- Volume 44,Issue 2,2014 Table of Contents
>综述
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2014, 44(2):1-6.
Abstract:This paper summarizes recent development of organic groups modified SiO2 aerogels. The modification
mechanism, preparation and the properties of the resulted SiO2 aerogels are reviewed in detail. The future of the organic
groups modified SiO2 aerogels is also prospected. -
2014, 44(2):7-12.
Abstract:
Formation and evolution of the thermally grown oxides(TGO) have great effect on the properties ofthermal barrier coatings( TBCs), suggesting a sticking point for analyzing TBCs failure and prolonging the life ofTBCs. The research progress of the oxidation behavior of TBCs worldwide is summarized,including oxidation kineticsof bond coating(BC),composition,structure and evolution of TGO,and transformation from metastable Al2O3 to stableAl2O3. Effects of elements from BC on the morphology and structure of TGO is analyzed,as well as the elements diffusedfrom substrate. Idea for research of BC-oxidation behavior and methods for properties-improvement of TBCs areindicated. >计算材料学
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2014, 44(2):13-18.
Abstract:
A new kind of structure of the directional composite laminated shell structure is designed in this paper,based on the composite laminated plate as the basic matieral. The weakness is precasted in the missile and the initialcontact area of the shell structure precast defect area. The missile launch cracking in the form of four petals,andthe efficiency of the missile launch is improved greatedil. Through the finite element simulation analysis software ANSYS,the design scheme of the layer is determined by the strength analysis, namely 0. 2 mm of the thickness for thesingle plate,the weakness is strengthen using the matrix itself,the kinds of the layer methods for [0°/90°/ ±45°]2S,the limit load is 0. 21 MPa and the minimum bursting load is 1 kN of the layer, so that it can meet the design requirementsto bear certain internal pressure and in smaller bursting load to crack in the work environment. -
2014, 44(2):19-23.
Abstract:
Based on heat transfer theory, mechanics of composite materials and cure kinetics, the temperature,degree, reaction rate of cure and thermal stress in the composite helicopter blade’s curing process under the recommendedtemperature cycle of F650 bismaleimide resin are calculated. The strong coupling multi-physics finite elementmethod for solving partial differential equation is applied in this paper. The result shows that during the curingprocess, the curing reaction of resin is highly synchronized, and the exothermic crosslinking reaction is faint; comparedwith the recommended heating cycle, the highest heating temperature lowers from 460 K to 393 K in the adjustedheating cycle, but the reaction time of the curing degree from 0. 1 to 1 only increases from 25 to 30 min, the peakvalue of the curing reaction rate decreases from 1. 35×10-3 / s to 1. 15×10-3 / s,and the maximal thermal stress in thePMI foam drops from 0. 82 MPa to 0. 482 MPa.
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2014, 44(2):24-28.
Abstract:
Ductile fracture in metals is the accumulative result of damage. The basic mechanisms of ductile fractureare divided into two modes (tension-type mode and shear-type mode) according to voids evolution model and meso-damage mechanism. A unified ductile fracture criterion is proposed for wide applicable range. The proposed ductilefracture criterion is implemented into quasi-static finite element method through a compilation of user’s material subroutineVUMAT of the commercial finite element platform ABAQUS. The ductile fracture model is validated by comparingbetween experimental data and numerical results. It is shown that the proposed ductile fracture model can accuratelyand effectively predict the whole damage process of ductile metals including crack initiation, propagation and finalfracture. Ductile metallic materials voids-fracture mechanism studies show that the formation of macroscopic crackmonotonic in the loading process are the growth of voids in the inclusions and second phase particles around the nucleationuntil the polymerization. >新材料新工艺
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2014, 44(2):29-32.
