A comparative analysis was done to reveal the advantage of a tensioned fast-slow set full-column bolt over a common full-column resin bolt.The interactional mechanics characteristics between a tensioned fast-slow set full-column bolt and rock mass were studied to find out the stress distribution of the bolt both in the axial and lateral directions.It is shown that the stress state of wall rock is effectively improved due to the axial action of the bolt.But the lateral action of the bolt includes filling the rock crevices and restraining the shear sliding,which effectively improve the mechanical properties of wall rock.Finally,the mechanics characteristics of the bolt in the jointed rock were discussed.The result indicates that there exist several axial stress peaks.
Abstract: The surface self-magnetization of weakly magnetic iron minerals was realized by using the dissolution characteristic of siderite and hematite in an acidic condition,without adding any iron ions,only adjusting the pH value in the slurry and controlling the reaction temperature.The effects of reaction time,ferric ions concentration,H2O2 addition and reaction temperature on the dissolution behavior of siderite in an acidic condition were investigated in this experiment.The recovery rate of siderite increased from 53.8% to 94.6% at 100℃ by the self-magnetization.So it can be determined that reaction temperature is an important factor to affect the self-magnetization.Mixture minerals made of siderite and hematite were used to repeat the self-magnetization experiment of siderite,and their recovery rate increased from 66.8% to 72.6%.Finally,actual mixture minerals made of siderite and hematite were also used to carry out the self-magnetization experiment.The results were consistent with those of the single-mineral experiments and the mixed mineral experiments.The recovery rate of the actual mixture minerals improved from 46.3% up to 63.1%,realizing the self-magnetization of mineral samples.
Abstract: Water content is an important factor which affects the granulation of a mixture and sintering.Research results show that with the water content for granulation increasing,the proportion of fine particles reduces in the granulated mixture,the mean size increases,and the permeability rapidly improves firstly,but then mildly changes even goes down.The point of water content at which the permeability grows smoothly can be used as a criterion of suitable values for granulation,and it is found that the sintering speed reaches maximum at the suitable water content for granulation.The mixture can be divided into two parts by the mathematical method of sieving,one is-0.5 mm as adhering fine powders,the other is +0.5 mm as nucleus particles,and the ratio of nucleus particles X+0.5 was measured.The suitable water content can be predicted based on the model of W=X+0.5Wc+0.72(1-X+0.5)Wp,in which the maximum capillary water content of adhering fine powders Wp is measured by a saturated water absorption method and the preserved water content of nucleus particles Wc is measured by a centrifugal method.The accuracy of prediction reaches 93.3% when the absolute error of the suitable water content for granulation is ±0.3%,which can satisfy the requirement of predicting accuracy.
Abstract: The existence form and transformation pattern of phases in Panzhihua titanium concentrate during the oxidation process were studied by thermogravimetry,constant temperature tests,X-ray diffraction analysis and microstructure observations.The results show that the titanium concentrate is not oxidized by oxygen below 500℃.Fe2Ti3O9 and TiO2 phases start to form when the temperature is 600℃ and the diffraction peak intensities of Fe2Ti3O9,TiO2 and original phase Fe2O3 strengthen with the experimental temperature rising.When the temperature rises at 900℃,Fe2Ti3O9 is substituted by Fe2TiO5 and the diffraction peak intensities of TiO2 and Fe2O3 gradually weaken with the experimental temperature rising.Four chemical reactions concomitant with sintering effect occur in the oxidation process;they accelerate the formation of porosities and make the surface of oxidation products rough and loose.
Abstract: The preparation of α-Al2O3 with a process of low-temperature alkaline melting,leaching and seed precipitation was explored by using secondary aluminum ash as a raw material.A series of experiments were done to investigate the effects of factors such as alkali-to-dross ratio,salt-to-dross ratio,smelting temperature,smelting time,leaching temperature,leaching time and solid-to-liquid ratio on the leaching rates of Al and Si.The feasibility of using seed precipitation as a successive treatment technology of leachate to prepare alumina was discussed.The optimum conditions of the process were determined as follows:alkali-to-dross ratio 1.3,salt-to-dross ratio 0.7,smelting temperature 500℃,smelting time 60 min,leaching temperature 60℃,leaching time 30 min,and solid-to-liquid ratio 1:4.The leaching rate of aluminum can reach to 92.71%.It is indicated that seed precipitation as a successive treatment technology of leachate is feasible and effective.
