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3041.35CrMoA钢在高应变率加载中的力学性能
[黑色金属冶炼和压延加工业] [2014-07-27]
The tensile properties of alloy steel 35CrMoA were measured by dynamic tension experimental apparatus,and the stress-strain curves of the material at strain rate range from 10-2/s to 103/S were obtained.The fracture appearance and metallurgical structure were observed for the recovered specimens.The influence of strain rates on mechanical properties and microstructure of the 35CrMoA steel was analyzed.Based on the experimental data of mechanical properties,the JC constitutive parameters were fitted for 35CrMoA.
关键词:力学性能;本构模型;35CrMoA钢;应变率;数值模拟
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3042.肯尼迪航天中心柠檬酸替代硝酸进行不锈钢钝化测试协议
[黑色金属冶炼和压延加工业] [2014-07-27]
John F. Kennedy Space Center (KSC) has equipment and processes which require the passivation of stainless steel. The standard practice for passivation uses nitric acid. While nitric acid exhibits excellent performance, there are a number of environmental and safety issues: nitrogen oxide (NOx) emissions are considered greenhouse gases, NOx are volatile organic compounds that contribute to smog, NOx increase nitrogen loading (oxygen depletion) in bodies of water, nitric acid can remove beneficial heavy metals (nickel, chromium, etc) from surfaces, and worker safety issues. The longtime military specification for passivation of stainless steel was Federal Specification QQ-P-35 (Passivation Treatments for Corrosion-resistant Steel), but that has been cancelled in favor of American Society for Testing and Materials (ASTM) A 967 (Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts) and Aerospace Material Specifications (AMS) 2700 (Passivation Treatments for Corrosion-resistant Steel). Both of the new specifications allow for the use of citric acid in place of nitric acid. In addition, KSC also uses NASA-STD-5005 (Standard for the Design and Fabrication of Ground Support Equipment) and ASTM A 380 (Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems). The primary objective of this effort is to demonstrate and validate citric acid as an alternative to nitric acid for the passivation of stainless steels. Citric acid offers a variety of benefits: it is naturally occurring and biodegradable; upon disposal, it is rarely classified as a hazardous waste; it does not remove beneficial heavy metals from surfaces; and there are no toxic fumes created during the passivation process. This project is follow-on to United Space Alliance (USA) work to optimize the parameters for the use of citric acid and verify effectiveness. USA evaluated the following parameters during their effort: concentration, temperature, and dwell time. This project will use the results from that testing to determine what process parameters will be used in the preparation of test coupons. This Test Protocol contains the critical requirements and tests necessary to qualify citric acid as an alternative to nitric acid for use at KSC. These tests were derived from engineering, performance, and operational impact (supportability) requirements defined by KSC participants. A Test Report will document the results of the testing as well as any test modifications made during the execution of the testing. The Test Report will be made available as a reference for future pollution prevention endeavors by other NASA centers, the Department of Defense, and commercial users to minimize duplication of effort. Users of this Test Protocol should check the project's Test Report for additional test details or minor modifications that may have been necessary in the execution of the testing. The technical stakeholders will have agreed upon test procedures modifications documented in the Test Report.
关键词:柠檬酸;耐腐蚀;硝酸;被动;污染控制;不锈钢
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3043.运用基于模型的系统工程到美国航空航天局的太空通信网络
[计算机、通信和其他电子设备制造业,信息传输、软件和信息技术服务业] [2014-07-27]
System engineering practices for complex systems and networks now require that requirement, architecture, and concept of operations product development teams, simultaneously harmonize their activities to provide timely, useful and cost-effective products. When dealing with complex systems of systems, traditional systems engineering methodology quickly falls short of achieving project objectives. This approach is encumbered by the use of a number of disparate hardware and software tools, spreadsheets and documents to grasp the concept of the network design and operation. In case of NASA's space communication networks, since the networks are geographically distributed, and so are its subject matter experts, the team is challenged to create a common language and tools to produce its products. Using Model Based Systems Engineering methods and tools allows for a unified representation of the system in a model that enables a highly related level of detail. To date, Program System Engineering (PSE) team has been able to model each network from their top-level operational activities and system functions down to the atomic level through relational modeling decomposition. These models allow for a better understanding of the relationships between NASA's stakeholders, internal organizations, and impacts to all related entities due to integration and sustainment of existing systems. Understanding the existing systems is essential to accurate and detailed study of integration options being considered. In this paper, we identify the challenges the PSE team faced in its quest to unify complex legacy space communications networks and their operational processes. We describe the initial approaches undertaken and the evolution toward model based system engineering applied to produce Space Communication and Navigation (SCaN) PSE products. We will demonstrate the practice of Model Based System Engineering applied to integrating space communication networks and the summary of its results and impact. We will highlight the insights gained by applying the Model Based System Engineering and provide recommendations for its applications and improvements.
