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    25 July 2015, Volume 43 Issue 7
    Materials Science & Technology
    Li Kang Li Wen-fang Zhang Guo-ge Duan Qi
    2015, 43(7):  1-7.  doi:10.3969/j.issn.1000-565X.2015.07.001
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    Four kinds of Al-Si alloys containing 0.5%,5.0%,9.0% and 12.0% Si respectively,were treated by means of the micro arc oxidation (MAO) for 15 min.Then,the MAO layers were investigated in terms of formation process,characteristics and energy consumption,and were characterized by means of SEM,EDS and XRD.The results show that (1) under the MAO treatment at constant current,as the Si content increases,the ascent rate of positive voltage,the striking voltage and the positive voltage during discharge stage,the average growth rate of the layer decease while the pores of discharge channels and the waiting time before spark discharges increase; (2) however,under the MAO treatment at constant voltage,the Si content has a weaker effect on the MAO of Al-Si al- loys,and as the Si content increases,the positive and negative current densities of the alloys both increase and the layers have a gradually-decreasing growth rate but with a similar surface morphology; (3) the layers on Al-Si alloys obtained through the two MAO modes at constant current and constant voltage are both composed of γ-Al2O3,α-Al2O3 and mullite,and the Al2O3 content in the alloys decreases with the increase of the Si content; and (4) the spe- cific energy consumption of the layers obtained through the same MAO mode increases with the Si content.Besides,both the characteristics and energy consumption of the layers on the same alloys through different MAO modes are quite different.
    Liu Huan-yu Zhang Gui-zhen Chen Jia-jia Qu Jin-ping
    2015, 43(7):  8-13.  doi:10.3969/j.issn.1000-565X.2015.07.002
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    The solid polymer deformation was observed on-line by using an assembled vane extruder,and then the effects of material properties,pellet size and process parameters on the deformation were investigated.The results show that (1) polymer pellets are deformed under the compaction of VPCU;(2) the solid polymer of a higher modulus experiences a larger plastic deformation;(3) big polymer pellets are turned into small slices after extrusion by VPCU is done,while small pellets experience a big deformation and then form bonded structure;and (4) the solid polymer deformation decreases with the rise of temperature as well as with the decrease of rotor speeds.
    Ye Jun Li Qing-yong Xiong Jian
    2015, 43(7):  14-19.  doi:10.3969/j.issn.1000-565X.2015.07.003
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    CMC /Tb nano-particles were synthesized in different reaction times. Then,the morphology, structure and fluorescence properties of the complexes were investigated by means of SEM, FT-IR and XPS and by using UVVis spectra and PL spectra. The results show that (1) CMC /Tb nano-particles are spherical particles and the particle sizes are around 100 nm; (2) for different reaction times, Tb3+ ions bind CMC in a similar way, specifically, all the Tb3+ ions react with the atom O of —OH, —COO and —COC groups on CMC chain; (3) however, the coordination structures of CMC /Tb nano-particles are different due to the dynamic equilibrium of CMC conformation during the reaction; (4) CMC acts as the primary light energy absorber and it can effectively sensitize Tb3+ ions to make the CMC /Tb nano-particles exhibit four characteristic narrow emission bands, namely, 5D47F6 ( 489 nm) , 5D47F5 ( 545 nm) , 5D47F4 ( 584 nm) and 5D47F3 ( 619 nm) ; and ( 5) in the four emission bands,the 5D47F5 transition with the green emission is the most prominent band of the Tb3+ ions, moreover, its half-peak width is less than 10 nm, and its intensity fluctuates with the reaction time and becomes steady after 75 minutes.
