An approach to selection of material and manufacturing processes for rocket motor cases using weighted performance index

Material selection is a very critical design decision, which has a profound influence on the entire development program for rocket motor cases. In the selection process, the main performance parameters and the most appropriate fabrication technology with proven processes must be considered. Many years of practical experience in material selection process with a thorough understanding of materials behavior under various loading environments and hands-on experiences with various available manufacturing processes are of immense help to the design and development engineer for successful completion of the development program. In this paper, an attempt has been made to present an approach for selecting appropriate material and manufacturing process for rocket motor case based on method of Weighted Performance Index (WPI) with the hope that this approach will also provide additional aid to the design engineer for the selection of material and manufacturing process for rocket motor cases. In this method, different properties are assigned a certain weight depending upon their importance to the service requirements. Different properties are normalized using a scaling factor, and finally a weighted property index is computed. The material that scored the maximum numerical value is chosen as the material for fabrication. This approach closely matches with the actual performance. Maraging steel and D6AC are found to be the preferred materials for rocket motor cases for critical missions. HSLA steels are appropriate for less-critical applications, in which rocket motor cases are required in very large numbers (e.g., flow-formed AISI 4130 motor cases^[8]). For the selection of an appropriate manufacturing method, the major parameters considered are dimensional accuracy, cost of production, minimum material waste, and flexibility in design. Again, these properties are given a relative grading, which is then converted into a scaled property. Finally, the weighted performance indices are estimated. The flow-forming method has emerged as the manufacturing method of choice for motor tubes.     

A new soft magnetic material for ac and dc motor applications

A new soft magnetic material has been developed for ac and dc motor applications. The motor components are made by a powder metallurgical process, in contrast to the traditional method of stacking punched laminations. This new material offers many manufacturing advantages. Also, because of its low eddy current loss, it has good high-frequency magnetic properties, 90 W/kg core loss when measured at 400 Hz and at an induction of 1.5 T. Components manufactured from this new magnetic material have demonstrated comparable performance at 60 Hz and superior performance for frequencies >60 Hz when compared to cold-rolled motor lamination steels. The new pressed material also has outstanding dc properties when sintered.     

应用BP神经网络的单机架可逆式冷轧机弯辊力预设定

针对单机架可逆式冷轧机生产过程中，由于不同热轧生产厂的热轧板形原料性能、板形差别较大、从而造成弯辊力预设定值和实际指标相差较大的问题，利用现场生产工艺数据丰富，采用人工智能BP神经网络的方法，通过大量数据输入进行训练，大大的提高了生产过程中弯辊力预设定值的准确性。     

成组技术在高铬铸铁磨球生产上的应用

在高铬铸铁磨球生产上,一直存在磨球介质使用寿命短,性能不稳定的问题。其主要原因:一是材料设计与制造工艺落后,二是20 mm~30 mm不等径系列磨球截面的组织和性能存在较大差异。引入成组技术后,以分类组别的方式进行逻辑假设、试验设计、调优设计,获得了4个基本组别磨球组织相同、性能一致的工艺设计方案。     

坐衬零件材料及其制造工艺

一种新的坐衬零件材料要求高耐磨性、高耐热性和高强度,热膨胀系数接近铸铁.采用粉末冶金工艺和双层材料研制的坐衬零件,经过力学和物理性能分析,测试结果表明满足使用要求.     

Fiber Orientation Effects in Fused Filament Fabrication of Air-Cooled Heat Exchangers

Fused filament fabrication (FFF) is a type of additive manufacturing based on material extrusion that has long been considered a prototyping technology. However, the right application of material, process, and product can be used for manufacturing of end-use products, such as air-cooled heat exchangers made by adding fillers to the base polymer, enhancing the thermal conductivity. Fiber fillers lead to anisotropic thermal conductivity, which is governed by the process-induced fiber orientation. This article presents an experimental study on the microstructure-property relationship for carbon fiber-filled polyamide used in FFF. The fiber orientation is measured by micro-computed tomography, and the thermal conductivity of manufactured samples is measured. Although the thermal conductivity is raised by more than three times in the fiber orientation direction at a load of only 12 vol.%, the enhancement is low in the other directions, and this anisotropy, along with certain manufacturing restrictions, influences the final part performance.     

Bridging the Design–Manufacturing–Materials Data Gap: Material Properties for Optimum Design and Manufacturing Performance in Light Vehicle Steel-Intensive Body Structures

As safety and fuel economy regulations become increasingly more challenging around the world, light vehicle manufacturers are facing increasing pressure to reduce the weight of their vehicles cost effectively while maintaining or improving safety performance. Optimum light vehicle steel body structure weight and performance are achieved when the constraints of design, manufacturing, and material properties are considered simultaneously. ArcelorMittal has invested heavily over the past several years to close the gap between material property knowledge and the inter-relation between material performance and design and manufacturing efficiency. Knowledge gained through this process is presented and the importance of achieving this simultaneous 3-way optimization is illustrated by a lightweight steel door design example from ArcelorMittal??s S-in motion catalog of lightweight steel solutions.     

