2017 Vol.37(4)

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2017, 37(4): 0-0.
[Abstract](123) [PDF 1389KB](2)
Synthesis and Properties of Novel High Temperature Transparent Cyclic Olefin Copolymers
Muquan YANG, Hongfeng ZHANG, Lei LI, Yue YAN
2017, 37(4): 1-6. doi: 10.11868/j.issn.1005-5053.2016.000207
[Abstract](314) [FullText HTML] (93) [PDF 1969KB](7)
Novel high temperature and transparent cyclic olefin copolymers (COC) derived from bulky cyclic olefin {exo-1, 4, 4a, 9, 9a, 10-hexahydro-9, 10(10, 20)-benzeno-l, 4-methanoanthracene (EHBMA)} were successfully synthesized by the copolymerization of EHBMA and propylene(PP). The glass transition temperature (Tg) of the resulted COC can be controlled easily by adjusting the feed ratio of the EHBMA and PP. The Tg can be adjusted from 170 to 220℃. The DSC and UV-Vis spectra results show that the Tg and transmittance are up to 220℃ and 92% respectively. The synthesized COC has a Tg about 40℃ higher than that of commercial TOPAS 6017 product. The tensile test showes that the COC material has good mechanical properties. The synthesized COC has high thermal stabilities, good mechanical properties and excellent transparencies, and it will be used in the aerospace, medical and other high-tech fields.
Optimal Design for Hybrid Ratio of Carbon/Basalt Hybrid Fiber Reinforced Resin Matrix Composites
Hong XU, Yan LU, Ke ZHANG, Shuan LIU, Xianghui WANG, Yanli DOU
2017, 37(4): 7-13. doi: 10.11868/j.issn.1005-5053.2017.000047
[Abstract](287) [FullText HTML] (59) [PDF 1696KB](4)
The optimum hybrid ratio range of carbon/basalt hybrid fiber reinforced resin composites was studied. Hybrid fiber composites with nine different hybrid ratios were prepared before tensile test.According to the structural features of plain weave, the unit cell's performance parameters were calculated. Finite element model was established by using SHELL181 in ANSYS. The simulated values of the sample stiffness in the model were approximately similar to the experimental ones. The stress nephogram shows that there is a critical hybrid ratio which divides the failure mechanism of HFRP into single failure state and multiple failure state. The tensile modulus, strength and limit tensile strain of HFRP with 45% resin are simulated by finite element method. The result shows that the tensile modulus of HFRP with 60% hybrid ratio increases by 93.4% compared with basalt fiber composites (BFRP), and the limit tensile strain increases by 11.3% compared with carbon fiber composites(CFRP).
Microstructures and Properties of FGH96/DD6 Joints Brazed at Vacuum Pressure State
Wenjiang ZOU, Bo CHEN, Yaoyong CHENG, Wei MAO, Huaping XIONG
2017, 37(4): 14-18. doi: 10.11868/j.issn.1005-5053.2016.000227
[Abstract](325) [FullText HTML] (129) [PDF 1576KB](6)
Ni-Cr-B brazing filler was used to braze FGH96 and DD6 at 1120℃/10 min and 1120℃/10 min/2 MPa. The tensile strength of the joints was tested, the microstructures and fractures were observed by OM and SEM, and the reaction products were analyzed by EPMA. The results show that the joints brazed at vacuum pressure process offer the average tensile strength of 1187 MPa, outclass the joints brazed without pressure which has average tensile strength of 621 MPa. Compared with vacuum brazing, the grains of FGH96/DD6 joints brazed by vacuum pressure state penetrate the brazing seam without grain boundary and ductile fracture occurred in the parent metal surface. The Ni3B exists in the joints brazed by vacuum brazing, but it is (Ni, Cr) solid solution in the joints brazed by vacuum pressure brazing instead of Ni3B.
Numerical Simulation of Mechanical Property of Post Friction Stir Weld Artificial Ageing of Aluminum Alloy
Zhenyu WAN, Xia ZHOU, Zhao ZHANG
2017, 37(4): 19-24. doi: 10.11868/j.issn.1005-5053.2016.000003
[Abstract](335) [FullText HTML] (79) [PDF 2437KB](10)
KWN model was used to establish the precipitation evolution model of friction stir welding of Al-Mg-Si alloy. The yield strength was divided into three parts:the contribution from grain size, the contribution from solid solution and the contribution from the precipitations. Based on this model, the yield strength and hardness of friction stir weld was predicted. The effect of post weld artificial ageing on mechanical properties of friction stir weld was further investigated. The results indicate that longer holding time can be beneficial to the recovery of mechanical properties in the stirring zone. Higher temperature can lead to quick recovery of mechanical properties in the stirring zone, but when the holding temperature is higher than 200℃, longer holding time can lead the base metal softened, which is harmful to the service of friction stir welds. The mechanical property in the heat affected zone cannot be improved by post weld artificial ageing.