    Yu Peng Chen Bin-yi Wang Bin-bin Huang An Peng Xiang-fang
    2015, 43(7):  20-27.  doi:10.3969/j.issn.1000-565X.2015.07.004
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    Polystyrene /active Talc ( PS /Talc) composites were prepared by means of a parallel triple-screw extruder with excellent mixing ability. Then, the dispersion of Talc in PS matrix was analyzed, and the mechanical properties and thermal stability of PS /Talc composites were investigated. Meanwhile, the key factors affecting cell structure were discussed via extrusion foaming orthogonal experiments. The results show that (1) the dispersion of Talc in PS matrix is improved by the triple screw extruder, and Talc can be dispersed in PS matrix evenly when the Talc content is below 6%; (2) the tensile strength, the impact strength and the elongation at break first increase and then decrease as the Talc content reduces, and they all reach the maximum when the Talc content is 6%; (3) with the increase of the Talc content, the flexural strength decreases while the flexural modulus increases; (4) the addition of Talc can enhance the thermal stability of PS /Talc composites, and the thermal stability reaches the maximum at the Talc content of 10%; (5) the primary factor affecting the foaming behavior of PS /Talc composites is the Talc content, which is followed by the die pressure and the die temperature; and (6) when the Talc content is 8%, the minimum cell size and the maximum cell density are obtained, which are 12.4μm and 2.4 × 108 cells /cm3 ,respectively.
    Zhao Zuo-fu Qi Jin-gang Wang Jian-zhong Liu Xing-jiang Wang Jia-yi
    2015, 43(7):  28-32,67.  doi:10.3969/j.issn.1000-565X.2015.07.005
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    The effects of the electric pulse treatment on the corrosion resistance of silicon brass are investigated by using an electrochemical workstation and a SEM. The results show that, after the electric pulse treatment, the corrosion potential of silicon brass increases while the corrosion current density decreases by about one order of magnitude, and that the electric field treatment increases the capacitive reactance diameter of silicon brass by 5~6 times and decreases the thickness of dezincification layer from 80~90 μm to 15~20 μm. It is thus concluded that the corrosion resistance of silicon brass alloy is improved after the electric field treatment.
    Architecture & Civil Engineering
    Chen Qing-jun Xue Hua Tang Xu-lin Zuo Zhi-liang Chen Ying-rui
    2015, 43(7):  33-41.  doi:10.3969/j.issn.1000-565X.2015.07.006
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    The low-cycle reversed loading experiments of four specimens were conducted to investigate the seismic behavior of the exterior through-beam joint between concrete-filled steel tubular (CFST) columns and reinforced concrete beams. Experimental results show that (1) as the relative reinforcement ratio ( the reinforcement ratio of ring beam / the reinforcement ratio of frame beam) and the relative radio width ratio ( the width of ring beam / the diameter of steel tube) decrease, the plastic hinge transfers from the frame beam to the ring beam, and three failure modes occur, which includes the failure at the frame beam root, the failure at the connection of the frame beam and the ring beam and the failure in the ring beam; (2) the internal force at the roots of the beams can be reliably transmitted to the joint, and the joint can work coordinately with the frame beam and the CFST column; and (3) for the specimens designed on the basis of the principle of“Strong Joint”, the plastic hinge appears at the frame beam root with plump hysteretic curves, relatively large ductility coefficient, concave and convergent stiffness curves and excellent energy dissipation ability, which means that the seismic behavior is good. Therefore, the exterior through-beam joint obtained through reasonable design is safe and reliable under stress, and it can realize the anti-seismic design principle of“Strong Column with Weak Beam is, Stronger in Joints”.

    Ning Xi-liang Ding Yi-ning
    2015, 43(7):  42-49.  doi:10.3969/j.issn.1000-565X.2015.07.007
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    Bending tests under four point loading were conducted on steel rebar-reinforced steel fiber-reinforced self-compacting concrete ( SFRSCC) beams, and the corresponding loading-mid-span deflection curve, longitudinal reinforcement strain-longitudinal reinforcement strain curve and failure mode were obtained. The flexural bearing capacity of the beams and the hybrid effect of steel rebar and macro steel fibers were also examined. It is found that the addition of steel fibers can improve the flexural bearing capacity by 10%~ 42%. Moreover, by taking into account the steel fiber distribution and its force transfer mechanism crossing the crack, a calculation formula is proposed to predict the flexural bearing capacity of the beams, and it is compared with the formulas of ACI 544 and CECS 38: 2004. Calculation results show that the proposed formula has a better fit with the test results. Thus, it is suitable for the flexural analysis and design of SFRSCC beams.
