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      20 November 2011, Volume 0 Issue 11 Previous Issue    Next Issue
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    Experimental Study on Pull-out Strength of Z-pins
    WANG Xiao-xu, CHEN Li
    2011, 0 (11): 1-4.  
    Abstract ( 242 ( PDF (377KB)( 322 Citation
    The pull-out strength of Z-pins was tested by the single Z-pin pull-out tests from the composite laminates,the critical embedded length has been calculated and tensile strength utilization ratio was introduced to characterize the utilization degree of tensile strength of Z-pins during the pull-out processes.The results show that,the critical embedded depth of the Z-pins with the diameter of 0.50mm and that of 0.28mm are 5.1mm and 3.1mm respectively.And,when the embedded depth is below the critical depth,Z-pins pull-out from the laminates and the pull-out strength of the Z-pins is proportional to the embedded depth,and is inversely proportional to the diameter.When the embedded depth is equal to or greater than the critical depth,breaks occur in the Z-pins,and the tensile strength utilization ratio of Z-pins reaches 100%.Finally,some suggestions for improving tensile strength utilization ratio of Z-pins were put forward.
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    Study of In-situ Synthesis and Properties of Ni-Zn-La Ferrite/Polyaniline Nanocomposite
    XU Xing-wen, ZHAO Hai-tao, ZHANG Gang, LI Xi-kun
    2011, 0 (11): 5-8.  
    Abstract ( 228 ( PDF (540KB)( 235 Citation
    The Ni-Zn-La ferrite/ polyaniline nanocomposite was prepared by in-situ polymerization method under the ultrasonic field.The structural characteristics,morphology and electromagnetic properties of the composites were analyzed by X-ray diffraction(XRD),scanning electron microscope(SEM) and HP8510 network analyzer,respectively.The results indicate that HCl doped polyaniline has some degree of crystallinity.There is some interaction between the Ni-Zn-La ferrite particles and polyaniline chains.The imaginary part of complex permittivity and dielectric loss tangent of the Ni-Zn-La ferrite/ polyaniline nanocomposite are higher than those of polyaniline.The real part of permittivity is less than polyaniline.The imaginary part of complex permeability and magnetic loss tangent of the Ni-Zn-La ferrite/ polyaniline nanocomposite are higher than those of polyaniline above 8.4GHz.
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    Study on Preparation and Properties of Attapulgite Reinforced Natural Rubber Nanocomposites
    ZHAO Guo-zhang, SHI Li-yi, ZHUO Jing, FENG Xin, DING Peng, FU Ji-fang
    2011, 0 (11): 9-14,79.  
    Abstract ( 260 ( PDF (1252KB)( 346 Citation
    Attapulgite(AT) reinforced natural rubber(NR) nanocomposites were prepared by mechanical compounding.The microstructures,mechanical properties and curing characteristics of the nanocomposites were investigated.The reinforcement mechanism of AT in NR was clarified.The results show that the modified AT exhibited outstanding reinforcement due to its homogeneous dispersion in the NR matrix and the strong polymer-filler interactions.AT needles not only act as crosslink points during the vulcanization,but also orient along the stretch direction and thus induce crystallization when the samples were stretched.The strain-induced crystallization of the nanocomposites is associated with the filler loading and the crosslink density on the surfaces of AT needles.Different modifiers result in different crosslinking characteristics,and affect the strain-induced crystallization and stress-stain behaviors of the nanocomposites.The layer-chain structure of AT is not influenced by the modification and mechanical compounding.
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    Study on Friction Thermal Behavior of PTFE Braided Composites Under High-speed Oscillating Conditions
    KANG Ke-jia, DU San-ming, ZHANG Yong-zhen, ZHAO Fei
    2011, 0 (11): 15-17,22.  
    Abstract ( 275 ( PDF (497KB)( 243 Citation
    The dry friction test of polytetrafluoroethene(PTFE) braided composites under high-speed Oscillating conditions has been carried out on the special high-speed tribo machine and 9Cr18Mo as counterpart,the influences and the variation rules of friction heat has been studied.Results show that friction temperature increases with the increasing of load;and the temperature decreases with increases in frequency of short duration in the initial friction stage,later increases with increased frequency,and finally reach temperature dynamic balance;the friction coefficient rises slowly in small range before a sharply reduces with the increase in time,ultimately,it maintains a relatively stable state,and has certain corresponding relationship with friction temperature;The main abrasion mechanism of friction pair is adhesive wear,and temperature is an important factor that influences friction process and the wear mechanism.
