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Table of Content

    25 July 2012, Volume 40 Issue 7
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    Traffic & Transportation Engineering
    Application Performance-Based Design of Epoxy Asphalt Concrete Applied to Steel Bridge Deck Pavement
    Zhang Xiao-ning Zhang Shun-xian Xu Wei Huang Zhi-yong Wu Wen-liang Yuan Miao-miao
    2012, 40(7):  1-7. 
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    In order to solve the problems existing in the application of epoxy asphalt concrete to steel bridge deck pavement,the shortcomings of the existing design theories and methods are analyzed,and the improved CAVF method is used to increase the skid resistance of the concrete. Then,based on the fracture mechanics and the energy method,the impact toughness is proposed as an evaluation index of the fatigue properties of epoxy asphalt concrete,and the residual stiffness modulus ratio is employed to reflect the fatigue properties. Moreover,the relationship between the
    impact toughness and the residual stiffness modulus ratio is revealed by tests. The results show that the skid resistance of the epoxy asphalt concrete designed by the CAVF method significantly improves,that there exists a good linear relation between the impact toughness and the fatigue properties,and that the impact toughness can be used to effectively evaluate the fatigue properties of epoxy asphalt concrete.

    Probability Analysis of Shrinkage and Creep Effect of Prestressed Concrete Cable-Stayed Bridges
    Su Cheng Chen Zhao-shuan Xu Yu-feng Pang Jian
    2012, 40(7):  8-14. 
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    As the commonly-used stochastic analysis methods such as the perturbation stochastic finite element method and the Monte Carlo method are inapplicable in analyzing the random shrinkage and creep effect of the prestressed cable-stayed concrete bridge subjected to a large number of uncertain factors,a response surface-Monte Carlo method ( RSMCM) that combines the response surface fitting and the Monte Carlo simulation is proposed. By the RSMCM,the standard deviation of the shrinkage and creep effect varying with each parameter is obtained,and the corresponding significance of each parameter to the effect is evaluated. Then,by introducing the concept of interval estimation,the confidence intervals of the shrinkage and creep effect corresponding to different confidence degrees are determined based on the stochastic analysis. The proposed method has been applied to the newly-built Ganzhuxi Bridge on the South Circular Highway in Guangzhou,China,with its feasibility being verified.

    Three-Dimension Virtual Uniaxial Creep Test of Asphalt Mixture by Using Discrete Element Method
    Zhang De-yu Huang Xiao-ming Gao Ying
    2012, 40(7):  15-20. 
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    In order to investigate the permanent deformation behavior of asphalt mixture considering its discontinuous feature,first,a three-dimension ( 3D) virtual uniaxial creep test of asphalt mixture was developed by the discrete element method ( DEM) . Next,a 3D discrete element ( DE) virtual specimen composed of coarse aggregates,asphalt mastic and air voids was generated,and the corresponding micromechanical models describing the
    interactions of micro-scale components of the virtual specimen were assigned. Then,an approach was presented based on the time-temperature superposition ( TTS) principle to optimize the computation efficiency of the virtual test. Finally,the results of 3D virtual test were compared with those of the two-dimension ( 2D) test and the laboratory measurements. It is found that the introduction of the TTS principle in DE viscoelastic model significantly reduces the computation time,that the 3D virtual test results almost accord with the measurement ones,and that the 2D virtual test results are greater than the 3D and the measurement ones,with their difference increasing with the load.

    Simulation of Fracture Process of Asphalt Mixture Using Three-Dimension Discrete Element Method
    Chen Jun Huang Xiao-ming
    2012, 40(7):  21-26. 
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    In order to reveal the fracture mechanism of asphalt concrete ( AC) from the viewpoint of microstructure,first,the irregular three-dimension ( 3D) shape of coarse aggregate particles was described with overlapping spheres,and a 3D discrete element model of a small AC beam specimen was established by using the Fish language provided in the finite element software PFC3D,the random aggregate packing algorithm and the generation method of air voids. Next,the micro-parameters for the discrete element simulation were obtained according to the test results of uniaxial compression and splitting,with the relationship between the macro and the micro mechanical parameters being also considered. Then,the midpoint-bending fracture test of a user-defined 3D AC beam at －10 and 15℃ was simulated with PFC3D and the corresponding fracture curves were obtained. Finally,AC beams with their asphalt dosage,porosity and gradation similar to those of the AC model were frabricated,and some practical
    fracture curves were obtained in laboratory. The results indicate that the established discrete element model fully considers the irregular shape,the gradation and the porosity of aggregate,so that it is capable of simulating the initiation and propagation of cracks during the bending fracture with high accuracy,and that the 3D discrete elementbased simulation can be used as a supplemental tool to evaluate the fracture properties of asphalt mixture.