Getting to grips with automated prepreg handling

Automated manufacturing of composite parts based on prepreg material is receiving increased interest with the rising use of composite materials for high-performance applications. The two main automation alternatives for prepreg layup, automated tape layup and fiber placement, are not cost-effective for all types of products, and manual labor is common for the manufacturing of complex parts in low manufacturing volumes. Alternatives to the two dominant automation solutions have been pursued, but so far these have had a limited impact in industrial applications. This paper presents four different solutions for automated layup of prepreg plies to flat laminates that can be formed in a subsequent forming process, which decrease the system complexity. The solutions target products where the layup of flat laminates today is done manually due to technical limitations or cost considerations. The layup solutions must manage challenges caused by material properties such as low material rigidity and tack, and be able to handle a high number of ply shapes. All four solutions are designed for prepreg that is covered with a stiff backing paper. The aim of the paper is to analyze and compare the four solutions. It can be concluded that the most versatile solution is a dual-arm robot equipped with simple end effectors. The dual-arm solution presents a possibility to control the pick-up and lay-down motions that make peeling motions possible, which is advantageous when picking material that has tacked to the pickup surface.     

Milestones in Functional Titanium Dioxide Thermal Spray Coatings: A Review

Titanium dioxide has been the most investigated metal oxide due to its outstanding performance in a wide range of applications, chemical stability and low cost. Coating processes that can produce surfaces based on this material have been deeply studied. Nevertheless, the necessity of coating large areas by means of rapid manufacturing processes renders laboratory-scale techniques unsuitable, leading to a noteworthy interest from the thermal spray (TS) community in the development of significant intellectual property and a large number of scientific publications. This review unravels the relationship between titanium dioxide and TS technologies with the aim of providing detailed information related to the most significant achievements, lack of knowhow, and performance of TS TiO₂ functional coatings in photocatalytic, biomedical, and other applications. The influence of thermally activated techniques such as atmospheric plasma spray and high-velocity oxygen fuel spray on TiO₂ feedstock based on powders and suspensions is revised; the influence of spraying parameters on the microstructural and compositional changes and the final active behavior of the coating have been analyzed. Recent findings on titanium dioxide coatings deposited by cold gas spray and the capacity of this technology to prevent loss of the nanostructured anatase metastable phase are also reviewed.     

X-Y-θ Nano-Positioning Table System for a Mother Machine

Within recent manufacturing environment, there is an increasing demand for nanometer positioning table system with high stiffness, high resolution and high repeatability. In this study, therefore, a high-stiffness X-Y-6 nano-positioning table system has been developed for ultraprecision machine tools. The table is levitated by high-stiffness aerostatic bearings with porous material and driven by six voice coil motors in a non-contact condition. The table system is designed symmetrically about the driving axis and consequently free from nonlinear behavior and direction dependency. The performance of the developed table system has been verified through a series of nano-positioning experiments.     

金属增材制造工艺、材料及结构研究进展

金属增材制造技术相比于传统制造技术有很大的优势,已经在很多领域得到了应用。基于金属增材制造工艺、材料以及结构的研究现状,分析当前的研究热点以及发展趋势。结果表明：金属增材制造当前的研究热点是材料应用、仿真模拟、智能检测和热处理强化,而且质量评估没有统一的标准;金属增材制造未来发展的趋势是建立标准材料工艺数据库、多材料打印工艺研发、仿真优化模拟、智能化监测管理和热处理强化工艺研发。     

增材制造金刚石工具研究现状及展望

随着金刚石工具朝着形状复杂化、结构精密化、性能高端化等方向发展,常规金刚石制造工艺受成形原理限制较难满足上述要求,亟须寻求新的金刚石工具制造工艺。增材制造是一项新兴的、降三维制造为二维制造的技术,近年来开始应用于复杂结构金刚石工具的制造。本文综述了激光选区熔化、激光选区烧结、立体光固化成形等目前主流增材制造工艺成形金刚石工具的研究进展,详细介绍了3种工艺的成形原理,重点阐述了不同工艺中金刚石与胎体材料的界面结合问题,简要对比了3种增材制造工艺成形金刚石工具的差异。最后,对未来增材制造金刚石工具的研究重点进行了展望。      

采用消失模铸造工艺生产蠕铁排气出口管

介绍了消失模法生产蠕铁排气出口管的工艺过程.试验发现,采用反直浇道结合侧注的模组形式为佳,每组8件、管口朝下;涂料直接影响铸件表面积碳及皱皮倾向;并采用消失模法批量生产了蠕铁排气出口管,材料性能及金相组织达到要求,铸件壁厚均匀,表面光滑,已用于红旗轿车的部分车型.     

