ZHANG Qing-ling, LI Xing-wu. Effect of Structure on Fatigue Properties and Fracture Toughness for TA15 Titanium Alloy[J]. Journal of Materials Engineering, 2007, 0(7): 3-5.
Effect of lamellar and bi-modal structure on fatigue properties and fracture toughness have been investigated for TA15 titanium alloy.The results show that fatigue strength of bi-modal structure is higher than lamellar structure in the low cycle region.however the fatigue limit of lamellar structure is higher than bi-modal structure in the high cycle.The damage tolerance properties of lamellar are better than bi-modal structure,i.e.fracture toughness is higher and crack growth rate is lower of lamellar structure.
WEN Wei-dong, XU Ying, CUI Hai-po. Damage Analysis of Laminated Composites Under Low Velocity Impact Loading[J]. Journal of Materials Engineering, 2007, 0(7): 6-11.
A new delamination criterion was proposed according to delamination damage mechanism under low velocity impact loading.The influence of through-thickness tensile stresses,interlaminar shear stresses and matrix cracking on delamination had been taken into consideration.The fiber crushing caused by the crushing stresses of impact surface and fiber cracking aroused by tensile stresses of impact back surface has been distinguished.The initiation and propagation of fiber tensile failure,fiber compressive failure,matrix crushing,matrix cracking and delamination were simulated in the improved model.A good agreement was found between the predicted results and the test data.
YU Ming-xun, DING Wen-hao, LI Yun-nan, HE Hua-hui. Design of and Research on Millimeter-wave/Centimeter-wave Compatible Absorbing Coatings[J]. Journal of Materials Engineering, 2007, 0(7): 12-15.
The design of millimeter-wave/centimeter-wave compatible absorbing coatings with double-layer structure is analyzed based on the theory of electromagnetic in this article and series of experiments are conducted according to the analysis.It is shown that good performance on millimeter-wave and centimeter-wave can be achieved respectively by electric loss and magnetic loss,then through improving the impedance matching between layers compatible absorbability will be obtained on the whole by double-layer structure letting the centimeter-wave absorbing layer be the inner layer and the millimeter-wave absorbing layer the outer layer.
XU Chun-jie, GUO Xue-feng, ZHENG Shui-yun, ZHANG Zhong-ming. Mg-Zn-Y Alloy with High Elongation Properties by Reciprocating Extrusion[J]. Journal of Materials Engineering, 2007, 0(7): 16-20,32.
As-cast Mg92.5Zn6.4Y1.1 magnesium alloys were prepared by reciprocating extrusion(RE) and forward extrusion processes.The as-cast alloys were firstly reciprocating extruded for 2,4,8 and 12 passes,and then further extruded into φ12mm bar,respectively.Microstructures and mechanical properties were investigated with optical microscope(OM),transmission electronic microscope(TEM),X-ray diffraction(XRD) and differential thermal analysis(DTA).The results show that RE process can prepare sound and solid material.The grain size is approximately 5μm and UTS preponderate over 300MPa and elongation attain 20 percent after reciprocating extruded for 2 passes and a forward extrusion.The grain refine and tensile properties are not improving clearly with increasing RE passes,and the tensile properties decrease very clearly with 12 passes,but the elongation properties up to 23 percent.Reason of the further increase of the elongation after several RE passes is due to that the micro-pores,shrinkage-pores and the nonuniform phase of element microsegregation have completely eliminated to yield a fully dense,refined,more equiaxed and uniform microstructure,and grain refinement involve fragmentation,dynamic recovery and dynamic recrystallization,repeated mass flow during reciprocating extrusion and forward extrusion.
JIAN Zhong-hua, MA Zhuang, CAO Su-hong, WANG Fu-chi, WANG Quan-sheng. Study on Wear Resistance of WC-Co and NiCr-Cr2C3 Coatings Sprayed by HVOF[J]. Journal of Materials Engineering, 2007, 0(7): 21-24.