    Active Multi-Layer Perimeter Control Strategy of Oversaturated Traffic Networks
    Li Yi-shun Xu Jian-min Wang Lin-hong
    2012, 40(7):  27-32. 
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    In order to prevent the oversaturated network from queue spillback,the oversaturated correlation degree of neighboring intersections is defined and the process of determining the initial congestion area is proposed. Then,a multi-layer perimeter control strategy,which takes the key intersection with excessive traffic demand as the center,is established. With this strategy,the control perimeter can be dynamically determined and the vehicles are
    limited in the multi-layer perimeter links when the traffic demand exceeds the network capacity. The results show that,as compared with the single-layer perimeter control strategy,the proposed strategy is more feasible because it fully uses the storage capacity of links in the oversaturated area, avoids the queue spillback of perimeter links,reduces the congestion coverage,and effectively decreases the stop delay and frequency.

    Semi-Quantitative Evaluation of Level of Service for Pedestrians
    2012, 40(7):  33-40. 
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    In order to scientifically and reasonably calculate the level of service ( LOS) for pedestrians at intersections,the quantitative reasoning method is combined with the discretization theory of class-related continuous attributes to explore the methods for establishing a semi-quantitative evaluation-index calculation model and a grading standard of LOS in fully-mixed and uncertain traffic environments. Then,by taking a signalized intersection in Beijing,China as an example,the establishment process of LOS evaluation system at the signalized intersection in mixed traffic situation is determined based on the proposed semi-quantitative method,and the corresponding semiquantitative model and grading standard of LOS evaluation indexes are obtained,which are proved simple and scientific in evaluating the LOS for pedestrians at intersections.

    Forecast of Injury Number Due to Traffic Accident Based on Ordered Probit Model
    Zong Fang Xu Hong-guo Zhang Hui-yong
    2012, 40(7):  41-45,56. 
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    In this paper,first,a forecast model of injury number due to traffic accident is established based on the Ordered Probit method and is calibrated via the maximum likelihood estimation. Then,the factors affecting the number of injuries are analyzed and the marginal contribution of each factor to the number of injuries is calculated. Moreover,a forecast of injury number is carried out with the proposed model. The results indicate that the major
    factors impacting the number of injuries are whether the surface of the road is dry,a bus or truck involved or not,and whether it happened at an intersection. The proposed model can be used to forecast the number of injuries in an accident and analyze the influence orientation and severity of each factor on the independent variable. The study provides decision-making supports for traffic management departments in terms of accident severity determination and fast accident response.

    Factors Influencing Injury Risk and Submarining Tendency of Child Occupant
    Tang Liang Wu Tao-tao Zhou Qing Deng Bin
    2012, 40(7):  46-50. 
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    In this paper,a trolley-crash simulation model of child restraint system,which includes a booster seat,an adult seatbelt system,a vehicle rear seat and a child dummy model,is established based on the multi-rigid-body dynamics software MADYMO. Then,the effects of load limiter and pretensioner of the adult seatbelt system on the impact response and the injury value of child occupant are investigated. The results indicate that the retractor
    pretensioner effectively reduces the injury value and the submarining risk of child occupant,while an anchor pretensioner alone may increase the submarining tendency,but an anchor pretensioner combined with an one-way locking tongue can reduce the submarining tendency,that the 4.0kN retractor-type load limiter widely applied in adult injury reduction has no obvious effect on the protection of child occupant,and a lower load level of the adult load limiter provides the best protection for child occupant.

