Abstract: In order to reveal the sequence of active functional groups, diffuse reflectance tests of Beizao lignite were carried out by in situ Fourier infrared spectrometry, and the proportions of active functional groups in the lignite were obtained. A simplified infrared molecular model of the lignite was built based on the same articulation condition of functional groups, and the model was analyzed by using the quantum chemical method. For the main active functional groups, the pr_oportions of methyl methylene and hydroxyl groups are the largest, followed by carbonyl, carboxyl and aromatic hydrocarbon. The frontier orbital and vibration frequency analysis of the model shows that the vibration locations of functional groups in the experiments are consistent with the calculated ones. Combined with the proportions of functional groups and the activity, it can be concluded that in spontaneous combustion the key functional groups are hydroxyl groups and methyl methylene, and then carboxyl.
Abstract: The architecture of three-dimensional dynamic simulation models for water inrush processes in underground mines was proposed by analyzing the influencing factors of spatial and temporal changes when water inrushes spread in roadways. A roadway space network system was developed through data modeling and regularization, transformation from arc lanes to straight lanes, and three-dimensional network processing of roadways. The path network of water inrush flowing through roadways was formed based on the path algorithm of water spreading downward and upward. The spread speed and time of water inrushes were resolved in combination with the hydraulic characteristics of water inrush flowing. In such a way, a three-dimensional dynamic simulation model was established which can simulate the spatial and temporal dynamics of water spread processes. A typical mine in China was exemplified to verify the feasibility and effectiveness of the established model.
Abstract: Lime-mediated sewage sludge was used in metallurgy sintering. Its impact on the sinter performance was discussed when partly replacing fuels and fluxes as a metallurgy ingredient. Thermogravimetry-differential thermal analysis (TG-DTA) and X-ray diffraction analysis (XRD) show that in the process of room temperature to 1100℃, organic matter in the sludge decomposes to generate heat, meanwhile CaCO3 and Ca(OH)2 turn into CaO. Sintering cup experiment results indicate that the sludge has a positive impact on sintering with appropriate carbon quantities and the sinter quality index is improved. When the sludge ratio is 3.00% and the ratios of replacing the flux and fuel with the sludge are 51% and 13.3% respectively, the vertical burning rate of sintering is 21.30 mm·min-1, the yield is 72.63%, the utilization coefficient is 1.458 t·m-2·h-1, and the fuel consumption per ton falls to 59.27 kg from 65.54 kg.
Abstract: Taking the treatment of zinc-bearing dust by rotary hearth furnaces (RHF) as the a direct reduction mathematical model of carbon-containing pellets made of zinc-bearing dust was built in combination with the actual production process of RHF. The model takes into account not only the reduction of iron oxides and Boudouard reaction but also the reduction of zinc oxide. Experimental results proved the validity of the model. The effects of furnace temperature, pellet radius and porosity on the reduction of the pellets were investigated on the basis of calculation data by the model. Furnace temperature has significant effect on the metallization rate and zinc removal rate; but pellet radius and porosity have less influence on metallization rate and no influence on the zinc removal rate.
Abstract: For the limitation of the single-pellet unreacted shrinking core model in studying a multi-pellet system, a mathematical model of iron oxide pellet reduction in an isothermal fixed bed was constructed based on the reduction behavior of single pellets. The analytical solution of the model was obtained by introducing dimensionless variables, and the characteristic line method was used for numerical analysis. At last the reduction experiments of the fixed bed consisted of multiple pellets were performed in a middle temperature tube furnace and the predicted results by the model agreed well with the measured ones by experiment.
Abstract: A two-dimensional CFD model was developed for pre-reduction of iron ore fines using a Z-path moving-fiuidized bed. The proposed model was solved using an integration of PHOENICS and FLUENT. Simulation results of cold state including pressure drop per perforated plate, gas flow patterns and solid flow patterns were compared to experimental results and the agreement between them was good. The model was applied to predict the performance of the reactor for gaseous reduction of iron ore fines using purified COREX export gas as reductant. It is indicated that under the simulation conditions gas temperature drop is about 700 K, utilization rates of the gas reduction potential of CO and H2 are about 38% and 26%, respectively, and the reduction fraction of the ore fines reaches 75%. This means that the reactor has the advantages of excellent gas-solid heat transfer and high reduction potential utilization. The reactor realizes a gradient utilization of the heat and reduction potential of the reducing gas.
