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THE STRAIN CYCLIC CHARACTERISTICS AND RATCHETINg OF U71Mn RAIL STEEL UNDER UNIAxIAL LOADINg

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Acta Metallurgica Sinica(English Letters) 2000年第3期13卷 893-900页

作者： g.z. kang Q. gao, x.j.yang and Y.F. Sun(Department of Applied Mechanics and Engineering, Southwest jiaotong University, Chengdu 610031, China) Southwest jiaotong Univ Chengdu China

An experimental study was carried out of the cyclic behavior of U71Mn rail steel subjected to uniaxial strain and stress. The effects of cyclic struin amplitude, mean struin,strain loading rate and their histories on the strain cyclic characteristics were *** the asymmetrical stress cycling, the effects of stress amplitude, mean stress,stress loading rate and their histories on the ratcheting were analyzed. The interaction between strain cycling and stress cycling was also discussed. It is shown that either the cyclic characteristics under strain cycling or the ratcheting under asymmetrical stress cycling depends not only on the cumnt loading state, but also on the previous loading history. Some significant results are obtained.

关键词： cyclic plasticity ratcheting U71Mn rail steel uniaxial loading

Effects of Current Stressing on Shear Properties of Sn-3.8Ag-0.7Cu Solder joints

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journal of Materials Science & Technology 2010年第8期26卷 737-742页

作者： x.j. Wang Q.L. zeng Q.S. zhu z.g. Wang j.K. Shang Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Department of Materials Science and Engineering University of Illinois at Urbana-Champaign Urbana IL 61801 USA

Effects of electromigration on microstructure, shear strength, and fracture behavior of solder joints were investigated by single-ball shear samples of eutectic Sn-3.8Ag-0.7Cu （SAC） joined by Cu plates at two sides. The electromigration tests were conducted at a current density of about 1.1×10^3 A/cm2 and a working temperature of about 83℃. The results showed that the shear strength and flow stress decreased greatly after current stressing. Such a decrease was associated with no significant loss of the fracture strain at short electromigration but a great reduction in the fracture strain after long-term current stressing. The variation of the fracture strain with the electromigration time was shown to result from the shift of the fracture surface from the center of the solder towards the intermetallic compound （IMC） interface at the cathode.

关键词： Strength Fracture strain Voids Solder

Refining constitutive relation by integration of finite element simulations and gleeble experiments

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journal of Materials Science & Technology 2019年第6期35卷 1039-1043页

作者： D.j. Yu D.S. xu H. W ang.z.B. zhao g.z. Wei R. yang College of Sciences Northeastern University Shenyang 110004 China Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

Thermo-mechanical coupled finite element calculations were carried out to simulate the gleeble compression of the samples of a titanium alloy(Ti60), and the results are analyzed and compared with the actual compression tests conducted on a gleeble 3800 thermo-mechanical simulator. The changes in temperature, stress and strain distribution in the samples and the source of error on the constitutive relations from gleeble hot compression test were analyzed in detail. Both simulations and experiments showed that the temperature distribution in the specimen is not uniform during hot compression, resulting in significant deformation inhomogeneity and non-ignorable error in the flow stress strain relation,invalidating the uniform strain assumption commonly assumed when extracting the constitutive relation from gleeble tests. Based on the finite element simulations with iterative corrections, we propose a scheme to refine the constitutive relations from gleeble tests.

关键词： Titanium alloy Constitutive relation Finite element Compression Temperature distribution

A two-scale method for identifying mechanical parameters of composite materials with periodic configuration

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Acta Mechanica Sinica 2006年第6期22卷 581-594页

作者： j.z. Cui x.g. Yu Academy of Mathematics and System Sciences Chinese Academy of Sciences Beijing 10080 China

In this paper, a two-scale method （TSM） is presented for identifying the mechanics parameters such as stiffness and strength of composite materials with small periodic configuration. Firstly, a formulation is briefly given for two-scale analysis （TSA） of the composite materials. And then a two-scale computation formulation of strains and stresses is developed by displacement solution with orthotropic material coefficients for three kinds of such composites structures, i.e., the tension column with a square cross section, the bending cantilever with a rectangular cross section and the torsion column with a circle cross section. The strength formulas for the three kinds of structures are derived and the TSM procedure is discussed. Finally the numerical results of stiffness and strength are presented and compared with experimental data. It shows that the TSM method in this paper is feasible and valid for predicting both the stiffness and the strength of the composite materials with periodic configuration.