    Mechanical Engineering
    Numerical Analysis of Influence of Solid Particles on Elastohydrodynamic Line Contacts Under Grease Lubrication
    Xie Xiao-peng Peng Chao-lin Chen Shu-lin
    2012, 40(7):  51-56. 
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    A model of elastohydrodynamic line contacts under grease lubrication with solid particles is established,and the corresponding lubrication equations are deduced. Then,the film pressure and thickness affected by the coordinate,dimension and velocity of solid particles are numerically analyzed and are compared with those without solid particles. Numerical analysis results show that the presence of solid particles has a certain influence on the
    film pressure and thickness,that sphere solid particles significantly influence the film pressure and thickness,especially the radius of sphere particles,and that flake-shape solid particles only have slight influence on the film pressure and thickness.

    Optimization of Block-Type Cold Forging Process Based on Forming Procedure
    Huang Zhen-yuan Zhang Xian Guo Lei Ruan Feng
    2012, 40(7):  57-61. 
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    Due to the great complexity of the block-type cold forging process,it is difficult to obtain the best forging parameters by optimizing the metal filling ability and the forming force only at a process stage. In order to solve this problem.a multi-objective optimization method based on the forming process is put forward. In this method,the finite element simulation and the orthogonal test are combined to achieve the best metal filling ability at the basic
    forming stage. Thus,the metal filling ability is optimized and a set of relevant process parameters is obtained. Then,the fitting optimization method based on objective function values is employed to analyze the relationship between the flash slots height and the drop quantity of punch. Thus,the forming force is optimized through controlling the flash slots height to achieve the minimum forming force at the last filling stage,and a set of optimum process parameters that simultaneously ensures the best metal filling ability and the minimum forming force is determined. Through the above-mentioned statements,the metal filing ability and the forming force are optimized at different stages,and the optimized results accord well with the physical experimental ones. It is demonstrated that,as the proposed method fully considers the forming characteristics of the block-type cold forging,it helps to obtain more accurate and reasonable forging parameters with simplicity.

    Investigation into Key Technologies of Numerical Simulation of Whole Process Chain During Multi-Position Progressive Stamping
    Xia Qin-xiang Wei Guang-ming Ye Fu-yuan Qiu Zun-wen
    2012, 40(7):  62-66,72. 
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    In this paper,first,a numerical model was established with UG,HyperMesh and Dynaform to simulate the strip layout of the whole 13-position progressive stamping process of automotive soleplate component parts. Next,the whole progressive stamping process was numerically simulated by using the multi-position and multiprocess method,and the forward and reverse drawing of the key positions 3 and 4 among the 13 positions was analyzed in detail. Then,the finite element model was rebuilt based on the modified shapes of blank and convex hull,by which satisfied simulation results were obtained. Finally,a progressive die with 13 positions was designed and manufactured,and a set of automotive soleplate component parts with bilateral symmetry was produced. Measured results obtained by checking fixture show that the forming quality meets the service requirements well. The designed 13-position progressive die has been used in mass production.

    Arc Stability of Shallow-Wet and Atmospheric In-Air Welding
    Shi Yong-hua Zheng Ze-pei Huang Jin
    2012, 40(7):  67-72. 
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    In order to overcome the low stability of the underwater wet welding due to the effect of water and pressure,the reciprocal of the difference coefficient of arc voltage was taken as the measurement index of arc stability,and some wet welding experiments were carried out in an underwater hyperbaric chamber. Then,according to the reciprocal of the difference coefficient as well as the voltage waveforms of the wet and the in-air welding at different
    parameters,the arc stability of shallow-wet and in-air flux-cored arc welding was quantitatively discussed. The results show that,within the range of welding parameters in the experiments,the arc stability of wet welding has a negative correlation with the current but a positive correlation with the voltage,and the CTWD value should be optimized to achieve the maximum arc stability. Moreover,it is found that the arc stability of underwater shallow-wet welding degrades with the increase of welding speed,while that of atmospheric in-air welding almost keeps unchanged,that the wet welding is of narrower range of acceptable welding parameters,and that higher welding voltage should be selected in wet welding for the purpose of improving the arc stability at constant welding current.

    Experimental Investigation into Scatter of Surface Residual Stress Caused by Turning
    Wu Bo Qin Meng-yang Ye Bang-yan He Ai-dong
    2012, 40(7):  73-77. 
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    This paper deals with the scatter of surface residual stress induced by the rough turning and the finishing turning of 45 steel under dry cutting and coolant-aided cutting conditions by using statistical methods. The results show that the scatter of surface residual stress is inevitable,that the scatter of residual stress exists even on the same machined surface,that the scatter degree of the residual stress varies with the part type and the processing conditions,that both the rough cutting and the dry cutting result in higher scatter degree respectively than the finishing and the wet cutting,and that,as the scatter of workpieces varies in a limited range,the processing and testing of workpieces can be guided with the residual stress tolerance to ensure the control accuracy of residual stress.

