Abstract: In order to make the best use of explosive energy in loosing soil or throwing it onto some area and ensuring the bottom meet some leveling requirements after blasting, a plane charge layout is often adopted according to blasting design and engineering quality requirements in open chamber blasting such as mine exploitation, field leveling and foundation pit excavation of construction. Through a lot of small scale simulated tests in construction field, this paper systemically analyzed the dependence of the open area and visible depth of blasting craters, the thrown distance and the accumulation state of rock on the row spacing and the column spacing of plane charge. The experimental result indicated that when the spacings meet some area, the blasting can gain the least visible depth, the biggest open area of blasting craters, the biggest thrown distance and a better accumulation state. It is believed that there is an optimal row spacing and column spacing in the plane charge layout which is beneficial to thrown pilling.
Abstract: According to the investigation on geological condition in the north region of China's Shuichang iron mine, this paper analyzes basic features and reasons of the landslide, and suggests that the slope be stabilized by cutting slope and anchorage. A contrast analysis of slope stability is made between unreinforced and reinforced slopes by using FLAC Software. The results show that there is a contradiction between conservatism and unstability in the original slope design, and taking a reasonable reinforcement measure is the key to solve this problem. It is verified that the reinforcment is a very effective measure for this kind of unstable slope.
Abstract: According to the unstable situation of an expressway cutting slope located in Zhengzhou city of China, four retaining regions were divided by reinforcement design and different reinforced structures were adopted in the four regions. Based on the design parameters of the reinforced structures and the natural mechanical properties of the rock cutting slope, the stability of the cutting slope after reinforcement was analyzed by numerical analysis. The result shows that besides the reinforced structures and the self-reinforced anchor bars perform high loading-capacity, the reinforced structures and the rock cutting slope have come into being a whole integer.
Abstract: Based on calculations of nonlinear stress-deformation by the 3-directional finite element method, this paper numerically analyzed the stability of a mountainous freeway deep cutting slope. The safety factors obtained by this method and Sauna's method were compared with engineering practice. The results show that the finite element method is more effective for analyzing the stability of a slope than traditional methods.
Abstract: According to the engineering construction characteristic of freeway tunnels, some methods were adopted to investigate and predict the geological condition of tunnel wall rock on the basis of dynamic wall rock classification. The information obtained by these methods was integratively analyzed and optimized so as to evaluate the dynamic stability of expressway tunnels. The results of practical application show that this evaluation method is simple and effective.
Abstract: Under controlled suction conditions, CD shear tests were conducted using a modified triaxial shear apparatus on dynamic compacted unsaturated silt from the foundation of the Local-Tax Building in Shijiazhuang city, China. The test results clearly demonstrated that suction severely influences the shear strength of the soil. The relationships of the effective cohesion and the friction angle to the suction are well linear. The effective cohesion increases and the friction angle decreases with increasing suction. In a given suction range, the influence of the suction on the effective cohesion is more evident than the friction angle. The failure envelope of the compacted silt is not a plane, which shows convergent with increasing the net average stress and the suction. When the confining pressure is higher than 300 kPa, it plays the leading role on strength, not the suction.
Abstract: A systematic study was conducted on the optimal growth conditions of photosynthetic bacteria. Experimental results showed that temperature, illumination intensity and pH value all influenced the growth of photo-synthetic bacteria, and the three factors restricted each other. Photosynthetic bacteria can grow better under the condition of 30℃, 2 250 lx, pH 7-8 and the absence of atmospheric oxygen.
Abstract: The effectiveness of classical sphericity and Krumbein sphericity was compared to discribe chip-shaped fossil fuel, and the influence of sphericity on fiuidization characteristics was studied. Some special pheno-mina in a 50 MW circulating fluidized bed boiler using an anthracit with Krumbein sphericities of 0.2-0.4 were discussed such as obvious fluctuations of dense phase temperature and furnace pressure as well as draining cold ash during operation, which can be explained by particle mophology.