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    Numerical Simulation of Lap-shear Strength of Self-piercing Riveting Joint
    ZHONG Yi, LIN Jian, LEI Yong-ping, YIN Lan-li
    2011, 0 (11): 18-22.  
    Abstract ( 230 ( PDF (733KB)( 475 Citation
    The numerical simulation method for predicting the lap shear strength of self-piercing riveting(SPR) joint is studied.The finite element models of 0.7mm low carbon steel+0.7mm low carbon steel similar material and 0.7mm low carbon steel+2mm AA6061 dissimilar material SPR joints are established based on the experimental results.Then,considering the contact conditions between the different parts of the SPR joint,the lap shear processes of these SPR joints are simulated.It can be seen from the simulating results that the failure modes of the similar and dissimilar materials SPR joints are different: for the steel-steel similar material SPR joint,the rivet is pulled out from the joint while the failure occurs in the base metal for steel-Al dissimilar materials SPR joint.Finally,experiments of SPR joint's lap shear process are carried out to validate the simulating results.It is shown that the simulating results of SPR joint's shear strength have a good agreement with the experimental results.That suggests the developed FE model,considering the contact conditions of the materials and the joint's shape,can be used to predict the shear strength and failure mode of SPR joint.
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    Preparation of Super Thermites and Their Compatibilities with DB Propellants Components
    AN Ting, ZHAO Feng-qi, GAO Hong-xu, MA Hai-xia, HAO Hai-xia, YI Jian-hua, YANG Yong
    2011, 0 (11): 23-28,34.  
    Abstract ( 263 ( PDF (896KB)( 490 Citation
    Super thermites Al/PbO and Al/Bi2O3 were prepared by an ultrasonic dispersion method using nano-Al,nano-PbO and nano-Bi2O3 as raw materials.The physical phase,composition,morphology and structure of raw materials and products were characterized by XRD,SEM-EDS and FT-IR.The vacuum stability test(VST) and DSC were employed to evaluate the compatibilities of two kinds of super thermites with double-base propellants components.The results indicated that Al/PbO and Al/Bi2O3 had good compatibilities with nitrocellulose(NC),nitrocellulose/nitroglycerine(NC+NG) and N-nitro dihydroxy ethylamine dinitrate(DINA).The systems of super thermites with cyclotrimethylene trinitramine(RDX) and 1,3-dimethyl-1,3-diphenylurea(C2) were judged to be compatible by VST,while to be incompatible by DSC.The reasons causing different results from different methods were discussed.
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    Effects of Aluminum Honeycomb Cell Structural Parameters on Its Macro-equivalent Characteristic Properties
    LIU Ye-hua, XIE Gui-lan, CAO Wei-nan, TANG Ya-nan
    2011, 0 (11): 29-34.  
    Abstract ( 273 ( PDF (1197KB)( 299 Citation
    The micromechanical model for predicting the equivalent macroscopic characteristic parameters of aluminum honeycomb core is established based on homogenization theory combined with finite element method.The effects of the aluminum honeycomb cell structural parameters on its macroscopic equivalent characteristic properties are investigated.And by using MATLAB software,the equivalent elastic parameters of irregular orthotropic hexagonal aluminum honeycomb cores with various high-to-length ratio,thickness-to-length ratio and cell wall angle are calculated.The effects of cell structural parameters on its macroscopic equivalent mechanical properties are obtained.The results have guiding signification for the structure design of aluminum honeycomb core and its engineering application in wind turbine blades.
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    Experimental Research on Thermo-mechanical Control Process for High Strength Non-quenched and Tempered Cold Heading Steel
    CAO Jie, YAN Jun, LIU Ya-zheng, ZHANG Jing, SUN Wei, YU Tong-ren, LIU Mei-ling
    2011, 0 (11): 35-38.  