    Fault Identification of Bearings Based on Bispectrum Distribution of ARMA Model and FCM Method
    Xu Hong-bo Chen Guo-hua Wang Xin-hua
    2012, 40(7):  78-82,89. 
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    According to the nonlinear and non-Guassian characteristics of vibration signals of rolling bearings,a novel fault identification method based on the bispectrum distribution feature of auto-regressive moving average ( ARMA) model and on the cluster analysis of fuzzy c-means ( FCM) method is proposed. In this method,first,original vibration signals are modulated via the empirical mode decomposition ( EMD),and an ARMA model of principal
    signal components is established. Then,a bispectrum estimation of the ARMA model is implemented. Finally,the binary images extracted from the bispectrum distribution are taken as the feature vectors and are used to construct a classifier of the class templates and the smallest-distance templates via the FCM clustering,thus implementing the fault identification successfully. Application results in the fault diagnosis of rolling bearings demonstrate that the proposed method is effective because it can accurately determine the actual conditions of rolling bearings.

    Development of Ceramic Friction Pairs Applied to Large Space Manipulator Brake
    Sun Jing-ting Shi Shi-cai Wang Da Zhang Fei Chen Hong Liu Yu Liu Hong
    2012, 40(7):  83-89. 
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    In this paper,first,a model describing the brake situation of large space manipulator was established to extract an integrated design criterion of brake friction pairs according to the safety requirements of large space manipulator. Then,with the moment stability and lifetime of the brake as the indexes, the equivalent radius and the spray depth of friction pairs were calculated,and a ceramic friction pair was designed. Moreover,a prototype of ceramic
    brake and the corresponding experimental table were developed. The results indicate that it is feasible to design the brake friction pairs based on the integrated design criterion verified by the brake safety indexes.

    Comparison of Crashworthiness Optimization Methods of Steel-Aluminum Hybrid Automotive Front Rail
    Chen Ji-qing Huang Xin-hong Zhou Yun-jiao Lan Feng-chong
    2012, 40(7):  90-94. 
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    In order to solve the conflict between the peak collision force and the total absorbed energy of vehicle’s front rail during collision,a new type of steel-aluminum hybrid structure is presented,in which aluminum alloy and advanced high-strength steel ( AHSS) are respectively used for the front and the back parts. Then,by taking the material type and the sheet thickness as the variables,a mathematical model for the multi-objective optimization in
    terms of lightweight and crashworthiness is established,and the feasibility and applicability of such three approximate methods as the polynomial,the Kriging and the radial basis function ( RBF) in solving the combinational optimization problem are investigated. The results show that RBF is more suitable for the combinational optimization concerning material type and sheet thickness,and that the use of steel-aluminum hybrid materials remarkably improves the crashworthiness and lightweight of front rails.

    Control of Hybrid Power System with Split Dual-Rotor Motor
    Chen Xing Yuan Shi-hua Hu Ji-bin Peng Zeng-xiong Wei Bin
    2012, 40(7):  95-100. 
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    According to the transmission structure of system the hybrid electric vehicle with split dual-rotor motor and by taking into consideration the mechanical coupling between the primary motor and the secondary motor,the mathematical model of the split dual-rotor motor is established. Then,the speed differential and torque differential of the primary and the secondary motors are respectively controlled by using the direct torque control method. Moreover,a simulation model is established with Matlab /Simulink and the corresponding simulation is performed,and the results show that the primary and the secondary motors can achieve torque synthesis control according to the torque change of the combustion engine and the load,at the same time,the inner rotor speed of the primary motor,the secondary motor speed and the actual speed can respectively track the engine speed,the load speed and the target speed well.