Abstract: A more accurate one-dimensional turbulent ignition model of pulverized coal air flow in a tube was established on the basis of the one-dimensional plane laminar flow ignition model. An experimental plat for high temperature air pulverized coal ignition was set up. To test the theoretical model, air heating and pulverized coal ignition experiments were done. The experimental results are in good agreement with the calculated ones. The feasibility of pulverized coal ignition by high-temperature air was proved.
Abstract: In sintering process, for melted mineral fines bind unmelted core ores when cooled, the self-intensity of binding phase in iron ores is one of the basic indexes to estimate sintered binding status. With eight kinds of iron ores, the self-intensity characteristic of binding phase was studied at the same temperature and different basicities and their influence factors were theoretically discussed. It is indicated that since different kinds of iron ores have different self-characteristics, the sintering intensity of binding phase and its dependence on basicity have obvious difference. As a result, the sintering intensity of binding phase can be considered as an important technical criterion for optimizing the sintering blending.
Abstract: The solidification in a beam blank was numerically simulated by using ANSYS commercial software in order to analyze surfacal and internal cracks in the beam blank. The boundary conditions were based on measured technical parameters in practical production. The simulated result is in accordance with the measured surface temperature of the beam blank. It is shown that the surfacal temperature of SS400 beam blank is in the brittleness temperature zone except that of the fillet under the present condition. In order to make the surface temperature of the beam blank into the plastic temperature zone before it goes into the straightening zone, it is necessary to weaken the intensity of secondary cooling.
Abstract: Hot deformation behaviors of pure iron and two kinds of low carbon steels with different pearlite contents were investigated by hot uniaxial compression using a Gleeble 1500 hot simulation testing machine at a deformation temperature of 700℃ and strain rates of 10 to 0.001 s-1. The results indicate that pearlite has an important effect on the behavior of dynamic recrystallization of ferrite, that is, the increase of pearlite content promotes the dynamic recrystallization process of ferrite and broadens the range of strain rate in which this process can occur.
Abstract: The dynamical microstructure evolution behavior of Q235 low carbon steel at high temperature was systematically investigated through physical simulated tests carried out on a Gleeble 2000 machine. The experimental results showed that hot working parameters such as forming temperature and strain rate affected the dynamical micro-structure evolution behavior of Q235 steel to a great extent. At a given temperature, dynamical recrystalization could be postponed with the increasing of strain rate; meanwhile, at a lower strain rate, this phenomenon could occur with the decreasing of temperature. The quantitative metallurgical technique and the linear/non-linear regression analysis were used to construct an Arrhenius-type phenomenological constitutive relationship and a Yada-type kinetically microstructure equation of Q235 steel at high temperature, which were coupled into the finite element software of Autoforge 3.1. The results of numerical simulation showed that the phenomenological constitutive relationship and microstructure evolution equation depicted the dynamical microstructure evolution behavior of Q235 low carbon steel at high temperature very well.
Abstract: Orientation mapping based on EBSD technique is applied to reveal the orientation features of dynamic recrystallized grains and their neighboring matrix in a magnesium alloy AZ31 with different initial textures. The results show that, irrespective of initial texture and strain amount, new grains are similarly orientated to their neighboring matrix, illustrating a dynamic recrystallization through progressive subgrain rotation. In addition, the new grains gradually rotate to basal orientation in different samples, which indicates an important role of plastic slip during dynamic recrystallization in stead of superplastic deformation. The less subgrain boundaries in deformed grains under heavy strain were observed and these deformed grains have high quality of Kikuchi bands, which indicates that the deformed grains are consumed by the shear stress of grain boundaries parallel to the compression plane, rather than non-basal slip. The misorientation between the new and the deformed grains are measured and discussed in terms of the influence of initial texture.
Abstract: The influence of electric pulse modification (EPM) process on the solidification structure of Sn-15% Pb alloy was experimentally investigated. It was shown that after the molten alloy was treated by electric pulse the solidification structure changed from dendrite shape to cellular shape, and the grains were obviously fined. The mechanism of the change in solidification structure by EPM was discussed. The results indicated that EPM process makes the liquid structure of the alloy change:The activity of Pb in the molten Sn-Pb alloy increases, the distribution coefficient tends to 1, the solute enrichment in front of the solid-liquid interface decreases, and the solute distribution changes. All these lead to the change of solidification structure from dendrite to cellular.
