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Experimental study of dynamic mechanical properties of reactive powder concrete under high-strain-rate impacts

Science China(Technological Sciences) 2010年第9期53卷 2435-2449页

作者： JU Yang1,2,LIU HongBin1,SHENG GuoHua1,3 & WANG HuiJie1 1 State Key Laboratory of Coal Resources and Safe Mining,Beijing Key Laboratory of Fracture and Damage Mechanics of Rocks and Concrete,China university of Mining and Technology,Beijing 100083,China 2 department of mechanical and Manufacturing engineering,university of Calgary,2500 university Drive,AB T2N 1N4,canada 3 School of Resources and Civil engineering,Northeastern university,Shenyang 110004,China 1. State Key Laboratory of Coal Resources and Safe Mining Beijing Key Laboratory of Fracture and Damage Mechanics of Rocks and Concrete China University of Mining and Technology Beijing 100083 China2. Department of Mechanical and Manufacturing Engineering University of Calgary 2500 University Drive AB T2N 1N4 Calgary Canada3. School of Resources and Civil Engineering Northeastern University Shenyang 110004 China

The dynamic mechanical properties of reactive powder concrete subjected to compressive impacts with high strain rates ranging from 10 to 1.1×102 s-1 were investigated by means of SHPB (split-Hopkinson-pressure-bar) tests of the cylindrical specimens with five different steel fiber volumetric *** properties of wave stress transmission,failure,strength,and energy consumption of RPC with varied fiber volumes and impact strain rates were *** influences of impact strain rates and fiber volumes on those properties were characterized as *** general forms of the dynamic stress-strain relationships of RPC were modeled based on the experimental *** investigations indicate that for the plain RPC the stress response is greater than the strain response,showing strong brittle *** RPC with a certain volume of fibers sustains higher strain rate impact and exhibits better deformability as compared with the plain *** a constant fiber fraction,the peak compressive strength,corresponding peak strain and the residual strain of the fiber-reinforced RPC rise by varying amounts when the impact strain rate increases,with the residual strain demonstrating the greatest *** the fiber content makes trivial contribution to improving the residual deformability of RPC when the impact strain rate is *** tests also show that the fiber content affects the peak compressive strength and the peak deformability of RPC in a different *** a constant impact strain rate and the fiber fraction less than 1.75%,the peak compressive strength rises with an increasing fiber *** peak compressive strength tends to decrease as the fiber volume exceeds 1.75%.The corresponding peak strain,however,incessantly rises with the increasing fiber *** total energy Edisp that RPC consumed during the period from the beginning of impacts to the time of residual strains elevates with the fiber volume increment as long as the fiber fraction

关键词： impact reactive powder concrete (RPC) high strain rate dynamic strength energy consumption dynamic stress-strain response

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DETECTION AND ANALYSIS OF WELD POOL SHAPE FOR CO_2 SHORT CIRCUITING ARC WELDING

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Chinese Journal of mechanical engineering 2001年第3期14卷 282-285页

作者： Sun Zhenguo,Wang Junbo,Chen Qiang,Kong Wende (department of mechanical engineering, Qinghua university) 清华大学机械工程系北京

A general industrial CCD( ICCD) camera is redesigned to detect the weld pool without arc at the period of short circuiting, so that the interference of arc and spatter during CO2 short circuiting arc welding is eliminated. Through the analysis of weld pool image, both size parameters (such as weld pool area A, weld pool length L1, L2 and weld pool breadth b) and contour parameters (b, which describe the curves of weld pool boundany) ,which could indicate the shape features of weld pool, had been defined to express weld pool information quantitatively. The investigation of the relationships between weld pool shape parameters and welding process parameters may be beneficial to the quality control of CO2 welding.

关键词： ICCD camera Pool image CO2 short circuiting arc welding

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Ferroelectric properties of Bi_(3.4)Ho_(0.6)Ti_3O_(12) thin films prepared by sol-gel method

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Science China(Technological Sciences) 2008年第9期51卷 1439-1444页

作者： FU ChengJu1, HUANG ZhiXiong1, LI Jie2 & GUO DongYun3 1 School of materials Science and Technology, Wuhan university of Technology, Wuhan 430070, China 2 School of mechanical engineering, Chongqing university of Science and Technology, Chongqing 400050, China 3 department of Physics, Wuhan university, Wuhan 430072, China School of materials Science and Technology Wuhan University of Technology Wuhan 430070 China School of mechanical engineering Chongqing University of Science and Technology Chongqing 400050 China department of Physics Wuhan University Wuhan 430072 China

We have prepared the Ho-substituted bismuth titanate (Bi3.4Ho0.6Ti3O12, BHT) thin films on Pt/Ti/SiO2/Si substrates using sol-gel method. The crystal structure and morphology of the films were characterized using X-ray diffraction and atomic force microscopy. The BHT film shows a single phase of Bi-layered Aurivillius structure and dense microstructure. The 2Pr and 2Ec of the 600-nm-thick BHT film were 38.4 μC/cm2 and 376.1 kV/cm, respectively at applied electric field 500 kV/cm. The dielectric constant and dielectric loss are about 310 and 0.015 at a frequency of 1 MHz, respectively. The Pr value decreased to 93% of its pre-fatigue values after 4.46×109 switching cycles at 1 MHz frenquency, and the BHT film shows good in-sulating behavior according to the test of leakage current.

