- Volume 45,Issue 5,2015 Table of Contents
>综述
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2015, 45(5).
Abstract:
Ultra鄄high temperature ceramics (UHTCs) are regarded as the most promising thermal protective ma鄄terials for the nose and leading edge of hypersonic or re鄄entry vehicles due to their stability of physical and chemicalproperties in extreme environment. The progress on UHTCs is reviewed in detail, including powder synthesis, densifi鄄cation and mechanical properties. Also, some problems exist in the material studies are preliminarily summarized. Itis expected that this review will provide some guidance for stimulating further research and practical applications of theUHTCs. -
2015, 45(5).
Abstract:
The pressure vessel of cylinder and tank are key components in space structural dynamic system. Thispaper summarized classification and current situation of cylinder and tank,introduced cylinder and tank manufacturingtechnology used in aerospace. The development trend of high鄄performance, light鄄quality, series cylinder and tankwere predicted. >计算材料学
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2015, 45(5).
Abstract:
The carbonization of resins owns a very complicated with physically and chemically phenomenon, in鄄volving heat and mass transfer, stress and strain generation and pyrolysis. The transient governing equations of cou鄄pled thermo鄄hydro鄄mechanical process are theoretically derived based on physical conservation, namely equations forresins deformation, gas flow and energy conservation. Analysis of coupling interaction of the multi鄄physics are carriedon. And some suggestions are proposed for further study. >新材料新工艺
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2015, 45(5).
Abstract:
In this work, the broadband wave鄄transparent materials were prepared via the composite of multilayerfrequency selection surface( FSS). Meanwhile, the FSS was made with conductive metal material platinum throughscreen printing process, and porous nitride ceramic materials were used for medium support of FSS. Detailed analysesare made for microstructure and properties of the wave鄄transparent materials. As a result of the study, multilayer FSSstruture shows excellent overlapping and consistent cycle; the FSS compostion is stable and acquires a dense structurelayer with well conductive properties; also the multilayer ceramic and metallic FSS has transmittance of 95% at 9. 5 to18 GHz frequency. -
2015, 45(5).
Abstract:
A 3D six鄄layer curved shallow鄄crossing linking lightweight fabric used for armed car interior was pre鄄pared using glass fiber with the linear density of 2 400 tex as raw material on a 3D loom modeled SGA598. The curvedshallow鄄crossing linking composite applying in armored car interior was successfully prepared by hand composite mod鄄eling. The curved shallow鄄crossing linking and resin system was composed of epoxy resin and polyether amine in amass ratio of 3 颐1,in the mass ratio of 2 颐1,3 颐2,1 颐1,2 颐3 and 1 颐2. Universal material testing machine modeled Instron3385H was employed to characterize the bending property of the composite and the effect of resin content to the ben鄄ding property of the composites was studied. Scanning electron microscope was employed to observe the fracture inter鄄faces of the composite and for further study on bending failure mechanism of the composite. the composite possessesexcellent mechanical. Both of the bending strength and the bending modulus reach the maximum when the mass ratioof fabrics and resin is 1 颐1. The fragmentation of resin matrix and the extraction and breakage of fiber is the main fail鄄ure mode of the composite. -
2015, 45(5).
Abstract:
Carbon nanotube film(CNTF) / carbon fiber reinforced resin composite were fabricated via autoclaveprocess with two kinds of carbon nanotube film interlayer toughening respectively. Effect of the molding process, ori鄄entation and planar density of the carbon nanotube film on the mechanical properties and interlaminar toughness ofcomposite were investigated. The result reveals that compared to the vertical direction, when the CNTF were layedparalleling to the carbon fiber, the compression strength,90毅flexural strength and interlaminar shear strength of com鄄posite were better. The toughening effect of the composite enhanced as the planar density of the carbon nanotube filmdecrease. The interlaminar fracture toughness of composite interlayer toughened by carbon nanotube film sprayed ismore outstanding evidently than carbon nanotube film drawed. When the planar density of the carbon nanotube ran鄄dom film was 0. 75 g/ m2, GIC and GIIC of composite were optimum, increased by 21% and 42%, respectively,com鄄pared to composite before toughening. -
2015, 45(5).
Abstract:
Isothermal chemical vapor infiltration(ICVI) was used to study carbon cloth stitched preform densifi鄄cation process,methane was the precursor,at the temperature of 1 368 K and residence time of 1 s. Carbon clothstitched preform porosity distribution under different time was characterized by mercury porosimetry, and the pyrocar鄄bon structure was observed by PLM. It is found that the porosity presented multipeek shape,and pyrocarbon depositionrate and [A / V]value showed a inverse correlation throughout the whole study process. The texture of the pyrocarbonhad a relationship with the specific surface area. Isotropic and low textured pyrocarbon was first got at the initial of in鄄filtration,then high textured pyrocarbon was discovered at larger size pores like the edge of the bundle. -
2015, 45(5).
