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Moment tensor analysis of the acoustic emission source in the rock damage process

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Progress in Natural Science:Materials International 2005年第7期15卷 609-613页

作者： YU Huaizhong, ZHU Qingyong, YIN Xiangchu and WANG Yucang ( state key laboratory of Earthquake Dynamics, institute of Geology, china Earthquake Administration, beijing 100029, china state key laboratory of nonlinear mechanics, institute of mechanics, chinese academy of sciences, beijing 100080, china School of Mathematics and Computational Science, Zhongshan University, Guangzhou 510275, china Center for Analysis and Prediction, china Seismological Bureau, beijing 100036, china Quakes, Department of Earth Science, University of Queensland, Brishbane, Austrialia) state key laboratory of Earthquake Dynamics Institute of Geology China Earthquake Administration Beijing 100029 China. state key laboratory of nonlinear mechanics Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China. School of Mathematics and Computational Science Zhongshan University Guangzhou 510275 China. Center for Analysis and Prediction China Seismological Bureau Beijing 100036 China. Quakes Department of Earth Science University of Queensland Brishbane Austrialia

To further investigate the mechanism of acoustic emission (AE) in the rock fracture experiment, moment tensor analysis was carried out. The AE sources characterized by crack sizes, orientations and fracture modes, are represented by a time-dependent moment tensor. Since the waveforms recorded by AE monitors correlate to the moment tensors, we prefer to select the P wave amplitude from the full-space Green's function of homogeneous and isotropic materials to determine the six independent components of the moment tensor. The moment tensor analysis was used to investigate the AE sources recorded in the experiment, and three types of micro-cracks were found, which are tensile mode, shear mode and mixture of the tensile and shear mode. In addition, the motion of micro-cracks was decided by eigenvectors of moment tensor. Results indicate that the moment tensor analysis may be used as a measurement to reflect the damage evolution of rock specimen.

关键词： moment tensor acoustic emission rock fracture.

Critical serrated flow features during nanoindentation in La-based bulk metallic glasses

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International Journal of Minerals,Metallurgy and Materials 2007年第S1期15卷 8-12页

作者： Wei Peng1), Taihua Zhang2), Yuan Liu1), Lei Li1), and Bingchen Wei1) 1) National Microgravity laboratory, institute of mechanics, chinese academy of sciences, beijing 100080, china 2) state key laboratory of nonlinear mechanics (LNM), institute of mechanics, chinese academy of sciences, beijing 100080, china

La57.6Al17.5(Cu,Ni)24.9 and La64Al14(Cu,Ni)22 bulk metallic glasses (BMGs) were prepared by copper-mould casting method. Plastic deformation behavior of the two BMGs at various loading rates was studied by nanoindentation. The results showed that the La57.6Al17.5(Cu,Ni)24.9 BMG with a glass transition temperature of 423 K exhibited prominent serrated flow at low loading rates, whereas less pronounced serrated flow at high rates during nanoindentation. In contrast, the La64Al14(Cu,Ni)22 BMG with a glass transition temperature of 401 K exhibited prominent serrated flow at high loading rates. The different rate dependency of serrated flow in the two La-based BMGs is related to the different glass transition temperature, and consequently the degree of viscous flow during indentation at room temperature. A smoother flow occurs in the alloy with relatively lower glass transition temperature, due to the relaxation of stress concentration.

关键词： bulk metallic glass nanoindentation serrated flow shear band

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Comments on the Recent Development of Nano/Micro Adhesion Contact Theories

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Comments on the Recent Development of Nano/Micro Adhesion Co...

2003年纳米和表面科学与技术全国会议

作者： Zhao Ya-Pu state key laboratory of nonlinear mechanics (LNM), institute of mechanics, chinese academy of sciences, beijing 100080, china

Because a large surface-to-volume ratio is a distinctive attribute of a nano/micro-mechanical structure, adhesion (stiction) in both MEMS and NEMS has caused great concerns in both scientific and industrial communities. Nano/micro adhesion contact mechanics is a fundamental subject for the understanding of stiction and anti-stiction in MEMS and NEMS, nanotriboly, nano-wear, nano/micro-manipulation, nanoindentation, etc.

