Abstract: The characters of outburst sandstone in rocks from Yongchuan Coal Mine were studied on the base of experimental investigation on its physical and mechanical properties. The outburst orientation of sandstone at the-350 m horizontal in this coal was analyzed and the criterion of outburst orientation was proposed. The results show that outburst sandstone has the physical characteristics of big porosity and big blowhole volume, and the mechanical characteristics of low Young's modulus, low strength, and not easy to produce plastic deformation. The launch process of rocks and gas outburst has uniformity with the rockburst characteristic, and the rockburst theory can be used to study the outburst orientation of sandstone, which depends on many kinds of factors. In these factors the mechanical factor is primary. The assessment method of outburst orientation of sandstone was established based on the energy criterion, strength criterion, and impact orientation criterion.
Abstract: According to the results of systematical engineering geological surveys, based on the rock mechanical experiment of specimens from-430 m level to-568 m level, the Q system which is well applicable to high geostress conditions and the RMR method were applied to rock engineering classification. The relation of rockbursts to the values of RMR and RQD was analyzed. It is known that there is the probability of rockbursts below-500 m level in Chengchao Iron Mine. The influence of high geostress environment on rockburst preparation was discussed by studying geostress distribution laws. Finally, the distribution state of energy in surrounding rockmass during deep mining excavation was studied by 3D FEM numerical analysis, and it is inferred that the critical depth of rockbursts is-500 m. On the base of simulation results, the in-situ stress strengthens significantly at-500 m level due to the impact of upper mining activities, higher than at-533 m level. Below-533m level, the maximum value of rockmass energy also progressively increase with the incremental vertical depth.
Abstract: The method of support vector regression (SVR) in combination with self organization feature mapping (SOFM) network was selected for grade interpolation in orebody, and was compared to the Thiessen polygons method, the distance power inverse ratio method and the Kriging method. The result shows that the prediction model of SVR is feasible and reliable for grade estimation.
Abstract: The four-period SPOT satellite images of years 1996, 2002, 2005, and 2007 were used as analyzed materials, and also the relevant map data were coupled to digitize the landslide area layer of Shoufong and Siouguluan watersheds in Hualien County of Taiwan. The changed conditions of two investigated watersheds were examined and their characters of environmental factors were also analyzed through calculating the vegetation recovery ratio (VRR), the increasing collapse ratio (ICR), and the centroid displacement vector of landslide area. The result shows that it is useful to monitor landslide area and then to know their cover changed conditions over a long period of time by utilizing multi-temporal satellite images. Obviously, precipitation is the directly influential factor of causing the happenings of serious collapses, and a large number of occurrences of collapses are triggered by precipitation. The calculations of VRR, ICR, and the centroid displacement vector of landslide area can efficiently quantify the recovery of vegetation and the increasing collapse situation. Finally, the frequency of collapsing increases with increasing elevation and slope. Thus, these influential factors mentioned above have to be paid carefully attention in future developments.
Abstract: A theoretical model of three-region coupling in consideration of non-Darcy flow in the matrix region with kickoff pressure gradient, ellipse flow in the matrix-fracture region and nonlinear flow in the fracture region was proposed on the base of the three-region physical models of matrix-fracture coupling for integer hydraulic fracturing in low-permeability oil reservoirs. A mathematical model of two-phase porous flow in low-permeability oil reservoirs in a five-spot pattern was developed. The factors influencing the productivity of the oil reservoirs were analyzed. It is shown that the productivity of low-permeability oil reservoirs calculated by the mathematical model is in agreement with practical data.
Abstract: In order to study the seismic behavior of steel reinforced concrete (SRC) columns, eight cross-shaped SRC columns with a span ratio of 3 were tested under low cyclic reversed loading. The influence of volume-stirrup ratio on the seismic behavior of SRC columns was discussed by analyzing the failure patterns, hysteresis loops, skeleton curves, ductility coefficients and energy dissipation capacities of such members. A formula between ductility and volume-stirrup ratio of SRC columns was put forward by fitting the experimental data. The test results confirm that the seismic behavior of cross-shaped SRC columns is good. The volume-stirrup ratio is an important influencing factor on ductility of the members, in favor of improving the seismic behavior of members significantly.
