2016 Vol.36(2)

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2016, 36(2): 0-0.
[Abstract](69) [PDF 875KB](1)
Preparation and Properties of Nb/Nb-Si Micro-laminated Composites
Rende MU, Zaoyu SHEN, Guanghong HUANG
2016, 36(2): 1-6. doi: 10.11868/j.issn.1005-5053.2016.2.001
[Abstract](207) [FullText HTML] (41) [PDF 4102KB](2)
Nb/Nb-Si based micro-laminated composite was prepared by ion beam assisted electron beam physical vapor deposition (EB-PVD) technology. The phase structure and composition of deposited Nb/Nb-Si composite were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The anti-oxidation property and resistance to hot gas corrosion of the specimens were evaluated and the influence factors were analyzed. The results show that the phase structure of deposited composite is mainly composed of cubic Nb and tetragonal Nb5Si3 phases. The oxidation resistance meets the state aviation industry standards under 1150℃ isothermal conditions. The average corrosion rate of specimens is 0.517 g/(m2·h) after 100 h test at 900℃. The improvement of anti-oxidation property and resistance to hot gas corrosion is possibly related to Cr and Ti doping.
Dielectric Properties of Double Layer Coating Composite Materials
Xiaoming ZHAO, Yuanjun LIU
2016, 36(2): 7-13. doi: 10.11868/j.issn.1005-5053.2016.2.002
[Abstract](246) [FullText HTML] (61) [PDF 1228KB](3)
Two kinds of flexible composite were prepared by applying double layer coating, which consists of epoxy and ferrite/silicon carbide and silicon carbide/graphite as absorbing materials, on the polyester woven fabric. The influence of the content of absorbing reagent on permittivity's real part of dielectric constant, permittivity's imaginary part and loss tangent of dielectric constant of the composites were discussed. Since the material is usually used in the engineering field, so the mechanical properties were tested. The results show that the composites have good dielectric properties and certain mechanical properties at low frequencies.
Forming Mechanisms and Tribological Properties of FeAlCrBSiNb Amorphous Coating Deposited by High Velocity Arc Spaying
2016, 36(2): 14-20. doi: 10.11868/j.issn.1005-5053.2016.2.003
[Abstract](257) [FullText HTML] (30) [PDF 12616KB](1)
A new FeAlCrBSiNb cored wire was designed to prepare coating by high velocity arc spraying on 45 steel.Phase composition and microtructure of FeAlCrBSiNb coatings were characterized by SEM, XRD and TEM.The formation mechanism of the amorphous coating was discussed.Then the wear behavior and mechanical properties of the coating were investigated by ring-block tribometer, universal testing machine and microhardness tester.The results show that the coating consists of amorphous, α-Fe, (Fe, Cr), Fe3Al microcrystalline phase, and the volume fraction of amorphous phase is 91.3%.The coating has very compact structure with low porosity of 2%.The average microhardness of the coating can reach approximately 850 HV0.1, which is 4 times of that of 45 steel.Wear resistance of the coating is excellent, which is 5 times of that of 45 steel under dry friction condition.The main wear mechanism is brittle flaking-off.
In-situ Synthesizing Al-Cr/Al Composites Assisted by High-energy Ultrasound
Qiulin WANG, Jinbo ZHU, Rutao XU, Xinhong GAO, Yong LI
2016, 36(2): 21-27. doi: 10.11868/j.issn.1005-5053.2016.2.004
[Abstract](177) [FullText HTML] (51) [PDF 9577KB](2)
Al-Cr/Al Composites were fabricated in-situ through casting technology aided by high-energy ultrasound. The size, morphology and distribution of the reinforcement particles were observed through SEM. The reinforcement phase was characterized by XRD, EDS, and the hardness of the composite was tested with hardness tester. The results show that the inter-metallic reinforced particles with polygon shape are distributed uniformly in aluminum matrix. The size of reinforced particles is smaller than that in composite fabricated by conventional casting technology. Firstly, inter-metallic Al0.983Cr0.017 is generated through in-situ reaction of Al and Cr. Then, with the increase of Cr content, high-chromium compound is generated. And with the increase of temperature, more stable compounds with better performance are generated. These inter-metallic compounds are diffused and eventually a homogeneous mixed reinforcement phase with a fixed atomic ratio of Al and Cr is formed. The hardness of the composite increases with the increase of Cr content, but a peak value appears with the increase of Cr particle size. When the Cr content is 10% and the particle size is 75 μm, the hardness of the composite is 2.5 times higher than that of matrix.
Microstructure of Surface Layer of 40CrNi2Si2MoVA Steel after Shot-peening
Tianqi LIU, Chunzhi LI, Wei SHENG, Qiang WANG
2016, 36(2): 28-32. doi: 10.11868/j.issn.1005-5053.2016.2.005
[Abstract](176) [FullText HTML] (34) [PDF 7648KB](1)
A strengthen layer can be formed on the surface of metal materials via shot peening strengthening, and the fatigue life of component could be prolong substantially. Shot peening is an important method to construct the surface integrity of metal component. In order to investigate the strengthening mechanism of 40CrNi2Si2MoVA steel, the microstructure of 40CrNi2Si2MoVA steel with shot peening has been studied using high-resolution electron microscope (HREM). The experimental results show that the microstructure of surface layer of 40CrNi2Si2MoVA steel is refined after shot peening, and the martensite "effective grain" phenomenon can be observed clearly.The sizes of the "effective grain" are from several to tens of nanometers, and the interface between "effective grains" shows twisting phenomenon apparently. The twisting angles between "effective grains" are from several to tens of degrees, and the largest angle reaches 30°.
