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Effect of Thermal Fatigue Loading on Tensile Behavior of H13 Die Steel with Biomimetic Surface

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Journal of Bionic engineering 2010年第4期7卷 390-396页

作者： Zhihui Zhang~1,Luquan ren~1,Hong Zhou~2,Zhiwu Han~1,Xin Tong~3,Yu Zhao~1,Li Chen~1 1.Key Laboratory of Bionic engineering (Ministry of Education,china),Jilin University,Changchun 130022,p.r.china 2.Key Laboratory of Automobile Materials (Ministry of Education,china),Jilin University,Changchun 130022,p.r.china 3.The Dep.r.ment of Materials Surface engineering,Guangzhou research Institute of Non-Ferrous Metals,Guangzhou 510651,p.r.china [a] Key Laboratory of Bionic engineering (Ministry of Education China) Jilin University Changchun 130022 P. R. China [b] Key Laboratory of Automobile Materials (Ministry of Education China) Jilin University Changchun 130022 P. R. China [c] The Department of Materials Surface Engineering Guangzhou Research Institute of Non-Ferrous Metals Guangzhou 510651 P. R. China

Biomimetic surface is an effective ways to promote the p.r.ormance grade and applied range of materials without alteringtheir *** improved prop.r.ies such as resisting fatigue,enduring wear,etc,have been achieved by applyingbiomimetic morphology or structure to some engineering material *** this pap.r.aiming to reveal the relationshipbetween thermal cracking behavior and mechanical prop.r.ies of engineering materials with biomimetic surface,biomimeticspecimens were fabricated using laser technique by imitating the heterogeneous structure on the surface of plant *** of thermal fatigue cycling on the tensile prop.r.ies of H13 die steel specimens with different surfaces (several types ofbiomimetic surfaces and a smooth surface) was comp.r.d and *** a result,due to the coupling effects of themorphological features on the surface and the microstructure characteristics within unit zone,these specimens with biomimeticsurface exhibit remarkably enhanced Ultimate Tensile Strength (UTS) and 0.2% Yield Strength (YS) comp.r.d with referencespecimens while corresponding ductility remains largely unaffected even heightened,whether the thermal fatigue loads or *** relative mechanisms leading to these improvements have been discussed.

关键词： biomimetic surface coupling thermal fatigue tensile prop.r.y H13 steel

Study and Application of Mold Filling Simulation of Shaped Castings

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Journal of Materials Science & Technology 1997年第2期13卷 107-112页

作者： Baicheng LIU Wei QIU Houfa SHEN Zhiqiang GAO (Dept. of mechanical engineering, Tsinghua University Beijing 100084, china) Dept. of mechanical engineering Tsinghua University Beijing 100084 China

In this pap.r. an algorithm for simulating fluid flow and heat transfer for mold filling of shaped castings is presented. The main features of the algorithm include: 1) a simple but practical technique based on VOF method to determine free surface, 2) an explicit scheme of enthalpy to solve the energy equation more efficiently, and 3) an effective treatment to modify the flux deviation due to pressure iteration. In order to verify these methods, well controlled exp.r.ments have been repeatedly done with both water analog and gray iron pouring exp.r.ments to record the flow patterns and temp.r.ture variations. The calculated results are in accordance with the exp.r.mental ones. For the applications, the simulated initial temp.r.ture distribution right after mold filling was used to analyse subsequent solidification and to predict shrinkage defects. Actual castings were poured and tested in a foundry plant. The reuslts show that the defects predication with considering fluid flow effects is more precise than that without considering the effects.

关键词： Simulation Study and Application of Mold Filling Simulation of Shaped Castings Mold

Water-Air Mixing Jet produced by Electro-hydraulic Impulse Technology Strengthening the Quality of Surface of Metal Materials

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Journal of Materials Science & Technology 2002年第3期18卷 194-196页

作者： Zhenfang LIAO and Shijin ZHANGCollege of mechanical engineering, Chongqing University, Chongqing 400044, china [ Manuscript received September 10, 2001, in revised form October 26, 2001] Chongqing Univ Coll Mech Engn Chongqing 400044 Peoples R China

Electro-hydraulic impulse water-air mixing jet by which the quality of metal materials can be improved is described in this pap.r. The exp.r.mental results proved that the hardness and the micro-hardness of the surface layer of metal materials can be improved with this method, for example, the microhardness of CrWMn can be increased by 35.62 p.r.ent.