    Structure of High-Power Density Thermoelectric Generator Used for Automobile
    Zhang Zheng Chen Yu-shan Xiao Guo-quan
    2012, 40(7):  101-106. 
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    Proposed in this paper is the structure of a thermoelectric generator with high power density. In the hot channel of the heat exchanger,a high-temperature part of conversion elements in cross and arc shapes is set,which enlarges the heat exchange area. In the cooling channel,centralized cooling is employed and a low-temperature part of conversion elements is installed. Moreover,hot convection is adopted in both the hot and the cooling channels. Lots of thermocouple arrays are installed in conversion elements,which connect with the parallel thin thermocouples,metal deflectors and transitional wires to form a loop that transmits heat and electric currents,and some loops are contacted to increase the output voltage. Numerical results show that the conversion elements are of uniform temperature distribution as well as low resistance,so that it improves the load characteristics of the thermoelectric generator.

    Architecture and Coordination Control of Automotive Electronic System Facing Multi-Mode Manipulation
    Zhang Xin-feng Yang Dian-ge Lian Xiao-min
    2012, 40(7):  107-112. 
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    With the continuously improvement of automotive riding comfortability,multi-mode manipulation for automotive body electronics has emerged in recent years. In this paper,first,the architecture and the coordination control method of the electronic system of automotive body facing multi-mode manipulation are proposed. Two types of system architectures,namely the modularized distribution system and the intellectualized completely-distributed system,are compared. Next,an associated subsystem is proposed to analyze the multi-mode manipulation between the implied working logics and the original logics. The symbolic logic as well as the Boolean algebra is used to describe the multi-mode control logic. Central coordination controller and a failure safety mechanism are designed. Finally,a prototype vehicle is developed and tested,from which the proposed architecture and multi-mode manipulation method are proved to be feasible.

    Materials Science & Technology
    Bending of Carbon Nanotubes Subjected to Concentrated Load and Corresponding Molecular Dynamics Simulation
    Liang Ying-jing Han Qiang
    2012, 40(7):  113-116. 
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    In this paper,the bending problem of cantilever carbon nanotubes ( CNTs) subjected to concentrated load is investigated by elastic shell model based on semi-moment theory,and the corresponding analytical expressions of the stress and the displacement are derived,which are then verified by the molecular dynamics simulation. It is found that,for both the zigzag CNTs with a length-to-diameter ratio of 5.2 ～ 12.0 and the armchair CNTs with a length-to-diameter ratio of 5.5 ～ 18.0,the theoretical results coincide well with the simulated ones.

    Stress Analysis of Laminated Composite Plates with Wavelet Finite Element Method
    Peng Hui-fen Meng Guang-wei Fan Sen Zhou Li-ming
    2012, 40(7):  117-122. 
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    In order to improve the accuracy and efficiency of numerical calculation of laminated composite plates,based on laminated composite plate theories, the element transformation matrixes of BSWI ( B-spline Wavelet on the Interval) for laminated composite plates are constructed. The tensor product of scaling functions of BSWI with the same scale but different orders is used as interpolation function; the matrixes have the characteristics of continuity
    and compatibility for node displacement,deflection and its derivatives. Based on the principle of virtual work,the BSWI element stiffness equation of laminated composite plates is derived. The relationship between deflections of nodes on diagonal OA and their distances to the center of the laminated composite plate is analyzed. The distributions of stress and strain of laminated composite plates under axial loads are also analyzed. Numerical experiments show that BSWI finite element method for stress analysis of laminated composite plates can achieve higher numerical accuracy with fewer elements and freedoms.

    Monitoring of Formation Process of Nanocomposite Hydrogels with Pyrene Fluorescence Probe
    Wang Tao Zheng Shu-dian Liu Xin-xing Fu Shi-yu Tong Zhen
    2012, 40(7):  123-127,154. 
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    Cationic pyrene fluorescence probe 1-pyrenemethylamine hydrochloride ( PyMA·HCl) was used to monitor the gelation of poly( N-isopropylacrylamide) ( PNIPAm) /hectorite Laponite nanocomposite hydrogel via the insitu polymerization. First,the adsorption of PyMA·HCl on Laponite platelets was verified with UV-Vis spectra after aggregation and centrifuge by increasing the ionic strength of Laponite suspension. The results of fluorescence
    emission of excimer show that the milky nontransparent drops appear after a 20min polymerization are related to the heterogeneous distribution of synthesized PNIPAm chains. Moreover,it is found that,as polymer chains are adsorbed around Laponite platelets and occupy part of platelet space,which shortens the distance between the fluorescence probes on Laponite platelets and results in the formation of the excimer,both the change of transmittance during the polymerization and the interaction between polymer chains and Laponite platelets can be determined according
    to fluorescence spectra. This finding provides an effective method to explore the crosslinking structure of nanocomposite hydrogels.

