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Mathematical Delineation of the Thermophysical Process of Electron Beam Welding

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稀有金属材料与工程 2011年第S4期40卷 134-137页

作者： Wang Xuedong1,2.Fu Pengfei 1,Shi Qingyu 2.1National Key Laboratory of Science and technology on power Beam Processes,Beijing Aeronautical Manufacturing Research {2.,Beijing 10002.,China2.department of Mechanical engineering,Tsinghua University,Beijing 100084,China Beijing Aeronaut Mfg Res Inst Natl Key Lab Sci & Technol Power Beam Proc Beijing 100024 Peoples R China Tsinghua Univ Dept Mech Engn Beijing 100084 Peoples R China

Multiple factors and complicated coupling relationships exist in the weldment during EBW,in order to comprehend this process,a mathematical delineation method based on a main line was presented in this *** on the main line,the complicated coupling relationships existing in EBW were reproduced by mathematical *** calculational results were in well agreement with the experimental *** mathematical delineation was an effective method to comprehend the features and essence of EBW.

关键词： electron beam welding mass transfer identification of phase interface keyhole

The dust emission law in the wind erosion process on soil surface

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Science China(Physics,Mechanics & Astronomy) 2009年第2期52卷 258-269页

作者： XING Mao1 & GUO LieJin2.1 Mining technology institute, Taiyuan University of technology, Taiyuan 03002., China 2.State Key Laboratory of Multiphase Flow in power engineering, Xi’an Jiaotong University, Xi’an 710049, China Mining technology institute Taiyuan University of Technology Taiyuan 030024 China State Key Laboratory of Multiphase Flow in power engineering Xi’an Jiaotong University Xi’an 710049 China

The dust emission models to date cannot describe the relation between the transport rate of different sized grains and their grain size composition in soil surface, so Aeolian grain transport on a soil-like bed composed of fine sand and silt powder was measured in a wind tunnel. Six types of soil-like beds with different silt fractions have been tested in this experiment. The mass flux profiles of silt dust and sand grains are much different due to their different motion modes. Analysis of the vertical distribution of the powder and sand grains reveals that for a given soil bed, the ratio of the horizontal dust flux to the horizontal sand flux is directly proportional to their mass ratio in the bed. The dust flux is closely linked to the sand flux by the bombardment mechanism. For a given wind velocity and grain size of the bed, the slopes of the vertical mass flux profiles of sand grains larger than 100 μm are nearly equal in a log-linear plot and the ratio between the fraction of transport rate of each size group to the whole transport rate and the mass fraction of each size group in the bed is a constant only dependent on grain size. With this law, the transport rate of dust and different sized grains can be related with the grain size composition in the soil surface.

关键词： wind erosion dust transport rate grain size

Characteristics of Joint Welded by Laser Welding of Aluminium-Lithium Alloy with Filler Wire

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稀有金属材料与工程 2011年第S4期40卷 138-141页

作者： Yang J1,2.Li X Y1,Gong S L2.Chen L2.Xu F2.1 School of Material Science and engineering,Beijing University of technology,Beijing 100083,China 2.Science and technology on power Beam Processes Laboratory,Beijing Aeronautical Manufacturing technology Research institute,Beijing 10002.,China Beijing Aeronaut Mfg Technol Res Inst Sci & Technol Power Beam Proc Lab Beijing 100024 Peoples R China Beijing Univ Technol Sch Mat Sci & Engn Beijing 100083 Peoples R China

The characteristics of weld shape,microstructure,mechanical properties and defects of 5A90 Al-Li alloy joint by laser welding (LBW) and laser welding with filler wire (LWFW) were studied and *** results indicated that the microstructure of joint by LWFW was fine-grained layer and the equiaxed grain in most of seams,which were similar to the joint by *** with the joint by LBW,the microstructure of joint by LWFW tended to fine,and the range of the columnar crystals zone was prone to *** Microhardness of the joint by LWFW (92.57HV0.2. was lower than that by LBW (95.65HV0.2.,but the uniformity was *** ultimate tensile strength of the joint by LWFW was lower than that by LBW slightly,which reached to 73.03% and 79.2.% of the base metal ***,the elongation of the LWFW joint was higher than that of the LBW joint significantly,which reached to 38.65% and 2..38% of the base metal *** microstructure and mechanical properties of 5A90 Al-Li alloy by LWFW were better than that by *** defects of joint were mainly forming defects which were caused by improper parameters and porosity inside the joint,which was caused by uncleaned surface and incomplete penetration.