Abstract: The Nb segregation regulation and behavior in liquid phase were calculated using a thermodynamic calculation method and corresponding Ni-base database for two Nb-rich superalloys. The calculated results are agreeable with experimental values from references. Based on this model, the Nb segregation degree and the maximum Nb segregation content in liquid-solid temperature range do not linearly increase with increasing Nb content, but rising to the maximum then droping. However, the Nb segregation degree monotonously increases with increasing liquid-solid temperature range. According to this theoretic calculation, a method for alloy design was discussed in term of reducing Nb segregation and enlarging ingots.
Abstract: In situ tensile tests with special designed SEM were conducted to trace the whole process of crack initiation and propagation till to fracture of Al2O3 seeded P/M Rene 95 Ni-base superalloy. The experimental results show that a non-metallic inclusion can induce crack initiation. When the inclusion size is larger than a certain critical size, the crack can propagate to be the main crack inducing the specimen to fracture. Consequentially, both the yield strength and the tensile strength of the specimen are remarkably decreased.
Abstract: The RF reactive sputtering method was used to deposit wear resistant chromium oxide coatings and the properties of the coatings were studied. The results showed that there existed two modes of sputtering during RF reactive sputtering, i.e., metal sputtering mode and nonmetal sputtering mode caused by the reaction between the target and reactive gas. The deposition rate was very low in the nonmetal sputtering mode. The hardness of chromium oxide coatings depends mainly on the content of Cr2O3 in the coatings and low hardness CrO will form when oxygen is not enough during sputtering. Feeding oxygen near the substrate is an efficient technology for depositing hard chromium oxide coatings at high deposition rate.
Abstract: YSZ electrolyte thin films were prepared by tape casting from nanocrystalline powder. The properties of YSZ nanocrystalline powder, adobe by tape casting and sintered thin films were analyzed. The YSZ nanocrystalline powder has a narrow size distribution of 0.1-0.2 μm and the median size is 0.157 μm. The beginning shrinkage temperature of the YSZ nano-powder is 968.9℃ from its sintering curve. The highest shrinkage rate appears at 1279.9℃, and by 1400℃ the shrinkage rate is stable, almost up to 20%. The adobe by tape casting has high density and its relative density is up to 64.1%. The relative density of the sintered YSZ thin films is 97.8%. The grain size of YSZ is in the range of 1-4 μm, which show uniform with the microstructure by SEM, as well as grain boundaries are obvious. The YSZ thin films show good electrical properties with increasing temperature and their conductivity is 0.106 S/cm at 900℃.
Abstract: A painting method based on a microarc oxidation (MAO) coating was applied to protect magnesium alloys. The MAO coating was simultaneously electrodeposited on the anode and cathode of AZ91D magnesium cast alloy with AC symmetric pulse method in composite silicate solution. Salt spraying tests were used to investigate the corrosion resistance of sol-gel, polysilicone, and organic epoxy primer and polyurethane acrylic topcoat coverings, which were considered as three post-coating methods to MAO specimens. After painted with epoxy primer and polyurethane acrylic topcoat, the barrier property of MAO samples was compared with that of Mg/paint and traditional Mg/chromate conversion coating (CCC)/paint specimens by salt spraying tests and electrochemical impedance spectroscopy (EIS). It was demonstrated that sol-gel, polysilicone and organic coatings all bear some validity, especially epoxy primer with polyurethane acrylic topcoat worked so well that no corrosion happened after 480 h of salt spraying. The shielding property of Mg/MAO/Paint was better than that of Mg/paint and Mg/CCC/paint.
Abstract: Epoxy resin was modified by liquid butadiene-arylonitrile rubber and nano-SiO2 powder. The morphology of the modified epoxy resin and the toughening mechanism of liquid butadiene-arylonitrile rubber and nano-SiO2 powder were studied by SEM and impact toughness tests. The results show that epoxy resin can be effectively toughened by liquid BN rubber and nano-SiO2 powder.