Abstract:
In this paper, wet鄄hot cycling test, salt鄄fog test, accelerated aging test and solar radiation test weredesigned to simulate three special environments to test the performance change of HCFC-141b blowing polyurethaneplastic foam. Compressive strength, closed cell proportion, liner expansion coefficient and thermal conductivity weretested before and after environment tests. The results indicate that after the three special environment tests HCFC-141b blowing polyurethane plastic foam have higher compressive strength and thermal conductivity, smaller liner ex鄄pansion coefficient and equivalent closed cell proportion. Solar radiation test on properties of foam effect maximum.Compressive strength of sample SD-4 increased by 32%, and obturator first increased and then decreased, linear ex鄄pansion coefficient decreased by 19%, the thermal conductivity increased 30%. -
2015, 45(5).
Abstract:
The three鄄dimensional finite element model of foam core sandwich panel with non鄄penetrating damageof SR20 airplane is established. The convergence of the model is analyzed and the effective mesh density is given.Stress analysis of the sandwich panel with non鄄penetrating damage under uniaxial and twin鄄axial tensile loading is car鄄ried out. The material principle direction stresses distribution of the sandwich panel with no defects and repaired panelare given. The uniaxial and twin鄄axial tensile strengths of the intact and repaired panel are calculated based on thestrength criterion of maximum stress. It is shown that under uniaxial tensile loading, the initial damage mode of the re鄄paired panel is shear failure. The failure occurs on the motherboard which is beside the boundary of the repair areaand about 30毅to the x symmetry axis of the panel. Under twin鄄axial tensile loading, the initial damage mode of re鄄paired panel is the fracture of the reinforce fiber. The failure occurs on the motherboard which is near the boundary ofthe repair area and is about 45毅to the x symmetry axis of the panel. In the ideal repair status, the strength recoverycoefficient of the repaired panel under uniaxial tensile loading is 85. 8%, and 96. 7% for the same repaired panel un鄄der twin鄄axial tensile loading. The strength of the repaired sandwich panel decreases due to the stress concentrationcaused by the material discontinuity of the repair area. The strength of the repaired sandwich panel decreases with theincrease of the number of surface patches. This happens thanks to the increase of local stiffness caused by the addi鄄tional surface patches. -
2015, 45(5).
Abstract:
AZ31 was as the research object based on thermal simulator Gleeble1500 under the conditions of hotcompression experiment to obtain material stress鄄strain curve. Under different temperature and strain rate,using metal鄄lographic microscope analysis of metallographic observation was condensate, and comparative analysis of the micro鄄structure before and after compression was nerforel. At the same time the mechanical behavior of materials under dif鄄ferent temperature and strain rate was analyzed, its behavior belongs to the typical type of dynamic recrystallization.When hot compress temperature is 350益and 400益, material strength increases with the strain rate, and strain hard鄄ening is also increased. When the strain rate is 0. 01/ s and 0. 1/ s, with the increase of deformation temperature andstress of the material is gradually reduced. Compared with strain rate of 0. 01/ s,the stress with strain rate of 0. 1/ s islower under different temperature -
2015, 45(5).
Abstract:
In this thesis, prepared Nb-38Ti-12Al alloy is processed into sheet. The thickness of sheet is 0. 50mm. Based on this, X鄄ray Diffraction(XRD),optical microscope(OM),scanning electron microscope(SEM)and box re鄄sistor鄄stove, and analytical balance are used to study the oxidation behavior of alloy. The oxidation behavior of Nb-38Ti-12Al at 1 200益is studied. The oxidation layer appeared layering phenomenon. The calculation of oxidation weightgain per unit area made it possible to draw oxidation weight gain curves. The kinetic equation of the intimal oxidationlayer can be expressed by x1. 228 =34. 50t and x1. 480 =288. 73t,respectively,at 1 000益and 1 200益. -
2015, 45(5).
Abstract:
This paper is focus on the mechanical properties of similar and dissimilar clinched joints in 1420 alu鄄minum鄄lithium and titanium alloy sheet materials. Load鄄bearing and buffering capacity are the main standards whichcould assess quality of clinched joints. Force鄄displacement curves and energy absorption drawn from the test could getload鄄bearing and buffering capacity indirectly and also show that TA1-1420 joint owns great mechanical properties.Besides, compared with TA1-TA1 joint, TA1-1420 joint爷weight is lighter because of its lighter lower sheet. Resultsshowed that TA1-1420 joint is more suitable for the part which require higher load鄄bearing and buffering capacity -
2015, 45(5).
