航空材料学报

The influence of high temperature exposure on fracture behaviors of TC11 titanium alloy

ZHANG Wei-fang, GAO Wei, LIU Gao-yuan, ZHAO Ai-guo, TAO Chun-hu

2004, 24(2): 1-5.

[Abstract](1477) [PDF 1020KB](256)

Abstract:
The tensile properties at room temperature of TC11 titanium alloy after high temperature exposure with different temperature and time investigated. The variation and cause of fracture behaviors for TC11 titanium alloy after different high temperature exposure were analyzed. The results show that the tensile properties of TC11 titanium alloy are slightly affected when temperature is lower than 550℃, and on which fractures there are fiber zone and shear lip zone instead of radial zone. When temperature is beyond 550℃, the tensile elongation of TC11 titanium alloy decrease rapidly, and on which fracture there is no fiber zone but only radial zone and shear lip zone. The radial lines converge to a pot adjacent sample surface. Mixed morphology characteristics of ductile ripple, quasi-cleavage and separation along phases and grains were found on radial zone instead of the isometric ductile ripple on fiber zone. Furthermore, quasi-cleavage and cleavage morphology were observed on shear lip zone. The fracture of TC11 titanium alloy after different high temperature exposure resulted from the notch effect of oxygen contamination layer, the precipitation of α2（Ti3Al） and the growth of secondary α and β.

The weld nugget formation of friction stir welded AZ31 magnesium alloy and its affecting factors

ZHANG Hua, LIN San-bao, WU Lin, FENG Ji-cai

2004, 24(2): 6-10.

[Abstract](1404) [PDF 263KB](385)

Abstract:
The main character of friction stirred weld is the formation of the weld nugget. The shape and size of the weld nugget have great effect on the joint mechanical properties. AZ31 magnesium alloy used as base metal and the effect of welding parameters including welding pressure, welding speed and probe tilt angle on the weld nugget formation was studied and a simple model was built to explain the weld nugget formation process. The results showed that the welding pressure and the probe tilt angle are the most important factors on weld nugget formation and the formation of superplastic material depends on the welding pressure. The shape of the weld nugget was affected by the material flow pattern, and the flow movement was caused by the probe and the welding speed, then affecting the weld nugget formation. A good understanding of the weld nugget formation can be used to choose reasonable welding parameters.

Study on the contact fatigue resistance of Cr12V and Cr12MoV steels

LIU Tian-qi, ZHI Min-xue, LI Zhi

2004, 24(2): 11-14.

[Abstract](1532) [PDF 191KB](330)

Abstract:
The contact fatigue resistance of Cr12V and Cr12MoV steels has been investigated. The results showed that the contact fatigue resistance of Cr12V was better than that of Cr12MoV, the rate life and the median life of Cr12V were 2.11 and 1.62 times to those of Cr12MoV respectively.These results were attributed to the higher hardness, smaller carbonides and more V content of Cr12V comparing to Cr12MoV.

A study of hot-water aging and properties for some special fibers

ZHANG Ji-hua, ZHAN Mao-sheng, DUAN Yue-xin, WANG Ying

2004, 24(2): 15-21,35.

[Abstract](1419) [PDF 361KB](300)

Abstract:
The hot-water aging experiments at 25℃,50℃ and 96℃ on Kevlar29,Kevlar49 and PBO fiber are conducted. The relationship between water absorbtion,tensile strength and hot-water aging condition are evaluated. The change of chemical-structure possibly occurred during fibers absorbing water is analyzed by FTIR spectra. The change of microscopic surface appearance made by hot-water is observed by SEM and the mechanism of water absorbtion on three kinds of fibers is discussed.

Study on the mechanical properties of microwave-absorbing composite with circuit analogue

XING Li-ying, JIANG Shi-cai, LI Bin-tai

2004, 24(2): 22-26.

[Abstract](1337) [PDF 821KB](280)

Abstract:
The influence of the content of absorbent and the structure of circuit analogue on the mechanical properties of microwave-absorbing composite materials was investigated. The properties of bend, compression and shearing in room temperature and 80℃ were tested. The mechanical properties testing results show that rational structural design can effectively improve the mechanical properties of the microwave-absorbing composite systems, and make the wave-absorbing and loading property integrative in microwave-absorbing composite materials.

Experimental investigation on mechanical property of metal rubber used in Lunar Lander in high or low temperature

WANG Shao-chun, DENG Zong-quan, GAO Hai-bo, HU Ming

2004, 24(2): 27-31.

[Abstract](1437) [PDF 237KB](494)

Abstract:
Metal rubber was used in a principle model machine of Lunar Lander at first as a damping element with elastic behavior. Quasi-static rigidity experiments for a metal rubber ring were completed with Э-71 type universal draw-frame in low temperature at the range of the Moon temperature, and the curve of force and displacement was obtained. Method of least square was adopted to fit the experiment curves and force, and displacement regression equations of metal rubber specimen were obtained with Matlab software. Spontaneous decay method and impact experimental method were used to test damping ratio and other dynamic character of the specimen in high or low temperature, respectively. At last, the conclusion that metal rubber specimen is fit for cushion element of Lunar Lander was obtained.