WC-Co and NiCr-Cr2C3 coatings were prepared on 45 steel substrate by means of high velocity oxy-fuel spraying(HVOF).Coating porosity,micro-hardness and loss of coating in the sliding wear test with lubricant were studied.Profiles of the sliding wear coefficients were described and the wear mechanisms of coatings were discussed as well.The results show that both of coatings are compact and the porosities are 1.29% and 1.08%,the hardness of two coatings are 1140HV and 950HV under the press of 300 gram.Abrasion of two coatings are stable and friction coefficient are both 0.1 when the time is beyond 25 minutes.The main abrasion modes of WC-Co coatings are the fatigue desquamation and the micro-cutting and adhesive wear.Carbide flake and scratches of NiCr-Cr2C3 coating are serious and micro-cracks are enhanced greatly.
SONG Jiang-xuan, LIU Ping-gui, HE Li-hua, LIANG Xing-quan, LI Ke-wen, TANG Zhong-feng. Morphology and Thermal Properties of Polycaprolactone/Polydimethylsioxane/Epoxy Resin Composites[J]. Journal of Materials Engineering, 2007, 0(7): 25-28.
Epoxy resin was modified with triethylsiloxane-terminated polycaprolactone-polydimethylsiloxane,which was directly synthesized via OH and NCO nuclephilic addition reaction.The modified system was cured with amino curing agent via anmio-glycidyl reaction and sol-gel process.The cured system was characterized by FT-IR,scanning electron microscopy(SEM),thermogravimetry analysis(TGA) and swelling in toluene.The results showed that the crosslinking network density decreased with the increasing of the PCL-TESi/PDMS-TESi,and the toughness was also greatly improved by the elastomer particles,which was formed by flexible chain—Si—O—and—C—O—.And in TG analysis,the characteristic decomposition temperature at 5% mass loss was evidently increased from 155.8℃ of pure epoxy to 310.2℃ with PCL-TESi/PDMS-TESi:EP=1:1(mass ratio).
SONG Mei-juan, WANG Ling-yun, LIU Rao-chuan, XIANG Yi. Research on Superplastic Forming Limit of Magnesium Alloy Sheet[J]. Journal of Materials Engineering, 2007, 0(7): 29-32.
The superplastic bulging test of AZ31B magnesium alloy sheet of 0.6mm thick was carried out on Alliance RT/50 tensile machine at 573K and 3.3×10-4s-1.the superplastic forming limit diagram(FLD)at 573K and 3.3×10-4s-1 was established for the first time.It is found that,either in tensile-compressive deformation or in bi-axis tensile deformation,the judgment criterion for local necking of superplastic deformation is d2=0.
ZHU Wei, DONG Xiang-huai, ZHANG Zhi-liang, SHU Shi-xiang. Numerical and Physics Simulations of Variable Blank Holder Force in Process of Deep Drawing Complex Overlay[J]. Journal of Materials Engineering, 2007, 0(7): 33-39.
In order to effectively solve the problem that how to optimize the technics of variable blank holder force(BHF) in the process of deep drawing complex automotive forward-soleplates in real manufacture,one simplified simulation model was built based on the Similitude-theory.Then numerical simulations were carried out to search out which one was the best from lots of typical variable BHF modes,with better uniformity in thickness distribution and without wrinkling and cracking phenomena.Finally,physics tests were done to validate above results.Both numerical simulation and physics simulation results show that under the control of U curve of variable BHF,not only the maximum thickness-reduction of workpiece is the lowest,but also the whole mean-squared error of thickness-reduction is the minimal.
YAN Lu-ke, KOU Kai-chang, HA En-ping. Research on the Application of a Newly Silane Adhesive in Bonding Fluorine Rubber to Steel[J]. Journal of Materials Engineering, 2007, 0(7): 40-43.