Abstract: The effects of different inclusions on antimony precipitation and enrichment in steel during high-temperature oxidation were investigated. It is found that in the Fe-1.5%Sb alloy specimen, antimony-enriched phases precipitate at grain boundaries after water-quenching at 1100℃. Manganese sulfide is more favorable for antimony precipitation than oxide inclusions. The chemical composition of antimony-enriched phases is close to that of FeSb, which is consistent with the result calculated by the disregistry of lattice parameters between antimony particles and the inclusions. Reducing the oxygen content or adding Ti in steel can increase the amount of manganese sulfide and promote antimony precipitation, thereby decrease the amount of antimony segregation and solid solution, and change the precipitation location of Sb in steel.
Abstract: The effects of cooling rate and finish rolling temperature on the microstructure refinement and marten-site/austenite (M/A) islands in X70 pipeline steel were studied with a Gleeble thermal-mechanical simulation machine. When the cooling rate increasing, the grain size of ferrite decreases, the volume fraction of M/A islands increases first and then decreases, but the dimensional change of M/A islands is opposite to the volume fraction. With the finish rolling temperature rising, ferrite in the steel slightly grows up and the volume fraction of M/A islands increases; but when the finish roiling temperature increases from 900 to 940℃, the volume fraction of M/A islands slightly decreases and the size of M/A islands increases.
Abstract: Austenite grain growth behavior of DP590 dual-phase steel was studied and the influence rule of heating rate on the initial grain size was analyzed by changing the heating rate and heating time. The initial grain size decreases with the heating rate increasing and finally comes to a constant. When the soaking time is long enough, the austenite grain size increases and tends to remain unchanged. These experimental data were fitted by the Sellars model. In order to avoid the deviation caused by model parameters, a new data processing method was proposed. With this method, the models of initial austenite grain size and austenite grain growth were built. It is found that the model parameters are much more reasonable and reliable, and the calculated data is in good agreement with the experiment data.
Abstract: The thermal expansion curves of 1000 MPa cold rolled dual phase steel during continuous heating were tested on a DIL805A dilatometer. The volume fraction of austenite in the steel was calculated by the lever rule method, and it is in good agreement with the result of quantitative metallography. The JMAK equation can predict the austenite isochronal transformation kinetics quite well. The influence of cold rolling reduction and heating rate on austenite isochronal transformation kinetics was also investigated. Finally, the equilibrium condition of phase interfaces during transformation was studied by thermodynamic calculation.
Abstract: Transmission electron microscopy (TEM) was used to detect the grinding surface modificative layer thickness of M50NiL carburized steel, and the surface integrity indicators of M50NiL were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), micro-Vickers hardness tester, and X-ray residual stress analyzer. It is found that a surface modificative layer is built on the surface carburized hardened layer after grinding and its basic microstructure characteristics are grain refinement and deformation. The selected area electron diffraction pattern (SAED) shows an elongated blur polycrystalline spot ring. It can be concluded that the modificative layer is about 0.5 μm in thickness, has higher compression stress and hardness, but lower surface stress concentration factor.
Abstract: Dewing behavior on specimens during warming and wetting processes in a weathering test chamber was predicted by computational fluid dynamics (CFD), and corresponding experiments were performed for validation. The effects of specimen size and materials on the dewing behavior were examined. The results show distinct size effect and material effect on the time of wetness (TOW) in the weathering test of engineering materials/components, indicating that these two effects should be emphatically taken into account in evaluating the safety of materials/components. Through deliberating and optimized modeling, good agreement between numerical simulation results and test data was achieved, which demonstrates that numerical simulation can be conducted to predict the heat transfer behavior and water condensation tendency on engineering components in weathering test.
Abstract: The morphologies and interface structure of self-assembled 0.65BiFeO3-O.35COFe2O4 nanocomposite thin films on (001)-SrTiO3 single crystal substrates were studied by advanced transmission electron microscopy (TEM) techniques at the atomic scale. During the process of thin-film epitaxial growth, BiFeO3 (BFO) and CoFe204 (CFO) separate spontaneously and form a self-assembled composite nanostructure. The ferromagnetic spinel CFO forms nanopillars presenting a rectangular shape embedded in the ferroelectric perovskite BFO matrix, and both grow epitaxially along the[001] orientation and then get a vertical columnar nanostructure. The two phases give a cube-on-cube orientation relationship,[001]BFO//[001]CFO and (100)BFO//(100)CFO, and the interface between them lies in the {110} orientation. The surface of the composite film is rough with {111} facets of CFO and a smooth surface of BFO resides on the (001) plane. Energy-dispersive spectroscopy (EDS) studies show that the constituents of each phase present homogeneous distribution and no obvious interdiffusion is observed across the interface.