Abstract:
The effect of the way of cut fiber, glass fiber length, the type and amount of dispersants on dispersionof glass fiber suspension was investigated. The results showed that the dispersion degree of glass fiber after cutting issignificantly higher than that of glass fiber before cutting. The percentages of fiber mass area in the suspension beforeand after cutting are 72. 6% and 2. 4%, respectively. The dispersion of rectangular cotton-block after beating is betterthan that of the square cotton-block. The longer glass-fiber length or the higher reunite phenomenon, the more difficultdispersion of the glass fiber suspension. The appropriate length of glass fiber, about 10 ~12 mm, is helpful tothe dispersion of the suspension. When the mass fraction of the suspension is up to 0. 2%, the optimum addition amountsof hydroxyethyl cellulose, hydroxypropyl methyl cellulose and sodium hexametaphosphate are 0. 008%,0． 012% and 0. 04%, respectively. Correspondingly, the absorbances of glass fiber suspension under the optimalmass fraction of three types of dispersants are 0. 344, 0. 703 and 0. 663 A, respectively. The sedimentation experimentshowed that the glass fiber suspension added the sodium hexametaphosphate had the best dispersion, the minimumsuspension sedimentation height and the slowest sedimentation rate. The dispersion of the glass fiber suspensionadded hydroxypropyl methyl cellulose is better than that of the glass fiber suspension added hydroxyethyl cellulose. -
2014, 44(2):33-36.
Abstract:Hygroscopic behavior was investigated with different scarf patch repair methods of GFRP laminates, then hygroscopic law and damage behaviors were gained. Main factors leading to decrease of hygroscopic property and interlaminar fracture were investigated and analysed through the in-plane shear properties tests and morphology observation, whch show that hygroscopic behavior increases with the increase of porosity, while the interlaminar fracture tendency decreases, the important factors influencing hygroscopy and interlaminar cracks is the porosity of GFRP laminates. Step ratio has a great influence on intensity of laminates, selecting the best step ratio is a good way to improve strength retention and decrease the strength reduction influenced by hygroscopic behavior. The investigation also confirms that hygroscopic behavior can seriously weaken fibre resin interface bonding state and the hygroscopic behavior is one of the main reasons which lead to the significant reduction of in-plane shear strength of laminates after moisture absorption.
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2014, 44(2):42-48.
Abstract:
An extensive investigation was carried out on the retractable friction stir welding of 2219 aluminiumalloy with the thickness of 8 mm, and the retractable track, microstructure and mechanical properties of the weldingjoint at the different locations have been analyzed. The results indicated that the actual trajectory of the RPT is thecombination of welding speeed and retracting speed, and showed a linear relationship. The morphology at the beginningand end of the retractable FSW welded seam showed a typical conventional FSW microstructure, while the jointlocated in the middle of the retractable FSW welded seam can be considered as the composite of a 100% penetrationwelded joint and a joint with gradually shallower depth. The results of the tensile test indicated that the mechanicalproperty of the joint at the end of weld seam is the highest, followed by the joint loacated at the beginning and middleof the retractable FSW welded seam. With the retracting distance increasing gradually, the performance of the joint inthe middle of the retractable FSW welded seam also gradually increased. The fracture mechanism of the joint at differentposition is all ductile fracture. >测试分析
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2014, 44(2):49-53.
Abstract:
In future, the characteristic of reentry thermal environment is high enthalpy,high heat flux and lowpressure. In order to meet the requirements,the performance of different light weight charring ablators in high enthalpyablation test must be known. These kinds of tests have been carried out by using super-enthalpy arc-heater. Subsequentlythrough the description of test data, the characteristics of light weight charring ablators ablated in high enthalpyand low pressure are given. At last contrasting to the normal test with middle enthalpy,the ablative performances affectedby enthalpy of light weight charring ablators are detailedly analyzed. The results show that super-enthalpy archeatercan produce a high enthalpy and low pressure flow field stably and uniformly. The performances of light weightcharring ablators are improved in high enthalpy environment. -
2014, 44(2):54-57.
Abstract:
With the quartz lamps and arc-heated wind tunnel, the high temperature supersonic flowfield wasbuilt. A principle thermal protection specimen with a high temperature heat-pipe and high thermal conductivity graphitewas heated in this flowfield, the surface temperature distribution was measured by infrared temperature instruments.Compared with contrastive carbon/ carbon composite material specimen, the stagnation point temperature ofhigh temperature heat-pipe was decreased 9. 5% as well as the cylinder surface temperature is increased 14. 6%, thestagnation point temperature of high thermal conductivity graphite is decreased 14. 4% as well as the cylinder surfacetemperature is increased 11. 4%,both of the two specimens can transfer the heat load effectively from the high heatfluxfield to the lower one. -
2014, 44(2):58-61.