Adhesion between metal and fluorine rubber is a difficult problem.The objective of this work was to improve adhesion properties in bonding metal with fluorine rubber.Prepared the complex from urotropine and resorcinol,adopted two kinds of silane coupling agents KH-560,A-151 and other agent developed FM adhesive,compared with Chemlok 607 adhesive and FA-1 adhesives in bonding steel to fluorine rubber vulcanized by amine compound at the same experimental conditions.The result showed that 1:1 complex formed between urotropine and resorcinol is an ideal accelerant agent for FM adhesive in bonding steel to fluorine rubber vulcanized by amine compound,its property in shear by tension loading exceeds 5MPa,can achieve 6.28MPa,that is superior to Chemlok 607 and FA-1.The complex decomposes activated substances with methylene,can promote formation the chemical bond between fluorine rubber and silane coupling agent;meanwhile,these activated substances can produce many kinds of amino resin containing a large number of activated function(-OH) in the course of vulcanization,and improves adhesion forces with metal.
LIN Yan-qin, NIE Li-chuan, LIU Ruo-yu, ZHANG Ju-hua. Study on the High-efficient Mildewproof Polysulfied Sealant[J]. Journal of Materials Engineering, 2007, 0(7): 44-47.
The kind of three antimoulds including thiazole species,organo-metallic compounds and imidazole species were applied in the research of a polysulfide sealant.By studying their mildrewproof effect and their influence on technical and mechanical properties of the polysulfide sealant,the result comes out that the thiazole species antimould is the best choice.
ZHOU Yong-jiang, HONG Run-zhou, YAO Wei-bin, ZHANG Zhe. Study of Composite Mould Integral Precision Casting of Aluminium Alloy Complex Structure[J]. Journal of Materials Engineering, 2007, 0(7): 48-50.
Use the illustration of the casting process of electronic cabin,the method of composite mould integral precision casting is studied.In casting process,the thin wall part which is difficult to cast form use the invested mould,so it can be formed integrally;and the other part use the resin sand mould,which guarantees its dimensional accuracy and internal soundness.And then,the electronic cabin with integral external form,compact-grain structure and accurate dimension is produced use this method.
CHENG Ru, ZHU Meng-bing, HUANG Pei. Properties of Polyimide Films Based on ODPA and ODA by Thermal and Chemical Imidization[J]. Journal of Materials Engineering, 2007, 0(7): 51-54,58.
Two kinds of polyimide films were prepared based on the ODA and ODPA in NMP through two-step thermal or chemical imidization process and characterized by the cone and plate viscosimeter,GPC,FTIR,DSC,TGA and strain properties tests.The results showed that the films prepared from different imidizations had been totally transformed to polyimide films.The glass transition temperature,thermal decomposing temperature of the film from chemical imidization is higher than the one from thermal imidization.The strain tests showed that the film from thermal imidization had larger elongation at break,and the film from chemical imidization had larger tensile strength and elasticity modulus.
YU Zhong-liang, ZHAO Yong-qing, ZHOU Lian, SUN Jun. Fractography Analysis of Smooth and Notched High Cycle Fatigue Specimens in TC21 Alloy at 315℃[J]. Journal of Materials Engineering, 2007, 0(7): 55-58.
The HCF fatigue tests of smooth and notched specimens in TC21 alloy were performed at 315℃,and the fractography was observed by SEM,the effect of notch on fatigue life was investigated.The results indicate that,the fatigue strengths ratio of the smooth and notched specimens decreases with the decrease of fatigue life.The main crack length of smooth specimens increases with the decrease of the maximum cyclic stress,but the ultimate fracture stress of the final fracture zone increases with the decrease of the maximum cyclic stress,which means that the ultimate fracture of fatigue specimens is controlled by the destabilization of fatigue cracks.For the notched specimens,there are multiple crack initiation sites on the fractography.When the nominal section stress multiplied by stress concentration factor equals the nominal stress of the smooth specimens,the main crack length of notched specimens is longer than that of the smooth specimens,meaning that the weight percent of fatigue cracks propagation life in overall life of notched specimens is larger than that of smooth specimens.
YAN Shi, WU Lin-zhi, SUN Yu-guo. Experimental Investigation Compressive Mechanical Properties of 3D 4-directional Braided Composites[J]. Journal of Materials Engineering, 2007, 0(7): 59-62,66.