Abstract: The microstructure and mechanical properties of 0.21C-1.43Si-1.35Mn steel heated by a quenching and partitioning (Q&P) process in the two-phase region and the full austenite region were investigated. The results show that if heating the steel in the two-phase region, the microstructure consists of martensite, retained austenite and ferrite, and the tensile strength, elongation and strength ductility are 1013 MPa, 25% and 25 655 MPa·%, respectively. While heating the steel in the full austenite region, the micro-structure consists of martensite and retained austenite, and the tensile strength, elongation and strength ductility are 1 257 MPa, 17% and 21 454 MPa·%, respectively. There is mainly lath martensite along with high-density dislocations in the Q&P steel. A few twinning martensite transformed after partitioning can be observed as well. Retained austenite with a volume fraction of 10. 67%, distributed within lath martensite, can be acquired in the shape of films after the Q&P process.
Abstract: The mechanical properties and corrosion resistance of nickle-saving nonmagnetic Cr18Ni6Mn3N stainless steel were studied after hot rolling and solution heat treatment.The microstructural evolution after solution heat treatment and aging treatment,the variation trend of deformation induced by martensite during cold working,and the magnetic property of the stainless steel were analyzed.The results indicate that single austenitic phase appears in the stainless steel at room temperature after solution heat treatment.Compared with SUS304 stainless steel,the mechanical properties and corrosion resistance of the stainless steel are better.Granular nitrides precipitate along grain boundaries after a 4h holding time at 800℃;however,when the holding time prolongs,lamellar precipitates begin to emboss along grain boundaries and then grow into grains.After a 20h holding time,the diameter of the embossed lamellar precipitates reaches to 20 μm.Deformation-induced martensite does not appear at a reduction rate of 18.3%,and with increasing deformation the amount of martensite gradually increases.Although the relative magnetic conductivity rises,it is less than that of SUS304 stainless steel under the same condition.After solution heat treatment the relative magnetic conductivity of the cold rolled plate drops to 1.002,and thus the stainless steel can be a low-cost candidate in the nonmagnetic stainless steel field.
Abstract: 00Cr25Ni7Mo3N duplex stainless steel was treated by different solutions,its super plastic deformation was tested on an isothermal tensile machine,and the diffusion bonding by super plastic deformation was performed on a Gleeble 3500 thermal simulator.The solution treated microstructures and the bonding interface voids were observed by scanning electron microscopy(SEM).The results indicate that the volume ratio of α phase to γ phase(xα/xγ) varies with the solution temperature.During the tensile process,the elongation and the peak stress increase with the initial value of xα/xγ increasing under the same deformation condition.The elongation of the specimen solution-treated at 1 350℃ reaches to 1 186% at a deformation temperature of 960℃ and a strain rate of 1×10-3s-1.At a bonding temperature of 1 100℃ the diffusion bonding mechanism depends on loading modes,but the influence of loading modes on the interfacial shear strength is not significant.During the bonding,the closure degree and retention position of the interfacial voids are related with the relative migration velocity of grain boundaries.
Abstract: Single and double-pass cold rolling and annealing tests were carried out aiming at the poor control of grain size uniformity for 690 alloy tubes in China.A heterogeneous factor Z was introduced to evaluate the uniformity of microstructures.The results show that the grain size is most homogeneous in 690 alloy pierced billets by single-pass cold rolling with a deformation of 50% and annealing at 1 100℃ for a holding time of 5 min.The best uniform grain size distribution can be obtained by the first pass cold rolling with a deformation of 50%,the second pass cold rolling with a deformation of 70%,and annealing at 1 100℃ for a holding time of 5 min between the two cold rolled processes,followed by solution heat treatment at 1 060℃ for 5 min or 1 100℃ for 3 min.