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THE LIQUID BRIDGE GROWTH IN ATOMIC FORCE MICROSCOPE

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THE LIQUID BRIDGE GROWTH IN ATOMIC FORCE MICROSCOPE

中国力学学会学术大会'2005

作者： Wei Zheng Zhao Yapu (state key laboratory of nonlinear mechanics, institute of mechanics, chinese academy of sciences, beijing, 100080, china)

Capillary forces are significantly dominant in adhesive forces measured with an atomic force microscope (AFM) in ambient air, which are always thought to be dependent on water film thickness, relative humid, and the free energy of water film. In this report, we study the nature of the "pull-off force on a variety of surfaces as a function contact time. It is found that the capillary forces are of relatively strong dependence on contact time. A simple diffusion model is presented to describe the equilibrium time of the liquid bridge formation. The

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THE SIZE-DEPENDENT ELASTIC PROPERTIES OF NANOFILM WITH SURFACE EFFECTS

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THE SIZE-DEPENDENT ELASTIC PROPERTIES OF NANOFILM WITH SURFA...

中国力学学会学术大会'2005

作者： Guo Jian gang Zhao Yapu (state key laboratory of nonlinear mechanics (LNM), institute of mechanics) (chinese academy of sciences, beijing 100080, china)

Size-dependent elastic constants are investigated theoretically with reference to a nanoscale single-crystal thin film. A three-dimensional (3D) model is presented with the consideration of the relaxation on the surface of the nanofilm. The constitutive relation of the 3D model is derived by using energy approach, and the analytical expressions of four non-zero elastic constants of the nanofilm are obtained. Then the size effects of four elastic

关键词： Size effect elastic constants nanofllm surface relaxation

Multiscale coupling:challenges and opportunities

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Progress in Natural Science:Materials International 2004年第6期 1-4页

作者： HE Guowei 1,XIA Mengfen 1 *,KE Fuju 1,2 and BAI Yilong 1 (1. state key laboratory of nonlinear mechanics,institute of mechanics,chinese academy of sciences,beijing 100080,china 2. Department of Applied Physics,beijing University of Aeronautics and Aerospace,beijing 100083,china) state key laboratory of nonlinear mechanics，institute of mechanics，chinese academy of sciences，beijing 100080，china state key laboratory of nonlinear mechanics，institute of mechanics，chinese academy of sciences，beijing 100080，china Department of Applied Physics，beijing University of Aeronautics and Aerospace，beijing 100083，china

Multiscale coupling is ubiquitous in nature and attracts broad interests of scientists from mathematicians,physicists,machinists,chemists to biologists. However,much less attention has been paid to its intrinsic implication. In this paper,multiscale coupling is introduced by studying two typical examples in classic mechanics: fluid turbulence and solid failure. The nature of multiscale coupling in the two examples lies in their physical diversities and strong coupling over wide-range scales. The theories of dynamical system and statistical mechanics provide fundamental methods for the multiscale coupling problems. The diverse multiscale couplings call for unified approaches and might expedite new concepts,theories and disciplines.

关键词： multiscale coupling statistical mechanics fluid turbulence solid failure.

