Abstract: The one-dimensional damage variable was defined based on the elasto-brittle behavior of rock under uniaxial loading. To define the damage and its evolution in three-dimensional loading, the twln-shear theory was introduced to generalize the one-dimensional damage model into the three-dimensional model. The elastic behavior of the damaged material under loading can be expressed by reducing the elastic module, and the plastic flow can be represented by the slide on the plane between the two parts of the fractured rock. To establish the elastoplastic model of the damaged material, the concept of effective stress was used to contain the effects of damage in the yielding equation as well as in the function of plastic potential. The model was established in the frame of the classical plasticity theory in which the Mohr-Coulomb criterion was employed as the yielding criterion, and the friction law on the pre-sliding plane was taken as the hardening-softening rule to describe the change of the yielding surface with the progressive yielding. The comparison of the calculated results with tested results by a CT machine shows that the damage model presented in the paper can accurately describe the damage evolution of rock in Nanqiao Sandstone, and that the damage-elasto-plastic model is indeed feasible in describing the mechanical properties of the damaged material.
Abstract: The influence of random-distributing structure surfaces in rock mass on the soft rock rheology is mainly expressed by scale effect. Multi-step incremental cycling loading and unloading uniaxial compression creep tests on 4 different sizes of sand-shale specimens showed that soft rock rheology could be described by the Salustowicz model and the values of its constitutive parameters of E H(linear elastic parameter), EK(viscoelastic parameter) and ηK(viscous parameter) would decrease and tend towards being constant as the specimen size increased, which might be expressed by nonlinear regressive equations with extremum conditions. Then an extrapolation method was gained to determine the dimension of the continuous micro element of engineering rock mass with randomly distributing structure surfaces. It may be used to gain the rheological model and its mechanical parameters of engineering rock mass in the continuity schematization range by rheological tests on the different sizes of rock specimens in the laboratory.
Abstract: Particle flow code (PFC) simulation was performed to investigate meso-response of sand soil under critical flow condition using a coupled liquid-particle model. The effects of hydraulic gradient amplitude and particle stiffness were discussed and the occurrence of sand boil was analyzed from the viewpoint of micro-mechanism. The numerical results indicated that under critical or overcritical gradients, a layer of clustered particles formed near the top wall, and the remainder of the particles formed a suspension and underwent convective-like motion. The thickness of the top layer was proportional to the gradient amplitude. The gradient amplitude based on microanalysis was a little lower than that based on the traditional theory, which reflected the dynamic behaviour of the adopted model. The pore flow was mainly laminar but deviated from Darcy's law under critical or over-critical gradients.
Abstract: According to a retaining wall failure instance on 205 National Road in Shandong Province of China, the numerical simulation method was used to analyze the effect of slope angle on the retaining wall stability under vehicle loading. The results show that slope angle can sensitively influence the whole stability of the retaining wall. The horizontal deformation and plasticity scale of the retaining wall increase with increasing slope angle, and the slippage of the slope can result in additional deformation of the retaining wall. During the construction of the retaining wall on a slope, the effect of slope angle should be considered to determine the whole reinforcement scheme for roadbed, wall, and slope body.
Abstract: Waste water containing acid red B (ARB) was treated with Y2O3/WO3. The reaction mechanism of photocatalysis was studied. The relations of the composition and amount of heterogeneous photocatalyst, pH value of solution, H2O2 amount and illumination time with the decolorizing rate of ARE were discussed, The results showed that the decolorizing rate of ARB could reach 99.3% by using Y2O3/WO3 as heterogeneous photocatalyst with the Y2O3 mass fraction of 3.0% in Y2O3/WO3, 50mL of 20mg·L-1 ARB (initial concentration), the catalyst mass of 0.4 g, pH 6.0, the H2O2 amount of 7.35 mmol·L-1, and the illumination time of 6 h.
Abstract: In order to develop fluorine-free mold fluxes into stable properties for slab continuous casting of low carbon steel, the formation regions of fluorine-free mold fluxes were investigated. Based on the test of the physical properties of traditional fluorine containing (F- ≥ 3%) fluxes, the slag samples, fitting to the compositional characteristics of mold fluxes, were designed by using the mathematical complex method in the slag system of CaO-SiO2-Al2O3-Fe2O3-MgO-Li2O-TiO2-Na2O-MnO-B2O3. By fixing some variable components step by step, the multidimensional composition space was transformed into two-dimensional plain grids, from which the nodal points were used as compositions of fluxes. Compared with the properties of fluorine containing fluxes, three formation regions of fluorine-free fluxes, with a lower basicity, melting point, viscosity and breaking temperature, and solidified in the glassy state, were found. The typical components in one of the regions were CaO 31.2%, SiO2 36.8%, Al2O3 3%, Fe2O3 1%, MgO 2%, Li2O 2%, TiO2 6%, Na2O 7%-12%, MNO 3%-8%, and B2O3 0-3%.