Abstract: The microstructure and properties of AZ31 magnesium alloy sheets containing Y element after annealing were studied.The results indicate that the grain size of the magnesium alloy gradually increases with the increase of annealing temperature,but the mechanical properties slightly increase and then decrease.Annealing time has little effect on the grain size.After annealing at 300℃ for 1h,the magnesium alloy achieves the best mechanical properties,with a tensile strength of 255 MPa,a yield strength of 175 MPa,and an elongation of 24%.The fracture mode of the magnesium alloy is quasi-cleavage fracture and ductile fracture after heat treatment.
Abstract: Two titanium clad steel plates were prepared by exploding and exploding-rolling,respectively.In order to study the fracture behavior of the clad plates during the bending process,crack initiation and propagation were observed by scanning electron microscopy(SEM).The result shows that the crack initiation angle in external bending is less than that in internal bending,the capability of resistance to crack initiation in internal bending is stronger than that in external bending,but.During the bending process,cracks in the exploding clad plate mainly initiate on the interface junction of wave front and the center of whirlpools,but cracks in the exploding-rolling clad plate initiate at the hard lump interfaces of Ti-Fe intermetallic compounds.The main reason of cracking is that the interface junction of wave front and the center of whirlpools of the exploding titanium clad steel plate and Ti-Fe intermetallic compounds in the exploding-and-rolling clad plate are difficult to compatibly deform because of their high hardness.
Abstract: Carr's flowability index was used to evaluate the flow ability and the jet flow characteristic of pulverized coal for a blast furnace.The effects of coal characteristics including maceral and coal rank on the flow ability during pulverized coal injection in a blast furnace were investigated.The results show that the correlation between the flow ability and the jet flow characteristic is almost negative.Coal rank has remarkable effect on the flow ability and the jet flow characteristic.Bituminous coal with a low metamorphic grade has a poor flow ability and an excellent jet flow characteristic,but anthracite coal with a high metamorphic grade has an excellent flow ability and a poor jet flow characteristic.When the volume fraction of vitrinite is between 60% and 70%,the flowability index is poor.There is no correlation between the flow ability and vitrinite when the volume fraction of vitrinite is between 83% and 90% because of too many influencing factors.Inertinite shows a positive correlation with the jet flow but a negative correlation with the flow ability.It is not correlative between mineral and the flow ability.
Abstract: A method of production quality monitoring and diagnosis based on the kernel principal component analysis was introduced in the hot rolled strip process.The squared prediction error(SPE) statistic was used in process monitoring.The diagnosis criterion could express the influential importance to SPE,which was computed by the data construction method and the optimal neighbor selection strategy.Finally,simulation data and actual production data were used for model validation.The result shows that the SPE statistic based on the kernel principal component analysis can detect the abnormality and track the causes of faults effectively for adjusting the production process to prevent from substandard products.
Abstract: The flow and heat transfer characteristics of slot jet impingement to a cylindrical convex surface were investigated by the numerical method.Suitable turbulence models were determined by comparing experimental data with the numerical results of four turbulence models.The flow structure,boundary layer separation and wall heat transfer enhancement characteristics of slot jet impingement to a cylindrical convex surface were discussed on the basis of the pressure gradient distribution.The results show that RNG k-ε and Realizable k-ε models are suitable to predict.The slot jet impinges to a cylindrical convex surface,the gas flows along the convex surface,the velocity decreases and the boundary layer separation appears downstream.The dimensionless adverse pressure gradient increases with the dimensionless radius of curvature(D/B) decreasing,leading to an earlier boundary layer separation.Nu in the stagnation region can be enhanced by decreasing D/B.However D/B has almost no effect on heat transfer in the downstream flow.The pressure gradient is a key factor in affecting the heat transfer distribution in slot jet impingement to a cylindrical convex surface.
