CHEN Li, LIANG Zi-qing, MA Zhen-jie, LIU Jing-yan, LI Jia-lu. Experimental Investigation on Longitudinal Properties of 3-D 5-Directional Braided Composites[J]. Journal of Materials Engineering, 2005, 0(8): 3-6.
The longitudinal tensile and compression tests were conducted on the 3-D 5-directional braided composites with different braiding parameters. The effect of braiding parameters on the longitudinal tensile and compressive properties was discussed, and the failure mechanism of materials was investigated.The stress-strain curves showed that the longitudinal tensile and compressive properties of 3-D 5-directional braided composites were linear elastic, and had brittle fracture cha-racteristics.Tensile modulus was almost equal to compressive modulus, but the tensile strength was far higher than compressive strength. Braiding angle and fiber volume fraction had significant influence on the mechanical properties of 3-D 5-directional braided composites, but the linear density of yarns had little effect. Increasing the proportion of axial yarns could improve the longitudinal pro-perties of materials. Moreover, shot-gauge plate samples were used to avoid the buckling and end cracking.
YAN Yue, WANG Xiao-li, ZHANG Guan-li, HU Ping, LIU Hai-peng. Experimental Study on Mechanical Behavior of Polycarbonate at High Temperature[J]. Journal of Materials Engineering, 2005, 0(8): 7-9,14.
Uniaxial tensile tests for polycarbonate at high temperature were performed on the newest type of Meissner rheometer. Tests were conducted for constant strain rates varying from 0.001s-1 to 0.1s-1, at the temperature varying from 150℃ to 200℃. The results showed that the mechanical behavior of polycarbonate was obviously affected by the strain rate and temperatures,and its true stress-true strain curves exhibited nonlinear characteristics.
LUO Yu-shi, LI Jia-rong, LIU Shi-zhong, SUN Feng-li, CAO Chun-xiao. Strengthening Effect of Re on Stress Rupture Properties of Single Crystal Superalloys[J]. Journal of Materials Engineering, 2005, 0(8): 10-14.
The stress rupture properties of four batches of experimental single crystal superalloys containing various levels of Re were tested at 1100℃/140MPa,and the strengthening effects of Re on the stress rupture properties of single crystal superalloys at elevated temperature were investiga-ted. The results showed that stability of single crystal superalloys significantly influenced the strengthening effects of Re on the stress rupture properties. The stress rupture properties of single crystal superalloys were enhanced with appropriate Re addition, the stability of single crystal superalloys were depressed with superfluous Re content, therefore the strengthening effects of Re in single crystal superalloys were restrained obviously.
QU Ying-dong, CUI Cheng-song, CAO Fu-yang, CHEN Shan-ben, LI Qing-chun. Neural Network Modeling and Simulation of Characteristic Dimension of Spray Deposited Preform[J]. Journal of Materials Engineering, 2005, 0(8): 15-19.
Neural network technology was applied to establish a modeling of the characteristic dimension of spray deposited preform, which described the influence of the spray forming parameters on the deposit dimension.The relative error of the modeling output was 6.58% and the RMS(root-mean-square) was 0.372mm. The relationship between deposit characteristic dimension and processing parameters was given by simulation results of the neural network modeling, and suitable parameters were defined according to simulation results of static spray forming processes; the simulation results of dynamic spray forming processes showed both atomizing gas pressure and translating speed of substrate were important factors influencing deposit characteristic dimension. Furthermore, it was preferred that the translating speed could be adjusted in a wide range, and became more suitable and effective parameter to control deposit dimension.
SUN Rong-lu, YANG Xian-jin. Microstructure and Tribological Properties of NiCrBSi Laser Cladding on 45 Steel Substrate[J]. Journal of Materials Engineering, 2005, 0(8): 20-23,27.
Laser cladding of NiCrBSi powders on 45 steel substrate was conducted, and microstructure of the laser cladding were analyzed using EPMA, SEM and TEM. The friction and wear pro-perties of the laser cladding were examined under different atmospheric pressures. The results showed that the laser cladding could be divided into three regions, the cladding, bonding and heat affected zones. In the cladding zone (CZ), fine CrB particles and Cr7C3 dendrites were distributed in matrix of the γ-Ni dendrites and the eutectics consisting of γ-Ni and Ni3B. The bonding zone (BZ) was a mixture of melted 45 steel and Ni-base alloy, and displayed directional crystallization. The heat affected zone (HAZ) had an acicular martensitic structure. The friction and wear properties of the laser clad layer were closely related to the atmosphere pressure. When the atmosphere pressure was lowered, the friction coefficient was increased, and the wear loss of mass was reduced.