    Effect of Controlled Rolling and Cooling Process on Carbonitride Precipitation from X120 Pipeline Steel
    Zheng Hong-wei Tang Di Wu Hui-bin Yang Liu
    2012, 40(7):  128-134. 
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    This paper deals with the effects of such rolling parameters as the deformation in non-recrystallization region,the cooling rate and the final cooling temperature on the carbonitride precipitation from X120 pipeline steel in different controlled rolling and cooling processes,and theoretically estimates the strength contribution of precipitated phase based on the Orowan mechanism. The results show that the rolling process has no effect on the type and structure of the precipitated phase,that the increase of deformation in non-recrystallization region mainly promotes the precipitation of Nb and improves the yield strength of X120 pipeline steel,and that the cooling rate and the final cooling temperature have little influence on the precipitation of carbonitride.

    Preparation of TPEE/ACM/Nano-SiO2 Composite via Dynamic Vulcanization
    Lu Xun Lin Yan-mei Wu Shu-qing Tian Min
    2012, 40(7):  135-141. 
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    By using thermoplastic polyeher ester elastomer ( TPEE) and acrylate rubber ( ACM) as the raw materials,thermoplastic vulcanizate composites with oil and thermal resistance,namely TPEE/ACM TPVs,were prepared via a dynamic vulcanization at different nano-SiO2 dosages. Then,the dynamic mechanical property,the rheological behavior,the thermal stability,the heat-aging property and the heat oil resistance of the product were investigated
    at different TPEE /ACM ratios and nano-SiO2 dosages. The results show that TPEE /ACM TPVs with high performance can be produced when the TPEE /ACM ratio achieves 60 /40,that the processability of TPVs becomes poor with the addition of nano-SiO2,that TPVs has only one glass transition temperature that increases after the addition of nano-SiO2,that the TPVs with a nano-SiO2 dosage of 20% ( mass fraction) is of high performance,and that better heat-aging property and strong heat oil resistance may obtained when the nano-SiO2 dosage varies from 10% to 20%.

    Purification of Sodium Alginate and Preparation of Porous Calcium Alginate Scaffolds
    Liu Yang Ren Li Ji Pei-hong Wang Ying-jun
    2012, 40(7):  142-147. 
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    Sodium alginate ( AlgNa) was purified via the acetone precipitation,and the product was tested by means of FT-IR and GPC. Then,the contants of residual protein in both the unpurified and the purified samples were measured,and several three-dimension porous calcium alginate scaffolds were fabricated through such three crosslinking systems as CaCl2-AlgNa,CaSO4 /GDL-AlgNa and Ca-EDTA/GDL-AlgNa. The results indicate that the
    porous Ca-EDTA/GDL-AlgNa scaffold with a sodium alginate content of 2.5%～ 3.0% possesses uniform micropore distribution,large specific surface area and excellent mechanical behavior,which means that it is suitable for the cell culture in tissue engineering and cell engineering.

    Study on the Adsorption of Copper Ions by Epichlorohydrin-Crosslinked Chitosan /Sodium Alginate Adsorbent
    Yuan Yi-hua Lei Li He Hui Jia De-min
    2012, 40(7):  148-154. 
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    In this paper,first,a new kind of crosslinked chitosan /sodium alginate absorbent was prepared,with chitosan and sodium alginate as the raw materials and with epichlorohydrin as the crosslinking agent. Next,the structure of the product was characterized by means of FT-IR. Then,the adsorption capacity affected by the adsorption time,the pH value,the adsorption agent dosage and the crosslinking degree was investigated. Finally,the adsorption properties of the prepared absorbent were analyzed and the corresponding adsorption kinetics was discussed. The results indicate that,when 0. 10 g of absorbent is added in 100 mL of 50 mg /L Cu2+ solution at pH 4. 0 ～ 6. 0 to perform an adsorption for 120min,the adsorption capacity reaches 46. 4mg /g,that the isothermal adsorption at low or high concentration respectively accords with the Freundlich or the Langmuir equation,and that the absorption kinetics accords with the pseudo-second-order equation with good linear correlation ( r2 = 0. 9444).

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