关键词： Al-Li alloy laser beam welding (LBW) laser welding with filler wire (LWFW) weld shape microstructure mechani-cal properties defects

Numerical Simulation and Assessment of Self-induced Tensile Stresses in Steel Ring Restrained Concrete

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Journal of Wuhan University of technology(Materials Science) 2010年第3期25卷 530-533页

作者：马新伟 department of Civil engineering Harbin Institute of Technology

For a better understanding of the strains and stresses,numerical simulation was conducted by using ANSYS under the assumption of absolute bond between the steel and *** results show that the stresses and strains in such concrete and steel rings are uneven;the curves of strains and stresses change gradually around the *** ease numerical computation,the mechanical system was simplified under the assumptions of synchronous deformation and uniform strains and *** results of the numerical simulation and simplified stress calculation can match almost *** means that the simplified mechanical model can be used in stress and visco-elastic behavior quantification.

关键词： restrained shrinkage numerical simulation model simplification

Effect of acid oxidization of carbon nanotube electrode on the capacitances of double layer capacitors

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Science China(Technological Sciences) 2004年第3期47卷 257-264页

作者： Li Chensha1,WANG Dazhi1,LIANG Tongxiang2.WANG Xiaofeng1 & LIANG Ji1 1. department of Mechanical engineering, Tsinghua University,Beijing 100084, China 2. {2. of Nuclear Energy technology, Tsinghua University,Beijng 102.01,China Tsinghua Univ Dept Mech Engn Beijing 100084 Peoples R China Tsinghua Univ Inst Nucl Energy Technol Beijing 102201 Peoples R China

Polarizable electrode of electric double layer capacitor was made from carbon nanotubes. The effect of acid oxidation of electrode on the specific capacitance was studied. Oxidation removed the redundant carbon, expanded the pore size and introducedf some kinds of functional groups on the surface of CNTs. The specific capacitance of the electrodes winth organic electrolyte was increased from 2..4 to 49.6 F/g after being oxidized at a volume ratio H2.O4 to HNO3 of 3:1.

关键词： carbon nanotubes, electric double layer capacitor, specific capacitance.

Analytical and numerical modeling of resonant piezoelectric devices in China-A review

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Science China(Physics,Mechanics & Astronomy) 2008年第12期51卷 1775-1807页

作者： YANG JiaShi1,2. & YANG ZengTao1 1 institute of Mechanics and Sensing technology, School of Civil {2. and Architecture, Central South University, Changsha 410083, China 2.department of {2. Mechanics, University of Nebraska, Lincoln, NE 68588-052., USA 1. institute of Mechanics and Sensing technology School of Civil Engineering and Architecture Central South University Changsha 410083 China 2. department of engineering Mechanics University of Nebraska Lincoln NE 68588-0526 USA

The results on theoretical and numerical modeling of resonant piezoelectric devices in China are reviewed. Solutions to dynamic problems of the propagation of bulk acoustic waves (BAW), surface acoustic waves (SAW), vibrations of finite bodies, and analyses of specific devices are discussed. Results from both the ultrasonics community and mechanics researchers are included. It is hoped that the paper will be useful for the understanding, communication and collaboration between Chinese and foreign scholars. The paper may also be helpful for bridging the gap between ultrasonics and mechanics researchers on piezoelectricity re- search. The paper contains 316 references.

