Z-pin参数对复合材料T型接头拉脱承载能力的影响

利用二维平面应变模型对Z-pin增强T型接头试样进行失效分析,采用内聚力模型模拟界面的破坏情况,通过在分层的上下界面加入非线性弹簧元模拟Z-pin的增强作用,非线性弹簧元的力学性能(桥联律)由细观力学方法获得,数值结果与试验值吻合较好。在已验证有限元方法的基础上,研究了Z-pin直径、密度及植入角度等对T型接头拉脱承载能力的影响。结果表明:Z-pin增强可显著提高T型接头的拉脱承载能力,与未Z-pin增强的T型接头相比,Z-pin增强明显延缓了掉载;T型接头的拉脱承载能力随Z-pin直径和密度的增加而增大,随植入角度的增大而减小;在所研究的角度范围内,当植入角度为60°时,T型接头的拉脱承载能力最好;Z-pin直径和密度对拉脱承载能力的影响远比植入角度的影响显著。     

T型接头蒙皮厚度对Z-pin增强效果的影响

在关于拉脱载荷下Z-pin增强T型接头的有限元模拟方法基础上,通过对2组蒙皮厚度分别为7.2 mm和4.0 mm的试验件的试验结果进行分析,研究了T型接头蒙皮厚度对Z-pin增强效果的影响。结果表明:Z-pin增强效果随着蒙皮厚度的减小而增大。蒙皮厚度大于5 mm,Z-pin不能提高结构的最大承载能力,但可显著提高结构首次掉载后的承载性能,使T型接头在较大的加载位移下仍保持较高的承载能力;无论蒙皮厚薄,结构首次掉载后,各Z-pin增强T型接头可达到的载荷平台是相当的,且该载荷平台随蒙皮的变厚有降低的趋势。      

Z-pin增强复合材料层合板断裂韧性试验研究

针对Z-pin增强复合材料层合板, 开展了断裂韧性的试验研究。研究选取了3种Z-pin直径(0.28、 0.52、 0.80mm)且每种直径下分别以3种分布形式(5×5、 8×8、 10×10)排布Z---pin的增强方式, 为了确定比较基准, 试验中同时测试了不含Z-pin的复合材料层合板试样。通过Z-pin拔出试验测试了3种直径Z-pin从基体拔出过程中的载荷位移关系。利用双悬臂梁试验和端部开口弯曲试验分别测试了不含Z-pin和含Z-pin试样的Ⅰ型断裂应变能释放率G_ⅠC、 Ⅱ型断裂应变能释放率G_ⅡC。试验结果表明:? 与不含Z-pin的结构相比, Z-pin增强试样的Ⅰ型断裂应变能释放率G_ⅠC增大了83%~1110%, Ⅱ型断裂应变能释放率G_ⅡC增大了23%~438%; 在相同Z-pin体积含量下, 与增大Z-pin直径相比, 增大Z-pin分布密度能更有效地提高复合材料层合板的断裂韧性。      

X-cor夹层结构压缩模量有限元分析

通过两种有限元模型的对比,提出了符合实际的X-cor夹层结构压缩模量有限元计算模型,利用大型有限元软件ANSYS对其压缩模量进行了数值计算,得到了X-cor夹层结构的应力场和压缩模量.研究了Z-pin半径、密度、植入角度和体积分数的改变对模型压缩模量的影响.结果表明:X-cor夹层结构压缩模量随Z-pin植入角度增加而减小,随Z-pin半径、密度和体积分数增加而增加,且与Z-pin体积分数呈线性关系,改变Z-pin半径与改变Z-pin密度对X-cor夹层结构压缩模量影响是等效的.通过有限元模型的计算,得到了X-cor夹层结构参数对其压缩模量的影响规律,验证了所提有限元模型的合理性.     

缝合增强复合材料帽型加筋壁板界面拉脱性能

为了防止复合材料帽型加筋壁板结构在服役过程中发生筋条与蒙皮的脱粘失效,引入了缝合技术来提高筋条-蒙皮界面拉脱性能.采用单线弯针缝合设备缝合纤维编织布,通过真空辅助树脂灌注技术(VARl)固化成型,制备缝合帽型加筋壁板试样.通过对试样进行筋条拉脱试验和有限元数值模拟,研究界面的失效机制及缝合参数对帽型加筋壁板界面结合性能的影响规律.结果表明:在拉脱载荷作用下,缝合试样的峰值载荷比未缝合试样明显增大.帽型试样的拉脱承载力随缝合密度的增大先增加后减小,在缝合密度(注:缝合密度表示缝合针距(单位mm)×行距(单位mm),下文同)为5×10时,相比未缝合试样,最高增加了26.7％;帽型接头的拉脱承载力随缝线细度的增加而增加,在缝线细度为1500 D时增加了39.7％.蒙皮/筋条厚度比为2时,结构拉脱承载力增加了27.35％,缝合的增强效果最明显.     