    Yang Hui-xian Huang Yan-sheng Li Jing
    2015, 43(7):  50-56.  doi:10.3969/j.issn.1000-565X.2015.07.008
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    The impact compression tests of hybrid fiber ( steel and polyvinyl alcohol ( PVA) fiber) -reinforced cement- based composites ( HFRCC) of different ratios were conducted at different strain rates by using a split Hopkinson pressure bar ( SHPB) . Then, their dynamic compressive strength, peak strain and tenacity are compared. The results show that (1) HFRCC is sensitive to strain rates; (2) the peak strain increases with the PVA fiber content and the addition of steel fiber can increase the dynamic compressive strength; (3) to increase the PVA fiber content can decrease the dynamic strength increase factor; and (4) at a low strain rate and before the stress reaches up to a peak, the relative contents of two kinds of fibers have little influence on the tenacity of HFRCC. At a high strain rate, however, the steel fiber can effectively improve the tenacity of HFRCC.
    Jiang Huan-jun Lei Jie Lü Shang-wen
    2015, 43(7):  57-67.  doi:10.3969/j.issn.1000-565X.2015.07.009
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    On the basis of the modal pushover analysis ( MPA) method, a method of improved modal pushover analysis ( IMPA) is proposed. This method overcomes the shortcomings of the fixed loading patterns of the MPA ( Modal Pushover Analysis) method, and its loading mechanisms before and after a structure yields are different. Then, by two examples, the IMPA method is compared with the MPA method in terms of roof displacement, interstory drift angle and elasto-plastic time-history. The results show that the IMPA method is much more accurate than the MPA method when the two methods are used to estimate the structural seismic response.
    Wu Li-li Liu Yan Jiang Yu-peng Zhang Dong-dong
    2015, 43(7):  68-74,99.  doi:10.3969/j.issn.1000-565X.2015.07.010
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    By combining the ANSYS-based finite element method with the test, the changes of the flexural bearing capacity and shear bearing capacity of specimens with the shear-span ratio are analyzed, and the influence of the shear-span ratio on the failure mode of specimens is investigated respectively under single-point and two-point symmetric loading on the midspan. The results show that (1) the debonding failure of steel plates occurs only when the shear connection are not complete; (2) under the single-point ( two-point symmetric) loading on the midspan with a shear-span ratio of less than 7.5 (7) , the flexural bearing capacity of section is more sufficient than the shear bearing capacity, so the shear failure of specimens occurs; (3) when the shear span ratio is between 7.5(7) and 10(9) , neither the flexural bearing capacity of section nor the shear bearing capacity is sufficient, so the bending shear failure of specimens occurs; and (4) when the shear span ratio is more than 10(9) , the flexural bearing capacity of section is more insufficient than the shear bearing capacity, so the bending failure of specimens occurs.
    Wu Kai Xue Jian-yang Zhao Hong-tie
    2015, 43(7):  75-83.  doi:10.3969/j.issn.1000-565X.2015.07.011
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    Steel reinforced concrete-reinforced concrete (SRC-RC) vertical hybrid structure is a special form with steel-reinforced concrete (SRC) columns in bottom floors and reinforced concrete (RC) columns in upper floors. SRC-RC transfer columns in the special hybrid structure are used to link the SRC columns below and the RC columns above. As shape steel partially exists in SRC-RC transfer columns, the cooperation problem between the shape steel and the concrete is serious, which causes SRC-RC transfer columns to fail in special patterns. In the investigation, by the low-cycle reversed loading experiments of sixteen SRC-RC transfer columns and one reinforced concrete column, the cooperation between the shape steel and the concrete is discussed and a mechanics model is constructed. The results show that (1) the proposed mechanics model can preferably illuminate the transmission of internal force between the shape steel and the concrete and can be used to analyze the failure mechanism of SRC-RC transfer columns; (2) with the increase of the ratio of shape steel area to section area, the shape steel bears more shear force and the damage of the concrete is more serious during the whole loading process; and (3) for some specimens, doubling the amount of stirrup at the area where shape steel is discontinuous or doubling the amount of stirrup all over the column both can obtain a better effect, and the increment of stirrup can relieve the partially- existed adverse effect of shape steel effectively; and (4) diminishing the ratio of shape steel area to section area helps improve the hysteretic performance and deformation ability of specimens.
