian Univ Technol Inst Math Sci Dalian 116024 Peoples R China

The purpose of this paper is to propose and study a class of quasi-interpolating operators in multivariate spline space S-1/2(Delta(mn)(2*)) on non-uniform type-2 triangulation. Based on the operators, we construct cubature formula for two-dimensional hypersingular integrals. Some computing work have been done and the results are quite satisfactory.

关键词： hypersingular integral finite-part integral quasi-interpolating operator non-uniform type-2 triangulation

Inconel 617 and Stellite 6 alloys for tooling in thixoforming of steels

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Transactions of Nonferrous Metals Society of China 2010年第9期20卷 1656-1662页

作者： y.BI ROL Materials Institute Marmara Research Centre

Thermal fatigue and high temperature wear are the two principle failure mechanisms for thixoforming dies. Samples of Inconel 617 and Stellite 6 alloys were submitted to thermal cycling under conditions which approximate thixoforming of steels and to sliding wear tests at 750 ℃. The experimental results thus obtained were compared with those of the X32CrMoV33 hot work tool steel. The Inconel 617 and Stellite 6 samples are much more resistant to oxidation and to softening than the hot work tool steel, providing a superior resistance to thermal fatigue cracking. The wear resistance of the Inconel 617 and Stellite 6 alloys at 750 ℃ is also markedly superior. The adhesive oxides growing slowly on Inconel 617 and Stellite 6 alloys sustain the wear action without spalling and are claimed to be responsible for the superior wear resistance of these alloys at 750 ℃.

关键词： steel thixoforming tooling thermal fatigue wear

AN IMPLEMENTATION OF A MODEL MANAGEMENT SySTEM

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中国有色金属学会会刊：英文版 1995年第4期5卷 151-157页

作者： Chen, XH Takahara, y CENT S UNIV TECHNOL DEPT BUSINESS ADMCHANGSHA 410083PEOPLES R CHINA TOKyO INST TECHNOL TOKYO 152JAPAN

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关键词： general systems theory(GST) model management model description language(MDL) model integration environment(MIE) decision support system(DSS) menu system annual production planning

DISPERSION AND TENSILE BEHAVIOR OF POLyPROPyLENE/MONTMORILLONITE NANOCOMPOSITES PRODUCED VIA MELT INTERCALATION

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Chinese Journal of Polymer Science 2003年第3期21卷 359-368页

作者： y.Men 傅强 Department of Physics Albert-Ludwigs University D-79104 Freiburg Germany Department of Polymer Science & Materials Sichuan University State Key Laboratory of Polymer Materials Engineering Chengdu 610065 China

Most of the articles on polymer nanocomposites focus on the importance of chemistry used to modify the surface of the clay, usually montmorillonite (MMT), and characterization of the nano-scale structure obtained. The role and importance of processing were also discussed recently. However, few papers concerning the correlation between morphology of MMT and mechanical properties were published. In order to understand. the tensile behavior of PP/Montmorillonite (MMT) nanocomposites better, and to further improve the reinforcement efficiency, we first prepared the PP nanocomposites via direct melt intercalation using conventional twin-screw extrusion. The dispersion and tensile property of the composites were then investigated by SEM, XRD, TEM and a video-controlled tensile set-up. The macroscopic and microscopic dispersion of MMT in PP matrix was verified by XRD and TEM, combined with SEM. The tensile properties were obtained by video-controlled tensile set-up, which gives true stress-strain curve. It was found that a partly intercalated and partly exfoliated structure (also called incomplete exfoliation) existed in the system. Though the tensile strength of PP nanocomposites is not much improved in engineering stress-strain curves, more than 20% increase of true stress was found in a true stress-strain experiment at high true strain, which indicates that only oriented silicate layers can have a big effect on tensile properties: Not only orientation of silicate platelets but also the degree of exfoliation is a key factor to determine the reinforcement efficiency. The reinforcement efficiency of MMT has been discussed based on the 'continuum' Halpin-Tsai equations. A good agreement was found between experimental data and theoretical prediction by changing N value (number of platelets per stack) which corresponding to different state of the dispersion of MMT in PP matrix.

