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41.
Rotating-bending uniaxial fatigue tests and micro-fatigue crack initiation tests were carried out using a permanent mold cast
(PMC) and semi-solid die cast (SDC) with Al−7%Si−0.35%Mg composition in order to examine the relationship between solidification
structures and fatigue behaviors. The crack length was measured using a replication method. Fatigue strength was improved
in SDC, which was almost consistent with the predicted fatigue strength using the size of Si particle cluster. Resistance
to fatigue crack initiation and fatigue strength were improved in SDC owing to the finer Si cluster and to higher ultimate
tensile strength. Fatigue crack in PMC was preferentially initiated at pores. For SDC, the fatigue crack was initiated at
the Si particle/matrix interface, and then sucessively grew along eutectic cell boundaries. 相似文献
42.
纤维混凝土在水工建筑工程中的应用(上) 总被引:1,自引:0,他引:1
概述改性混凝土垢发展情况,介绍纤维混凝土在国内外水工建筑物上的应用实例,提出钢纤维增强钢筋混凝土水工建筑结构强度计算方法。包括受弯构件正截面强度,斜截面抗剪强度的计算;重点介绍了网状钢纤维增强混凝土(FOC)在水工建筑物上的应用,包括在渡槽,闸门,小型拦河坝,轻型岸型等工程上的应用实例,T新梁正斜截面的强度计算,板材承载力计算的方法。 相似文献
43.
采用自行开发研制的超音速电弧喷设备,在45钢表面制成了钛铝合金复合涂层。并利用金相显微镜、X射线衍射仪、扫描电镜、电子探针,对涂层的成分、相结构、显微组织及其结合强度、显微硬度进行了研究。结果表明,利用超音速电弧喷涂设备,可以在45钢表面形成 度高、孔隙率低,结合强度较好和硬度高的Ti-Al合金涂层。 相似文献
44.
45.
Toshihiko Hoshide Junpei Fujita 《Journal of Materials Engineering and Performance》2008,17(5):627-632
Strength of ground ceramics may be affected by residual stress as well as surface flaws induced by grinding. Strength prediction
for ground ceramics is convenient for mechanical design of ceramic components. In this article, a numerical procedure based
on fracture mechanics was proposed to estimate strength distribution of ground ceramics by considering grinding-induced residual
stress. Bending strength and residual stress of ground ceramics were measured for three grinding-conditions. By comparison
of simulated results with experimental ones, it was revealed that strength characteristics in experiments were well simulated
by using the proposed procedure. 相似文献
46.
Xiang‐Dan Li Zhen‐Xin Zhong Sang‐Hoon Han Seung Hee Lee Myong‐Hoon Lee 《Polymer International》2005,54(2):406-411
From chloromethylated polyimide, a useful starting material for modification of aromatic polyimides, a thermocurable transparent polyimide having acrylate side groups was prepared. In the presence of 1,8‐diazabicyclo[5,4,0]undec‐7‐ene, chloromethylated polyimide was esterified with acrylic acid to synthesize poly(imide methylene acrylate). The polymer was soluble in organic solvent, which makes it possible to prepare a planar film by spin coating. The polymer film became insoluble after thermal treatment at 230 °C for 30 min. Optical transparency of the film at 400 nm (for 1 µm thickness) was higher than 98 % and not affected by further heating at 230 °C for 250 min. Adhesion properties measured by the ASTM D3359‐B method ranged from 4B to 5B. Preliminary results of planarization testing showed a high degree of planarization (DOP) value (>0.53). These properties demonstrate that poly(imide methylene acrylate) could be utilized as a thermocurable transparent material in fabricating display devices such as TFT‐LCD. Copyright © 2004 Society of Chemical Industry 相似文献
47.
Renjith Devasia CP Reghunadhan Nair P Sivadasan KN Ninan 《Polymer International》2005,54(8):1110-1118
Polyacrylonitrile terpolymers of various compositions consisting of acrylonitrile (AN), itaconic acid (IA) and methyl acrylate (MA) were synthesized by solution polymerization in dimethylsulfoxide. Increase in concentration of either IA or MA retarded the overall polymerization rate and the polymer molecular weight. The system consisting of AN + MA and varying IA concentration was more prone to retardation in comparison with the system composed of AN + IA with variable MA concentration. The retardation factors were quantified. Minor quantities of MA boost the reactivity of IA in the terpolymer system. The terpolymer was richer in MA vis‐à‐vis the feed. The thermal characteristics of the terpolymer were examined as a function of its composition. In contrast to the copolymer of AN and IA requiring 1–1.5 mol% IA, the terpolymer required an IA content of approximately 2.5 mol% for optimum thermal stability. The polymer with 90 mol% AN, 2.5 mol% IA and 7.5 mol% MA exhibited reasonably good char‐forming characteristics and thermal stability. The overall crystallinity and crystallite size of the polymers were found to decrease on incorporation of the comonomers. The ‘aromatization index’ of the copolymer increased with the temperature of pyrolysis through re‐organization of the tetrahydropyridine ladder structure. Copyright © 2005 Society of Chemical Industry 相似文献
48.
Polyelectrolite hydrogels are crosslinked polymers which display high sorption capacity in water and water solutions. They are widely used in the marked of personal hygiene products, as well as in other biomedical and industrial applications. In the most industrial application they are not biodegradable and prepared starting from acrylamide.In this work, the chemical-physical analysis of a novel class of natural polymers-based microporous superabsorbent hydrogels has been presented. The main focus is the definition of the relationship between material's chemical-physical structure and its equilibrium sorption properties.The effect of the variation of the degree of crosslinking, the polyelectrolyte nature of the backbone and the hydrogel microporosity on its swelling properties has been analysed, and a good agreement with the theoretical statements has been displayed.The effect of the ionic strength and the pH of the external solution in contact with the hydrogel on its equilibrium sorption properties has also been assessed, and an high sensitivity to these variations was detected for all the tested chemical compositions and physical structures.This work have to be considered part of the efforts towards the reduction of the environmental impact of the large scale consumption industrial polymer based products. 相似文献
49.
在薄板坯连铸连轧流程上,经过对Ti微合金化技术研究,有效解决了Ti微合金化强度性能波动大的问题,开发出屈服强度450~700MPa高强钢。对试制钢组织性能和工业应用分析研究,表明该产品通板性能良好,通板强度差30MPa左右;成形性能良好,d=0时冷弯测试全部合格;同时还具有良好焊接性能,焊接后,强度波动较小,均在母材部位断开;试制钢显微组织为珠光体和铁素体,晶粒均匀细小,平均尺寸为4~8/μm;实物质量满足集装箱和汽车制造行业要求,具有广阔市场前景。 相似文献
50.
Wang Xuegang Yan Fengjie Yan Qian Li Xingeng 《Frontiers of Materials Science in China》2007,1(2):225-227
An iron-based amorphous foil (FeNiCrSiB) was used as an interlayer for the amorphous diffusion bonding of low carbon steel
pipes under argon flux. The microstructure and mechanical properties of the joint were analyzed using an electron probe micro-analyzer
(EPMA), tensile test, bending test and impact test. The results show that the joint microstructure resembles that of the base
metal and no precipitates form at the joint. Melting point depressants (B, Si) diffuse far away from the joint and the base
metal element is homogenous across the joint. The joint impact toughness is greater than the base metal toughness and the
mechanical properties of the joint are similar around the pipe. 相似文献