2016 Vol.36(4)

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2016, 36(4): 0-0.
[Abstract](456) [PDF 873KB](14)
Simulation of Dendritic Morphology and Constituent Distribution of Al-4.7%Cu Alloy Under Convection
Jingchao ZHOU, Ri LI, Yingying YANG, Chaoyang ZHAO
2016, 36(4): 1-9. doi: 10.11868/j.issn.1005-5053.2016.4.001
[Abstract](333) [FullText HTML] (53) [PDF 13007KB](2)
A new two-dimensional modeling approach combining the cellular automaton(CA) and the lattice Boltzmann model(LBM) was developed to simulate heat transport, fluid flow, solute diffusion, and dendritic growth in the process of the Al-4.7%Cu solidification of the single-phase solid solution alloy. And the changes of dendritic morphology and constituent under convection were analyzed. The present model improved the solutal distribution approach at the solid-liquid (S/L) interface, which made the change of solute more consistent with the actual transport. The simulation results demonstrate that dendritic morphology is strongly influenced by forced convection, comparing with that without accounting for convection. Under the forced convection, the dendrite grain sizes tend to be similar; the constituent in the interdendritic region is more homogeneous; and the composition in the whole solidification region exhibits a certain gradient trend from upstream to downstream.
Effect of Solid Solution Treatment on Microstructure and Mechanical Properties of DS Superalloy DZ8
Shuaiqi ZHANG, Cui ZONG, Shengping CHEN, Wenxia ZHAO, Hongwei ZHANG, Qiang ZHANG, Yongning TAN
2016, 36(4): 10-15. doi: 10.11868/j.issn.1005-5053.2016.4.002
[Abstract](285) [FullText HTML] (52) [PDF 11040KB](3)
The microstructure of DZ8 after solid solution treatment at 1260 ℃ and 1240 ℃ was observed, and the tensile and stress rupture properties were compared. The results show that less than 1% γ+γ' eutectic remains in the microstructure of DZ8 after solid solution treatment at 1260 ℃, while incipient melting takes place in the Hf-rich phase; about 12% γ+γ' eutectic exists in the microstructure of DZ8 after solid solution treatment at 1240 ℃, but no incipient melting phase is discovered. After solid solution treatment at 1260 ℃, the stress rupture property of DZ8 in 980 ℃/725 MPa and the tensil property of DZ8 at room temperature, 700 ℃ and 980 ℃ show little different compared with those treated at 1240 ℃, but the stress rupture property in 760 ℃/725 MPa decreases to some extent.
Effects of KH-570 Silane Electrochemical-assisted Deposition on Corrosion Resistance of AZ31B Magnesium Alloy
Jing JIN, Xuan LI, Chenglin CHU, Chao GUO, Jing BAI, Feng XUE, Pinghua LIN
2016, 36(4): 16-23. doi: 10.11868/j.issn.1005-5053.2016.4.003
[Abstract](270) [FullText HTML] (70) [PDF 5881KB](3)
Electrochemical-assisted deposition was used to treat AZ31B magnesium alloy with silanes. The effects of additive amounts of γ-(methacryloxy) propyltrimethoxysilane (KH-570) on quality and corrosion resistance of the formed films were studied by the potentiodynamic polarization curve, the electrochemical impedance spectroscopy and so forth. Besides, films in this research were modified by hydroxyapatite (HA) and cerium ion (Ce3+) and then the films' anti-corrosive quality were studied. The results show that a uniform, dense silane transparent film is formed on AZ31B magnesium alloy after silane electrochemical-assisted deposition, which hinders corrosion behaviors of magnesium alloy effectively and reduces the corrosion current density to a great extent; there is an optimum volume of KH-570 in silane electrochemical-assisted deposition, and the best film can be got when 8 mL KH-570 is added; the quality of film formed by electrochemical-assisted depositing KH-570 can be improved further through modifying silane solutions.