关键词： Bi3.4Ho0.6Ti3O12 thin film sol-gel method ferroelectric property fatigue dielectric constant

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MESHLESS METHOD FOR 2D MIXED-MODE CRACK PROPAGATION BASED on VORONOI CELL

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Acta Mechanica Solida Sinica 2003年第3期16卷 231-239页

作者： Lou Luliang Zeng Pan (department of mechanical engineering,Tsinghua university,Beijing 100084,China) department of mechanical engineering Tsinghua University Beijing 100084 China

A meshless method integrated with linear elastic fracture mechanics(LEFM)is presented for 2D mixed-mode crack propagation *** domain is divided automatically into sub-domains based on Voronoi cells,which are used for quadrature for the potential energy. The continuous crack propagation is simulated with an incremental crack-extension method which assumes a piecewise linear discretization of the unknown crack *** each increment of the crack extension,the meshless method is applied to carry out a stress analysis of the cracked *** J-integral,which can be decomposed into mode Ⅰ and mode Ⅱ for mixed-mode crack,is used for the evaluation of the stress intensity factors(SIFs).The crack-propagation direction,predicted on an incremental basis, is computed by a criterion defined in terms of the SIFs. The flowchart of the proposed procedure is presented and two numerical problems are analyzed with this *** meshless results agree well with the experimental ones,which validates the accuracy and efficiency of the method.

关键词： meshless method crack propagation mixed-mode crack Voronoi cell

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Synthesis,field emission and microwave absorption of carbon nanotubes filled with ferromagnetic nanowires

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Science China(Technological Sciences) 2010年第6期53卷 1453-1459页

作者： LV RuiTao1,KANG FeiYu1,GU JiaLin1,WANG KunLin2 & WU DeHai2 1 Laboratory of Advanced materials,department of materials Science and engineering,Tsinghua university,Beijing 100084,China 2 department of mechanical engineering,Tsinghua university,Beijing 100084,China 1. Laboratory of Advanced materials Department of Materials Science and Engineering Tsinghua University Beijing 100084 China2. Department of Mechanical Engineering Tsinghua University Beijing 100084 China

Carbon nanotubes filled with ferromagnetic metal nanowires (M-CNTs) were synthesized by using chlorine-contained benzene (***) as *** wall thicknesses of M-CNTs synthesized by trichlorobenzene are much thinner than those by precursor without Cl (***).As-synthesized thin-walled M-CNTs exhibit remarkably enhanced field electron emission performance with a low turn-on field of 0.3 V/μm and better field-emission ***-absorption coatings were made by dispersing as-synthesized M-CNTs into epoxy resin *** is found that the reflection losses in S-band (2-4 GHz),C-band (4-8 GHz) and X-band (8-12 GHz) are enhanced in the order of FeCoNi-CNTs only 2.35 kg/m2 when the coating thickness is 2.0 *** demonstrates that M-CNTs are promising to be used as lightweight and wide-band microwave absorbers.

关键词： carbon nanotubes ferromagnetic nanowires field emission microwave absorption

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STRESS-STRAIN FINITE ELEMENT ANALYSIS AND FATIGUE LIFE PREDICTION FOR BOLTED CONNECTIONS

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Chinese Journal of mechanical engineering 2002年第1期15卷 75-78页

作者： Wang Ziqin Xie Qingsheng mechanical engineering department，Guizhou university of Technology，Guiyang 550003，China mechanical engineering department Guizhou University of Technology Guiyang 550003

A cyclic plasticity model is used into finite element (FE) method to obtainthe details of elastic-plastic stress-strain in the bolts under cyclic axial loading. Two criteriain multiaxial fatigue are employed to predict fatigue lives of bolts. The predicted fatigue livesare in favorable agreement with the experimental results for machined bolts.

关键词： Finite element Fatigue Bolted connection

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THE ROBUST CONTROL SCHEME FOR FREE-FLOATING SPACE MANIPULATOR TO TRACK THE DESIRED TRAJECTORY IN JOINTSPACE

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Acta Mechanica Solida Sinica 2001年第2期14卷 183-188页

作者： Chen Li (department of mechanical engineering, Fuzhou university, Fuzhou 350002, China) Liu Yanzhu (department of engineering Mechanics,Shanghai Jiaotong university, Shanghai 200030, China) ***

The control of a free-floating space manipulator system isdiscussed. With the augmentation approach, the nonlinearparameterization problem of the dynamic equations of the spacemanipulator system is overcome. Based on the results, the robustcontrol scheme for free-floating space manipulator with uncer- tainpayload parameters to track the desired trajectory in jointspace isproposed, and the global convergence of the tracking is verified byusing the Lyapunov method.