Abstract: The relationships between the heating furnace time of casting slabs and the ultrasonic testing quality of hot-rolling medium plates were investigated. It is concluded that, (1) when the heating furnace time of 220 mm thickness casting slabs was less than 3 h, very bad ultrasonic testing quality of the plates would happen; (2) increasing the heating furnace time of the slabs could effectively improve the ultrasonic testing quality of the plates; (3) what caused the ultrasonic testing lost was micro-cracks in the pearlite band; (4) reducing the centerline segregation of the slabs could obviously improve the ultrasonic testing quality of the plates.
Abstract: A thermo-simulating machine and a dilatometer were used to test the continuous cooling transformation (CCT) diagrams of a kind of Nb-V-microalloyed high-strength hull steel, including the dynamic (with deformation at three temperatures) and the static (without deformation) CCT diagrams, Experimental results show that the dynamic CCT diagrams shift to the left and upper compared with the static ones. With increasing cooling rate the onset temperature of γ/α transformation is gradually lowered, the starting temperature of bainitic transformation Bs increases to a plateau and then decreases, and the ferrite grains are dramatically refined. When the finish rolling temperature reduces from 900℃ to 800℃, the onset temperature of γ/α transformation and the upper critical cooling rate for bainite slightly increase while Bs decreases about 10℃, and the ferrite grains are refined.
Abstract: In order to ascertain the contribution of crack nucleation process in fracture, round tapered specimens of 304 stainless steel were used to determine the initiation time of stress corrosion cracking in boiling 42% MgCl2 solution. The results showed that the relation of the time to nucleation of stress corrosion cracking (SCC) to the applied stress obeyed ti=4310exp(-0.0097δ); however, the relation of the time to fracture to the applied stress was tf=6964exp(-0.0095δ). It was indicated that the majority of fracture process consisted of crack initiation. The fracture surface was related to the applied stress. The transgranular SCC area decreased with the increase in applied stress.
Abstract: Based on grey relational analysis, the relation changes between the environmental factors and corrosion rate of 2Cr13 and 1Crl8Ni9Ti were examined. It was shown that the changes of influencing factors of 2Cr13 and 1Crl8Ni9Ti varied due to exposure time. The atmosphere corrosion rate of 2Cr13 was affected mainly by the time when the relative humidity was greater than 80% in a year, rainfall, temperature and Cl- in the initial stage, while later affected by Cl-, SO2, the time when the relative humidity was greater than 80% in a year, relative humidity, and temperature. The relation sequence between the environmental factors and corrosion rate of 2Cr13 was changing ceaselessly in different periods of time. The corrosion rate of 1Crl8NigTi was affected by the time when the relative humidity was greater than 80% in a year, rainfall, dust and so on in initial stage. The effect of Cl- was boosted up with corrosion time. Cl- became the leading factor of 1Crl8Ni9Ti gradually. The relation sequence stabilized between the environmental factors and corrosion rate of 1Crl8Ni9Ti after long-term exposure.
Abstract: A microstructure model of ordered FePt:Au nanogranular films was constructed. The magnetization reversal mechanism of FePt:Au granular films with different percentages of non-magnetic Au were investigated by micro-magnetic simulation. The results show that the reversal mechanism significantly depends on the percentage of Au. As the interaction coefficient of proportionalityβ, which reflects the percentage of Au, is greater than 0.4, the reversal model is coherent and the coercive force increases slightly with reducing ft. But forβ〈 0.3, the coercive force increases quickly with reducing fl, and the consistency of magnetization reversal is weakened. It is estimated that as the space length between the FePt granulars varies from 3 nm to 4 nm, the interaction of granular exchange is near to zero and the magnetization reversal is incoherent.
Abstract: NiCo films were deposited on NiFeCr and Ta buffer layers by using a DC magnetron sputtering system on Si substrates respectively. After deposition the samples were annealed at different temperatures. The structural and magnetic properties were systematically studied. It is shown that the value of anisotropic magnetoresistance (AMR) of the film with a NiFeCr buffer layer is higher than that of the film with a Ta buffer layer. XRD results indicate that the average grain size of the sample with a NiFeCr buffer layer is larger than that of the sample with a Ta buffer layer, and the situation of the NiCo/NiFeCr interface is different from that of NiCo/Ta. These would be responsible for the difference in AMR between the two kinds of films. A suitable anneal treatment is good for the films.