Near-net-shape Tungsten-Rhenium Alloy Parts Produced by Shrouded Plasma Spray Forming
Yueming WANG, Menghua CHEN, Yue LI, Kewen TANG, Wangwang DING, Xiang XIONG, Qilong SHI, Lu XIE, Xuan XU
2016, 36(4): 24-34. doi: 10.11868/j.issn.1005-5053.2016.4.004
[Abstract](388) [FullText HTML] (80) [PDF 25508KB](5)
W-5% (mass fraction) Re composite powder was fabricated by a new cladding method. W-5%Re nozzles used for solid rocket motor (SRM) were produced by shrouded plasma spray forming (PSF). The change regularity with the sintering time for the compact density, structure, micro-hardness, tensile strength and compression strength of the nozzel under 2300 ℃ vacuum sintering was studied. The study result indicates that the lamellae structure, and vertical columnar grains, micron-sized pores and rough interlamellar contacts with gaps of sub-micron sizes between lamellaes are found in PSF deposits. The relative density, micro-hardness, ultimate tensile strength (UTS) and compressive strength of PSF deposits are 87.5 %, 321.4 HV0.025, 57.9 MPa and 390.2 MPa respectively. With the sintering time prolonged from 2 h to 6 h and 8 h, the relative density and mechanical properties of W-Re alloy parts increase with the initial lamellar structure transformed into granular structure.After vacuum sintering for 8 h, the relative density, micro-hardness, UTS, compressive strength and yield strength increase to 98.6 %, 529.7 HV0.025, 384.7 MPa, 1466.5 MPa and 879.6 MPa respectively. For the addition of Re element, the recrystallization temperature and grain size of W-Re alloy are improved and effectively refined respectively. Thus, the strength and plasticity of the alloy can be improved remarkably, and the Re effect is revalidated and double checked in W-Re alloy fabricated by PSF and Vacuum sintering.
Residual Stress Test and Finite Element Analysis of Titanium Alloy Surface Obtained by Electron Beam Welding
Xiaojia LIU, Jian LIN, Yongping LEI, Zhongwei WU, Xin LIU, Pengfei FU
2016, 36(4): 35-40. doi: 10.11868/j.issn.1005-5053.2016.4.005
[Abstract](295) [FullText HTML] (47) [PDF 1049KB](3)
Ti60 titanium alloy plates were welded by electron beam,and the welding residual stress was tested and simulated by the residual stress tester and finite element analysis. The comparison of the residual stress values caused in the three kinds of welding processes of pre-heating, slow cooling and both pre-heating and slow cooling was carried out. The residual stress distribution law was also studied. Results show that in the vertical welding section, the longitudinal welding residual stress tested is similar to that simulated as to the change trend; in the parallel welding section, the distributions of the tested and simulated longitudinal welding residual stress are similar. These prove that the finite element analysis is reasonable and reliable. The process of pre-heating has little influence on the welding residual stress, but the slow cooling process can change its distribution.
A Multilayer Rubber Board Radar Absorbing Material
Shan HE, Yehua LI, Chun ZHOU
2016, 36(4): 41-46. doi: 10.11868/j.issn.1005-5053.2016.4.006
[Abstract](328) [FullText HTML] (64) [PDF 1552KB](14)
Based on the theory of impedance matching, a multilayer absorbing material with the "pitfall" structure was designed. The multilayer absorbing material with 5 layers was obtained by optimization of the schemes, and the material shows 2 absorbing peaks in the broadband of 2~18 GHz frequencies. The peak in high frequencies can be adjusted with no effect on the peak in low frequencies through changing the thickness of the fifth layer. The changes of input impedances were displayed by analyzing the impedance chart. The prepared multilayer absorbing material was named JB-5, which processes the reflectivity no more than -12 dB in 6~17 GHz with the thickness no more than 5 mm and a good performance of standing the environment. The absorbing material can be produced in laboratory and pasted on surfaces of target with special adhesive by trimmed into required shapes so as to reduce the reflection of electromagnetic waves effectively.