Z-pin增强对泡沫夹层结构弯曲和振动性能的影响

通过试验研究了Z-pin增强泡沫夹层结构的弯曲性能,与未增强材料进行比较.提出采用树脂Z-pin对泡沫夹层结构进行横向增强,比较了碳pin和树脂pin的不同增强效果.结果表明,横向增强能够极大地改善泡沫夹层结构的弯曲性能,树脂pin的增强作用虽然弱于碳pin,但同样具有明显的增强效果.在此基础上,基于Z-pin增强泡沫夹芯的力学性能,对夹层结构的弯曲刚度和弯曲最大破坏载荷进行预测.最后考察了增强Z-pin各参数对泡沫夹层结构自振频率的影响,为其在航空航天等振动结构中通过合理的阻尼设计达到调频的目的打下基础.     

Z-pin增强酚醛复合材料层合板的层间拉伸性能

本文探索研究了Z-pin的植入对酚醛复合材料层合板层间拉伸性能的影响。通过向酚醛复合材料层合板中植入体积分数为0.78%(植入间距5mm×5mm)的石英/酚醛Z-pin,对其进行层间拉伸性能测试,结果表明,随着Z-pin的植入,层合板的层间拉伸性能显著提高,并伴随破坏模式的变化、材料韧性的增加。最后,根据复合材料力学,建立Z-pin增强层合板的简单力学模型,通过桥率试验与层间拉伸试验,对其进行验证和修正,得出Z-pin植入对层合板的层间性能的影响规律。     

X-cor夹层结构的力学性能试验研究

X-cor夹层结构比强度高,比刚度大,有望取代传统蜂窝夹层结构作为航空航天器的主承力结构材料。采用真空固化成型工艺,通过改变Z-pin的植入参数制备了X-cor夹层结构,研究了Z-pin植入角度、植入间距和直径对其平压、剪切和拉伸性能的影响。研究结果表明,Z-pin的植入参数对X-cor夹层结构的力学性能影响显著。随Z-pin植入角度的增加X-cor夹层结构的平压性能降低,剪切性能增强,拉伸模量减小,拉伸强度先增加后减小。随Z-pin植入间距和直径增加,X-cor夹层结构力学性能均增加。与泡沫夹层结构相比,X-cor夹层结构压缩、剪切和拉伸模量的测试值分别提高了1.26～5.15倍、2.50～13.56倍和1.90～2.71倍,压缩、剪切和拉伸测试值分别提高了1.63～9.20倍、1.28～2.03倍和1.01～2.30倍。     

微量Ag元素对Sn-O.7Cu-O.2Ni钎料性能的影响

在Sn-0.7Cu-0.2Ni钎料中添加微量的Ag元素,测试了钎料的熔化温度、热膨胀性能、抗腐蚀性能及其润湿性.结果表明,添加微量的Ag元素降低了Sn-0.7Cu-0.2Ni的熔点,但增加了钎料的熔程.当Ag含量为0.3％(质量分数)时,钎料熔点为224.07℃,熔程为6.1℃.钎料的热膨胀系数随Ag含量的增加而升高.当Ag含量为0.3％(质量分数)时,钎料的热膨胀系数(20～100℃)为1.84×10-5/℃.另外添加Ag元素提高了钎料在HC1溶液中的抗腐蚀性能,同时也提高了钎料在Cu基板上的铺展面积.     

H_2O_2原位发泡轻混凝土的制备与性能表征

以H_2O_2溶液(质量浓度30%)为发泡剂,粗、细膨胀珍珠岩颗粒为轻集料和发泡剂载体,明胶为稳泡剂,采用将加载发泡剂的载体拌入轻集料混凝土的水泥浆中原位化学发泡的方法,制备出了系列轻混凝土试样,并对其性能进行了系统表征。结果表明,原位发泡轻混凝土中外加1.5%(质量分数)胶凝材料量的稳泡剂后,对气泡有较为理想的稳泡作用,可获得均匀分布的细小气泡(气泡直径0.5~1mm)。原位发泡轻混凝土的体积密度随发泡剂量增加而降低,随稳泡剂量的增加而增大。当稳泡剂为胶凝材料量的1.5%(质量分数)时,原位发泡轻混凝土试样的抗压强度和导热系数均随着发泡剂量的增加而降低。其中,发泡剂量为胶凝材料量1.4%(质量分数)试样的28d抗压强度为21 MPa,体积密度为940kg/m3,比不发泡试样的强质比提高了14%,导热系数降低了13%。     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.