关键词： Two-scale method Stiffness Strength Composite materials Small periodic configuration

A Theoretical Approach for Estimating Fracture Toughness of Ductile Metals

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上海交通大学学报 2004年第Z2期38卷 114-119页

作者： Y.T. He F. Li g.Q. zhang L.j. Ernst x.j. FU College of Aeronautics University of Air Force Engineering Xi''an 710038 China College of Aeronautics Northwestern Polytechnical University Xi''an710072 China College of Aeronautics University of Air Force Engineering Xi''an 710038 China Philips Centre for Industrial Technology P.O.Box 218 5600 MD Eindhoven The Netherlands Delft University of Technology 2628 CD Delft The Netherlands College of Aeronautics Northwestern Polytechnical University Xi''an 710072 China

Fracture toughness is very important when applying Damage Tolerance Design and Assessment Techniques. The traditional testing approach for obtaining fracture toughness values is costly and time consuming. In order to estimate the fracture toughness of ductile metals, the fracture mechanics theory, materials plastic deformation theory and materials constructive relationships are employed here. A series of formulae and a theoretical approach are presented to calculate fracture toughness values of different materials in the plane stress and plane strain conditions. Compared with test results, evaluated values have a good agreement.

关键词： fracture toughness testing approach evaluated method fracture mechanics theory plastic deformation theory materials constructive relationship theoretical approach

THE FRACTURE CHARACTERISTICS OF δ-Al_2O_3/AlALLOY COMPOSITES

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Acta Metallurgica Sinica(English Letters) 1999年第6期12卷 0-0,0-0+0-0+0页

作者： g.z. kang Q. gao C. yang and j.x. zhang (Department of Applied Mechanics and Engineering, Southwest jiaotong University, Chengdu 610031, China )

The initial location of the crack and the controlling factor of the fracture in the squeeze casting composites δ-Al2 O3/Al-5.5zn, δ-Al2 O3/Al-5.5Mg and δ-Al2 O3/Al-cSi were studied by microscopic observation and finite element analysis(FEA). The in situ failure processes were obseroed bU the scanning electronic microscope mp. The distributions of stress components along the fiber length in matta, and the tnean axial stresses of fiber and matrix were calculated by three-dimensional elasto-plastic *** is found that the failure modes of short fiber reiwtreed metal matrix composites change with the variations of the micro-structurnl characteristics of composites, such as fiber orientation, matrix strength and intedecial bonding, etc.

关键词： metal matrix composite short fiber fracture characteristics finite element analysis

STUDY OF DYNAMIC RECRYSTALLIzATION OF LOW CARBON STEEL IN THIN SLAB CONTINUOUS ROLLINg PROCESS

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Acta Metallurgica Sinica(English Letters) 2006年第4期19卷 265-270页

作者： x.K. Liang x.j. Sun Q.Y. Liu H. Dong State Key Laboratory of Advanced Steel Processes and Products Central Iron and Steel Research Institute Beijing 100081 China

Combined with the technological characteristics of thin slab continuous rolling process （TSCR）, dynamic recrystallization of an extremely coarse austenite of low carbon steel is studied by Thermecmaster-z hot simulator. By the analysis of true stress-strain curves and the observation of microstructures at different deformation stages, the critical stress and critical strain are determined under different deformation conditions. The effect of z parameter on dynamic recrystallization of coarse austenite is studied. The microstructure evolution in real production is also discussed.

关键词： TSCR (thin slab continuous rolling process) coarse austenite dynamic recrystallization

A pathway to improve low-cycle fatigue life of face-centered cubic metals via grain boundary engineering

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journal of Materials Science & Technology 2022年第18期113卷 82-89页

作者： x.j.guan z.P.jia S.M.Liang F.Shi x.W.Li Department of Materials Physics and Chemistry School of Materials Science and EngineeringNortheastern UniversityShenyang 110819China State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China Key Laboratory for Anisotropy and Texture of Materials Ministry of EducationNortheastern UniversityShenyang 110819China

To probe a pathway to improve the low-cycle fatigue life of face-centered cubic(FCC)metals via grain boundary engineering(gBE),the tension-tension fatigue tests were carried out on the non-gBE and gBE Cu-16 at.%Al alloys at relatively high stress *** results indicate that the cyclic strain localiza-tion and cracking at grain boundaries(gBs)can be effectively suppressed,especially at increased stress amplitude,by an appropriate gBE treatment that can result in a higher resistance to gB cracking and a greater capability of compatible ***,the sensitivity of fatigue life to stress amplitude can be weakened by gBE,and the low-cycle fatigue life of Cu-16 at.%Al alloys is thus distinctly improved.

关键词： Cu-Al alloy grain boundary engineering Fatigue life Crack nucleation Stress amplitude

REVIEW ON RESEARCH AND DEVELOPMENT OF MAgNESIUM ALLOYS

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Acta Metallurgica Sinica(English Letters) 2008年第5期21卷 313-328页

作者： z. yang j.P. Li j.x. zhang g.W. Lorimer j. Robson Department of Materials Science and Engineering Xilan Jiaotong University Xilan 710049 China Department of Materials Science and Engineering Xi＇an Technological University Xi＇an 710032 China Manchester Materials Science Centre University of Manchester Manchester M 1 7HS UK

The current research and development of magnesium alloys is summarized. Several aspects of magnesium alloys are described： cast Mg alloy, wrought Mg alloy, and novel processing. The subjects are discussed individuall... 详细信息

关键词： Magnesium alloys Novel processing grain refined