关键词： Electro-hydraulic impulse Water-air mixing jet Quality of surface

Effect of process Factors on Microstructure of Semisolid Continuous Casting Billets

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International Journal of Minerals,Metallurgy and Materials 2000年第4期14卷 242-245页

作者： Shuming Xing, Qijie Zhai, Hanqi Hu ( Dep.r.ment of mechanical engineering, Tsinghua University, Beijing 100084, china School of Material Science and engineering, Shanghai University, Shanghai 200072, china Material Science and engineering School, Univer Dep.r.ment of mechanical engineering Tsinghua University Beijing 100084 China School of Material Science and engineering Shanghai University Shanghai 200072 China Material Science and engineering School University of Science and Technology Beijing Beijing 100083 China

Semisolid continuous casting (SSCC) is a new technology to produce billets for semisolid metal forming (SSMF). The effect of process factors, such as pouring temp.r.ture, stirring rate, preheating temp.r.ture and thermal conductivity of stirring chamber, on the microstructure of SSCC billets was studied by means of the factorial exp.r.mental method. The results show that the microstructure of SSCC billets can be controlled by the above-mentioned four process factors. In order to obtain fine and rounded granular grains in an SSCC billet, the pouring temp.r.ture, preheating temp.r.ture and stirring rate should be kept in a moderate range, and the thermal conductivity of stirring chamber should be high. The regression equations with the process factors connecting the microstructure was also set up based on exp.r.mental data.

关键词： semisolid metal continuous casting process factors microstructure Metallurgy

Noether-type theory for discrete mechanico-electrical dynamical systems with nonregular lattices

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Science china(physics,Mechanics & Astronomy) 2010年第9期53卷 1687-1698页

作者： FU JingLi1,CHEN LiQun2 & CHEN BenYong3 1 Institute of Mathematical physics,Zhejiang Sci-Tech University,Hangzhou 310018,china 2 Dep.r.ment of Mechanics,Shanghai University,Shanghai 200072,china 3 Faculty of mechanical-engineering & Automation,Zhejiang Sci-Tech University,Hangzhou 310018,china 1. Institute of Mathematical physics Zhejiang Sci-Tech University Hangzhou 310018 China2. Department of Mechanics Shanghai University Shanghai 200072 China3. Faculty of Mechanical-Engineering & Automation Zhejiang Sci-Tech University Hangzhou 310018 China

We investigate Noether symmetries and conservation laws of the discrete mechanico-electrical systems with nonregular *** op.r.tors of discrete transformation and discrete differentiation to the right and left are introduced for the *** on the invariance of discrete Hamilton action on nonregular lattices of the systems with the dissipation forces under the infinitesimal transformations with respect to the time,generalized coordinates and generalized charge quantities,we work out the discrete analog of the generalized variational *** this formula we derive the discrete analog of generalized Noether-type identity,and then we present the generalized quasi-extremal equations and prop.r.ies of these equations for the *** also obtain the discrete analog of Noether-type conserved laws and the discrete analog of generalized Noether theorems for the *** we use an example to illustrate these results.

关键词： Noether symmetry variational formula quasi-extremal equation conservation law discrete mechanico-electrical dynamical system

Nonequilibrium Thermodynamic and Dissipative Structure Mechanism of Fluidized Beds

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International Journal of Minerals,Metallurgy and Materials 1999年第2期13卷 90-93页

作者： Maozhan Qi Li Wang Xuezi Ni (mechanical engineering School, University of Science and Technology Beijing, Beijing 100083, china) mechanical engineering School University of Science and Technology Beijing Beijing 100083 China

Fluidized beds are nonlinear dynamic systems that exchange mass and energy with outside. They are governed not only byfluid dynamics, but by thermodynamics, especially the second law of thermodynamics as well. According to prigogine's dissipative structure theory, the following have been concluded: (l) a fixed bed is on thermodynamic blanch, and bubbling, turbulent and fast beds areon the dissipatve structure branches. (2) Entropy in fluidized beds is divided into tWo p.r.s: entropy production and entropy flux. The latter increases with gas velocity and decreases with pressure of the systems. That means the entropy of a system may reduce and the systemwith higher gas velocity behaves as dissipative structure characteristics. (3) For a giVen velocity, a fluidized bed op.r.tes stably on thewhole, but it is unstable to local gas-solid phases. The unstable phases are described by fluid dynamic equations, While the minimum ofsystem energy function assures whole stability of the system. (4) A transition criterion of a bubbling bed is derived from prigogine's stability theory.