Pitting Corrosion Topography Characteristics and Evolution Laws of LC4 Aluminum Alloy in Service Environment
Zhiguo LIU, Xudong LI, Zhitao MU
2017, 37(4): 25-32. doi: 10.11868/j.issn.1005-5053.2016.000229
[Abstract](315) [FullText HTML] (76) [PDF 3393KB](5)
Aircraft aluminum alloy is easy to initiate pitting corrosion in the service environment, the pitting corrosion topography characteristics could directly affect the fatigue mechanical property of structure material. In order to obtain the pitting corrosion topography characteristics of LC4 aluminum alloy in the service environment, the accelerated corrosion test was carried out along the accelerated corrosion test environment spectrum which imitated the service environment spectrum, and the corrosion topography characteristic parameters of corrosion pit depth H, corrosion pit surface length L and corrosion pit surface width W were defined respectively. During the corrosion test process, the three parameters of typical corrosion pit were successively measured in different equivalent corrosion years for obtaining the corrosion pit damage size data, then the data were analysed through the statistics method and fractal theory. Further more in order to gain the pit topography characteristics in the same equivalent corrosion year and the topography evolution laws during different equivalent corrosion years were gained. The analysis results indicate that LC4 aluminum alloy corrosion pit topography characteristics in the service environment include the following:firstly, the pit topography characteristic parameters conform to the lognormal distributions in the same equivalent corrosion years; secondly, the pit topography characteristic parameters gradually reflect the fractal feature in accordance with the equivalent corrosion year increment, and the pits tend to be shallow, long and moderate wide topography character.
Corrosion Electrochemistry of Aluminum Alloy for Aviation in Acid Salt Spray Environment
Juan DU, Yiying ZHANG, Qiaochu CHEN, Hui TIAN
2017, 37(4): 33-38. doi: 10.11868/j.issn.1005-5053.2016.000129
[Abstract](367) [FullText HTML] (90) [PDF 3576KB](11)
The corrosion processes of 2A12, 5A06 and 7A04 aluminium alloy in neutral and acid (pH≈5) continuous salt spray environment were studied with weight loss method and electrochemical method. The morphology and surface condition in the interface of metal phase was studied by metallographic microscope and contact angle surface analyzer, and the corrosion mechanism was analyzed. Weight loss method, polarization curves by Tafel extrapolation and electrochemical impedance spectroscopy show that the 3 kinds of aluminum alloy have the relationship of corrosion rate 7A04 > 2A12 > 5A06 in neutral salt spray as well as 7A04 > 5A06 > 2A12 in acidic salt spray. The contact angles of the aluminum alloys surface with neutral and acidic salt solution conditions are 70.9ånd 52.6°respectively. The reason why the contact angle with acid salt solution is smaller than that with neutral salt solution is probably that the increase of the hydrogen ions may cause the cathodic reaction to move to the right, accelerate anodic dissolution and destroy the oxide film on the surface of the aluminum alloy.
Dynamic Recrystallization Behavior and Critical Conditions of SiCp/A1-Cu Composite
Shiming HAO, Jingpei XIE, Weining LIU, Huiping FU, Jiabin LIU
2017, 37(4): 39-44. doi: 10.11868/j.issn.1005-5053.2016.000184
[Abstract](242) [FullText HTML] (67) [PDF 3846KB](2)
Using the Gleeble-1500D simulator, the high temperature plastic deformation behavior of 40%SiCP/Al-Cu composite were investigated at 350-500℃ with the strain rate of 0.01-10 s-1. The stress-strain curves were obtained during the tests. The critical conditions of dynamic recrystallization for onset of DRX during deformation of 40%SiCP/Al-Cu composite was obtained by computation of the strain hardening rate (θ) from initial stress-strain data and introduction of the inflection point criterion of ln θ-ε curves and the minimum value criterion of (-∂(ln θ)/∂ε)-ε) curves. The results indicate that the softening mechanism of the dynamic recrystallization is a feature of high-temperature flow stress strain curves of the composites, and the peak stress increases with the decrease of deformation temperature or the increase of strain rate. The inflection point in the ln θ-ε curve appears, and the minimum value of the (-∂(ln θ)/∂ε)-ε) curve is presented when the critical state is attained for this composite. The critical strain decreases with the decrease of strain rate and the increase of deformation temperature. There is linear relationship between critical strain and peak strain, i.e. εc=0.528εp. The predicting model of critical strain is described by the function of εc=4.58×10-3Z0.09. Electron microscopic analysis show that the dynamic recrystallization occurs when the strain is 0.06 (T=400℃, ε=10 s-1), and the dynamic recrystallization grains fully grow up when the strain is 0.2.
