Materials Science Forum Vols. 704-705

Abstract: Taking a large hydropower station in Xinjiang Autonomous Region as an example, and based on the limited unit method, the structure and seism forces features and response rules of rolling concrete gravity dam under different construction conditions were studied. The purpose for the paper is to understand dam working status under the different design conditions, and to evaluate anti-earthquake safety capability. It is proved that the present findings should play an important significance in the development of rolling concrete dam construction technology. Key words: Rolling Concrete Gravity Dams, Limited Unit Methods, Static Force Analysis, Dynamic Features.

Abstract: Rigid plastic finite element method (RPFEM) is one of the most efficient numerical methods during the rolling process. Realizing FEM online application has been main target for many researchers. The influence of compile method, elements number, compressible parameter, friction factor and convergent criteria were investigated and RPFEM model of fast solution to strip rolling was proposed in this work. Compile method and compressible parameter have less influence on calculated rolling force. However, the iteration steps are reduced and computational efficiency is improved greatly with compile method of release and compressible parameter 0.01. The change of calculated rolling force becomes less but iteration steps become more and more with the increment of elements number. Both accuracy and efficiency is satisfying with the change of elements number from 50 to 200. In addition, the typical rolling schedule from a certain plant has been solved with the developed program FFEM-2D by FORTRAN. The predicted rolling force has a good agreement with the measured value. The iteration steps change from 12 to 36 and computational time is less than 200(ms) with the model in one pass rolling. Therefore, the accuracy is satisfying and computational time fully meets the basic requirements of FEM online application. Keywords: Rolling; RPFEM; Fast solution; Computational time

Abstract: The ultrasound intensification crystallization process of aluminium trihydroxide from seeded sodium aluminate solution is investigated with various α_k (the molecule ratio of Na₂O/Al₂O₃). The experiment results indicate that ultrasound intensification can enhance precipitation ratio of seeded sodium aluminate solution, while large α_k does not good to improvement of the precipitation under ultrasound. When α_k is 1.45, 2.0 and 2.5, the precipitation ratio increase 2.5%, 2.0% and 0.9%, respectively under ultrasound intensification. The mechanism of enhancement on precipitation of alumina hydrate is acoustic cavitations that enhance or alter reactions process of aluminate ions, Al (OH)^-₄. The mass percentage of precipitation production grain size <45μm is increased by 4.3 % under ultrasound intensification with initial α_k at 2.0, which is the biggest. Key words: ultrasound; sodium aluminate solution; precipitation; aluminium trihydroxide

Abstract: We numerically investigated the grating-assisted phase matching (GAPM) of high harmonic generation (HHG) from the interaction of intense femtosecond laser pulse and rare gas in hollow core photonic crystal fiber (HCPCF). Our results show that the GAPM of HHG in HCPCF is especially suitable for photon energies in the range of 100~1keV. The calculated modulation period for GAPM of HHG in HCPCF is on the order of micrometer or sub-micrometer. This makes it easy to implement the GAPM of HHG with a counter-propagating modulation laser light in HCPCF. The high harmonic conversion efficiency is expected to be dramatically improved for the longer interaction length provided by the very low loss of HCPCF.

Abstract: The temperature change process of the single sprayed composite powder during the self-reactive spray forming process for preparing the Ti (C,N)-TiB₂ ceramic preforms was numerically simulated by means of finite element analysis. The results show that after the sprayed composite powder with grain size of 50μm has entered the flame field for 0.35ms, the surface temperature of it will reach the igniting temperature and the self-propagating high-temperature synthesis (abbr. SHS) reaction will take place. The heating rate of the particle in this period is about 2.82×10⁶°C/s. After the SHS reaction has taken place, the heating rate becomes quicker because of the double function of the flame and the reactive heat release. When the temperature of the sprayed particle is higher than that of the flame, the heat exchange process will turn into heat absorption from heat release, which leads to the great drop of the heating rate (about 1.20×10⁶°C/s). The composite powder completes the reaction in 0.88ms and reaches the highest temperature of 2920°C, which makes it become a ceramic droplet. After the reaction has finished, the droplet cools down quickly from exterior to interior, and the surface temperature of it descends to the theoretic eutectic melting point of the composite ceramics (2620°C) after 0.34ms. Then the droplet begins to solidify at some degree of supercooling and becomes ceramic particle. The numerically simulated results before, during and after the reaction match the water-quenching experiments of the sprayed particle with particle size of 50μm during the corresponding period. It indicates the heat process of the sprayed composite powder on the whole, which is composed of being heated, heat releasing, cooling and solidifying.

