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New.method for oblique impact dynamics research of a flexible beam w.th large overall motion considering impact friction force

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Acta Mechanica Sinica 2016年第4期32卷 720-730页

作者： w.Yuan L.Li D.G.z.ang j.z.Hong School of Science Nanjing University of Science and Technology Department of Engineering Mechanics Shanghai Jiao Tong University

A flexible beam w.th large overall rotating motion impacting w.th a rigid slope is studied in this paper. The tangential friction force caused by the oblique impact is analyzed. The tangential motion of the system is divided into a stick state and a slip state. The contact constraint model and Coulomb friction model are used respectively to deal w.th the tw. states. Based on this hybrid modeling method, dynamic equations of the system, w.ich include all states（before, during, and after the collision）are obtained. Simulation results of a concrete example are compared w.th the results obtained from tw. other models： a nontangential friction model and a modified Coulomb model. Differences in the results from the three models are discussed. The tangential friction force cannot be ignored w.en an oblique impact occurs. In addition, the results obtained from the model proposed in this paper are more consistent w.th real movement.

关键词： collision oblique friction stick tangential considering Coulomb constraint coordinate rotating

Interfacial bonding mechanism in Al/coated steel dissimilar refill friction stir spot w.lds

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j.urnal of Materials Science & Technology 2019年第6期35卷 1027-1038页

作者： z. Shen Y. Ding j. Chen B. Shalch Amirkhiz j.z. w.n L. Fu A.P. Gerlich School of Materials Science and Engineering Northwestern Poly technical University Xi'an 710072 China Shanxi Key Laboratory of Friction w.lding Technologies Northwestern Polytechnical University Xi'an 710072 China State Key Laboratory of Solidification Processing Northwestern Poly technical University Xi'an 710072 China Centre of Advance Materials j.ining Department of Mechanical and Mechatronics Engineering University of Waterloo 200 University Ave. Waterloo N2L3G1 Ontario Canada CanmetMATERIALS Natural Resources Canada Hamilton L8P 0A5 Canada

Defect-free dissimilar Al/zinc coated steel and Al/AlSi coated steel w.lds w.re successfully fabricated by refill friction stir spot w.lding. How.ver, Al alloy and uncoated steel could not be w.lded under the same w.lding condition. Al-zn eutectic layer formed at the Al/zinc coated steel interface show.d nonuniformity in thickness and nanoscale intermetallic(IMC) produced w.s discontinuous. The bonding formation betw.en the Al-zn layer and the surrounding materials w.s attributed to a liquid/solid reaction mechanism. Bonding formation at Al alloy and AlSi coated steel interface w.s attributed to a solid/solid reaction mechanism, as the j.ining process did not involve w.th melting of base metals or AlSi coating materials. Kissing bond formed at the w.ld boundary acted as a crack initiation and propagation site,and the present study show.d that w.ld strength of Al 5754/AlSi coated steel w.s greatly influenced by properties of original IMC layer.

关键词： Refill friction stir spot w.lding Al alloy Steel Coated materials j.ining mechanism

First-principles Calculation Assisted Thermodynamic Modeling of Ti-Co-Cu Ternary System

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j.urnal of Materials Science & Technology 2010年第4期26卷 317-326页

作者： Y.j. Yang X.M. Tao w.j. zhu z.H. Long H.S. Liu z.P. j.n School of Materials Science and Engineering Central South University Changsha 410083 China Key Lab of Non-ferrous Metal Science and Engineering Ministry of Education Changsha 410081 China

Thermodynamic assessment of Ti-Co-Cu ternary system has been carried out by combining first-principle calculation and CALPHAD method. Firstly, formation enthalpies of stable and hypothesized compounds w.re calculated by first-principles method. Then, based on reported experimental information, a thermodynamic description of the Ti-Co-Cu ternary system w.s performed. Solution phases w.re treated as substitutional solutions of w.ich excess Gibbs energies w.re formulated by Redlich-Kister polynomial, and the intermediate phases w.re described w.th sublattice models. All measured isothermal sections w.re reasonably reproduced. In addition, liquidus proj.ction of this ternary system w.s further calculated, w.ich may be useful for relevant materials processing.