Abstract:
In this paper, a thermal treatment apparatus was established to take local heat treatment on zinc鄄coa鄄ted clinched joints. Then mechanical test was conducted on the specimens under tensile鄄shear condition, and the met鄄allographic specimens were prepared to observe the metallographic structure of the clinched specimens with heat treat鄄ment. The micro鄄hardness of metallographic specimens with heat treatment and non鄄heat treatment were also meas鄄ured. The results exhibited that compared with the clinched specimens with non鄄heat treatment, local heat treatmentlargened the degree of joint neck tear and the static strength increased by 16. 7%. The material structure of theclinched joints has changed from ferrite and pearlite to lath martensite after thermal treatment. In comparison to un鄄heated treatment, the micro鄄hardness of the new microstructure is increased by 12. 1%. >测试分析
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2015, 45(5).
Abstract:
In order to solve the lack of fusion, A-MAG welding was invented, which obtained welded joints ofhigh quality. The experiment results show that surface appearance of A-MAG weld, internal quality of welding jointand the welding operation perform very well. Experiments also show that the A-MAG welding can improve weld pene鄄tration, compared with MAG welding on the same heat input. The tensile property and bending strength of A-MAGare not reduced while impact strength is improved, especially in the HAZ. Dimples size of A-MAG welded joint frac鄄ture becomes finer. It is shown that the active MAG welding can improve the welding quality and weld penetration ofweathering steel, which has the value of engineering application. -
2015, 45(5).
Abstract:
The high cycle fatigue fractography of 5A06 aluminum alloy was investigated by means of optical mi鄄croscopy(OM), scanning electron microscopy( SEM) and energy dispersive spectrometer( EDS). The results showthat the fatigue cracks mainly initiate at the interface between impurities and matrix when the loading stress is near thefatigue limit. Multi鄄source fatigue cracks appear with the increase of the stress and the cracks originate mainly fromthe broken impurities. The crack deflection path becomes more complex, the fatigue striation increases and the fatigueexpansion area becomes smaller with the stress increasing. The direction between adjacent grain favored slip planesdetermines the deflection of the micro鄄crack in the early stage of the fatigue crack propagation. -
2015, 45(5).
Abstract:In this paper, the modal flexibility curvature matrix FCM of composite was used to discuss the NDT composite materials, the natural frequency of the composite beam and shift values of each node are simulated by modal analysis. The damage of composite beam is detected by calculating the modal flexibility curvature matrix. According to the beam theory we put forward a new theory based on the modal flexibility curvature matrix to detect the damage of composite plate,namely longitudinal and transverse flexibility curvature matrix. The results show that for a single de鄄 lamination, longitudinal and transverse flexibility curvature mutation rates were 3. 6310 and 5. 4078 times respecting. For multiple delamination the longitudinal and transverse flexibility curvature mutation rates were 3. 5350,5. 9028 times at the small damage location. While at the big damage location,the longitudinal and transverse flexibility curva鄄 ture mutation rates were 5. 6803,10. 0109 times. Mutation position of flexibility curvature mutation coincides with the preset position. So longitudinal and horizontal flexibility curvature can determine the location and size of composite de鄄 lamination, and relatively speaking, longitudinal flexibility curvature works better than transverse flexibility curvature in damage detection.
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2015, 45(5).
Abstract:
The traditional ultrasonic B scan and C scan detection are unable to fully show overall perspective ofcomposite defects in composites. In this paper, the specimen with an artificial prefabricated flaw was detected by im鄄mersion ultrasonic C scan imaging through the experimental method . Based on the principle of ultrasonic C scan thebottom wave amplitude imaging, through one scan , ultrasonic reflected signals were acquired in different depth posi鄄tion to form slice C scan imaging and slice C scan images were used for observe defects inside the material. Experi鄄mental results have shown that, complex defects in composite materials can be multi angle imaging and full range ofclearly displayed by combined ultrasonic A, B, C scan imaging method with slice C scan imaging method. -
2015, 45(5).
Abstract:
To improve oxidation resistance, the granule of refractory metal compound is intermingled with car鄄bon鄄carbon composite. The change of matrix influences the mechanical property greatly. The cutting temperature in鄄creased slightly, which was lower than the temperature of common metal obviously. The influence of the cutting tem鄄perature for the tool life is minimal. However the high hardness of the granule of refractory compound caused the abra鄄sive increas dramatically, and the decreased of tool life. The dominant wear mechanism was abrasive wear, meanwhilethere was different form of tool wear and tool breakage.