DEFORMATION TWINNING MECHANISMS IN NANOCRYSTALLINE NI

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DEFORMATION TWINNING MECHANISMS IN NANOCRYSTALLINE NI

中国力学学会学术大会'2005

作者： Wu Xiaolei MaEn Hong Youshi Lu Ke (state key laboratory of nonlinear mechanics, institute of mechanics, chinese academy of sciences, beijing 100080, china) (Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218) (Shenyang National laboratory for Materials sciences, institute of Metal Research, chinese academy of sciences. Shenyang 110016, china)

Twinning has recently been identified as a contributing plastic deformation mechanism in nanocrystalline (nc) metals. Deformation twins and stacking faults indicate the presence of dislocation activities in nc grains;and especially the operation of partial dislocation mediated processes. When nc metals are forced to deform to large strains, in the deforming nanostructure there will inevitably be build up of local stress concentrations that are at sufficient levels for deformation twinning to become a competitive response. In the present paper, we studied

关键词： nanostructure deformation twinning plastic deformation nickel

Investigation of Young’ s Modulus and Residual Stress of Copper Film Electroplated on Silicon Wafer

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Investigation of Young’ s Modulus and Residual Stress of Co...

上海市真空学会成立20周年暨第九届学术年会

作者： Yong Zhou ChunshengYang Jian Chen Guifu Ding Li Wang Mingjun Wang and Yaming Zhang key laboratory for Thin Film and Microfabrication of Ministry of Education, National key laboratory of Micro/Nano Fabrication Technology, Shanghai Jiao Tong University, Shanghai 200030, china Tai Hua Zhang state key laboratory of nonlinear mechanics (LNM), institute of mechanics, chinese academy of sciences, beijing 100080, china.

＜正＞Microbridge testing method is used to measure the Young’s modulus and residual stresses of metallic films. Samples of copper film microbridges are managed to be fabricated by the MEMS （ Microelectromechanical Systems ） technology. Special ceramic shaft structure is designed to solve the problem of getting the load-deflection curves of Cu film microbridge by Nanoindenter XP system with normal Berkovich probe. Theoretical analysis of the microbridge load-deflection curve is proposed to evaluate the Young’ s modulus and residual stress of the films simultaneously. The calculated results based on experimental measurements show that the average Young’s modulus and residual stress for the electroplated copper films are: 115.2 GPa and 19.3 MPa, respectively, while the Young’ s modulus measured by Nanoindentation method on the same copper film based on silicon substrate is 110±1.67 CPa.

关键词： Copper film microbrides MEMS mechanical properties load-deflection measurements

LURR'S twenty years and its perspective

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LURR'S twenty years and its perspective

作者： Yin Xiangchu~(*,**1)) Zhang Langping~(**) Zhang Huihui~(**) Yin Can~(***) Wang Yucang~(***,2)) Zhang Yongxian~(**,+) Peng keyin~(**,+) Wang Haitao~(**,++) Song Zhiping~(**,+++) *(institute of Earthquake Science,china Earthquake Administration(CEA),beijing 100036,china) **(LNM(state key laboratory of nonlinear mechanics),institute of mechanics,chinese academy sciences(CAS),beijing 100080,china) ***(ESSCC,University of Queensland,Australia,The University of Queensland,St.Lucia,Brisbane, QLD 4072,Australia) +(china Earthquake Network Center,CEA,beijing 100036,china) ++(Xinjiang Earthquake Bureau,CEA,Urumchi 830011,china) +++(Shanghai Earthquake Bureau,CEA,Shanghai 200062,china)

根据1956年制订的"十二年科学发展纲要",中科院力学所和清华大学合作创办了工程力学研究班,于1957年初开始招生。我由清华大学选拔推荐进了工程力学研究班。授课的都是当代顶级的力学家如钱学森、郭永怀、钱伟长、李敏华、郑哲敏、杜庆... 详细信息

根据1956年制订的"十二年科学发展纲要",中科院力学所和清华大学合作创办了工程力学研究班,于1957年初开始招生。我由清华大学选拔推荐进了工程力学研究班。授课的都是当代顶级的力学家如钱学森、郭永怀、钱伟长、李敏华、郑哲敏、杜庆华老师等。李敏华老师教我们"塑性力学"。关于加卸载的概念,

关键词： Load-Unload Response Ratio(LURR) earthquake prediction numerical simulation laboratory study