    Lei Zhen Qu Jun-tong Wang Yong
    2015, 43(7):  84-91.  doi:10.3969/j.issn.1000-565X.2015.07.012
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    An experiment on three 1:2 scaled reinforced concrete-brick composite walls with opening was conducted to evaluate the seismic performance of severely-damaged low-strength composite walls strengthened by fiber-reinforced polymer (FRP). By a pre-damage experiment simulating earthquake and the low-cycle reversed loading experiments with no strengthening, strengthening by using fibers and rehabilitating the specimen after pre-damage,  the specimens were compared in terms of experimental phenomena, cracking load, ultimate bearing load and displacement, hysteretic curves, energy dissipation capacity, bearing capacity, stiffness degradation, deformation recovery capacity and FRP strain. The results show that (1) FRP-strengthened walls exhibit the shear-flexural failure mode, which is superior to the shear-dominant failure mode of the specimen without strengthening; (2) FRP strengthening can improve the seismic performance of the composite walls significantly, but not for the initial cracking load; and (3) the seismic performance of the damaged composite masonry walls strengthened with BFRP can recover or even exceed that of the specimen without strengthening.
    Zha Xiao-xiong Zuo Yang Liu Le Wang Xin-jie
    2015, 43(7):  92-99.  doi:10.3969/j.issn.1000-565X.2015.07.013
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    Aiming at the widely-used multilayer container buildings, a new sliding isolation system is proposed on the basis of the friction energy dissipation between containers. Firstly, a sliding isolation structure model is constructed, and a relationship between the equivalent damping ratio and the friction coefficient of each layer of layerupon- layer sliding isolation structure is derived through the random vibration theory. Then, a six-layer container model are constructed on the basis of the nonlinear finite element software Abaqus, and the elasto-plastic nonlinear time history of dynamic response for strong earthquake is investigated on an isolated structure, a non-isolated structure of ordinary damping ratio and a non-isolated structure of equivalent damping ratio. Finally, the relative structure indexes, such as the top displacement, the angular displacement between structural layers and the slip between structural layers, are analyzed. The results show that (1) the proposed sliding isolation system can reduce the maximum displacement of each structural layer effectively; (2) the isolated structure and the non-isolated structure with equivalent damping ratio have much smaller maximum angular displacement between structural layers than the non-isolated structure with specification damping ratio does; and (3) the spectral characteristics of seismic waves can affect the dynamic response of layer-upon-layer sliding isolation structures significantly.
    Bian Yu Ma Yuan Yu Da-xing
    2015, 43(7):  100-105.  doi:10.3969/j.issn.1000-565X.2015.07.014
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    In this paper, by combining the method of observing the sky luminance distribution in a given area and the structure of reference sky model, a calculation model named as CSRS (China South Reference Sky Model) is constructed and then verified by a measurement in model classroom. Then, on the condition of summer climate of South China and by taking a classroom with side-window as the research objective, a daylight optimization design procedure is proposed on the basis of CSRS model. Finally, an optimized daylight scheme is designed for this case, and corresponding quantization parameters and daylight performance are analyzed. The results show that CSRS model is more accurate than CIE model in the building daylight analysis
    Liu Jin-ping Lu Zhi-tao Liu Xue-feng Xing Kong-zu Mai Yue-bang
    2015, 43(7):  106-117.  doi:10.3969/j.issn.1000-565X.2015.07.015
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    Proposed in this paper is an evaluation method of energy consumption suboptimization with chilled water pump group, and according to this evaluation method, an optimized random step optimization method is used to optimize the design of the model in pumps group. Then, the influences of control pressure difference and rated flow on annual energy consumption characteristics are analyzed by an example, and different frequency conversion control modes are compared. The results show that (1) the optimized random step optimization method performs better in coping with locally-optimal and convergent problems than traditional optimization methods do; (2) the annual total energy consumption differences caused by different load rate distribution can reach more than 50%, so the annual load distribution must be taken into account in the energy consumption evaluation of system; (3) the system of bigger bypass pressure and lower rated flow has wider low and middle energy regions, its energy consumption under different load rate limits is far away from the lowest energy consumption and the corresponding energy consumption evaluation is more tolerant; and (4) in most cases, adopting synchronous frequency conversion control becomes advantageous with the increase of flow or control bypass pressure rating.