Abstract: As to the difficulty of frequent work-piece failure and technological parameter selection by experiment in multi-wedge cross wedge rolling (MCWR) for long-axle parts, a multi-wedge command stream program in FEM was developed by authors to simulate the MCWR rolling process. The effects of forming angle, spreading angle and reduction in area on the inner equivalent stress, strain and axial displacement of work-pieces were theoretically analyzed and the corresponding regularities were obtained. The rule of the effect of reduction in area on the axial displacement of work-pieces was verified by experiment.
Abstract: The process, microstructure evolution, strengthening mechanism and microstructure characteristics of high-strength low-carbon automobile steel plates (ZJ510L steel) by EAF-CSP technology at Zhujiang Steel of China were studied by optical microscope, TEM and mechanical property tests. It is shown that the microstructure of ZJ510L is refined by increasing the rolling pass and the cooling rate. The size range of final ferrite is about 5-6 μm. Precipitates consist mainly of Al2O3, MnS, AlN and lots of carbonide particles, and their size range is about 20-150 nm. It is verified that ZJ510L steel possesses a good combination of strength and plasticity due to its fine microstructure and has excellent formability and notched bar impact strength. Refinement strengthening is the primary strengthening mode.
Abstract: The surface roughness and flatness of cold rolled strips are important control aims, especially when cold strip coils are processed in batch-type annealing furnaces. However, it is found that surface roughness control is in contradiction with strip flatness control in the production of 2030 mm cold tandem mills. Based on lots of tests and measurements, originating and developing principles of strip flatness and surface roughness were studied. According to the results of research, solutions for the problem were proposed and proved to be effective in strip production.
Abstract: The theory of metallurgical process engineering was applied to further analysis of steel ladle cycling, and general research was done to extensively optimize the temperature of liquid steel in steelmaking production. A ladle running control technology was summarized, which included six contents:process analysis of ladle cycle, mathematical description of ladle running time, three calculating methods of employed ladle, temperature drop of ladle cycling, frequency of ladle operating, and optimization of ladle turnaround. This technology has been put into five converter plants, and good effects were acquired.
Abstract: Schedule rules for two-strand thin slab casting and rolling were established. Based on the characteristic of the casting and rolling process, a kind of coding, crossover operator, mutation operator and the concept of amendment operator for the genetic algorithm were proposed. In the genetic algorithm, the schedule rules were introduced into the modeling of initial population and the operation of amendment. A scheduling system of two-strand thin slab casting and rolling was developed by using the schedule rules and the genetic algorithm. This system can solve the dynamic schedule problem of two-strand thin slab casting and rolling and optimize production management.
Abstract: The paper proposed an immune algorithm based on the mechanism exhibited in biological immune clone selection and the immune network theory. The algorithm eliminates antigen by clone selection and mutation, accumulates knowledge by selection of antibody memory cells which inspired by the immune network theory, and realizes immune homeostasis. The function of antibody memory cells is immune surveillance. The self-adaptation of antibody is realized by the immune mutation mechanism, which makes the algorithm self-learning and self-adaptive. The results of an application study on the pattern recognition of heat furnaces shows that the algorithm has good abilities of pattern recognition and data compress.
Abstract: Despite the advantage of high average power output, a wide bandwidth ultrasonic transducer is needed in the ultrasonic ranging system with traditional continuous wave frequency modulation. But the transducer with wide bandwidth is not commonly available. This paper proposed a new method of distance measurement named the continuous wave narrow bandwidth frequency modulation (CWNBFM) method. An important feature of the ultrasonic ranging system with CWNBFM is that by using narrow bandwidth frequency modulation, a commonly commercial available ultrasonic transducer instead of the wide bandwidth ultrasonic transducer can be used in this system.
Abstract: The key structure of main circuit of a line-frequency synchronous induction motor drive system and its snubber parameters were described. The harmonic wave assimilation algorithm and current control strategy for this system based on flux orientation vector computation were analyzed. The system's current response performance under the typical industrial application condition was studied. It is concluded that the line-frequency synchronous induction motor drive system has excellent current response performance and some similar characteristics compared with the standard synchronous motor.
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