LI Zhi-jun, ZHOU Lan-zhang, GUO Jian-ting, YAO Jun. Effect of Revert Proportion on Thermal Fatigue Properties of K44 Superalloy[J]. Journal of Materials Engineering, 2005, 0(8): 24-27.
The thermal fatigue test was conducted on a new corrosion-resistant K44 superalloy with different revert proportion. The results showed that the relationship between length of main crack and thermal cycle index could be described as L=bNa for both virgin and revert alloys.The crack initiation rate and crack propagation rate of virgin alloy was the lowest.With the increase of revert proportion, the crack initiation rate and crack propagation rate increased. Thermal fatigue cracks initiated near the V-type notch tip,propagated mainly along interdendritic zones, grain boundaries or splitting carbides. The main crack grew with continual splitting of the crack tip. The high content of nitrogen and oxygen in revert alloy induced the increment of (γ+γ′) eutectics and inclusions and the agglomeration of carbides,which accordingly accelerated the initiation and propagation of the thermal fatigue crack. Oxide and γ′ depleted areas existed on both sides of thermal fatigue crack.
BAI Pei-kang, LI Ming-zhao, FANG Ming-lun, CHENG Jun. Study on Selective Laser Sintering Mechanism of Polymer-coated Stainless Steel Powder[J]. Journal of Materials Engineering, 2005, 0(8): 28-31.
A type of polymer-coated stainless steel (1Cr18Ni9Ti) powder used in selective laser sintering technology was prepared. The laser sintering experiments of polymer-coated stainless powder were conducted with selective laser sintering machine. The method of microscopic analysis was used to investigate the dynamic laser sintering process of polymer-coated stainless steel powder. Based on the study, the laser sintering mechanism models of polymer-coated stainless powder were construc-ted. It was found that the viscous flow mechanism could best describe sintering process when the laser sintering temperature ranged from 100℃ to 130℃, and melting/solidification mechanism when the temperature was above 130℃.
HA En-hua, KOU Kai-chang, YAN Lu-ke, YAN Hai-yan. Study on Properties of Epoxy/Nano-silica Encapsulating Materials Obtained from In situ Polymerization[J]. Journal of Materials Engineering, 2005, 0(8): 32-34,38.
Epoxy resin/nano-silica encapsulating materials were obtained from in situ polymerization, and microstructure and properties of the materials were investigated by transmission electron microscopy(TEM),scanning electron microscopy(SEM) and differential scanning calorimetry(DSC).The results showed that the interfacial interactions differed between material systems,whereas impact strength and flexural strength of encapsulating materials were all improved by adding pretreated nano-silicas by an optimal content of 3%(mass fraction).The encapsulating materials containing pretreated nano-silicas had slightly higher viscosities,higher electricity properties and lower linear thermal expansion coefficiency compared with neat epoxy resin.DSC analyses showed that the addition of nanosilica increased the viscosity of epoxy resin.
LUO Yu, JIANG Xiao-ling, DENG De-an. Influence of Mechanical Properties of Materials on High Frequency Inducting Plate Bending[J]. Journal of Materials Engineering, 2005, 0(8): 35-38.
The ANSYS software was used for thermal-elastic-plastic finite element analysis of mild carbon plate bending process using high frequency induction heating apparatus.Numerical results were used to qualitatively analyze the influences on the final shrinkage and angular distortion, which were caused by the changes of material, yield stress and Young's modulus.It can provide digital support for ship plates' automatic machining.
HE Xiao-dong, ZHANG Jian-xun, GONG Shui-li, FENG Yao-rong. Finite Element Analysis of Laser Welding Residual Stress and Distortion in Welded Joints of TC4 Titanium Alloy[J]. Journal of Materials Engineering, 2005, 0(8): 39-42,63.
The laser beam welding residual stress and distortion of titanium alloy were investigated by numerical simulation and experimental tests. The finite element calculations were performed using the ANSYS software. The laser beam was modeled as three-dimensional moving heat source. The results showed that the prodigious longitudinal stress was produced in the welded joints, nevertheless the transverse stress were lower correspondingly. When the heat input increased, the region of tensile of longitudinal stress widened out and its peak value fell, but the magnitude of transverse stress became larger. When the heat input of laser welding exceeded the critical penetration process, with the increase of energy input the angular distortion decreased, but the magnitude of transverse shrinkage increased. As the welding specimens were fully penetrated, the effects of heat input on the angular distortion weakened. Experimental tests were carried out to measure the angular distortion and the distributions of residual stresses in welded joints. The calculated values were in goodagreement with experimental measurements. Moreover, the internal relationships of residual stress, deformation and heat input were further investigated by metallographic section of weld.