Abstract: A carrying energy optimization model of an electric arc furnace(EAF) was proposed by introducing an energy carrier and considering the factors of EAF charging structures,oxygen supply,carbon addition and power supply.Due to the complexity of its constraints,the model could not be solved by linear programming.In this paper the model was solved by a genetic algorithm.The energy values of BH1H,BHDDQ and SUS304 steels were calculated by the model.The results showed that under the premise of ensuring the indicators of EAF molten steel such as chemical composition,temperature and slag basicity to meet the requirements,the energy values of the molten steel in each furnace were reduced by 22.8%,21.4% and 23.6% for BH1H,BHDDQ and SUS304 steels,respectively.
Abstract: According to the technical demand of hot-rolling production,the lot planning of slab hot rolling was summed up as a multiple traveling salesperson problem with uncertain traveling salesman number.A production scheduling mathematical model considering the energy consumption of the heating section was proposed,with minimizing the production cost as the primary objective and optimizing the product quality as the secondary objective.A hybrid algorithm based on the genetic algorithm and the tabu search algorithm was proposed to solve the problem.Simulation results of practical data show that the mathematical model fully meets the demand of hot-rolling production.On the basis of the optimal number of rolling units,the transport time is shortened,the hot charging rate is increased and the product quality is optimized.Compared with a human-computer method,the results from the mathematical model and hybrid algorithm have a better performance of high production and energy-saving efficiency.
Abstract: A block image encryption algorithm with a 256 bit key was designed based on a logistic map and a spatiotemporal chaotic system.The algorithm encrypts a block of original image into a block of cipher image with the same length of 256 bit.An auxiliary key brought in and iterations designed in the algorithm are sensitive to the original image and secret keys.An alternating iterative chaotic system and an Arnold map disturb pixel values and shuffle the positions of pixels.The results of computer simulation and cryptanalysis show that the algorithm is characteristic of excellent sensitivity to the original image and keys,large secret key space and high expansibility.The algorithm also has excellent effective encryption and strong anti-attacking performance.It is indicated that the algorithm is suitable for security communication.
Abstract: Based on the forgetting strategy,an improved genetic algorithm was proposed to solve the problem of local optimization,and a forgetting operator as well as its forgetting probability was given.For the search space was increased by forgetting some genes during the period of inheritance,the algorithm can break away from local optimization and avoid the premature convergence to the greatest extent.By using the algorithm to deal with the credit scoring of telecom customers for different arrears rates,the optimum solution of credit weights in the case of high rate of arrears was found,so it solves the problem that the fitness of credit weights is low for the credit scoring of telecom customers in high arrears rates.Experimental results demonstrate that the algorithm is effective and feasible.Compared with the standard genetic algorithm,the proposed algorithm can obtain better quality results.
Abstract: In order to study the influence of fluid-solid coupling on the dynamic response of a simplified desulfurization tower structure model,the fluid-solid coupling effects of the model under seismic waves were simulated by using the finite element program Adina.Firstly,the desulfurization tower structure was reasonably simplified,its modal analysis was done at different liquid levels,and the influences of the liquid level on its self-oscillation frequency and vibration mode were analyzed.Secondly,the effects of the liquid level,the input angle and the peak value of earthquake acceleration on the acceleration and displacement of the desulfurization tower were discussed by loading seismic waves and were compared with experimental results.The result shows that the self-oscillation frequency intensifies with the liquid level rising.The liquid level,the input angle and the peak value of earthquake acceleration all have great influence on the acceleration of the desulfurization tower,but they have little effect on the displacement of the desulfurization tower.
Abstract: The effect of blasting vibration on Heishan tunnel with soil-rock interfaces was numerically analyzed with FLAC3D when the tunnel was excavated by blasting excavation.In the analysis the blasting excavation was simulated by a method of spherical blast waves.According to the numerical result,the safe charge of explosives was proposed and its application was analyzed in the blasting control.It is indicated that that the stress is redistributed at the vault and the bottoms of the arch waist.Soil zones in the vault are sensitive to blasting vibration.Although plastic failure develops mainly in the vault of the tunnel and there are also some damages in the center soil connecting with rock,they do not affect the overall stability of the tunnel.
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