关键词:空间通信;通信网络;系统工程;数据整合;系统集成
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3044.超音速火焰喷涂Cr_3C_2-NiCr涂层对高温下锅炉钢的微观结构表征和循环氧化行为
[黑色金属冶炼和压延加工业] [2014-07-27]
The oxidation behavior of HVOF sprayed Cr_3C_2-NiCr coatings on 310S stainless steel for 50 cycles in air at 700℃ under cyclic conditions has been investigated in the present work. The microstructure, hardness and porosity of the coating were characterised. X-ray diffraction, field emission scanning electron microscope with energy dispersive spectroscopy and X-ray mapping were used to analyze the scales formed on the surface of the oxidised samples. The microstructure of the as sprayed coating showed uniformly distributed chrome carbide-rich ceramic grains attached with nickel chrome-rich binder phase. The Cr_3C_2-25NiCr coated specimen exihibit negligible microspalling of the scales upon oxidation. The improved oxidation resistance of Cr_3C_2-NiCr coatings may be attributed to the formation of oxides of chromium, nickel, and spinels of nickel and chromium.
关键词:钢铁;高速氧燃料;显微硬度;显微组织
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3045.用于高压水液压元件的现代涂料
[化学原料和化学制品制造业] [2014-07-27]
Water hydraulics is coming back as an alternative to oil and other not environment friendly working fluids used in very wide range of fluid drive and control systems. One of the barrier causing that water hydraulics is cost of water resistant materials for components, especially moving parts such as pump pistons, surface of cylinder tubes and rods, poppet and seats, etc. to avoid corrosion. One of common solution is to use stainless steel there, where it can cooperate with other nonmetallic material such as plastic or other noncorrosive metallic composite to reduce friction. Thus some of research were directed to elaboration of special coating for covering surfaces in critical regions of water hydraulic components. The article describe results of pilot research on selected components where such coating were introduced on regular carbon steel parts, same as used for oil hydraulics. First part of the article contents description of coating technology and some characteristics of coating layers. Second quotes selected results of conducted by authors research on coated hydraulic cylinders and poppet valves.
关键词:钢铁;水压;涂料;液压缸;座阀
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3046.冷轧薄带钢的新型板形仪研究
[黑色金属冶炼和压延加工业] [2014-07-27]
Based on the shape detecting principle and the digital signal technology,a new shape meter was developed thorough theoretical analysis and industrial adjustment to develop the shape detecting roll,the shape signal processing method,the original signal compensation mechanism and so on.The shape meter has good performance and stability,which can effectively avoid the scratchof steel strip surface,accurately detect real online strip shape and provide accurate online shape datum for shape control system.It was applied in 1250 mm cold rolling mill,the actual industrial tests prove that the shape signal was stable and reliable,met the harsh condition and the online technical requirements,and could improve shape quality significantly.
关键词:钢铁;冷轧带钢;冷轧机;板形仪
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3047.截断双电容成核站点开发
[石油加工、炼焦和核燃料加工业] [2014-07-27]
During heterogeneous nucleation within a metastable mushy-zone, several geometries for nucleation site development must be considered. Traditional spherical dual cap and crevice models are compared to a truncated dual cap to determine the activation energy and critical cluster growth kinetics in ternary Fe-Cr-Ni steel alloys. Results of activation energy results indicate that nucleation is more probable at grain boundaries within the solid than at the solid-liquid interface.