Study of nanometer ZnO reinforced PTFE

LI Wei-jing, ZHAO Yang, LI Rong-hua, HAN Jian-min, WANG Jin-hua

2004, 24(2): 32-35.

[Abstract](1427) [PDF 633KB](415)

Abstract:
Nanometer ZnO reinforced PTFE(polytetrafluoroethylene) composite was prepared by employing nanometer ZnO as reinforcements and the way of latex commixing. Comparative combining process was determined in this research, which enables the improvements on a plurality of properties of the composite while the cost kept unchanged. Furthermore, the microstructures of the composite were investigated with the aid of scanning electron microscope, and the size distributions of nanometer ZnO were studied as well. The relationship between properties of the composite and the volume fraction of the ZnO reinforcements was analyzed in accordance to the experimental results. Based on the above-mentioned work the strengthening mechanism of nanometer ZnO reinforced PTFE was developed.

Research on rheology of composition of nano-CaCO₃/PPS

LONG Sheng-ru, HUANG Rui, YANG Jie, WEI Gang, YUAN Shao-yan, SONG Bo

2004, 24(2): 36-39.

[Abstract](1419) [PDF 954KB](281)

Abstract:
The research on the rheology of the composition of nano-CaCO3/PPS of various proportions has been conducted with the high-pressure capillary and the rheological behaviors of 0%, 3%, 5%,10%, 20% and 40% have been observed at the temperature of 290℃. The result shows that when the component of nano-CaCO3 is at the low level, the viscosity of the system is not changed greatly and the rheologcial behavior of the composition system is found to be pseudo-plastic and thus satisfy the power model.

Synthesis and properties of phenol-starch resin

CHEN Guo-min, CHEN Zhao-hui

2004, 24(2): 40-45.

[Abstract](1476) [PDF 1749KB](238)

Abstract:
The one-step synthesis of a new phenol-starch resin by polycondensation with phenol, starch as raw materials under catalysis of sulfuric acid is introduced.The synthetic reaction mechanism and the resin structure are characterized, the effects of amount of catalyst, technological parameters (total reaction time, highest reaction temperature) and raw material ratio (phenol/starch) on the product are discussed.The typical raw materials formula, synthetic technological route and technological parameters are determined, the analysis of the properties and the beneficial superiority is conducted. Results show that phenol-starch resin belongs to thermoplastic phenolic resin, it is similar in the properties to the thermoplastic phenol-formaldehyde resin, specially it has very good heat resisting property, and the economic and environmental beneficial superiority is obvious.

Change in interfacial toughness of EB-PVD thermal barrier coatings during isothermal oxidation

XU Qian-gang, TANG Jian-xin, WANG Ning, LU Feng, WU Xue-ren

2004, 24(2): 46-49.

[Abstract](1512) [PDF 1035KB](208)

Abstract:
Indentation test was used to measure the change in the interfacial toughness of EB-PVD TBCs at 1100℃. Measured interfacial toughness （Гi） of TBCs is about 38～45 J/m2 and changes slightly. Due to the rapid increase of elastic strain energy （G0） induced by the thickening of TGO, the normalized interfacial toughness （Гi/G0） decreases sharply and approaches 1 gradually. This result indicates that the thickening of TGO formed by the oxidation of bond coat plays an important role in the failure of TBCs.

Development of manufacturing cost estimation models for advanced composites materials

WANG Dian-fu, LIU Ling, ZHANG Bo-ming, WU Zhan-jun, ZHANG Bao-yan, XING Li-ying

2004, 24(2): 50-55,62.

[Abstract](1630) [PDF 307KB](663)

Abstract:
The reduction of manufacturing cost could be a key element in expanding the use of composites. Cost estimation model is not only the basis in evaluating quantitatively the processing cost of composites but also a vital technical measure of decreasing the procedure cost of composite materials. Central to design for manufacturing of composites is the selection of the best material and manufacturing process for a particular product, and realizes the tradeoff between performance and cost for the product. Cost estimation is an essential part of design for manufacturing because it can establish a quantitative relationship between the technical process and the cost. The main objective of this article is to provide a comprehensive overview of the foreign manufacturing cost estimation models of advanced composites and presents the future research direction about the integrated analysis of process-performance-cost based on cost estimating.

Progress in molding technology of polyimide tubular film

XU Yi-kun, ZHAN Mao-sheng

2004, 24(2): 56-62.

[Abstract](1464) [PDF 319KB](406)

Abstract:
Several methods for manufacturing polyimide tubular film were discussed in this review. These methods include spiral winding, metal wire method, casting, centrifugal molding, core gasifying method, extruding, and so on. The key technical problems and the solutions during the process for producing polyimide tubular film were proposed. It is really necessary to research and develop the molding technology of polyimide tubular film.The extensive application was in prospect.

2004 Vol. 24, No. 2