Computational Simulation of VARI Fluid Process Molding for Stiffened Panel Structural Composites
Fei XIAO, Chongxin YUAN, Jingjie CONG
2016, 36(4): 47-54. doi: 10.11868/j.issn.1005-5053.2016.4.007
[Abstract](316) [FullText HTML] (80) [PDF 6022KB](12)
The resin filling time can be predicted and the flow pattern of resin can be simulated in Composites VARI Fluid Process Molding with simulation software PAM-RTM. The permeability is important parameter in VARI process. In-plane and transverse permeability are usually tested with complicate and expensive enclosed mold.A set of model with simple structure, easy operation, low cost, was built to obtain accurate permeability by using a process of vacuum-assisted resin infusion (VARI). Besides, the method of equivalent model was employed. The simulation results of effective model is compared with those of experimental VARI process. The filling times for simulation method is 254 s which is shorter than 301 s of the experimental process. Based on flow runner project with equivalent model, the stiffened panel structural composite is prepared to validate the selective process.
Buckling and Post-buckling Performance of Advanced Composite Stiffened Panel Under Compression
Haoyu ZHANG, Yuting HE, Yu FENG, Xiangfei TAN, Jie ZHENG
2016, 36(4): 55-63. doi: 10.11868/j.issn.1005-5053.2016.4.008
[Abstract](356) [FullText HTML] (69) [PDF 13742KB](7)
The axial compressive experiment was conducted on the domestic advanced composite stiffened panel, and its buckling and post-buckling performance was analyzed by monitoring strain and out-of-plane displacement of typical positions. The initial buckling load and buckling mode of panels were calculated by engineering methods to direct the follow-up axial compressive experiment. The experimental results show that the buckling patterns are mainly local buckling of panels between stiffeners, the second buckling of few positions of panels and cylindrical buckling of all 4 stiffeners successively; after local buckling of panels, part of load bearded by panels before is transferred to stiffeners and then stiffeners become the main bearing part; after fracture failure of stiffeners, the specimen is destroyed rapidly; the average value of failure load is 482.67 kN, which is 2.37 times of 204 kN of the average value of buckling load; the composite stiffened panel can bear more load after buckling.
Design of Ultrasonic Fatigue Specimen of MB8 Wrought Magnesium Alloy by Analytic Method
Haipeng DENG, Bolin HE
2016, 36(4): 64-70. doi: 10.11868/j.issn.1005-5053.2016.4.009
[Abstract](261) [FullText HTML] (67) [PDF 782KB](3)
Ultrasonic fatigue specimen of MB8 wrought magnesium alloy was designed by calculation. In order to reduce the vibration amplitude, heat and pressure of the cooling system and also to protect the phase change, the sample was designed into variable cross-section. Based on the vibration displacement equation, boundary condition and displacement continuity condition, the relationship between the resonant length and other dimensions of the sample was derived. A series of size of ultrasonic fatigue specimens was calculated, which provided reference for the research of ultrasonic fatigue test of magnesium alloy. The results show that the resonance length decreases with the increase of the length of transition section, and the arc transition radius increases with the increase of the length of arc transition section.With the decrease of the length of arc transition section, Cs and M decreases for the specimen without uniform cross section in middle. With the decrease of the length of uniform cross section in the middle, Cs and M decreased for the specimen with uniform cross section in the middle.
Statistical Distribution of Fatigue Life for Cast TiAl Alloy
Wenjuan WAN, Bo HAN, Wei HAN, Ji ZHANG
2016, 36(4): 71-77. doi: 10.11868/j.issn.1005-5053.2016.4.010
[Abstract](310) [FullText HTML] (52) [PDF 9480KB](5)
Statistic distribution of fatigue life data and its controls of cast Ti-47.5Al-2.5V-1.0Cr-0.2Zr (atom fraction/%) alloy were investigated. Fatigue tests were operated by means of load-controlled rotating bending fatigue tests (R=-1) performed at a frequency of 100 Hz at 750 ℃ in air. The fracture mechanism was analyzed by observing the fracture surface morphologies through scanning electron microscope,and the achieved fatigue life data were analyzed by Weibull statistics. The results show that the fatigue life data present a remarkable scatter ranging from 103 to 106 cycles, and distribute mainly in short and long life regime. The reason for this phenomenon is that the fatigue crack initiators are different with different specimens. The crack initiators for short-life specimens are caused by shrinkage porosity, and for long-life ones are caused by bridged porosity interface and soft-oriented lamellar interface. Based on the observation results of fracture surface, two-parameter Weibull distribution model for fatigue life data can be used for the prediction of fatigue life at a certain failure probability. It has also shown that the shrinkage porosity causes the most detrimental effect to fatigue life.