Reverse Pulsed Electrodeposition of Chromium Coating from Cr3+ Bath
Bei LI, Jingyin FEI, Yan ZHANG, Feifan ZHAO, Qiuyan PENG
2016, 36(2): 33-39. doi: 10.11868/j.issn.1005-5053.2016.2.006
[Abstract](221) [FullText HTML] (51) [PDF 7246KB](1)
The electrodeposition of chromium coating deposited from Cr3+ bath was investigated by means of pulse-plating technique with square wave current containing reverse pulse. The surface morphologies of chromium deposits were examined using scanning electron microscope (SEM). The relationships between current efficiency and pulse parameters were explored. Results show that the average current density, reverse current, frequency, and duty ratio have great impacts on the microstructure of the coating and current efficiency. Compared with the direct current (DC) plating, the grain size and surface appearance of chromium deposits are improved significantly by reverse pulsed electrodeposition.
Effect of Filler Systems on Properties of Fluororubber Vulcanized by Peroxide
Shan WANG, Zhengtao SU, Yanfen ZHAO
2016, 36(2): 40-45. doi: 10.11868/j.issn.1005-5053.2016.2.007
[Abstract](1356) [FullText HTML] (172) [PDF 2049KB](2)
The effect of nano inorganic filler systems on curability, mechanical property, thermal aging property, thermal conductivity and thermal stability of peroxide vulcanization of fluororubber was investigated. The results show that T90 of fluororubbers is delayed with the addition of different morphology of carbon nano-materials compared with BaSO4, BN and R930. The mechanical property and reinforcing efficiency of fluoroelastomer filled by CNTs, graphite and N990 are increased more than the others, when all the vulcanized rubbers possesse the same hardness. CNTs shows the best reinforcing efficiency. Inorganic filler CNTs can increase the tear strength, but it can also result in a higher compression set. Thermal aging property and compression set resistance of fluororubber filled with Graphite and N990 have better performance. Compression set of fluororubber is minimum with the addition of rutile type TiO2(R930). Graphite and BN are benefit to thermal conductivity. Fluororubber with BaSO4 possesses the highest decomposition temperature and the smallest mass loss.
Aging Effects on Mechanical Characterization of NR1151 Natural Rubber
Zuqun DING, Ping'an HOU, Yalan MIN
2016, 36(2): 46-50. doi: 10.11868/j.issn.1005-5053.2016.2.008
[Abstract](201) [FullText HTML] (34) [PDF 829KB](1)
The aging effects on mechanical performance of natural rubber were studied. The samples were aged in three different ways: thermal aging, thermal aging under stress and high-low temperature cycling aging. The hardness, degree of cross linking, retention ratio of elongation at break and tensile strength of the aged samples were measured. The results show that the elongation at break and tensile strength is decreased with the increase of aging time and temperature. The stress has an accelerating effect on aging when the temperature is 90℃.The aging rate is relatively lower in the high-low temperature cycling aging experiment, and the shorter the cycle period is, the lower the aging rate is.
Study on 4211 Epoxy Resin System
Peigang WEN, Lianwang ZHANG, Xiangyu ZHONG, Jianwen BAO
2016, 36(2): 51-55. doi: 10.11868/j.issn.1005-5053.2016.2.009
[Abstract](190) [FullText HTML] (49) [PDF 1373KB](3)
The chemical and physical properties of 4211 epoxy resin system usually used as the matrix of composites were studied in detail. Cure reaction characteristics of 4211 epoxy resin were tested using differential scanning calorimeter (DSC), and the processing characteristics of epoxy resin system were analyzed by rheometer. The glass transition temperature of 4211 epoxy resin cured by different heat treatments was studied by dynamic thermal mechanical analysis (DMA). The mechanical properties of this resin system were tested by mechanical testing machine. The results demonstrate that 4211 epoxy resin is suitable for the preparation of prepreg. The cured 4211 epoxy resin exhibits high glass transition temperature with the characteristics of rigidness and brittleness, which has elongation of 1.1% at break. Therefore, the 4211 epoxy resin system is in good agreement with high modulous M40 carbon fiber.