Abstract: Ta(10 nm)/NiFe(8 nm)/Cu(2.6 nm)/NiFe(3.6 nm)/FeMn(9 nm)/Ta(10 nm) spin valve multi-Myers were prepared by magnetron sputtering, It is found that an enhancement of exchange coupling field can he achieved by depositing a Bi layer with appropriate thickness at the Cu/NiFe interface. The results of X-ray photoelectron energy spectra show that the segregation of Cu atoms to the surface of the NiFe layer can he depressed effectively. Excessive Bi atoms can further migrate to the FeMn layer, which may produce lots of impurities. Consequently the ferromagnetism of the FeMn layer is damaged and the exchange coupling field is decreased.
Abstract: Based on the thermodynamic theory, the critical phase transition temperature of 1-3 type multiferroic composite BaTiO3-CoFe2O4 was investigated by linear stability analysis, Taking into account the coupled elastic stress on the interfaces of ferroelectric/ferromagnetic phases and film/substrate, the analytic expressions of para-ferro transition temperature of the epitaxial multiferroic composite thin film were derived as a function of volume fraction, lattices parameters, material constants and thin film thickness, The results show that the critical phase transition temperature can be controlled by adjusting the volume fraction or thickness of the composite thin film.
Abstract: Nano-crystalline MnZn ferrites, ZnxMn1-xFe2O4(x=0.2-0.4), were produced by the high energy milling method with high pure iron oxide prepared by chemical precipitation process as the starting material. Their structural properties were analyzed and characterized by means of X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The results showed that forma-tion of the nano-crystalline MnZn ferrites had two stages; the phase of ZnMn204 grew in the presintering first and then turned into Zn0.2Mn0.8Fe2O4 during the sintering process. The crystal growth mechanism was compendiously discussed.
Abstract: Zn-doped magnetite Fe3O4 samples were prepared at different doped concentrations and annealed at high temperature in ambient air and N2 respectively. X-ray diffraction (XRD) results showed that samples annealed in air were oxidized and the consequent products were partially in α-Fe2O3 form. While for the samples annealed in N2, ZnxFe3-xO4 products of high purity were obtained. The doping of Zn2+ on the tetrahedral sites (A sites) changed the valence distribution of Fe2+ ions on the octahedral sites (B sites). The electron transporting mechanism remained to be variable range hopping (VRH) conduction. Measurement results of magnetic properties indicated that the super exchange coupling interaction between Fe2+ ions was affected by the low doping concentration of Zn2+ ions in the crystal, and the negative magnetoresistivity of ZnxFe3-xO4 was improved as well.
Abstract: The effect of grain orientation on the magnetic properties of anisotropic and sintered strontium ferrite was examined by scanning electron microscopy, transmission electron microscopy and magnetic measurement. The results showed that the needle-like particles of ferrite with arranging along C axis in good order were found in the strontium ferrite powder, originating from the crushed and milled waste magnet, which did not have bad effect on the quality of products. The particles in sintered permanent magnetic strontium ferrite presented hexagonal structure. The higher the orientation degree, the better the magnetic properties were. The strength of magnetic field and the addition of binder had significant effect on the orientation degree and magnetic properties of permanent magnetic strontium ferrite.
Abstract: By using technical grade TiOsO4 as the precursor and urea as the precipitating agent, N-doped TiO2 nanopowders were prepared by hydrothermal homogeneous precipitation and heat treatment. The properties of the prepared powders were characterized by XRD, XPS, BET, UV-Vis absorbance spectra, FTIR, and BET methods. By using an electronic energy-saving lamp as the light source, taking methylene blue as the model pollutant, their photo catalytic activities under visible-light irradiation were also investigated. The result showed that the products after 900℃ heat treatment were all anatase. When the temperature came to 1000℃, almost all of them were converted into rutile. Taking urea as the nitrogen source, XPS analyses of particles prepared by hydrothermal powders after heat treatment indicated that the Nls peak was close to 399 eV, Furthermore, N replacing a small amount of lattice oxygen to form TiO2-xNy(y ≥ x) was further demonstrated by FTIR. UV-Vis absorbance spectra showed that adding the nitrogen source during heat treatment was necessary to the red-shifted in the absorption band-edge and the binding ratio of photo-generated electrons. The particle size calculated by XRD accorded with the result analyzed by TEM, All results show that nitrogen-doped TiO2 after heat treatment had a higher photo catalytic activity in visible light.