    Abstract ( 264 ( PDF (669KB)( 276 Citation
    Tests were carried out on a Gleeble-3500 simulator to simulate the low temperature rolling process for a newly developed non-quenched and tempered cold heading steel.The effects of deformation and cooling rate on microstructure transformation were analyzed.The results show that the microstructure of the steel is mainly granular bainite when the cooling rate is above 5℃/s.The matrix of the granular bainite changes from massive shape to lath shape with the increasing of cooling rate.The deformation of austenite not only promotes the nucleation and growth of ferrite,but also has an influence on the microstructure of granular bainite.Large deformation induces ferrite transformation.The hardness testing suggests that the hardness decreases with the increasing of deformation.
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    Investigation of Retained Austenite and Its Stability in Hot Rolled TRIP Steel
    GAO Xu-tao, ZHAO Ai-min, ZHAO Zheng-zhi, ZHANG Ming-ming, ZHANG Yu-guang
    2011, 0 (11): 39-43.  
    Abstract ( 956 ( PDF (870KB)( 424 Citation
    By means of X-ray diffraction(XRD),transmission electron microscopy(TEM) and tensile test,retained austenite and its carbon content and stability of hot rolled transformation-induced plasticity(TRIP) steels which were prepared through three processes was investigated.Result reveals that bainitic zone residence time has greater impact on the amount of retained austenite,the experimental steel obtained the maximum amount of retained austenite when it was coiled in the bainitic zone;the carbon content in retained austenite of the final organization will increase with the relaxation time extension;Carbon content in retained austenite,as well as retained austenite grain size,the shape and phase around retained austenite all exert an influence on stability of the retained austenite.
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    Simulation and Optimization of Heat Treatment Process for Large Press Die Holder
    FAN Meng-ting, SUN Ming-yue, LI Dian-zhong
    2011, 0 (11): 44-50.  
    Abstract ( 239 ( PDF (1450KB)( 424 Citation
    Database of thermal-physical parameters and CCT curves of 55NiCrMoV7 steel were firstly obtained by experimental study.Based on the commercial FEM software ABAQUS,the models of oil-quenching and water-quenching for a large press die holder were established separately,the temperature and stress evolution were calculated for each process.Combined with the cooling rates of each node and CCT curves of 55NiCrMoV7,the final microstructure and stress distribution on the die holder were predicted.According to the FEM results,upper bainite can be obtained in the surface layer by oil quenching,while lower bainite can be obtained under water cooling condition.However,cracks are easily generated in the inner chamfer by water quenching because of the severe stress concentration.On basis of the analysis,double quenching process was proposed to avoid crack and obtain lower bainite,the simulation results show that 30min water-cooling before oil-cooling is favorable toward safe production and optimizing the microstructure of the die holder.
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    The Influence of Crucible Graphite on the Quality of Ni47Ti44Nb9 Shape Memory Alloys During the Vacuum Induction Melting Process
    YANG Gen-lin, WANG Er-min, HAN Jin, NI Zhi-ming
    2011, 0 (11): 51-52,57.  
    Abstract ( 1690 ( PDF (406KB)( 417 Citation
    The performance of three different kinds of crucible graphite materials used during vacuum inductive melting of Ni47Ti44Nb9 shape memory alloys(SMAs) was explored.One low-density extruded graphite and two isostatically pressed graphite-materials with different porosity and purity were used for melting Ni47Ti44Nb9-SMAs from pure Ni,Ti and Nb raw materials.The use of a low grade,lower density graphite crucible led to a high carbon contamination of the alloy ingot.Much better results were obtained using graphite crucibles with higher density and higher purity.
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    Relationship Between the Dendritic Length and Width of Fusion Zone in ZL114A Casting Alloy Welding Joints by Laser-MIG Hybrid Welding
    CHEN Guo-zhu, XIA Feng, HU Yong-gang, XIAO Jian-zhong
    2011, 0 (11): 53-57.  