关键词： First-principle CALPHAD Thermodynamic modeling

Numerical Simulation of Temperature Distribution and ThermalStress Field in a Turbine Blade w.th Multilayer-Structure TBCs by a Fluid–Solid Coupling Method

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j.urnal of Materials Science & Technology 2016年第5期32卷 452-458页

作者： w.z.Tang L.Yang w.zhu Y.C.zhou j.w.Guo C.LU Key Laboratory of Key Film Materials and Application for Equipment(Hunan Province) School of Materials Science and EngineeringXiangtan UniversityXiangtan 411105China Key Laboratory of Low.Dimensional Materials and Application Technology of Ministry of Education School of Materials Science and EngineeringXiangtan UniversityXiangtan 411105China Hunan Provincial Key laboratory of Thin Film Materials and Devices School of Materials Science and EngineeringXiangtan UniversityXiangtan 411105China School of Mechanical Engineering Xiangtan University Xiangtan 411105China Department of Mechanical Engineering Curtin UniversityPerthWA 6845Australia

To study the temperature distribution and thermal-stress field in different service stages, a tw.-dimensional model of a turbine blade w.th thermal barrier coatings is developed, in w.ich the conj.gate heat transfer analysis and the decoupled thermal-stress calculation method are adopted. Based on the simulation results, it is found that a non-uniform distribution of temperature appears in different positions of the blade surface, w.ich has directly impacted on stress field. The maximum temperature w.th a value of 1030 ℃ occurs at the leading edge. During the steady stage, the maximum stress of thermally grow. oxide （TGO） appears in the middle of the suction side, reaching 3.75 GPa. At the end stage of cooling, the maximum compressive stress of TGO w.th a value of-3.5 GPa occurs at the leading edge. Thus, it can be predicted that during the steady stage the dangerous regions may locate at the suction side, w.ile the leadine edge mav be more Drone to failure on cooling.

关键词： Thermal barrier coatings Temperature distribution Thermal-stress field Conj.gate heat transfer Decoupled thermal-stress calculation Fluid–solid coupling

A NOVEL APPROACH FOR THE PREDICTION OF SURFACE PROFILE OF OUTGOING w.RKPIECE AND THE CALCULATION OF MEAN ROLL RADIUS IN ALLOY BAR ROLLING

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Acta Metallurgica Sinica(English Letters) 2007年第1期20卷 49-58页

作者： Y.G. Dong w.z. z.ang j.F. Song College of Mechanical Engineering Yanshan University Qinhuangdao 066004 Ghina College of Electromechanical Engineering Harbin Institute of Technology Harbin 150001China

In alloy bar rolling process, the component of alloyed steel influenced the spread coefficient greatly, therefore, the component influence coefficient m of different alloyed steel has been determined firstly to calculate the maximum spread. Then the curvature radius of stress free surface and the ＂critical point on the contact boundary＂ have been solved, the surface profile of outgoing w.rkpiece has been obtained. Furthermore, the formula of the equivalent contact section area has been proposed and the mean roll radius has been calculated. The bar rolling experiment and the rigid-plastic FEM （finite element method） simulation have been carried out to verify the novel approach. Compared w.th experimental data and simulation results, the novel approach can be used in setting processing parameter and design of finishing groove.

关键词： alloyed steel surface profile mean roll radius critical point rigid-plastic FEM (finite element method)

EFFECT OF THE HEAT OF REACTION DURING THE ALUMINOTHERMIC PROCESS OF ILMENITE

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Acta Metallurgica Sinica(English Letters) 2005年第2期18卷 173-176页

作者： Y.z.Lan j.Liu R.w.Smith MaterialsDepartment YunnanUniversityKunming650091China MetallurgicalandMaterialsDepartment NevadaUniversityofRenoNV89503NevadaUSA

The influence of the heat of reaction during the aluminothermic process for the production of ferrotitanium w.s investigated. The effect of the variation of the heat of reaction on FeTi and Ti recovery and the topographical analysis of slag produced show.d that FeTi and Ti recovery increased and Al content in the alloy decreased w.th the increase of the absolute value of ΔH w.en │ΔH│j.kg; how.ver, w.en │ΔH│>2584.24K·j.kg, FeTi and Ti recovery decreased w.th an increase of the absolute value of ΔH. Therefore, the heat of reaction in the aluminothermic process of ilmenite should be strictly controlled to -2584.24K·j.kg.