Abstract: A new type of spray gun was placed at the wall of a hot metal ladle (relative to the outlet of slag removal). Before slag removal, high pressure N2 was injected and floated, and slag on the ladle surface was pushed aside to the ladle outlet. The operation is positive to removing slag from the ladle, the efficiency improves, and the loss of hot metal and the time of slag removal decrease. A model in a proportion of 1:3.5 was made to simulate the hot metal ladle. Air was injected to blow slag. The simulation was operated with various parameters. At the same time, numerical simulation was made to testify the result. It is shown that when the submerged depth varies from 200 mm to 400 mm, the ratio of lack-slag area to sum area rises from 10% to 30%. When the flux of gas changes from 4 m3·h-1 to 6 m3·h-1, the ratio of lack-slag area to sum area increases from 30% to 37%. The increases of submerged depth and gas-blowing flux are positive to the quantity of slag removal. The result of water modelling is well accorded with the numerical simulation.
Abstract: Based on the present situation of research on the on-line refinery technology and its application in China, the refinery gas distribution in a molten aluminum purifying reactor on the base of the on-line MINT technology was simulated in an Euler-Euler multiphase flow model. Three incidence angles of molten aluminum were used to calculate multiphase flow in the optimization numerical simulation. The results of numerical calculation and comparative analysis on mixture uniformity showed that the refinery gas distribution changed remarkably with incidence angle, and the best uniformity of gas distribution was gained in a 45° incidence by comparing three simulated results of different incidence angles.
Abstract: A microstructural prediction model of low carbon Nb-containing steels based on the interaction of precipitation, recovery and recrystallization was developed to simulate the evolution of precipitation and recrystallization of coarse-grained austenite in low carbon Nb-containing steels during pass interval of hot deformation. The application of this model in making the recrystallization-precipitation-temperature-time diagram (RPTT) of low carbon Nb-containing steels was discussed. The simulation results are well coincident with the experimental data of two low-carbon Nb-containing steels, indicating that the behaviors of precipitation and recrystallization can be predicted using this model for different low carbon Nb-containing steels at various processing conditions.
Abstract: Optical microscopy, hardness measurement and transmission electron microscopy (TEM) were employed to investigate the thermal stability of microstructures in a Nb-bearing microalloyed steel during isothermal holding, which had been curved or twisted before being heated. It is found that both curving and torsion increase the hardness of the microalloyed steel in a large scale. In subsequent isothermal holding at 550℃, the hardness of the zone subjected to curving drops rapidly in company with the evolution of bainite towards equilibrium microstructure while the hardness of the zone undergoing torsion is higher than that of the undeformed zone all the time and bainite remains in the zone. The larger the torsion degree is, the stronger the hardening effect is. The higher hardness can be preserved during isothermal holding. Both curving and torsion result in an obvious increase of dislocation density in bainite laths. Dislocations distribute inhomogeneously in the curved zone and polygonal ferrite tends to nucleating at sites with low dislocation density during subsequent heating, while dislocations distribute homogeneously in the twisted zone and do not markedly change the distribution during subsequent isothermal holding. These results indicate that different deformation methods produce different influences on the thermal stability of bainite in a microalloyed steel.
Abstract: Equilibrium precipitated phases in R5 offshore mooring chain steel in the temperature range of 400 to 1 600℃ were calculated using thermodynamic software Thermo-Calc. The effects of alloying elements on these equilibrium precipitated phases were studied. The results show that main equilibrium precipitated phases in R5 offshore mooring chain steel at temperatures of 400 to 1 600℃ are M23C6, M6C, MX and AIN, where M represents Cr, Fe, Mn, Mo, Nb, Ni and V, and X is C, N and vacancy. On this basis the influences of alloying elements C, Cr, Mo and Nb on the equilibrium mole fraction and initial precipitated temperature of M23C6, MrC and MX phases were discussed. The composition system and heat treatment condition of new R5 offshore mooring chain steel were optimized. The optimized heat treatment process is quenching at 920 ±30℃ and tempering at 600 ± 30℃, and the optimum content of metal element Mo is 4.3%.
Abstract: Dynamic recrystallization (DRX) in 316 L stainless steel was systematically studied by high temperature compression tests on a Gleeble-1500 thermal simulation testing machine. The results show that 316 L stainless steel has a large hot work-hardening tendency and there is no peak stress on its true stress-strain flow curves. DRX occurs in the hot working of 316 L stainless steel, but DRX grains can be observed only in the local area of metallographic phase. The activation energy for deformation and the thermal deformation equation of 316 L stainless steel were derived after the fitting analysis of experimental data of DRX. The critical strain and the critical stress of DRX as well as the relationship between steady state stress during hot deformation and Zener-Hollomon parameter of 316 L stainless steel were obtained.
