发动机用碳酚醛材制烧蚀影响因素分析

一．概述 碳酚醛材料由于具有石墨或碳／碳材料相似的优良耐烧蚀特性以及成本低廉等特点,而且制作工艺和一般增强塑料相近,可沿用模压、层压和缠绕等工艺,因此碳酚醛材料作为功能烧蚀材料已被广泛应用于火箭和导弹的发动机防热部位,如喷管等。     

航天飞行器外防热复合材料发展概况

航天飞行器再入环境由于飞行任务的不断艰巨而愈加恶劣,故对外防热材料的要求也越来越高。本文通过简要分析气动加热环境所造成的外防热材料结构特性给出气动加热环境对于外防热材料的性能要求。接着以耐烧蚀树脂基防热复合材料为主对外防热材料的发展概况给出相关介绍,并提出利用混编纤维增强复合材料各方面的应用优势。     

低密度树脂基防热材料研究进展

随着各国航天工业的发展,飞行器朝着高马赫数和长时间飞行发展,由此带来的热防护问题不容忽视,因此研究新型防热材料以应对严酷的飞行环境显得十分重要。自20世纪50年代开始,树脂基热防护材料因其高残碳率、高防热性能及低成本等优点已经成功应用在美国与前苏联各类型号的导弹与火箭上。针对热防护系统轻量化及防隔热一体化的需求,总结了国内外低密度树脂基防热材料的研究现状,简述了添加空心微球减重、构造多孔结构以及密度梯度纤维化设计等3种减重思路及逐渐从均一的低密度材料向梯度化材料演变的设计理念,展望了低密度树脂基防热材料的发展趋势。     

陷阱式探测器的发展

陷阱式探测器是光辐射计量中一种重要的探测器,本文介绍了这种探测器的发展过程、结构特点,并指出了研制新陷阱探测器的发展方向     

航空航天飞机结构材料的应用及发展

本文简要地评述了航空航天飞机结构材料当前的进展与水平,包括空间环境及选材要求,多次反复使用的防热材料,非金属材料及其复合材料,金属基复合材料,金属材料,材料的力学和物理性能与测试,并指出航天飞机结构材料今后的发展趋势。     

碳/酚醛防热复合材料烧蚀行为的数值模拟

碳/酚醛复合材料被广泛地应用于钝头体表面,是飞行器优秀的热防护材料。为了准确地预测其烧蚀性能,本文从复合材料的组成物纤维和基体的角度出发,基于能量、质量守恒和热分解方程,考虑了烧蚀过程中材料热属性的非线性变化和烧蚀面的退缩,分别计算了纤维和基体的烧蚀性能,预测了烧蚀过程中防热复合材料的温度分布、密度变化、质量损失规律及热属性和线烧蚀率等。结果表明：碳/酚醛复合材料的烧蚀是各种因素相互作用、相互影响的高度非线性过程;烧蚀过程中材料结构具有不均匀的温度分布,烧蚀面区域材料密度衰减最大并且材料的质量损失和损失率几乎呈线性增加;纤维和基体的烧蚀行为存在明显差异,分别预测两者的烧蚀性能,可以为热防护材料的设计提供更加准确的参考和依据。     

酚醛纤维研究新进展

酚醛纤维具有很好的阻燃、隔热、耐腐蚀、服用性而被广泛应用于阻燃、防腐织物、宇航复合材料、密封和摩擦材料,也可作为炭纤维和活性炭纤维的前驱.对酚醛纤维的制备、结构、性能及应用以及酚醛纤维研究的国内外最新进展进行了介绍.     

生物质改性酚醛泡沫的研究进展

近年来酚醛泡沫塑料发展迅速,遇到的问题也越来越多。综述了各种生物质材料在酚醛泡沫中的最新研究进展。重点介绍了腰果酚、单宁、木质素、纤维素和生物油等生物质材料在酚醛泡沫塑料中的应用。并对生物质改性酚醛泡沫塑料的应用前景做了展望。     

酚醛SMC、轻质酚醛层压板的新发展(法)

酚醛SMC(片状模塑料)的阻燃性、耐热性极好,系新型、高性能工业半成品,其产品广泛用于建筑等。法国CDFCHIMIERT公司研制成Norsophen牌酚醛SMC(亦即:P-SMC),其生产工艺与聚酯SMC相同。本文的目的在于:1.研制能满足工业要求的增稠剂,2.研制适用上述增稠剂的优质酚醛树脂,3.研制能在模温下安全贮存P-SMC,效率高的催化剂,4.探索最佳生产工艺、最短模塑周期。本文介绍了P-SMC的配方,还介绍了微质玻纤增强酚醛层压板。本文的第一部分:酚醛树脂的选择,曾在第41届美国SPIRP/C年会上发表过,这里从略。      

柔性热防护系统的发展与应用

热防护系统是发展航天器必须解决的关键技术,而柔性隔热材料由于具有可重复使用、质量轻、维修时间短等优点被广泛采用。介绍了当前各种热防护系统结构与材料的发展状况,并具体叙述了飞行器减速伞的结构、展开、热流分布以及所用柔性材料,对我国柔性防热材料的发展提出了建议。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

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.……     

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...     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

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.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

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.