The mechanical properties of three dimensional and four-directional braided composites were investigated by the macroscopic compressive experiments.Experimental results show that the mechanical properties and mechanism of compressive failure of the composites change with the increase of the braided angles.When the braided angle is small,the material behaves as the brittle characteristics.But if the braided angle is larger than a critical angle,the stress-stain curve of specimen approaches nonlinear,behaving mostly as the characteristics of plastic failure.
YANG Hai-long, NI Wen, LIANG Tao, XU Guo-qiang, XU Li. Preparation and Characterization of Nanoporous Super Insulation Materials Reinforced with Aluminum Silicate Fiber[J]. Journal of Materials Engineering, 2007, 0(7): 63-66.
To solve the low strength problem of silica aerogel,the nanoporous super insulation materials,reinforced with aluminum silicate fiber,were prepared from TEOS through sol-gel process and supercritical drying technology.Their bulk densities were 74-189 kg·m-3,and their thermal conductivity and pore diameter distribution were measured by using the transient hot-strip and BET methods respectively.The test results indicated that their thermal conductivity is 25.3-30.5 mW·(m·K)-1 at normal temperature and pressure,the thermal conductivity of the typical sample(103 kg·m-3) is 93.78 mW·(m·K)-1 at 723K and the pore diameter of it is mainly in the range of 10-20 nm.Additionally,these materials have adequate strength compared with silica aerogel,so they can be used in project and have wide application.
CHENG Huan-wu, CAI Hong-nian, WANG Lu, WANG Yang-wei, XUE Yun-fei. Research on Fracture Mode Under Dynamic Tension of W Fiber/Zr-based Amorphous Alloy Matrix Composites[J]. Journal of Materials Engineering, 2007, 0(7): 67-69.
The dynamic tensile properties of tungsten fibers(80%,volume fraction) reinforced Zr based amorphous alloy matrix composite was investigated by means of the Split Hopkinson Pressure Bar(SHPB),and Scanning Election Microscope(SEM) was used to evaluate the fracture mode of the composite under dynamic tension.It is found that the tensile strength and fracture strain of the composite appeared to enhance with the increase of impact speed;the fracture behavior is dominated by transgranular cleavage of the tungsten fibers,combined with the vein pattern of metallic glass matrix and splitting of tungsten fibers;the vein pattern under dynamic tension is different from that under dynamic compression,no ridge-like structure was observed.
HU Ben-run, LIU Jian-zhong, CHEN Jian-feng. Relationship Between Fatigue Notch Factor Kf and Stress Concentration Factor Kt[J]. Journal of Materials Engineering, 2007, 0(7): 70-73.
Fatigue notch factor Kf is usually used to express the reduction in fatigue strength of the component notch.The factor of Kf is very useful in fatigue design.In this paper analysis for many fatigue limit of aluminum alloy,titanium alloy and steel with stress ratio of 0.5,0.06,-1 showed that the relation between most of Kt and Kf is linear except some case.The relation of Kf and Kt not only depends on the kinds of material but also on the stress ratios.
ZHENG Yun-rong. Size Effects of Thin Section for Single Crystal Turbine Blade Superalloys[J]. Journal of Materials Engineering, 2007, 0(7): 74-77.
The size effects of thin section exist obviously in single crystal turbine blade superalloys.The stress rupture life decreased sharply with reduction of specimen thickness to 0.5mm,especially the stress rupture life at intermediate temperature.These effects contribute to the comprehensive factors,such as the variation of microstructure and surface integrity of specimens,and testing error caused by reduction of specimen thickness.
CAO Rui, MA Qin, CHEN Jian-hong. Current Situation and Prospects for Investigation of Fractal Fracture of Materials[J]. Journal of Materials Engineering, 2007, 0(7): 78-82.
This paper discusses some problems in the research of fractal fracture including the fractal characters of fracture surfaces and the measurement of their fractal dimensions,the relationship between fractal dimensions of fracture surfaces and macroscopic mechanical properties such as fracture toughness etc.,the fracture models and the fractal fracture mechanism.Furthermore,the prospects of performance of fractal theories on metal fracture are advanced in the paper.