Abstract:
Carbon fiber composite material is gaining wider use in aerospace systems. Its shielding effectivenessis limited due to the conductivity. The shielding effectiveness is theoretically modeled and its result is verified by experiments.The influence of frequency, thickness is analyzed on the basis of the model -
2014, 44(2):62-66.
Abstract:
The T700/3234 pipes manufactured by hot press were presented in this paper. The tensile, compressiveand flexural properties of the pipes were tested with or without memory alloy ring. The results show that the pipeswith memory alloy ring have an increase of 10. 1% on max tensile load, more than 10% on compressive load andcompressive strength and 5. 5% on flexural load. The pipes with memory ring demonstrate an improvement of mechanicalproperties except for compressive modulus. The work of this paper establishes a reference for design of high performancecarbon fibre composite pipes. -
2014, 44(2):67-70.
Abstract:
A 1420 aluminum-lithium alloy forging used in a key project cracked when it was deposited in quarry.In this paper, fraction analysis, metallographic analysis and mechanical property analysis were employed to investigatethe reason why cracking phenomenon happened. The results indicated that the cracking problem was delayedcracking. Local stress concentration appeared in the R area, where micro-surface cracking formed at the phase of water-cooling. In the process of the long-time storage, the surface of the forging was corroded, resulting in stress occurred.Under the gradual action of residual stress and stress corrosion, micro-crack enlarged to be perforated crack,which resulted in the cracking of the forging. Fortunately, such defect could be prevented by cutting the forging’s internal/external surface away and then detected with fluoroscopy. -
2014, 44(2):71-74.
Abstract:
The butt-joint pipe was made of bars of 1Cr18Ni9Ti, weld with the same type pipe after machining,then acid washing defects were found in the parts of suface. Through observation and analysis of suface morphology,composition,metallography,microhardness and acid test, we can conclude that chromium depletion areas along the deformationline was exist that cause the corrosion preventive becoming worse. In the machining process,the chromiumdepletion areas expose to the surface or near the surface,corrosion first happened in the areas with the process of acidwashing,then macroscopic defects of pitting are formed. The chromium depletion phenomenon is the defects of raw material. >工程实践
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2014, 44(2):75-78.
Abstract:
The research of chemical milling for LD10 aluminum alloy plate have been studied in order to solvethe problem of poor surface quality of cover which is processed by chemical milling used in the launch vehicle structuresystem. Experiment was conducted following same chemical milling process parameters for parts with same batch,same deformation and different heat treatment state (quenching and artificial aging, quenching and over aging). Andthe chemical composition and microstructure of the parts were analyzed. The results of theoretical study and experimentshow that: surface quality of LD10 aluminum alloy parts processed by chemical milling is related with the heattreatment, moreover, the better surface quality belong to the part with annealing and quenching and artificial agingstate. The surface quality of chemical milling part is improved by over aging without affecting mechanical properties. -
2014, 44(2):78-82.
Abstract:
In order to explore the strength of the structure with lap joints, the adhesively bonded single lap jointswith differential temperature were tested in tension loading which creates shear across the bondline. The equivalentstress was obtained through finite element analysis to define the effect of temperature, which helped to get the conclusionsthat the higher of the temperature, the bigger of the thermal stress and thermal stress value and the stronger ofthe adhesive strength. Then, the failure modest of the adhesive varioused with the increasing of the temperature. -
2014, 44(2):83-86.
Abstract:
NC Machining Processes of central bearing column shell was implemented by constituting reasonablescheme. The machining precision and surface quality were guaranteed. The production efficiency was improved. Thetechnical scheme of NC machining proved by the experiments carried out on 5-aixs linkage computer numerical controlmachine was available >科技信息
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2014, 44(2):87-90.
Abstract:
The development of material and process of the POGO suppress device is overviewed, such as bladderaccumulator, piston accumulator, mental bellows accumulator, ball gas-charged accumulator which used in the rocketdevelopment history. Through the introduction of the materials and technology of U. S. POGO suppress device, a referencefor the development of materials and processes related fields is provided.