关键词： piezoelectricity wave vibration transducer resonator

Effect of Activator and Curing Mode on Fly Ash-based Geopolymers

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Journal of Wuhan University of technology(Materials Science) 2009年第5期24卷 711-715页

作者：侯云芬 institute of Civil engineering and Traffic Beijing Institute of Civil Engineering and Architecture department of Material China University of Mining and Technology

The influences of concentration and modulus of sodium silicate solution and curing mode on the phase composition, microstructure and strength development in the geopolymers prepared using Class F fly ash were investigated. X-ray diffraction （XRD）, Fourier transform infrared spec-troscopy （FTIR） and MAS NMR were utilized. Results show that the compressive strength increases as sodium silicate solution modulus increases, but when modulus exceeds 1.4, the compressive strength decreases, and it decreases markedly while the modulus is greater than 2.0. The compressive strength was improved by the increase of sodium silicate solution concentration. When the concentration is 32., the compressive strength reaches the maximum, then it reduces as concentration increasing. Elevated temperature can increase the strength of samples that synthesized from sodium silicate solution with 32. concentration and modulus 1.2. Compared to the strength of the sample cured at 50 ℃, the strength of the samples cured at 65 ℃ and 80 ℃ are higher at 1 d and 3 d, but the same at 7 d. At high temperature, prolonged curing time will decrease the strength. Long precuring at room temperature before application of heat is beneficial for strength development, and there is about 50% increase in strength of the samples cured at 1 d precuring and 2.d elevated temperature as compared to the strengths of the samples cured for 3 d at elevated temperatures or cured for 2. d at room temperature. The main product of reaction in the geopolymeric material is amorphous alkali aluminosilicate gel.

关键词： geopolymers fly ash activator elevated temperature

Active control of structural vibration with on-line secondary path modeling

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Progress in Natural Science:Materials International 2004年第6期 49-56页

作者： YANG Tiejun 1,2. * and GU Zhongquan 2.1. Research institute of power Plant {2.,Harbin engineering University,Harbin 150001,China 2. National Key Laboratory of Rotorcraft and Aeromechanics,nanjing University of Aeronautics and Astronautics,nanjing 2.0016, China) Research institute of power Plant {2.，Harbin engineering University，Harbin 150001，China National Key Laboratory of Rotorcraft and Aeromechanics，nanjing University of Aeronautics and Astronautics，nanjing 2.0016，China National Key Laboratory of Rotorcraft and Aeromechanics，nanjing University of Aeronautics and Astronautics，nanjing 2.0016，China

An active control strategy with on-line secondary path modeling is proposed and applied in active control of helicopter structural vibration. Computer simulations of the secondary path modeling performance demonstrate the superiorities of the active control strategy. A 2.input 4-output active control simulation for a helicopter model is performed and great reduction of structural vibration is achieved. 2.input 2.output and 2.input 4-output experimental studies of structural vibration control for a free-free beam are also carried out in laboratory to simulate a flying helicopter. The experimental results also show better reduction of the structural vibration, which verifies that the proposed method is effective and practical in structural vibration reduction.

关键词： structural vibration on-line secondary path modeling active control.

Calculation of the yield and tensile strength in the alloying non quenched-tempered steel by the electron structure parameters

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Progress in Natural Science:Materials International 2005年第9期15卷 832-837页

作者： LIU Zhilin1**, LIN Cheng1, LIU Yan1 and GUO Yanchang2.1. department of Materials and Chemical engineering, Liaoning {2. of technology, Jinzhou 12.001, China 2. The Technical Center of Benxi Iron and Steel Group Corporation, Benxi 117000, China) department of Materials and Chemical engineering Liaoning Institute of Technology Jinzhou 121001 China. Technical Center of Benxi Iron and Steel Group Corporation Benxi 117000 China

Based on the phase transformations and strengthening mechanisms during rolling, the strength increments Δσbunder different strengthening mechanisms are calculated with the covalent electron number nAof the strongest bond in phase cells of alloys and the interface electron density difference Δρ matching the interface stress in alloys. The calculation method of the finishing rolling yield strength is proposed, and it is integrated with the proposed calculation formulas of strength of non quenched-tempered steel. Therefore, the general formulas to simultaneously calculate both the finishing rolling strength and the yield strength of the continuous casting-rolling and non quenched-tempered steel are given. Taken the pipeline steel X70 as an example, the predictions of properties and technological parameters are performed before production or online.

关键词： electron structure non quenched-tempered steel yield strength prediction of properties.