Numerical Study on Crashworthiness of Aluminum-Composite Square Hybrid Tubes
Xiaonan LI, Haolei MOU, Jian ZHOU, Tianchun ZOU, Jiang XIE
2016, 36(2): 56-64. doi: 10.11868/j.issn.1005-5053.2016.2.010
[Abstract](233) [FullText HTML] (41) [PDF 1882KB](2)
The finite element method was used to perform numerical investigation on crashworthiness and energy-absorbing characteristics based on the dynamic axial crushing results of aluminum-composite square hybrid tubes. The finite element mode of double shell elements of aluminum-composite hybrid tubes was built to obtain the failure modes and loading-displacement curves, and verified by comparing with the quasi-static crushing test results. The influences of triggers and composite ply angles on energy-absorbing characteristics of aluminum-composite hybrid tubes were studied based on the verified models. The results show that the energy-absorbing characteristics can be effectively improved by setting the hole triggers mechanism compared with the case of 45° outer chamfer; the energy-absorbing capacity improves with the increase of composite ply angles.
Strength Prediction of Primary Load-bearing Composite Joint
Xing LI, Shaohua JI, Tian ZHANG, Chuanjun LIU
2016, 36(2): 65-73. doi: 10.11868/j.issn.1005-5053.2016.2.011
[Abstract](346) [FullText HTML] (63) [PDF 3063KB](2)
Failure process of a primary load-bearing composite joint in wing root was analyzed by finite element methods, and the ultimate strength of the joint was predicted. Firstly the specimen configuration, test method and test process were described, then the bolt modeling technique and bearing/bypass coupling failure criteria were introduced, finally the predicted strain response and bolt load distribution were compared with experimental results. In the respect of nonlinear analysis, the influence of contact, geometry nonlinear and bolt nonlinear deformation were discussed. In the respect of modeling technique, the influence of bolt stiffness calculation formula, bolt modeling method, temperature and mesh density were investigated. The research shows that material nonlinearity has the most significant influence on the simulation, predicting bolt using CBUSH element and calculating bolt stiffness using Huth formula can obtain the most accurate predicted ultimate strength, mesh density and temperature have small influence on simulated result. The research can provide a reference for engineering strength prediction of composite joints, and offer a quantitative concept of the various influence factors.
Numerical Simulation of Fatigue Crack Initiation Using Crystallographic Constitutive Equation
Junqing LIU, Meng LI, Fan ZUO, Hong LIU, Shuwen CAO
2016, 36(2): 74-79. doi: 10.11868/j.issn.1005-5053.2016.2.012
[Abstract](226) [FullText HTML] (62) [PDF 1119KB](4)
At the early stage of fatigue loading, short crack initiated and then macro crack nucleation appeared on crystal scale in materials. In order to study the development of fatigue crack, the Voronoi finite element model of multi crystal grains was established by Monte Carlo method; crystallographic constitutive equation was programmed with the finite element model based on the user subroutine in ANSYS Usermat, a correction of the computer simulation method which mainly considered tension stiffening effect for fatigue crack initiation was developed. With the consideration of the dislocation dipole model suggested by TANAKA and MURA, fatigue crack initiation of multi crystal grains was simulated. A comparison with currently collected data shows that the corrected method was more consisted with test results and macro phenomenon.
DFR Method and Structural Detail Effect Based on Gerber Model
Junling FAN
2016, 36(2): 80-86. doi: 10.11868/j.issn.1005-5053.2016.2.013
[Abstract](174) [FullText HTML] (34) [PDF 1417KB](3)
During the actual engineering application, it is conservative and costly to estimate the detail fatigue rating (DFR) of structures by using the Goodman model.A calculation formula based on the Gerber model was derived to estimate the DFR value (stress ratio R=0.06), and a detail effect coefficient was introduced to analyze the influence of more details on the confidence coefficient and estimated DFR value. Through the comparison with the existed results, it is found that the developed method for the DFR value estimation based on the Gerber model can extent the material potential and reduce the development cost greatly. Finally, according to the detail rating coefficient of the component, the DFR values of structures with more details are estimated by use of the DFR values of structures with single detail. The comparison between the estimated results and the testing results has validated the correctness and applicability of the derived DFR method based on the Gerber model.
Development of Thermal Insulation Materials Technology for Spacesuit
Donghui YANG, Meng LI, Kun SHANG
2016, 36(2): 87-96. doi: 10.11868/j.issn.1005-5053.2016.2.014
[Abstract](244) [FullText HTML] (63) [PDF 917KB](6)
To clarify the development trend of the passive thermal protection technology for future spacesuits, considering the technical status of the thermal insulating materials (TIM) for low earth orbit spacesuit and the design requirements for advanced spacesuits, research on the TIM for advanced spacesuits is reviewed. Multi-layer insulation has performed best so far in the high vacuum environment of low earth orbit or moon, which still needs to be optimized for spacesuit mobility and space environmental adaptability. Fibrous material has lots of traditional advantages in the thermal insulating application of spacesuits; however, it cannot achieve the goal of thermal conductivity and material thickness in low vacuum environment during the deep space exploration such as Mars mission. Aerogel material has lower thermal conductivity and performs best in the atmosphere of Mars, but the problems of dust control and mechanical durability cannot be avoided. Studying the fibrous types with finer dimension and special porous structures, developing the organic aerogel material with excellent flexibility and durability, and trying the composite application of materials with different technological advantages, which can be the possible methods to deal with the issue of thermal insulation for advanced spacesuits in future.

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