Abstract: Cutting tests and high-temperature thermo-ductility experiment were carried out on low-carbon and high-sulfur free-cutting steel with low contents of tin and antimony or bismuth. The results show that the wear at the tool flank face for machining of experimental steel is very small after long-time and high-speed machining tests. The machinability of the new steel is significantly better than that of SAE1215. The thermo-ductility of the steel with Sn and Sb is poor within the range from 750 to 950℃ but good from 1050 to 1300℃. It is also showed by SEM and EDS that tin and antimony exist at grain boundaries in the steel, and in or around MnS inclusions. Most of bismuth element are attached to MnS inclusions, some are scattered in the steel matrix. The shapes of MnS inclusions are mainly spherical and spindle.
Abstract: The structure of oxide scales and corrosion resistance of SS400 hot-rolled strips at different positions in plate width were studied by scanning electron microscopy (SEM), X-ray diffraction quantitative analysis, salt spray test and electrochemical methods. The results show that oxide scales at the plate edge are the thickest, relatively uniform and compact, and there is obvious magnetite/iron eutectoid in them. Oxide scales at the edge and one-fourth of plate width mainly consist of magnetite, hematite and magnetiteiron eutectoid, but oxide scales at the center are composed of magnetite and iron. It is shown by salt spray corrosion test that the corrosion rate is the minimum at the edge, the second at one-fourth of plate width, and the most serious at the center. By potentiodynamic polarization curve test, the corrosion potential at the edge is bigger than those at the two other parts, and the current is the minimum. After the hot rolled strips being coiled, the difference in oxygen supply in the width direction leads different structures of oxide scales, which influence the corrosion resistance of oxide scales.
Abstract: A short-term prediction model for soil corrosion of carbon steel in the regional soil environment of Daqing area was established by measuring the physical and chemical properties of soil in this area, the short-term corrosion data of carbon steel and analyzing the logical relationship among mass transfer processes. The reasonableness of the corrosion model was verified by using BP artificial neural network to learn, train, simulate and compare to the corrosion test results of buried carbon steel samples. The results show that water content, air content, pH, Cl- content, SO42- content and total dissolved salts are the six key factors on soil corrosion of carbon steel in the local soil environment. It is indicated that a stable forecasting model with good generalization ability can be built based on BP artificial neural network through Matlab platform software, by continuous accumulation of soil corrosion information and after adequate training. The model predicts the corrosion rates of carbon steel in Daqing soil accurately.
Abstract: The initial corrosion laws and electrochemical behaviors of 2A12 aluminum alloy were investigated by using alternate immersion test, scanning electron microscopy (SEM) as well as electrochemical impedance spectroscopy (EIS). The results showed that obvious pitting phenomena were observed for all the specimens in various Cl- containing solutions after 48h alternate immersion. With the increase of Cl- concentration, the initiation and development of pitting corrosion were promoted and more corrosion products formed. At a lower Cl- concentration, the corrosion process was mainly controlled by charge transfer resistance; with increasing Cl- concentration, the electrochemical characteristic transferred to the mixed control of charge transfer resistance and Warburg resistance.
Abstract: The reheated microstructures and influencing factors of semi-solid ingots of 4.4% TiCp/7075 composites were investigated by SEM, TEM and DSC. The results show that the optimal remehed parameters of 4.4% TiCp/7075 composites are the remolded temperature of 590 to 610℃ and the holding time of 10 to 20 min. 4.4% TiCp/7075 composites are of high stability during the remelting process and the size of spherical grains can hardly increase with the increase of temperature and holding time. The coarsening velocity of grains in 4.4% TiCp/7075 is 118.96μm3·s-1, which is less than 311.7 μm3· s-1 for 7075 matrix alloy, and more suitable for semi-solid thixoforming.
Abstract: The effect of the kind and content of silica fume, the contents of magnesia fine and sodium tripolyphosphate (STP), and particle size distribution coefficient (Andreasen coefficient) on the theological property of bauxite-based Al2O3-MgO castable were researched with a new developed castable rheometer. The results show that under vibration conditions, the castable has characteristics of the Bingham model, with shear-thinning and thixotropic property. The type of silica fume has some effect on the rheology of the castable. The content of silica fume in the range of 3% to 5% has significant effect on the theology of the castable; with the increase of silica fume's addition, the rheology of the castable gets better. At the particle size of magnesia fine in this experiment, the content of magnesia fine in the range of 4% to 12% has little effect on the rheology of the castable. The addition of STP in the range of 0.13% to 0.19% has obvious effect on the rheology of the castable. With the increase of STP's addition, the rheology of the castable get better, but the effect gets worse at the addition of 0.19%. The best addition of STP is 0.15% to 0.17%. With the increase of particle size distribution coefficient in the range of 0.23 to 0.31, the water demand for the same flow value is decreased, and the rheology get better too, but no more effect when higher than 0.29. There is good relevance between the rheology and flow ability. The better the rheology, the better the flow ability is.