Effect of Fabric Preform Structure on Mechanical Properties of SiCf/PyC/SiBCN Composites
Xi TAN, Wei LIU, Lamei CAO, Shenglong DAI
2017, 37(4): 45-51. doi: 10.11868/j.issn.1005-5053.2016.000225
[Abstract](304) [FullText HTML] (102) [PDF 5047KB](12)
Three continuous silicon carbide fiber reinforced SiBCN composites (SiCf/PyC/SiBCN) distinguished by different weaving methods of fibers (including two dimensional woven, 2.5 dimensional woven with the fiber tow through the thickness and three dimensional five directional braiding) were fabricated by resin transfer molding (RTM), polymer impregnation and pyrolysis (PIP) technology. In order to study the impact of waving methods, the microstructures of fabricated composites were observed and the mechanical properties such as tensile, compression strength and bending strength of the composites were tested. The results show that different distributions of fibers on different directions lead to anisotropy of mechanical properties for each composite, and fabric preform structure has a significant influence on the mechanical properties of the composites.
Tribological Property of C/C-SiC Composites Fabricated by Isothermal Chemical Vapor Infiltration
Yueming WANG, Qilong SHI
2017, 37(4): 52-60. doi: 10.11868/j.issn.1005-5053.2016.000199
[Abstract](297) [FullText HTML] (66) [PDF 4546KB](7)
Four kinds of C/C-SiC composites were fabricated by isothermal chemical vapor infiltration (ICVI), and the 2.5D needle-punching carbon felt was taken as the preform. The volume fraction of carbon fiber in felt is 30%. The density of C/C-SiC composites is similar (1.87-1.91 g/cm3), while the weight ratio of SiC is decreased from 56% to 15%. The microstructure and phase composition of C/C-SiC composites were observed by SEM and XRD respectively. Friction and wear behavior of the C/C-SiC composites were investigated with the MM-1000 friction machine. The results show that the average macro hardness of matrix is decreased from 98.2HRA to 65.1HRA with the decrease of SiC content from 56% to 15%, and uniformity of hardness distribution is significantly decreased. Finally, by the analysis of microtopography of friction surface and wear debris, it is found that the superficial hardness has an obvious influence on mechanism of wear during braking process. The wear mechanism of the C/C-SiC composites transforms from grain wear to the combination of grain wear and adherent wear with the decrease of surface hardness. At the same time, the average friction coefficient and mass wear rate is increased obviously during breaking process.
Numerical Simulation of C/SiC Plain Weave Composites with Defects under Unidirectional Tension
Xianglong ZENG, Qizhi WANG, Fei SU
2017, 37(4): 61-68. doi: 10.11868/j.issn.1005-5053.2016.000086
[Abstract](327) [FullText HTML] (74) [PDF 4093KB](4)
The second time develop of the ANSYS was realized by using APDL language, and an ovoid sectional multi-scale unit cell model for fiber bundle section with pre-made defects was established. At first the initial modulus, the strength and the ultimate strain of fiber bundle were calculated. Then the unit cell model of C/SiC woven composites was established according to the SEM photographs. By introducing the periodic boundary conditions, the initial anisotropic constants of C/SiC woven composites were predicted. The failure criteria proposed by Linde was utilized to set up the progressive damage mode, and the C/SiC plain weave composites with defects under unidirectional tension was simulated. So, the damage evolution process of the fiber bundle could be interpreted, when the unit cell of C/SiC plain weave composites was under the unidirection load. The numerical results show that the proposed model accurately captures the data from the experiments, which demonstrates the validity of the present analytical model. Furthermore, the numerical model provides an alternate way to design and predict the mechanical properties of plain weave composites.
Critical Plane Damage Method for Fatigue-creep Life Prediction of Nickel-based Superalloy
Chengli DONG, Huichen YU
2017, 37(4): 69-76. doi: 10.11868/j.issn.1005-5053.2016.000102
[Abstract](294) [FullText HTML] (66) [PDF 1809KB](8)
Adopting the classical critical plane damage method coupling fatigue-creep life models with adequate technique modification, the life predications of ZSGH4169 superalloy at 650℃and DZ125 superalloy at 980℃ were investigated to compare the predication accuracies of the five kinds of fatigue-creep life models, i.e. based on Walls, Ccb, Swt, Glk and Fin. The results of typical examples show that the fatigue-creep model based on Walls is the best for ZSGH4169 superalloy at 650℃, and the predicted life falls within ±3 scatter band of the test data, while the fatigue-creep model based on Glk is the best for DZ125 superalloy at 980℃, and the predicted life falls within ±2.5 scatter band of the test data.
