XIA Yuebo ZHANG Tianyi State Key Laboratory for Fracture and Failure of Materials.Institute of Metal Research
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Academia Sinica.Shenyang.China DENG Jun Shenyang Polytechnical University.China Associate Professor
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Institute of Metal Research
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Academia Sinica
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Shenyang 110015
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China
金属学报(英文版)
The symmetrical push-pull fatigue tests at strain amplitude of 2×10~3 with different slip orientation of Al single crystals,were carried out at room temperature in air.The peak stresses of various cycles were measured and the stress-strain hysteresis loops for selected cy- cles were recorded.The energy losses.friction stresses,back stresses and shape
关键词:
crystal orientation
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Physical Review Letters
We find that the failure of bulk metallic glassy (BMG) materials follows three modes, i.e., shear fracture with a fracture plane significantly deviating from 45degrees to the loading direction, normal tensile fracture with a fracture plane perpendicular to the loading direction, or distensile fracture in a break or splitting mode with a fracture plane parallel to the loading direction. The actually occurring type of failure strongly depends on the applied loading mode and the microstructure of the material. Extensive evidence indicates that the Tresca fracture criterion is invalid, and for the first time, three fracture criteria are developed for isotropic materials with high strength, such as advanced BMGs or the newly developed bulk nanostructural materials.
关键词:
amorphous-alloys;enhanced plasticity;zr-ti;flow;deformation;composite;strength;microstructure;ribbons;failure
新型炭材料
Electrochemical capacitors (ECs) store energy in eletric double-layers formed along the interface of electrode material and electrolyte, this produces an extremely large capacitance compared with the traditional capacitors. The fundamental principles of electrochemical capacitors are briefly introduced, and the key materials used like electrode materials, electrolytes, separator and current collector materials are summarized. Electrochemical capacitors with pseudocapacitance, such as metal oxides, polymers and hybrid capacitors, are also discussed. The characteristics, possible application fields, the development state, the future R&D prospects for electrochemical capacitors are highlighted.
关键词:
electrochemical capacitors;supercapacitors;storage of electric energy;principles
Journal of Applied Physics
The fracture morphology plays a much important role not only for the failure analysis of materials but also for the clarification of their fracture mechanisms. However, quantitative analysis of the fracture morphology of bulk metallic glasses (BMGs) is still very lacking. In this study, both model and mechanical experiments were conducted to reveal the development of the fracture morphology and the effect of stress state. Inclined notch tensile specimens of a Zr-based BMG with different notch angles were designed to obtain various stress states. For the first time, some new parameters to describe the tensile fracture surfaces of the BMG specimens were proposed. Statistical analysis of these parameters shows that the stress state has a significant influence on the features of fracture surfaces. Through a discussion on the structure and heat evolution during tensile deformation, two damage mechanisms associated with thermal softening and weakening by defects are found to have a combined effect on the tensile fracture of BMG. (c) 2010 American Institute of Physics. [doi:10.1063/1.3487968]
关键词:
brittle fracture;deformation;failure (mechanical);metallic glasses;notch strength;statistical analysis;stress effects;zirconium alloys;shear bands;amorphous-alloys;plastic-flow;deformation;mechanism;localization;liquid
G.Q. Zhang
金属学报(英文版)
The status of research, development of superalloys and materials processing & fabrication technologies for aero-engine applications in China Aviation Industry, with an emphasis on recent achievements at BIAM including directionally solidified and single crystal superalloys for blade and vane applications, wrought superalloys for aero-engine disks and rings, and powder metallurgy (PM) superalloys for high performance disk applications were described. It was also reviewed the development of new class of high temperature structural materials, such as structural intermetallics, and advanced material processing technologies including rapid solidification, spray forming and so on. The trends of research and development of the above mentioned superalloys and processing technologies are outlined. Cast, wrought and PM superalloys are the workhorse materials for the hot section of current aero-engines. New high temperature materials and advanced processing technologies have been and will be the subject of study. It is speculated that high performance, high purity and low cost superalloys and technologies will play key roles in aero-engines.
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superalloy
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Xinzhu Wang
材料科学技术（英）
Two types of experiments were designed and performed to evaluate the adhesive bond in metal foam composite sandwich structures. The tensile bond strength of face/core was determined through the flatwise tensile test (FWT). The test results show that the interfacial peel strength is lower than the interlaminar peel strength in FWT test. The mode I interfacial fracture toughness (GIC) of sandwich structures containing a pre-crack on the upper face/core interface is determined by modified cracked sandwich beam (MCSB) experiment. It is found that the crack propagates unsynchronously on the two side of the specimen and the propagation of interfacial debonding always stays on the face/core interface during the MCSB tests. In order to simulate the failure of metal foam composite sandwich structures, a computational model based on the Tsai-Hill failure
criterion and cohesive zone model is used. By comparing with experiment results, it can be concluded that the computational model can validly simulate the interfacial failure of metal foam composite sandwich structures with reasonable accuracy
关键词:
Interfacial fracture toughness
WADSWORTH Jeffrey and FLUSS Michael(Chemistry and Materials Science Directorate
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Lawrence Livermore National Laboratory
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Livermore
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CA 94551)
金属学报(英文版)
The role of the National Laboratories is summarized from the era of post World War II to the present time. The U.S. federal government policy for the National Laboratories and its influence on their materials science infrastructure is reviewed with respect to .determining overall research strategies, various initiatives to interact with industry (especially in recent years),building facilities that serve the nation, and developing leading edge research in the materials sciences. Despite reductions in support for research in the U.S. in recent years, and uncertainties regarding the specific policies for Research &Development (R&D) in the U.S., there are strong roles for materials research at the National Laboratories. These roles will be centered on the abilities of the National Laboratories to field multidisciplinary teams, the use of unique cutting edge facilities, a focus on areas of strength within each of the labs,increased teaming and partnerships, and the selection of motivated research areas. It is hoped that such teaming opportunities will include new alliances with China, in a manner similar, perhaps, to those recently achieved between the U.S. and other countries.
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: U.S. Materials Science. U.S. National Laboratories and Facilities
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Yiwang BAO(China Building Materials Academy
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Beijing 100024
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China)R. W Steinbrech (IWE1
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Juelich Research Center
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Germany)
材料科学技术（英）
The fracture behaviour of glass in biaxial stress state has been investigated. Fracture toughness of disk specimen with a straight-through crack was measured under biaxial tension and uniaxial tension loads respectively. The difference between them and the reasons for the difference are discussed. The influence of the stress parallel to crack on fracture of brittle material was demonstrated in theory and experiments. The results show that plane stress fracture toughness of glass is not a material constant. and that the fracture toughness measured in biaxial tension state is higher than that measured under uniaxial tension. The conventional fracture criterion upon the stress intensity factor is questioned in the case of biaxial stress problem, and the strain dependence of crack growth is discussed.
关键词:
X.H.Song(Centre for Materials Research and Analysis
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Wuhan University of Technology
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Wuhan 430070
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China Manuscript received 6 November 1995
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in revised form 24 May 1996)
金属学报(英文版)
The theoretical calculation formulas for the plane strain fracture toughness of mode Ⅰand Ⅱcracks of ceramic materials are deduced in this paper by using the nonlocal elasticity theory and maximum tensile stress criterion The deduced formulas, which are independent of crack geometry,bear a relation to material parameters.It is shown through experiment that the theoretical value of fracture toughness is the lower limit of testing value. The theoretical calculation formulas for fracture toughness relate the macro-mechanical performance of materials with the micro-structural parameters and,therefore, are beneficial to fully understanding the physical mechanism of material rupture.
关键词:
:nonlocal elasticity theory
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