Abstract: The high concentration of different rheological properties of viscous materials determines the properties of the material advantages and disadvantages of piped varying degrees, this article in order to slime represented by a variety of high concentration of viscous test material for pipeline transportation, according to pipeline pressure loss of various materials to determine rheological characteristics of pipeline transportation, obtained pipeline flow equation, and then determine the delivery pressure, flow, length of experience in relationship, through the material and the wall friction and power calculation To further determine the energy loss of control resistance laid the basis for optimal design of transportation systems. Key words: viscous materials, sensing devices, pressure testing, pressure distribution, pressure drop

Abstract: The mechanical properties in low-alloy steel are studied systematically from the view of valence electrons using the Empirical Electron Theory in solid and molecules (EET). Two new valence electron structure parameters ρ^c_v and ρ^l_v, which have closely relation with the mechanical properties of alloy steel are summed up according to the basic idea of EET. The values of the two new valence electron structure parameters in carbon steel and alloy steel which contains Cr, Mn, Ni, Si, W and Mo are calculated. The result demonstrates that ρ^c_v has a very good corresponding relationship with intensity, and ρ^l_v has a very good corresponding relationship with plasticity. In this note, a quantitative empirical formula between the valence electrons structure and the intensity and plasticity of alloy steel is initially set up. Keywords: EET, valence electron structure, mechanical property, low-alloy steel

Abstract: To further understand the magnetic separation washability of pulverized coal, washability curve and mathematical model were done based on internal relations of curves. The model included non-magnetic substance accumulated curve, ash characteristic curve and magnetic susceptibility curve mathematical model. The theoretical separation indicators and the non-magnetic product yield among the adjacent sub-selections susceptibility can be found and determined from these. We also can make a quantitative assessment of the magnetic separation washability and predict the actual results. Results showed that simulation results and experiments results can tally well according to choose reasonable parameters. Evaluation criteria of magnetic separation washability of pulverized coal has yet to make a further investigation. These indicate as a powerful tool of studying magnetic separation washability of pulverized coal can not only be qualitative reasonably but also investigate quantitatively. Key words: pulverized coal; magnetic separation; washability; mathematical model

Abstract: Molecular dynamics (MD) techniques were employed to simulate the diffusion properties of molecular hydrogen on all-silica ZSM-5 zeolite. The results indicated that in the temperature range of 77-293K and the pressure range of 14-3360 kPa, the diffusion coefficients are found to range from 1.2×10^-9 m²/s to 3.8×10^-7 m²/s, and increase with increasing temperature, and decrease with increasing pressure. The activated energy for hydrogen diffusion determined from the simulation is pressure-dependent. The diffusion of the molecular hydrogen in all-silica ZSM-5 zeolite channels is anisotropic duo to the increase of the temperature. The diffusion coefficients in straight channels are higher than that in zigzag channels. The difference results from the structural difference of the two channels and the different loadings of hydrogen. Keywords: Hydrogen; Zeolite; Diffusion; Molecular-dynamics simulation

Abstract: Variation of dynamic electrostatic discharge (ESD) on human body that miners’ voltage,capacitance and resistance varies with the body’s dynamic change in coal mine environment is studied. A circuit model of the body’s dynamic ESD in coal mine environment is constructed. The simulation experiment system of the gas detonation by the human body ESD in coal mine is developed successfully. System principle, system hardware design and system software design is expounded. Simulation experiments with different body’s ESD model and the discharge gap has been done. Experimental results show that the system can be carried out series of experiments of the human body ESD model detonating mixed gas, it is concluded that the gas concentration that is the easiest to be detonated is about 8.7%. but not the higher gas concentration is , the more explosive is. The results provide an theoretical and experimental evidence for the safe electrostatic production and management in coal mine Keywords:simulation experiment system; dynamic ESD model ; hardware and software design ; human body capacitance