关键词:凝固;液固界面;界面能
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3048.改良后的9Cr-1movnb钢激光焊接和焊后处理
[黑色金属冶炼和压延加工业] [2014-07-26]
Laser welding and post weld laser treatment of modified 9Cr-1MoVNb steels (Grade P91) were performed in this preliminary study to investigate the feasibility of using laser welding process as a potential alternative to arc welding methods for solving the Type IV cracking problem in P91 steel welds. The mechanical and metallurgical testing of the pulsed Nd:YAG laser-welded samples shows the following conclusions: (1) both bead-on-plate and circumferential butt welds made by a pulsed Nd:YAG laser show good welds that are free of microcracks and porosity. The narrow heat affected zone has a homogeneous grain structure without conventional soft hardness zone where the Type IV cracking occurs in conventional arc welds. (2) The laser weld tests also show that the same laser welder has the potential to be used as a multi-function tool for weld surface remelting, glazing or post weld tempering to reduce the weld surface defects and to increase the cracking resistance and toughness of the welds. (3) The Vicker hardness of laser welds in the weld and heat affected zone was 420-500 HV with peak hardness in the HAZ compared to 240 HV of base metal. Post weld laser treatment was able to slightly reduce the peak hardness and smooth the hardness profile, but failed to bring the hardness down to below 300 HV due to insufficient time at temperature and too fast cooling rate after the time. Though optimal hardness of weld made by laser is to be determined for best weld strength, methods to achieve the post weld laser treatment temperature, time at the temperature and slow cooling rate need to be developed. (4) Mechanical testing of the laser weld and post weld laser treated samples need to be performed to evaluate the effects of laser post treatments such as surface remelting, glazing, re-hardening, or tempering on the strength of the welds.
关键词:电弧焊接;激光焊接;钢;焊接接头
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3049.金属军用零件中金属(DDM)修复过程的直接沉积
[黑色金属冶炼和压延加工业,金属制品业] [2014-07-26]
In 2005 Focus: HOPE began working on a Technical Area Task to investigate advanced manufacturing in the area of Direct Deposition of Metal (DDM) for the Tank and Automotive Command (TACOM). In 2006, the scope was expanded to include basic research areas of Direct Deposition of Metal applicable to repairing military equipment and Focus: HOPE demonstrated the feasibility of conducting repairs on military equipment using Direct Deposition of Metal (Work Directive WD-FH-0001). The study also demonstrated that there could be a potential cost saving by repairing parts using DDM over purchasing new replacement parts. The overall project was extended in 2010 to provide additional time to conduct additional certification testing of repaired components and demonstrate the effectiveness of the parts repaired using Direct Deposition of Metal. For the present project, extensive studies were conducted on the metallurgical properties and bonding between the newly deposited metal and the parent metal substrate. The findings, results and conclusions of this process certification testing are provided in this report.
关键词:金属;军钢铁;弯曲;腐蚀;沉积零件
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3050.氧燃烧技术的激光诊断
[计算机、通信和其他电子设备制造业,化学原料和化学制品制造业] [2014-07-26]
When a fossil fuel is burned, oxygen in the air chemically reacts with combustible elements of the fuel to produce heat. Since nitrogen is nearly inert, it is mainly a diluent that carries away some of the energy released during the combustion process and produces pollutants. Oxygen-enhanced combustion has been considered as an attractive alternative in order to increase efficiency, to reduce volume of the flue gas, to lower emissions of NO_x and CO_2, and to improve heat transfer and flame stability characteristics. With decreasing costs involved in production of oxygen from air, oxygen-enhanced combustion may not only be limited to glass-melting and steel-making furnaces but also may have potential in the power-generation industry using fossil fuels such as coal and natural gas. Substantial research has been conducted to evaluate the effects of oxygen enrichment on overall efficiency, fuel savings, heat transfer rates, and pollutant emissions.
关键词:钢铁;矿物燃料;熔化;稀释剂