Abstract: A new method was proposed for analyzing metal transverse flow in hot rolling processes. Firstly a static roll-strip coupling model was established by ANSYS finite element simulation software, and the work roll contour under loading was extracted from the calculation results. Secondly, with the extracted work roll contour, a dynamic roll-strip coupling model was built by ANSYS/LS-DYNA simulation software and the rolling process was well simulated, then the metal transverse flow state in the whole strip width range was solved. Besides, the influences of bend force, initial roll contours, and strip crown on the metal transverse flow were analyzed. On the basis of these analyses, a calculation model of metal transverse flow during hot rolling was obtained by an interpolation method. The model was proved to be reliable by the finite element method.
Abstract: Based on the mechanism of twice wedge rolling for valves, changes in stress and strain of a 21-4N valve at the center with forming angle were investigated using the finite element software DEFORM-3D. The effect of forming angle on the central quality of the rolled piece was analyzed. It is found that a larger forming angle can lead to a more reasonable distribution of both stress and strain in the center of the rolled piece, which is positive to prevent central cavities. Laboratory experiments show the same result.
Abstract: It is difficult for designers to determine proper initial parameters for the optimal design of hydraulic supports. Based on the thought of visualized optimization design, the Euler-Savary equation and the inflection circle generation technology were applied to designing an approximate straight-line linkage for a hydraulic support. Firstly, some conditions were determined such as the pivot points which link the base with the front and back rod, the position of the pivot between the caving shield and roof beam, and the motion direction of the caving shield. Then, a mathematical model was established with the direction angle of the back linkage and the position angle of the inflection circle as design parameters, and it can be solved for all possible mechanisms with at least the second-order osculating straight-line. Mechanism property graphs of interest were computed and graphical visualization of the property information was implemented. Feasible solution regions adhering to design constraints were visually represented, which can rapidly guide designers to find the optimal mechanism with the minimum deviation for a given mining height, or the one with the maximum height for a given deviation, and provides a group of preliminary values with inherent advantage for the optimization design of hydraulic supports.
Abstract: In order to get and control acid concentration values in cold-rolled strip steel pickling, a soft measurement method was proposed for real-time predicting the acid concentration. Because of the influence of irrelevant components and outliers in acid concentration data on the accuracy of the acid concentration prediction model, orthog-onal signal correction (OSC) and iterative weighted least squares (IRLS) regression were combined to build the model. Firstly, orthogonal signal correction was used to remove irrelevant components which have nothing to do with tile mea-sured variables. Then robust regression based on the iteratively reweighted least squares algorithm was applied in the model to reduce the influence of outliers. Finally, the prediction results were compared with multiple linear regression (MLR), IRLS, and OSC-MLR. It is found that OSC-IRLS has the best prediction accuracy. In comparison with MLR, the relative error of OSC-IRLS decrease from 1.82% to 1.17% in predicting the concentration of ferrous ions and from 5.87% to 4.73% in predicting the concentration of hydrogen ions. The proposed method has a better model prediction accuracy to meet the requirements of industrial applications.
Abstract: Objects in actual decision tables are often changed dynamically. Aiming at this problem, the concept of a simplified decision table is introduced firstly, and a large number of repeated objects are deleted. A simplified matrix based on the positive region is constructed, which can reduce the searching space. What's more, it is theoretically analyzed that the definition of attribute reduction based on the simplified matrix is equal to that based on the un-simplified matrix. The proposed method scans only once the simplified matrix and it can be effectively utilized to the old attribute reduction. On this condition, an efficient algorithm for dynamic attribute reduction based on a matrix was designed. Finally, an example and its experimental comparison were employed to illustrate the efficiency and feasibility of the proposed algorithm.
Abstract: The numerical simulation of vertically stiffened steel plate shear wails (SPSWs) with two-side connections was performed with ANSYS software. A comparison was made between the theoretic initial stiffness of un-stiffened SPSWs with two-side connections and the initial stiffness of vertically stiffened SPSWs with two-side connections cal-culated by the finite element method. The effects of stiffeners and axial compression ratio on SPSWs were studied elementarily. Under shear force, the mechanism and destroying order of members in two-side connected SPSWs with boundary frame members were studied. Push-over analysis was made both in vertically stiffened SPSWs with two-side connections and with four-side connections, whose boundary frame members were designed to be the same. Some seismic performances of these two kinds of SPSWs were compared.
Abstract: A denitration project in Zhejiang Huaneng Yuhuan Power Plant in China was taken as the research object, and the finite element method was used to simulate elastic properties in small deformation and large deformation. The mechanical properties of the flue in practical load were studied, and the influence of the flue length on the stress and deformation were discussed. It is found that because of considering large deformation effect, the equivalent stress of the flue is well-distributed, and its values decrease by 5% to 50% The influence of the change in flue length on the stress is less than 20%. At last, monitoring was used to show the reliability of numerical simulation.
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