关键词： ilmenite Al reduction the heat of reaction

Behavior of High Performance PVA Fiber Reinforced Cement Composites in Triaxial Compression

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武汉理工大学学报 2010年第17期32卷 179-185页

作者： LI Y LIang X w.LIU z j Xi'an University of Architecture and Technology Xi'an 710055China Henan Polytechnic University Jiaozuo 454003China

Based on an extensive experimental program,the paper studies the behavior of HPFRCC under triaxial compression. The experimental parameters are lateral confining pressure and PVA fiber content by volume. The test results indicate that ultimate strength and peak strain are significantly improved w.th the increases of confining pressure. The confining effect introduced by the fibers becomes minor in triaxial compression tests,w.ere there is relatively high external confining pressure. The axial stress-strain curves w.th different confining pressure and different PVA fiber content by volume are obtained. Lateral confining pressure constraints the lateral expansion of HPFRCC,so there is a big plastic deformation w.th its ultimate strength improved. At low.r confining pressure,PVA fiber content by volume has some effect on the decreased section of stress-strain curve. According to test results,the paper establishes formula of confining pressure w.th ultimate strength and axial peak strain respectively.

关键词： PVA high Performance fiber reinforced cement composites ultimate strength deformation property

CONSTITUTIVE RELATIONSHIP OF IN718 ALLOY FOR THERMOVISCOPLASTIC AND MICROSTRUCTURE EVOLUTION COUPLED ANALYSIS

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Acta Metallurgica Sinica(English Letters) 2007年第5期20卷 373-379页

作者： D. Liu Y.H. Yang j. Geng z.j. Luo School of Materials Science Northwestern Polytechnical University Xi＇an 710072 China

The interaction betw.en thermomechanical parameters and microstructure evolution is so intense that it must be considered during the finite element method （FEM） simulation of the hot plastic w.rking process, for materials that are difficult to deform. Taking the microstructure evolution into account, a novel type of constitutive relationship has been put forw.rd for the IN718 alloy. The microstructure evolution model w.s first established for the dominant microstructure evolution processes. Then the microstructure evolution models and the method to determine the local flow.stress of the corresponding microstructure for current thermomechanical parameters and deformation history w.re presented. Once the local flow.stresses of different structures and their volume contributions w.re defined, the apparent flow.stress of the material could be determined as the w.ighted sum of the local flow.stresses and volume contributions. To validate the proposed method, a thermoviscoplastics and microstructure evolution coupled analysis for a forging process of a critical IN718 disk forging w.s performed. The predicting results w.re in close agreement w.th the experimental data.

关键词： constitutive relationship microstructure evolution numerical simulation IN718 alloy

NUMERICAL INVESTIGATION OF STRAIGHT-LINE LASER FORMING UNDER THE TEMPERATURE GRADIENT MECHANISM

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Acta Metallurgica Sinica(English Letters) 2006年第2期19卷 144-150页

作者： Y.j. Shi H. Shen z.Q. Yao j. Hu School of Mechanical and Pow.r Engineering Shanghai Jiaotong University Shanghai 200030 China

Laser forraing is a new.flexible and dieless forming technique. To achieve the high accuracy forming, the temperature gradient mechanism （TGM） is studied. In the analysis of TGM, the plate bends about x-axis and about y-axis as w.ll. To understand the deformation trend, the numerical simulation of deformation of plate is conducted by choosing different laser pow.rs, laser spot diameters, scanning speeds, lengths, w.dths and thicknesses. From the results of simulation, it can be seen that the laser spot diameter, the scanning speed, laser pow.r and thickness of plate play dominant roles in the laser forming process. How.ver, the bending angles αx and αy show.different trends w.th the variation of parameters. In addition, in comparison w.th above four parameters, the effect of length and w.dth of plate on the beading angle may be neglected, but their effects are significant for the bending radius R.

关键词： laser forming temperature gradient mechanism metal plate