关键词： polypropylene/montmorillonite nanocomposites dispersion orientation tensile property

A SPLINE METHOD FOR SOLVING TWO-DIMENSIONAL FREDHOLM INTEGRAL EQUATION OF SECOND KIND WITH THE HyPERSINGULAR KERNEL

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Journal of Computational Mathematics 2001年第3期19卷 225-230页

作者： Wang, RH Lu, y Dalian Univ Technol Inst Math Sci Dalian 116024 Peoples R China

Provides information on a study which proposed a spline method for solving two-dimensional Fredholm Integral Equations of second kind space with hypersingular kernels. Details on the quasi-interpolating operators; Inf... 详细信息

关键词： hypersingular integral finite-part integral quasi-interpolating operator nonuniform type-2 triangulation

Theory and Modeling of Phase Transformations under Stress in Steel

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材料热处理学报 2004年第5期25卷 1-7页

作者： T.y. Hsu School of Materials Science and Engineering Shanghai Jiao Tong University Shanghai 200030 China

Thermodynamic prediction of the increment of the formation temperature of proeutectoid ferrite by appliedstress is nearly consistent with the wxperfimental *** models for ferrite,pearlite and bainite transformations can be shown as modified Johnson-Mehl-Avrami equation in which parameter b() varies with the level of applied *** effects of tensile and compressive stresses on enhancement of the ferrite/pearlite and bainite transformations are discussed,The necessity and approach of modification of additivity hypothesis are introduced and the results from modified equation in which some parameters are obtained by rfegression of two experimental results or taken from TTT and CCT diagrams of a cerftain steel are superior than that from Scheil’s *** calculation of Ms and nucleation kinetics equations of martensitic transformation under stress are *** of phase trasformations under stress in ferrous alloys is briefly

关键词：钢相位转换受力状态热力学动力学成核现象相加性假设铁合金

COMPLEXITy AND INTRANSITIVITy IN TECHNOLOGICAL DEVELOPMENT

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Journal of Systems Science and Systems Engineering 2014年第2期23卷 128-152页

作者： Alexander y.KLIMENKO The University of Queensland

This paper investigates the existence of a fundamental link between two disciplines that emerged during last few decades： complexity science and advanced engineering. During this time many industries, especially those related to the high-tech end of technological development, have faced the problem of increasing complexity of design, production and operation. Industrial projects have grown to become multidisciplinary, tightly interconnected, costly and difficult to control and predict. Two trends can be identified in this respect： one is the consistent effort of systems engineering in reducing the uncertainties of complex industrial operations and the other is the effort undertaken in complexity studies to account for uncertainties present in the real world. In this work, we provide a brief overview of recent developments in advanced engineering and give a consistent interpretation of technological evolution from the perspective of complexity science in general and complex competitive systems （CCS） in particular. CCS is a general framework that was recently developed for analysis of complex systems involving competition. Transitivity of the decision-making process and the cyclic nature of technological progress are considered. Correctness of intransitive decisions is inherently relativistic： the same decisions can be seen as correct or incorrect when considered from different perspectives. When treated simplistically, intransitivity may seem to be illogical but, nevertheless, it is common in nature and needs to be studied. CCS provides a formalised scientific framework for analysis of intransitivity and establishes the existence of an important connection linking complexity and uncertainty with intransitivity. Implications of intransitivity for engineering decision-making and strategic planning are considered in the context of CCS. A working example of intransitivity in competition between major car mantifacturers is presented.

关键词： Complexity technology strategy systems engineering industrial strategy and decision-making complex competitive systems.

Effect of Temperature on Material Transfer Behavior at Different Stages of Friction Stir Welded 7075-T6 Aluminum Alloy

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Journal of Materials Science & Technology 2013年第10期29卷 955-960页

作者： S.D.Ji y.y.Jin y.M.yue S.S.Gao y.X.Huang L.Wang Faculty of Aerospace Engineering Shenyang Aerospace University State Key Laboratory of Advanced Welding and Joining Harbin Institute of Technology

In this work, the morphologies of weld of 7075-T6 aluminum alloy via friction stir welding （FSW） were analyzed by optical microscopy, the temperature field was attained by numerical simulation, and the effect of temperature on material transfer behavior in the thermal-mechanical affected zone （TMAZ） at different stages was mainly investigated. The FSW process consists of three stages. It is very interesting to find that the maximum transfer displacement of material appears at the final stage of welding process, then at the stable stage and at the initial stage, which results from the difference of peak temperatures at different stages. At any stage, the material in TMAZ near the surface of weld transfers downwards, the material in the middle of weld moves upwards and the material near the bottom of weld hardly moves. In any cross section of weld, the largest transfer displacement of material appears in the middle of weld. The increase of rotational velocity and the decrease of welding speed are both beneficial to the transfer displacement of material in the middle of weld.

关键词： Friction stir welding 7075-T6 aluminum alloy Thermal-mechanical affected zone Material transfer Numerical simulation