    Mechanical Engineering
    Li Jing-rong Su Hang-peng Huang Zhong-dong Wang Qing-hui
    2015, 43(7):  118-123,129.  doi:10.3969/j.issn.1000-565X.2015.07.016
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    Under the condition of three types of basic mechanical fits, namely clearance fit, interference fit and transition fit, the offset resistance and the ongoing resistance in assembly process are investigated on the basis of physical constraints of actual assembly and the characteristics of virtual assembly. Then, a one-point force feedback model is constructed to describe the resistances. Finally, the examples and the evaluation experiments prove that the proposed model can enhance the immersion of users in virtual environment and can effectively help users identify different mechanical fits according to force feedback perception.
    Mo Hai-jun Lin Zhi-sheng
    2015, 43(7):  124-129.  doi:10.3969/j.issn.1000-565X.2015.07.017
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    On the basis of the force screw theory, the relationship between the grasp matrix of multi-fingered dexterous hand and the external force screw is established to investigate the ability of multi-fingered dexterous hand to grasp an explosive. Firstly, a mechanical model of multi-fingered dexterous hand which can grasp an explosive is constructed and the parameters influencing the grasp are determined. Then, with the maximum grasp being the goal, a mathematical model of the grasp is constructed under the constraint of force closure. Finally, through the neural network and optimization methods, the multi-fingered dexterous hand grasping an explosive is simulated, so as to reveal corresponding the relationship between the grasp position and the explosive weight. Thus, the best grasp position is obtained.
    Liao Gao-hua Lai Xin Wu Jian-zhong
    2015, 43(7):  130-135.  doi:10.3969/j.issn.1000-565X.2015.07.018
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    In order to solve the coupling problem of multi-hammer excitation, firstly, a dynamic model of two vibration hammers is constructed and a mathematical equation of system is deduced by means of the Lagrangian method. Next, the energy distribution during the electromechanical coupling process is solved through the energy distribution method, the coupling laws of the excitation system in each frequency range are discussed, and the conditions of system vibration synchronization are deduced on the basis of the Hamilton principle. Thus, the stable region of phase difference is obtained. Then, a synchronous control system for multi-Hammer excitation is established to investigate the synchronous control with coupling, and a control mode on the basis of the speed regulation of adjacent deviation coupling and the dynamic phase regulation of virtual master bang-bang is proposed. Finally, both the theoretical analysis and the proposed control mode are verified by tests. The results show that (1) the coupling energy of resonance points do not affect the phase difference; (2) the phase difference tends to be zero in a low frequency range, ±π/2 in the region close to resonance and ±π in the super-harmonic resonance region; and (3) the proposed control mode achieves a good system synchronization effect.
    Tang He-sheng Li Jing Yin Yao-bao
    2015, 43(7):  136-141,146.  doi:10.3969/j.issn.1000-565X.2015.07.019
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    A thermodynamic lumped parameter model for oil film in slipper pair clearance of axial piston pump is constructed by means of the control volume method on the basis of the law of conservation of energy, and the instantaneous temperature of oil film is thus solved. The results show that the shaft work losses of slipper pair are positively correlated with the piston chamber pressure and the cylinder speed, and the losses are converted into heat energy; and that, the increase of internal energy of oil causes oil temperature to rise and changes the heat transfer rate between slipper pair and oil film. In addition, the multi-element complex brass is selected as the material of slipper, because it has a high thermal conductivity and a low thermal resistance, which results in good heat dissipation and excellent wear resistance.
    Wang Zhi-qiong Shen Gui-xiang Zhang Ying-zhi Gu Dong-wei Zhang Li-min
    2015, 43(7):  142-146.  doi:10.3969/j.issn.1000-565X.2015.07.020
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    In the risk priority number (RPN) analysis, each evaluation index weight is the same, and it is impossible to conduct risk ranking for the same RPN value. In view of the above issues, the data envelopment analysis (DEA) and the risk priority number analysis are combined to analyze the failure mode risks of clamping and releasing tools. This method can increase the distinction of RPN, objectively search the failure mode ranking method and determine the risk grades of various failure modes of clamping and releasing tools. Therefore, it is beneficial for the designer to preferentially handle the most dangerous failure mode and can provide a basis for realizing the reliability allocation of function parts and improving the reliability of clamping and releasing tools.
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