    Abstract ( 269 ( PDF (1303KB)( 392 Citation
    ZL114A casting alloy plate with 8mm thickness was welded by Laser-MIG hybrid welding,the size and distribution of welding joints microstructure were investigated.The results show that the dendritic length has certain correlation with the width of fusion zone in different welding joints,which obtained by different process parameters.The dentritic length can be determined when the width of fusion zone is fixed.What's more,the dendritic length shows a nearly linear decrease from top to root along the thickness direction of the welding joints.
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    Numerical Simulation of Directional Solidification Process on the Vane of Single Crystal Superalloy DD6
    XIE Hong-ji, LI Jia-rong, JIN Hai-peng, LIU Shi-zhong, XIONG Ji-chun
    2011, 0 (11): 58-61,67.  
    Abstract ( 251 ( PDF (414KB)( 335 Citation
    The three-dimensional model of the vane was built,temperature fields of DD6 single crystal vane was calculated with finite element software ProCAST.The temperature values of vane were indicated from the measurement during directional solidification.The simulated results were compared to the measured results,and the results showed that good consistency was observed and the deviation of temperatures was less than 5%.The temperature gradient of airfoil was between 25℃/cm and 45℃/cm,and the temperature gradient of platform was about 35℃/cm,and the isotherm of vane was tilted.
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    Morphological and Distribution Characteristics of Mg2Si Particles in Mg-4Al-2Si Alloy Prepared by Reciprocating Extrusion
    GUO Xue-feng, YANG Wen-peng, SONG Pei-wei
    2011, 0 (11): 62-67.  
    Abstract ( 237 ( PDF (996KB)( 323 Citation
    Microstructure of as-cast Mg-4Al-2Si(AS42) alloy was refined by reciprocating extrusion(REX),the morphologic and distribution characteristics of Mg2Si particles were investigated by employing optical microscopy,scanning electron microscopy,and transmission electron microscopy.The results show that the Mg2Si particles in as-cast AS42 alloy are in the forms of eutectic Chinese scripts and primary polyhedral particles.After 2-pass REX,all eutectic Mg2Si particles are broken and distributed uniformly.After 6-pass REX,all primary Mg2Si particles are broken and the fine Mg2Si particles are spheroidized basically.The distribution of the Mg2Si particles in the extruded alloy follows Weibull function.After 8-pass REX,the average size,uniformity and the relative density of Mg2Si particles are 1.3μm,0.7μm and 540%,respectively.
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    Study on AZ31 Magnesium Alloy Rolled Process
    ZHANG Ding-fei, XU Xing-xing, LAN Wei, DAI Qing-wei, QI Fu-gang
    2011, 0 (11): 68-73.  
    Abstract ( 261 ( PDF (1534KB)( 343 Citation
    The rolling processes of the AZ31 magnesium alloy at 400℃ were studied.And the microstructure and mechanical properties of the sheets rolled under the condition of different reduction and passes were investigated.The results show that in 410℃,when the reduction per pass of rolling is 1mm,the excellent conditions of process rolling is 8th,and the total deformation is 50%;when the reduction per pass of rolling is 2mm,2nd is the outstanding condition of process rolling and the total deformation of 25%.It is easy for AZ31 magnesium alloy under large deformation to cause the cracks,which is due to that the stress is increased intensely when the accumulated deformation is added.The stress concentration in some areas,such as the hard orientation and deformation or the second part,causes the crack.Because of the large the deformation in these regions.Moreover,the recrystallized grain size in these regions is very fine.
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    Study on Properties of Drag Reduction and Shear Stability of Ionomer Based on Laurel Metharylate
    LI Chang-yu, MU Chun-ling, CHEN Shi-wei, FANG Shu, CHEN Xiang-jun, ZHANG Chang-qiao
    2011, 0 (11): 74-79.  
    Abstract ( 209 ( PDF (571KB)( 282 Citation
    On the basis of molecular design using molecular dynamics simulation method,a new type of ionic polymer drag reduction agent(DRA) based on laurel metharylate was synthesized by emulsion polymerization.The selecting of monomer constituted the ionomer DRA and synthesis methods were discussed,and yields of the reaction were also investigated.The properties of drag reduction and shear stability were tested by a circular evaluation system and its transmission subsystem.And the hydrodynamic radiuses of polymer were also investigated by dynamic laser scattering shaped DAWN HELEOS 18.The results show that the ionomer drag reduction agent has obvious properties of drag reduction and shear stability and the drag reduction rate has a certain degree of improvement with the increase of molecular weight;the yield of polymerization change little when the reaction volume enlarged;with the increasing number of shear time,the drag reduction rate of ionomer DRA slows down.However,shear stability of the ionomer DRA performs well.
