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Xu Z.,Zhangjiajie Institute of Aeronautical Engineering | Song H.,Hunan University
Yingyong Lixue Xuebao/Chinese Journal of Applied Mechanics | Year: 2011

The interaction between a screw dislocation dipole and an interfacial blunt crack is dealt with in this paper. Utilizing the conformal mapping technique, the closed-form solutions are derived for complex potentials and stress fields due to a screw dislocation dipole located near the interfacial blunt crack. The stress intensity factor on the crack tip and the critical stress intensity factor for dislocation dipole emission are also calculated. The influence of the orientation and length of the dislocation dipole and the morphology of the blunt crack as well as the material elastic dissimilarity on the shielding effect and the emission criterion is discussed in detail. The results show that screw dislocation dipole can reduce the stress intensity factor of the interfacial blunt crack tip (shielding effect) only when the screw dislocation located in certain region. The shielding effect increases with the increase of the length of the dipole. The critical loads at infinity for dislocation dipole emission increases with the increase of emission angle and the curvature radius of the blunt crack, and the most probable angle for screw dislocation dipole emission is zero. The dislocation dipole emission is more difficult than the single dislocation emission. The present solutions contain previous results as special cases. Source

Luo Q.,Lianyuan Iron and Steel Co. | Lu D.,Zhangjiajie Institute of Aeronautical Engineering | Luo J.,Chongqing University
Advanced Materials Research | Year: 2010

In this paper, a new welding experiment is studied by applying an additional longitudinal electromagnetic field to CO2 welding process (abbr. LEM-CO2 welding).The characteristics of droplet transfer, macrostructure and microstructure are compared between LEM- CO2 welding and general CO2 welding on Q235 low carbon steel thick plate joint. The research results shows that, an additional longitudinal magnetic field can have a significant effect on properties of the droplet transfer in CO2 welding, the frequency and stability of the droplet transfer in LEM-CO2 welding are improved. The grains of welding seam are refined and welding joints has a higher quality. So the additional longitudinal magnetic field is a very simple and effective method to improve the properties of CO2 welding thick plate joint. © (2010) Trans Tech Publications. Source

Chen S.,Aerospace Research Institute of Materials And Processing Technology | Chen S.,Zhangjiajie Institute of Aeronautical Engineering | Chen L.,Zhangjiajie Institute of Aeronautical Engineering | Song X.,Zhangjiajie Institute of Aeronautical Engineering
Tezhong Zhuzao Ji Youse Hejin/Special Casting and Nonferrous Alloys | Year: 2015

The orthogonal experiment was designed for heat treatment of ZL102 aluminum alloy. Combined with the tensile strength test, range analysis and variance analysis of orthogonal results were carried out. The desirable heat treatment parameters for aluminum alloy were presented as follows: solid solution treatment at 500℃ for 7 h and aging treatment at 220℃ for 3 h. Effects of heat treatment on mechanical properties of ZL102 alloys were investigated by wheatstone bridge conductivity measurement, optical microscope and scanning electron microscope. The results indicate that, tensile strength and hardness of ZL102 are improved dramatically after heat treatment, and conductivity can also be improved. Consequently, the heat treatment system is feasible. ©, 2015, Tezhong Zhuzao Ji Youse Hejin/Special Casting and Nonferrous Alloys. All right reserved. Source

Xia L.,Zhangjiajie Institute of Aeronautical Engineering | Zhu S.,Zhangjiajie Institute of Aeronautical Engineering | Zhu S.,Hunan University
Xiyou Jinshu/Chinese Journal of Rare Metals | Year: 2013

With the rapid development of fuel cell and fuel cell electric vehicle, LiBH4 was considered to be one of the most promising materials for hydrogen storage. However, the high sorption, desorption temperature and slow sorption kinetics limited their practical applications. In order to improve the performance of LiBH4, a small amount of Al was dissolved into LiBH4 . A first-principles plane-wave pseudopotential method based on the density functional theory was used to calculate negative formation heat, dissociation energy of H atom, the crystal and electronic structure and stability of LiBH4-Al system. The calculation results of negative formation heat and dissociation energy of H atom showed that after the Al was alloyed, the structural stability deteriorated, the heat absorbed diminished in the process of dehydrogenation, dissociation energy of H atom reduced, dehydrogenating properties of the system were improved. After analyzing the densities of states (DOS), Mulliken populations and the charge distribution, it was found that the B-H bond was covalent, the violent formation of which was one of the reasons for difficult dehydrogenation of LiBH4. The role of Al alloy in improving LiBH4 dehydrogenation solution was mainly because Al caused the energy gap near the Fermi level to change and Li-BH, B-H bonding declined in the LiBH4 system. The results matched well with the actual situation, which could provide a theoretical guide to practical applications for LiBH4 because it revealed the microscopic mechanism of dehydrogenation with Al addition in LiBH4 system. Source

Xia L.,Zhangjiajie Institute of Aeronautical Engineering | Zhu S.,Zhangjiajie Institute of Aeronautical Engineering | Zhu S.,Hunan University
Xiyou Jinshu/Chinese Journal of Rare Metals | Year: 2014

Hydrogen, which has the characteristics of clean, efficient and renewable utilization, was one of the promising new energies in the future. The safe, efficient and economical hydrogen storage was the key technique for the large scale application of hydrogen energy, relative to the high pressure gaseous hydrogen storage and liquid hydrogen storage, the solid state hydrogen storage technology could store hydrogen in materials by forming solid solution or hydrides, which was regarded as the most promising technique because of its good safety and high energy density. LiBH4 was the typical representative of high capacity of hydrogen storage material and research hot spot because of its theory capacity of 18.5%(mass fraction), far from overtaking hydrogen source system load weight greater than 5% of hydrogen storage capacity requirements, but it was faced with serious thermodynamics and kinetics problems. Starting from improving performance of the absorption and releasing LiBH4 hydrogen, the research progress of hydrogen storage technology and hydrogen storage material was analyzed, and the major measures taken in recent years were reviewed, such as adding reactants to form a composite hydrogen storage system, the appropriate doping anion and cation to change the electronegativity, adding catalyst, reducing the grain size and nanometer filling method. The emphases were focused on the mechanisms, hydrogen storage capacity, temperature and condition thermodynamics and kinetics. High capacity LiBH4 hydrogen storage materials were the key to practical onboard hydrogen source system, the focus of future research was to develop method and system of quick hydrogen absorption, a large amount and reversibility of hydrogen absorption and desorption, and room temperature operation. Source

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