关键词： free-floating space maniulator augmentation approach robust control

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EFFECTS OF GAS TYPE AND TEMPERATURE on FINE PARTICLE FLUIDIZATION

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Particuology 2006年第Z1期 114-121页

作者： Chunbao Xu1,* and J.-X. Zhu2 1department of Chemical engineering, Lakehead university, Thunder Bay, ontario, P7B 5E1, canada 2Powder Technology Research Centre, department of Chemical & Biochemical engineering, The university of western ontario, london, ontario, N6A 5B9, canada

The influence of gas type (helium and argon) and bed temperature (77?473 K) on the fluidization behav- iour of Geldart groups C and A particles was investigated. For both types of particles tested, i.e., Al2O3 (4.8 μm) and glass beads (39 μm), the fluidization quality in different gases shows the following priority sequence: Ar > He. In the same gaseous atmosphere, the particles when fluidized at an elevated temperature usually show larger bed voidages, higher bed pressure drops, and a lower umf for the group A powder, all indicating an enhancement in fluidization quality. Possible mechanisms governing the operations of gas type and temperature in influencing the fluidization behaviours of fine par- ticles have been discussed with respect to the changes in both gas properties and interparticle forces (on the basis of the london-van der Waals theory). Gas viscosity (varying significantly with gas-type and temperature) proves to be the key parameter that influences the bed pressure drops and umf in fluidization of fine particles, while the interparticle forces (also varying with gas-type and temperature) may play an important role in fine-particle fluidization by affecting the ex- pansion behaviour of the particle-bed.

关键词： fluidization fine particles gas type temperature interparticle forces

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PRECIPITATION HARDENING IN B2-ORDERED NiAl BY Ni_(2)AlTi COMPOUND

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Acta Metallurgica Sinica(English Letters) 2001年第5期14卷 313-318页

作者： W.H. Tian, K. Ohishi and M. Nemoto 1)department of materials Physics and Chemistry, university of Science and Technology Beijing, Beijing 100083, China 2)department of materials Science and engineering, Faculty of engineering 36, Kyushu university, Fuk Dept. of Mat. Phys. and Eng. Univ. of Sci. and Technol. Beijing Beijing 100083 China

Microstructural variations and correlated hardness changes in B2-ordered NiAl containing fine precipitation of Ni2AlTi have been investigated by means of transmission electron microscopy (TEM) and hardness tests. The amount of age hardening is not large as compared to the large microstructural variations during aging. TEM observations have revealed that the L21-type Ni2AlTi precipitates keep a lattice coherency with the NiAl matrix at the beginning of aging. By longer periods of aging Ni2AlTi precipitates lose their coherency and change their morphology to the globular ones surrounded by misfit dislocations. The temperature dependence of the yield strength of precipitate-containing B2-ordered NiAl was investigated by compression tests over the temperature range of 873-1273 K. The fine precipitation of Ni2AlTi was found to enhance greatly the yield strength and the high-temperature strength is comparable with that of superalloy Mar-M200.

关键词： Aluminum Hardening mechanical properties Nickel Precipitation (chemical)

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Shape Memory Effect of As-aged Fe-14Mn-5Si-8Cr-4Ni-0.2C Alloy

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Journal of materials Science & Technology 2000年第4期16卷 424-426页

作者： Yuhua WEN, Ning LI and Mingjing TU (department of materials Shaping and Controlling engineering, Sichuan university, Chengdu 610065, China) department of materials Shaping and Controlling engineering Sichuan University Chengdu 610065 China

The effects of aging temperature on shape memory effect, mechanical properties and microstruc-ture of Fe-14Mn-5Si-8Cr-4Ni-0.2C shape memory alloy have been studied. The results showed that the second phase particles rich in chromium, manganese and silicon precipitate during aging, and thereby increase the hardness and strength of the alloy. The shape recovery ratio can be remarkably improved by aging and a maximum value can be obtained at 1223 K, which is 68% higher than that of the specimen in solid solution state. When the aging temperature is below 1223 K, the amount of second phase particles increases as the aging temperature increases. The size of austenite grain increases with increasing aging temperature. When the temperature is over 1223 K, the second phase particles can not precipitate. The lack of second phase particles and the increase of grain size make the hardness and shape recovery ratio drastically decrease, when the temperature is over 1223 K.

关键词： Mn Shape Memory Effect of As-aged Fe-14Mn-5Si-8Cr-4Ni-0.2C Alloy As Fe Cr Ni Si

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