Preparation and Three-point Bending Performance of Steel Foam Plate
Yadong SUN, Yun ZHOU, Kunshan GUO, Yiqun YANG, Heting LI, Xiaoqing ZUO
2017, 37(4): 77-83. doi: 10.11868/j.issn.1005-5053.2016.000216
[Abstract](251) [FullText HTML] (78) [PDF 3316KB](8)
In order to fabricate steel foams with high porosity, uniform pore structure and high-performance, steel foams with different porosities and cell sizes were fabricated by a sintering-dissolution process using 316L stainless steel powder as raw material and CaCl2 as pore forming agent, and steel foam-sandwich panels were fabricated by physical bonding. Three-point bending tests were carried out to explore the bending performance of steel foam and steel foam-sandwich panels. The influence of the porosity and cell size of foam sample on the bending load was analyzed and discussed, and the bending strength of steel foam -sandwich panel was compared with steel foam sample. The results show that the bending deformation of steel foam is started at the weakest cell wall firstly, then the cracks are initiated and propagated, eventually the macroscopic fracture is caused. For steel foam-sandwich panels, the maximum load is reduced from 2345 N to 1254 N when the porosity is increased from 69.4% to 82.5%, whereas the maximum bending load of steel foam-sandwich panels is increased by 15%-43% with the same porosity. When the cell size is increased from 1.9 mm to 3.9 mm and the porosity is about 73%, the maximum bending load is reduced from 2070 N to 1528 N, whereas the maximum bending load of steel foam-sandwich panels is increased by 15%-28% with the same pore size. Under the same porosity and pore size, the steel foam-sandwich panels have excellent resistance to bending at least 15% higher than the steel foam.
Rheology of Prepreg and Properties of Silica/bismaleimide Matrix Copper Clad Laminate
Shankai DAI, Ronghui HUANG, Lifu JI, Xiangxiu CHEN
2017, 37(4): 84-89. doi: 10.11868/j.issn.1005-5053.2015.000209
[Abstract](345) [FullText HTML] (83) [PDF 2165KB](6)
The effects of the silica surface treated by coupling agents KH550, KH560 and KH570 on the rheological properties of bismaleimide (BMI) resin system were investigated. The rigidity, coefficient of thermal expansion (CTE) and thermal stability of the copper clad laminate (CCL) were studied by DMA, TMA and TGA. The resin system containing silica surface treated by KH-560, comparing to KH550, KH570 and without surface treatment resin system has better rheological properties and low melt viscosity. The comprehensive properties of the copper clad laminate can be effectively improved by the introduction of silica in the resin system, exhibiting higher storage modulus and lower CTE compare to no silica in the CCL. When the silica mass fraction is 50%, the storage modulus is increased by 83% at 50℃, and the CTE below the glass transition temperature is decreased by 153%.
Development and Application of 3D Digital Image Correlation (3D DIC) in Deformation Measurement of Materials
Yajun CHEN, Shengjie SUN, Chunming JI
2017, 37(4): 90-100. doi: 10.11868/j.issn.1005-5053.2016.000139
[Abstract](421) [FullText HTML] (137) [PDF 1279KB](31)
As a non-conduct and whole field measurement method, 3D DIC (3D digital image correlation) is widely used in mechanical properties test of many types of materials in varies fields. Compared with other optical measurement methods, it has advantages as automation, simple optical path, strong universality and anti-interference and so on. But it has some problems in the process of application, i.e. the measurement accuracy is uncertain, the high temperature test condition seriously affects the experimental results, and the measurable area of large curvature specimen is limited. This paper gives a general introduction to the application of 3D DIC in the conventional mechanical property test of different types of materials, and verifies its accuracy by comparing with the traditional extensometer measurement results and the finite element simulation results. It focuses on some latest technological progress, such as the high-temperature speckle preparation and multi-camera DIC, as the application of 3D DIC in the high temperature and large deformation measurement is mostly studied. Moreover, it is pointed out that 3D DIC should be further studied for the influence of speckle on measurement precision, the effect of environmental factors, the measurement of micro strain scale and the application in fields of military and biomedical materials.

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