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    The Analysis in Linear Friction Welding Joint Interface Behavior of Dissimilar Titanium Alloy
    ZHANG Chuan-chen, HUANG Ji-hua, ZHANG Tian-cang, JI Ya-juan
    2011, 0 (11): 80-84.  
    Abstract ( 192 ( PDF (822KB)( 239 Citation
    The dissimilar titanium alloy TC4/TC17 was welded on a linear friction welding machine.After welding,optical microscope,SEM and TEM were used to analyze the microstructure of the welded joint.The results indicated a sound bonding interface.The microstructural features of both the weld and thermomechanically affected zone(TMAZ) are characterized for the weld.It was found that in the weld region,exposure to supertransus temperatures combined with hot-deformation working,and cooling after joining,resulted in recrystallization of the beta grain structure that had a refined needle-like structure.The recrystallization occurred in the mixture zone of the welded joint interface,and in particular,part of the microstructure equiaxed and even spheroidized.There was little dislocation in the mixture zone of the welded joint interface.The dislocation density is high in the area where the recrystallization was little.
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    Microstructure and Performance of WC-17Co Coatings Fabricated by High Velocity Oxy-fuel Spraying
    CUI Yong-jing, WANG Chang-liang, TANG Zhi-hui, ZHANG Xiao-yun
    2011, 0 (11): 85-88,96.  
    Abstract ( 278 ( PDF (984KB)( 350 Citation
    Different structural WC-17Co coatings were deposited by high velocity oxy-fuel(HVOF) spraying.The properties of the two coatings were tested,and the effect of WC size on the performance of the coatings was investigated.The results indicated that G coating,which had submicron WC particle,showed more advantages in hardness,porosity,and fracture toughness,while H coating with bigger WC particle had excellent performance in adhesive strength and corrosion resistance.Obviously,the WC particle size showed great influence to the coating properties.
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    Effects of Two-step DC Electrochemical Pretreatment Method on Diamond Coatings on Fine Grinding Cemented Carbide Surfaces
    ZHANG Xiang-hui, WANG Ling, LONG Jian-ping, ZHU Bi-wu, CHENG Wei, FENG Yan-hua
    2011, 0 (11): 89-96.  
    Abstract ( 276 ( PDF (1468KB)( 346 Citation
    Due to the fine grinding WC-Co substrate which has been polished to provide a keen/cutting edge must be pretreated before depositing CVD diamond coating.However,conventional chemical etching methods may have the drawbacks of difficulties in corrosion efficiency and process repeatability for its large-scale applications.An investigation had been carried out to study the influence of the two-step DC electrochemical pretreatment(firstly using DC electrolytic etching,and then using acid etching) on the fine grinding cemented carbide substrates and diamond coatings by means of Scanning Electron Microscope(SEM),profilometer,Atom Absorption Spectrometry(AAS),Energy dispersive X-ray diffraction analysis(EDXA) and Rockwell hardness tester respectively.The results showed that the two-step DC electrochemical pretreatment method can effectively remove the "skin" of grinding substrates surface and reduce the Co content.Through changing the electrolytic time,the relationship amongst substrate surface roughness,the substrate surface Co concentration removal and the hardness of substrate surface after Co removed are balanced,and effectively control CVD diamond coating from microcrystalline cubic-octahedron to cauliflower type nanocluster transformation process,which has a good controllability.According to the substrate/coating hardness,coating quality and coating adhesion strength testing results,optimized the best process parameters of the two-step DC electrochemical pretreatment method at fine grinding cemented carbide substrates,which firstly using DC(direct current) 1A electrolytic etching for 5 minutes in 10% sodium hydroxide(NaOH) solution,and then etched in an aqua regia(HNO3:3HCl:H2O=1:1:1) solution for 90 seconds.
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