Creep Rupture Life Prediction Based on Analysis of Large Creep Deformation
Wenming YE, Xuteng HU, Xiaojian MA, Yingdong SONG
2016, 36(4): 78-83. doi: 10.11868/j.issn.1005-5053.2016.4.011
[Abstract](301) [FullText HTML] (67) [PDF 1034KB](7)
A creep rupture life prediction method for high temperature component was proposed. The method was based on a true stress-strain elastoplastic creep constitutive model and the large deformation finite element analysis method. This method firstly used the high-temperature tensile stress-strain curve expressed by true stress and strain and the creep curve to build materials' elastoplastic and creep constitutive model respectively, then used the large deformation finite element method to calculate the deformation response of high temperature component under a given load curve, finally the creep rupture life was determined according to the change trend of the responsive curve.The method was verified by durable test of TC11 titanium alloy notched specimens under 500 ℃, and was compared with the three creep rupture life prediction methods based on the small deformation analysis. Results show that the proposed method can accurately predict the high temperature creep response and long-term life of TC11 notched specimens, and the accuracy is better than that of the methods based on the average effective stress of notch ligament, the bone point stress and the fracture strain of the key point, which are all based on small deformation finite element analysis.
Effect of Surfacial Opening-pore Area of Porous Silica Transition Layer on Mechanical Properties of Laminated Glass
Zhijun FENG, Xibao LI, Jinshan LU, Xufeng WANG, Jian ZHONG, Shiyao WU, Junhao ZHU
2016, 36(4): 84-88. doi: 10.11868/j.issn.1005-5053.2016.4.012
[Abstract](214) [FullText HTML] (43) [PDF 3954KB](2)
The effect of opening-pore size in the silica transition layer surface on mechanical properties of aeronautic laminated glass was investigated. The microstructure of the pore of porous silica transition layer was analyzed by scanning electron microscopy. The interfacial shear strength between inorganic glass and polyurethane of porous silica transition layer in laminated glass was tested by universal testing machine. The finite element models of laminated glass with porous silica transition layer were established by ANSYS software based on the pore shape obtained by experiments. The tensile stress between porous silica and polyurethane with different pore area was simulated. The results indicate that with the increasing of pore area, the shear strength between inorganic glass and polyurethane in laminated glass first increases rapidly, and then decreases slowly. When the pore area is 52.61 μm2, the laminated glass has the best mechanical properties.
Application and Research Status of Alternative Materials for 3D-printing Technology
Yanqing WANG, Jingxing SHEN, Haiquan WU
2016, 36(4): 89-98. doi: 10.11868/j.issn.1005-5053.2016.4.013
[Abstract](886) [FullText HTML] (352) [PDF 705KB](48)
Application features and research status of alternative 3D-printing materials for six typical 3D-printingtechniques were reviewed. From the point of view of physical forms, four kinds of materials of liquid photosensitive resin material, thin sheet material (paper or plastic film) , low melting point filament material and powder material are included. And from the composition point of view, nearly all kinds of materials in the production and life are included such as polymer materials: plastic, resin, wax; metal and alloy materials; ceramic materials. Liquid photosensitive resin material is used for stereo lithigraphy apparatus(SLA); thin sheet materials such as paper or plastic film are used for laminated object manufacturing(LOM); low melting point polymer filament materials such as wax filament, polyolefin resin filament, polyamide filament and ABS filament are used for fused deposition modeling(FDM); very wide variety powder materials including nylon powder, nylon-coated glass powder, polycarbonate powder, polyamide powder, wax powder, metal powder(Re-sintering and infiltration of copper are needed after sintering), wax-coated ceramic powder, wax-coated metal powder and thermosetting resin-coated fine sand are used for selective laser sintering(SLS). Nearly the same above powder materials are used for selective laser melting(SLM), but the printed parts own much more higher density and better mechanical properties. Powder materials are likewise used for threedimensional printing and gluing(3DP), however, the powders are stuck together by tricolor binder sprayed through nozzle and cross-section shape of the part is color-printed on it. Finally, the development direction in both quality and the yield of 3D-printing materials were pointed out to be a bottle-neck issue and a hot topic in the field of 3D-printing.

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