A robust design approach to determination of tolerances of mechanical products

Tolerance specifications of design parameters influence both functional performance and manufacturing cost of products. Product functional performance is usually affected by uncertainties of design parameters, robust design can make product functional performance insensitive to those uncertainties. Based on the robust design method and the cost-tolerance models, a mathematical model has been developed for describing the relationships among functional performance, manufacturing costs, design parameters and tolerances. A new robust optimization method has also been developed to determine tolerances and design parameters simultaneously. This new approach has been used for determining design parameters and tolerances of a coating head of printing machinery.     

Metal Additive Manufacturing: A Review

This paper reviews the state-of-the-art of an important, rapidly emerging, manufacturing technology that is alternatively called additive manufacturing (AM), direct digital manufacturing, free form fabrication, or 3D printing, etc. A broad contextual overview of metallic AM is provided. AM has the potential to revolutionize the global parts manufacturing and logistics landscape. It enables distributed manufacturing and the productions of parts-on-demand while offering the potential to reduce cost, energy consumption, and carbon footprint. This paper explores the material science, processes, and business consideration associated with achieving these performance gains. It is concluded that a paradigm shift is required in order to fully exploit AM potential.     

停车设备型材组合机床控制系统的设计与实现

为提高停车设备型材加工效率及加工精度,针对停车设备型材组合机床设计中钻削、铣削和等离子切割的要求,开发了一套基于EtherMAC实时工业以太网总线平台的21轴组合机床控制系统。文章分析了控制系统硬件和软件需求,并阐述了系统方案的构建及功能实现过程。实际应用中,可加工型材最大长度达7.5m,钻削、铣削、等离子切割可同时进行,效率明显提高,实现了预期加工要求,为停车设备型材的自动加工提供了一个新的可行的方案。     

Development of a Superabrasive Grinding Wheel With Defined Grain Structure Using Kinematic Simulation

This paper presents the concept of superabrasive electroplated grinding wheels based on defined grain structures. The aim is to improve process stability, minimize heat generation and achieve a high surface quality while preserving a high material removal rate. Based on geometrical models, different patterns of grit settings have been investigated by means of kinematic simulation. Applying the results of the simulation, a prototype grinding wheel with an optimized defined grain structure has been constructed. The performance potential of the prototype has been analyzed through experimental examinations.     

Role of manufacturing towards achieving circular economy: The steel case

Circular economy (CE) has been promoted worldwide as a strategy to reduce material use and to increase the material use efficiency by closing material loops at the societal level. The core concept of CE is to improve the circularity of material use through turning materials at the end of their service life into resources for others, however, there is very little information about the role of manufacturing in achieving CE. Using the concepts of dynamic material flow analysis and stock dynamics, this paper proposes a methodological approach to help understand the role of manufacturing in achieving CE. A number of other strategies such as material efficiency in conjunction with CE are also tested using the case of global steel use to draw conclusions.     

Metal additive manufacturing via a novel composite material using powder and polymers formed in sheets

In additive manufacturing, PowderBed Fusion (PBF) has been shown to be a highly reliable approach for prototyping of metal parts, but has several disadvantages: relative slow production time, inherent safety issues involved with using loose metal powders, and difficulty in printing multi-material parts. A novel method for additive manufacturing of metal parts, Metal Additive manufacturing using Powder Sheets (MAPS), is hereby described. MAPS uses rollers of a novel composite material as feedstock, which eliminates the need for loose powder in the build chamber, potentially reducing risks and enhancing applications while still producing material on par with that produced by established PBF methods.     

中子衍射技术测量残余应力的研究进展

随着我国中子大科学装置技术的发展和进步,中子衍射技术已广泛应用于航空、航天、核电、汽车等各领域。本文介绍中子衍射残余应力测量原理及相关基础知识,与其他深部应力测试结果进行对比,中子衍射具有高穿透力,是无损获得材料及工程部件内部三维应力的最有效方法,尤其适用于局域位置的应力测量,在工程部件残余应力测试与分析,揭示制造加工工艺或使用过程中残余应力的演变及相关的形变、相变机理方面独具优势,相应原位实验与测试技术的发展为材料研制及性能评价提供重要的技术手段,中子衍射技术将在材料与工程领域发挥不可替代的作用。