关键词： fluidized bed nonequilibrium thermodynamics dissipative structure energy extremum

prOpULSIVE p.r.OrMANCE AND VOrTEX SHEDDING OF A FOIL IN FLAppING MOTION

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Journal of Hydrodynamics 2003年第5期15卷 7-12页

作者： Yang Yan, Lu Xi yun, Yin Xie zhen Dep.r.ment of Mechanics and mechanical engineering, University of Science and Technology of china, Hefei 230026, china, Dep.r.ment of Mechanics and mechanical engineering University of Science and Technology of China Hefei 230026 China

The propulsive p.r.ormance and vortex shedding of oscillating foil, whichmimics biological locomotion, were numerically investigated. The objectives of this study were todeal with unsteady force, in p.r.icular thrust force, exerted on the foil in pitching and plungingmotions, and to explore the relation of the propulsive p.r.ormance with vortex structures near thefoil and vortex shedding in the near wake. The two-dimensional incompressible Navier-Stokesequations in the vorticity and stream-function formulation were solved by fourth-order essentiallycompact finite difference schemes for the space derivatives and a fourth-order runge-Kutta schemefor the time advancement. To reveal the mechanism of the propulsive p.r.ormance, the unsteady forceand the shedding of the trailing- and leading-edge vortices of the foil were analyzed. The effectsof some typical factors, such as the frequency and amplitude of the oscillation, the phasedifference between the pitching and plunging motions, and the thickness ratio of the foil, on thevortex shedding and unsteady force were discussed.

关键词： vortex dynamics vortex shedding thrust force unsteady flow flappingmotion

Effect of current pulses on fracture morphology in sup.r.lastic deformation of 2091 Al Li alloy

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中国有色金属学会会刊：英文版 1999年第3期9卷 514-518页

作者： Liu Zhiyi(刘志义) mechanical Dep.r.ment, University of petroleum, Dongying 257062, p. r. china Univ petr Dept Mech Dongying 257062 Peoples R China

The effect of current pulses on the fracture morphology in the sup.r.lastic deformation of 2091 Al Li alloy at two kinds of initial strain rate ( 1=3.33×10 -3 s -1 ; 2=3.33×10 -2 s -1 ) was *** results show that current pulse turns fracture of sup.r.lastic deformation at low strain rate from local interior fracture morphology to typical fracture by growth and interlinkage of cavities, and at high strain rate from rough grain boundary surface to smooth grain boundary surface. It is indicated that the characteristic, that current pulse promotes atomic diffusion, maintains an equiaxial grain microstructure at low strain rate, and accelerates the development of diffusional type of cavity and relaxes stress concentration at triple junction of grain boundaries at high strain rate, and makes the sup.r.lastic deformation at two kinds of strain rate show a normal sup.r.lastic fracture morphology.

关键词： Al Li alloy sup.r.lastic deformation fracture morphologyDocument code: A

TrANSMISSION MOMENTArY EFFICIENCY BASED ON THE D'ALEMBErT-LAGrANGE EQUATION FOr INVOLUTES GEArS

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Chinese Journal of mechanical engineering 2004年第2期17卷 272-275页

作者： Liang Yi Lai Changying School of mechanical engineering,Nanjing University of Science and Technology,Nanjing 210094, china School of mechanical engineering Nanjing University of Science and Technology Nanjing 210094 China Dep.r.ment of Science and Technology Studies University College London WC1E 6BT UK

The D'Alembert-Lagrange equation is introduced and used to derive theformulas of momentary efficiency for external gearing of standard involutes sp.r.gears. The gearingswith correct and increased center distance are discussed. The momentary efficiency formula iscalculated and analyzed using software Matlab. The derived formula of momentary efficiency is alsocomp.r.d with the traditional formula.

关键词： D'Alembert-Lagrange equation Involutes gear Momentary efficiency