Abstract: In order to synthesize high quality surface acoustic wave devices and explore the deposition process of diamond films, large-area high-quality diamond films were deposited on silicon substrate by DC-arc plasma jet CVD. Deformation of the silicon substrate which happened in the deposition process was eliminated by a special poly-substrate technique. The influences of the concentration of methane and the temperature of the substrate on the diamond films were studied, and the deposit process was optimized. The results showed that fine grain diamond films were gained when the volume fraction of methane was 1.8% and the temperature of the substrate was 1000℃. The roughness of the diamond films deposited under this condition is the lowest.
Abstract: Directional solidification experiments were carried out using the analogue casting system of NH4Cl-H2O solution by cooling it from below. The transient velocities of fluid flow within the micro-channel of mushy layer were measured by using observation facility and tracer coal particles of 30 μm in diameter. It turned out that during the solidification process, the mean solid fraction of mushy layer descended rapidly at first, so the mushy layer got more permeable and natural convection was more likely to occur. When the mean solid fraction was down to 0.42, and closed to the smallest value of 0.38, and the equivalent Reynolds number exceeded the critical value, about 247, plume convection with associated micro-channel occurred in the mush. With the expanding of channel width, the solution of liquid region, whose temperature was higher than that of mushy layer, flowed into the micro-channel. The convection within the channel was found to consist of upward flow and downward flow. The counter flow advected heat away and solute which was favorable to solidification, so that solution within the channel recrystallized.
Abstract: Confronted by the present state that the rules for hot metal temperature forecasting are made merely on the base of the experience of blast furnace (BF) experts, a new approach to the rules established through association rules mining from BF data was put forward. The algorithm of multidimensional time series rules mining was improved. The improved algorithm, which bases on the fuzziness of both subsequence and suhsequence interval, avoids the influence of "time border sharpness" on the result of mining. The algorithm was applied to No. 1 BF at Wuhan Iron and Steel Group Corporation, and its effects turned out to be satisfactory.
Abstract: The configuration of dissymmetrical CVC work roll contour and symmetrical conventional backup roll contour results in bad self-maintenance of backup rolls in downstream stands. After the analysis on the effects of backup roll wear contour in No. 4 stand on the profile control and roll contact pressure distribution by ANSYS finite element method, it was found that the severe wear of the backup roll affected the controllability of the mill for the profile and flatness of products, and led to the spalling accident of the backup roll, which may increase roll consumption. Based on the ANSYS analysis, a new backup roll contour was proposed, which was proved of good self-maintenance by experiment, and could work well during the whole service period, especially could mitigate the roll contact pressure peak of backup roll wear contour.
Abstract: Traditional wavelet transform based on frequency domain is too long to meet the need for real-tlme control of roller eccentricity. A novel wavelet based on lifting scheme is used to decompose and deal with eccentricity signals at different resolutions. Through analyzing roll force and thickness deviation signals, the lifting and dual lifting scheme theory is applied to distinguish eccentricity signals from disturbances and noise, and self-optimization is employed to real-time control the roller eccentricity. The results of simulation show that the control strategy is effective and at the same data length, the operational speed of lifting scheme is enhanced at least twice as that of traditional wavelet.
Abstract: According to the characteristics of the rolling and casting process in BOF special steel plants, the rolling plan compiling rules were described. The heuristic algorithm based on the rules for rolling production planning optimization was put forward, and some procedures to make the plan were given out in detail. On the basis of the analysis of real production state, cast plan compiling rules were described, and the model of cast plan optimization was established. Moreover, the overall design and technology realization of a production planning system were processed. By using Delphi 7.0 and SQL Server2000, the production planning system was developed and applied to one medium-sized converter special steel plant, and its practicality, reliability and versatility were proved in practice.
Abstract: The correlation function, a means to quantitatively describe contradictory problems, was introduced into an arc furnace expert system to distinguish if the composition of molten steel was qualified before tapping. The neural network prediction model was used as an evaluation basis of the arc furnace expert system, which was trained by the hybrid genetic algorithm to a high precision. Simulation results show that many reasonable advices can be given to operators in steel-making process by the expert system.
Abstract: A design method was introduced to efficiently implement an interpolator by Farrow structure, which can be used in an all-digital timing recovery scheme. An algorithm was presented to calculate the interpolator coefficients of Farrow structure and minimize the mean square error (MSE) at the output of the receiver. Simulation results show that compared with other conventional interpolation filters, the per/ormance with this optimized Farrow coefficients was improved in minimum MSE and the implementation complexity was reduced.
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