Abstract: A ultrasonic dipping method was used to prepared mesoporous MnO2 with SBA-15 as a hard template and Mn(NO3)2 as a Mn source. The texture/structures of the samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), nitrogen adsorption-desorption and thermogravimetry-differential thermal analysis (TG/DTA). Galvanostatie charge-discharge, cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were performed to investigate the electrochemical performanee of the samples. The results indicated that the synthesized MnO2 fabricated SBA-15 structure. The specific surface and mesopore size of the synthesized MnO2 were 282 m2·g-1 and 2.75 nm, respectively. As an electrode material of supercapaeitors, mesoporous MnO2 exhibited favorable reversible kinetic characteristics, low charge transfer resistance and high electrochemical activity, which had a initial specific capacitance of 285 F·g-1 and retained at 210 F·g-1 after 500 cycles.
Abstract: Magnesium trisilicate was synthesized by precipitation using Na2O·nSiO2 and Mg (NO3)2 as raw materials. The precipitate was subjeet at 450℃ or activated by 15% H2SO4, following whieh the samples were characterized by XRD, IR, TG/DTA and BET to investigate the effects of strike methods, acidic activation and calcination on the crystal phase and surface texture. It is shown that the samples activated by different methods are amorphous. TG/DTA analysis indicates that the samples have the same composition as magnesium silicate hydrate with different contents, pH in the reaction has significant effect on the surface texture of the samples. BET analysis reveals that the sample synthesized by adding Mg(NO3)2 to the sodium silicate solution is microporous with the specific surface area of 568.93 m2 · g-1 and exhibits a multimodal pore width distribution at the micropore regions of 1 to 3 nm and 0.7 to 0.9 nm. The sample with the specific surface area of 179.4 m2·g-1 synthesized by adding Mg(NO3)2 to the sodium silicate solution is mesoporous. Calcination and acidic activation increase the crystalline degree, reduce the specific surface area and change the distribution of pore width. The reactive mechanism was discussed primarily. Calcination increases the quantity of mesopores. Acidic activation makes H+ replaced by Mg2+ to form the Si-OH, and most of the acidic activation samples are mesoporous.
Abstract: The concept of the characteristic curves of roll eccentricity was proposed. Based on cyclic statistics of the tested signal, a linear prediction model was established to on-line determine the compensation data of roll eccentricity for realizing the real-time compensation control of roll eccentricity. Simulation results show that the method can accurately trace roll-eccentricity-induced disturbances and meet the needs for real-time compensation for the control of roll eccentricity.
Abstract: Taking the UCMW mill, a cold roiling mill, for an example, the finite element method (FEM) was employed to estimate the effects of tapered work roll shifting and the change in roll contour of the work roll end on edge drop control. The results show that the edge drop of cold rolled strips decreases with the increase in penetration length of the tapered part into strip edge when the work roll end is defined as a sinusoid curve, and the function of edge drop to work roll shifting is parabolic. The effect of work roll shifting on edge drop control increases with the increase in taper at the work roll end. Edge drop can be alleviated by increasing the taper of the work roll end at the same work roll shifting, whereas it can be also reduced when the roll contour at the work roll end does not change but the taper length decreases. In addition both the unevenness of pressure distribution and the maximum pressure between the work roll and the intermediate roll can be alleviated in terms of decreasing the taper and increasing the taper length.
Abstract: Based on the analysis of some kinds of low oxygen combustion, a low oxygen burner with self-circulation of flue gas was developed with contracted/dilated air channels. The Fluent software was used for numerical simulation of the burner. The results show that the negative pressure at the throat is the driving force of fume entrainment, and the volume of fume entrainment increases dramatically with the decrease of throat area. Because of the increase of fume entrainment, the oxygen concentration in the furnace decreases, the high-temperature zone of the flame moves to the burner, and the length of the flame also becomes short. At last, the low oxygen burner with self-circulation of flue gas was applied to a melting holding furnace, and the anticipated effect was achieved.
Abstract: An optical detection technique was applied to on-line detection of surface defects for continuous casting slabs with high temperature. Green linear lasers with high luminance were projected on the slab surface. According to laser monochromaticity, a narrowband color filter was added to lens to prevent slab radiation coming into CCD cameras, and the image contrast was improved. Non-sampling wavelet decomposition was applied to surface images of the slabs, and the scale co-occurrence matrixes of low-pass components and original images were calculated as textural features of images, as well as the scale coccurrence matrixes of high-pass components. A classifier based on AdsBoosting algorithms was developed for classification of defects with textural features. The technique was tested with samples of surface cracks, water marks, slag marks, scales and vibration marks, and the results show that the classification rate of surface cracks is 86.75% and the classification rate of all the samples is 87.16%.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