CHEN Yi-min, XU Jing, XIE Kai, XIAO Jia-yu. Preparation and Characterization of Cu/SiO2 Nanocomposite Aerogels[J]. Journal of Materials Engineering, 2005, 0(8): 43-46.
Cu-rich Cu/SiO2 nanocomposite aerogels ,in which mass fraction of Cu could reach as high as 66%, were firstly prepared by sol-gel process of Cu-containing tetraethyl orthosilicate (CuTEOS).The influence of H2O,catalyst,solvent and composition of Cu-containing tetraethyl orthosilicate on the sol-gel process was discussed. The particle diameter, pore diameter and specific surface areas of Cu/SiO2 composite aerogels were smaller than 25nm, 50nm and in the range of 400~650m2/g respectively.
WANG Fei, WU De-yi, HE Sheng-bing, KONG Hai-nan, HU Zhan-bo, YE Chun. Property Characterization of NaP1 Zeolite From Coal Fly Ash by Hydrothermal Synthesis[J]. Journal of Materials Engineering, 2005, 0(8): 47-50.
Coal fly ash was transformed to NaP1 zeolite through hydrothermal reaction in NaOH medium and the synthesized product was characterized. The main crystalline mineral in zeolitized coal fly ash was NaP1, with small amount of partially dissolved residual quartz and mullite as identified by XRD. SEM photographs showed that the particle of raw coal fly ash was spherical and smooth, while zeolitized one was rough. The synthesized product contained large amount of exchangeable cation (Ca2+ in this case). The amount of SiO2 decreased markedly and that of Al2O3 increased slightly during the synthesis process, which reduced SiO2/Al2O3 ratio from 3.3 for the raw material to 1.8 for the product. IR spectrum and DTA curves indicated the presence of zeolitic water in the synthesized product. The CEC of zeolitized coal fly ash was 213cmol/kg, and specific surface area was 29 m2/g, 100 times and 26 times greater than those of raw coal fly ash respectively.
LI Xiao-gang, LI Hong-yun, HU Hong-jun, TANG Bang-ming, YI Xiao-su. Study on Performance of Structure Part of Bismaleimide Matrix Two-dimensional Braided Composites[J]. Journal of Materials Engineering, 2005, 0(8): 51-52,58.
Compression properties of rectangular specimen of two-dimensional bismaleimide (BMI) matrix braided composites prepared with resin transfer molding technology were studied.The specimen exhibited obvious anisotropic properties. In addition, its performance was affected by its intrinsic properties and structure as well.
JING Min, WANG Cheng-guo, ZHU Bo, BAI Yu-jun, WANG Yan-xiang, CHEN Xin-mou. SiC Coating on Surface of Carbon Fibers at Low Temperature by Radio-frequency Direct-heating Method[J]. Journal of Materials Engineering, 2005, 0(8): 53-58.
A new technology of radio-frequency (RF) direct-heating method was used to fabricate silicon carbide (SiC) coatings on the surface of carbon fibers (CF) at low temperature by chemical vapor deposition (CVD) in order to satisfy the industry production requirements for energy conservation, high thermal efficiency, controllability of coating thickness and low cost. The correlation between technical parameters and coating structure, the microstructure of coatings, tensile strength and anti-oxidation performance was studied by XRD, EPMA and TEM. The results showed that the SiC coatings crystallized at 700~800℃ during deposition and the degree of crystallization improved with increasing temperature or decreasing running rate of the fibers. The tensile strength only had a slight drop and the anti-oxidation of CF was improved when the coatings were heated at low temperature. But a poor anti-oxidation happened when the coating was heated to high temperature. Technical parameters must be adjusted to obtain desired tensile strength and oxidation resistance performance.
YAO Xiu-rong, HAN Jie-cai, LIU Zhao-jing, GAO Yue-gang, LI Feng-zhen, REN Shan-zhi. Optimized Preparation Process of Spherical VCp Stainless Steel-based Composites by In-situ Synthesis[J]. Journal of Materials Engineering, 2005, 0(8): 59-63.
The VCp reinforced stainless steel-based composites were prepared by in-situ reaction. The optimal process of manufacturing composites was defined via experimental methods of orthogonal arrays design. The microstructure and phase structure of composites were investigated by means of SEM and XRD.It was confirmed that the spherical VCp strengthened particles were distributed dispersely on the base body of composites. The effects of reaction temperature and heat preservation time on the strengthened particles' formation of spherical VCp were discussed. The results further verified the optimal process of composites preparation.
