低密度支撑剂用酚醛/环氧树脂改性复合材料的研究

采用液体酚醛树脂浸渍,再用环氧树脂包覆的方法制备了以坚果壳为基体的低密度支撑剂用复合材料,通过IN STRON万能材料试验机,TGA,SEM等测试手段测试了复合材料的性能。研究表明,浸渍的酚醛树脂溶液浓度达到70%时,复合材料在60M Pa压力下变形量有一最小值;随着颗粒表面包覆层环氧树脂量的增加,复合材料在60M Pa压力下变形量逐渐减少,当树脂量大于25%时,变形量变化不大;TGA表明复合材料耐热性提高;SEM发现未包覆改性的颗粒表面有较多孔洞,包覆改性后的复合材料表面较光滑,孔洞明显减少;显微镜照片显示未包覆改性的颗粒60M Pa压力下严重破裂,而复合材料没有破裂现象,且颗粒表面有明显的树脂层;吸水能力由30.45%降至6.58%,耐溶剂性能明显提高。     

Coating of calcia-doped ceria with amorphous silica shell by seeded polymerization technique

Calcia-doped ceria is of potential interest as an ultraviolet (UV) radiation blocking material in personal care products. However, its high catalytic ability for oxidation of organic materials makes it difficult to use as a sunscreen material. Therefore, calcia-doped ceria was coated with amorphous silica by means of seeded polymerization technique in order to depress its oxidation catalytic ability. The catalytic ability as well as UV-shielding ability was investigated for coated particles.     

松散填充材料的缓冲性能研究

松散填充材料可以用于对任意规格尺寸及形状的产品进行缓冲包装和固定,具有包装作业的方便性和适用性。松散填充材料的载荷能力、缓冲包装性能及对产品的固定作用,决定了这一材料的包装保护功能。通过对4种结构形状的松散填充材料在静态压缩、动态冲击和迁移性方面的测试与评价,分析了各种松散填充材料的包装性能,并与纸浆模制松散填充材料进行了比较,说明了松散填充材料单体结构形状对其缓冲性能和固定作用的影响。     

军用物资组套集装模式与对策探讨

目的推进军用物资组套集装化,提升军用物资的应急快速发付能力,缩短任务部队的物资需求响应时间。方法着眼现代战争中的物资保障需求,分析军用物资组套集装的意义,结合实际,按照内部、中部、外部包装3个层次开展组套集装工作,从物资组套集装方案、器具和包装基础标准3个方面避免组套集装的随意性。结果提出了"内部包装多样化、中间包装组合化、外部包装集装化"的军用物资组套集装基本模式构想,明确了做好军用物资组套集装工作的关键环节。结论军用物资组套集装对增强我军储备物资防护能力、提升战时应急保障能力具有积极的指导意义。     

铜质弹带生产成本探讨与分析

着重介绍了国营第一二三厂从弹带形式、材料利用率、能源消耗、工人工资等方面着手,结合生产任务和即将完善的生产能力,对弹带生产成本进行了详尽的探讨,部分成果成功运用于批量生产的实践过程,阐述了技术创新对企业降低能源消耗,节省人力、物力,从而降低生产成本,增强竞争能力,提高经济效益的巨大意义。     

Active vibration control of smart composites featuring electro-rheological fluids

Our experimental investigations are focused on evaluating the elastodynamic response characteristics of a beam fabricated in an electrorheological fluid when the beam is subjected to forced vibration. The beam which is designed in this experiment is composed of three kinds of materials, i.e. structural material, damping material and sealant material. Different ratios of structural material to damping material have been tested in an applied electric field. The results demonstrate clearly the ability to significantly change the vibrational characteristics of a beam fabricated in a smart composite by changing the electric field intensity imposed on the fluid domains. The ASTM standard E756-83 equations are used to evaluate the Young's modulus of the beam.     

PZT对Ni-Zn铁氧体衰减电磁波能力的影响

研究了Ni-Zn铁氧体与锆钛酸铅PZT复合材料在1～1000MHz范围内对电磁波的衰减情况.结果表明,PZT由于具有铁电性与铁磁性共存特点,在1～1000MHz范围内有较好的吸波能力.在Ni-Zn铁氧体中添加PZT后可提高Ni-Zn铁氧体在100MHz以下频段对电磁波的衰减能力,在>100MHz频段后则降低对电磁波的哀减能力.     

Determination of grinding conditions for renewal of a wheel cutting ability allowing for its variation during the machining process

The authors discuss the determination of rigid-mode grinding conditions with a periodic electric discharge action on the wheel working surface in a separate zone, taking into account the in-process variation of the wheel cutting ability. The calculation is based on the mathematical relations that describe variation of the wheel cutting ability in elastic-mode infeed grinding with a constant workpiece-to-wheel pressing force, where the process kinematics is similar to that of the rigid-mode grinding. The workpiece speed is determined for a specified machined surface roughness. The workpiece-to-wheel pressing force is chosen such that the surface layer of the workpiece material should undergo no phase-structural transformations. The variations of the wheel cutting ability during the rigid-mode grinding are taken into account through the use of the equations that describe the variations of the wheel's current limited cutting ability in the elastic-mode grinding. Based on the discussion of various methods of calculation of one of the grinding parameters—depth of cut—the authors have found its value ensuring that no phase-structural transformations will occur in the surface layer of the workpiece material under maximum feasible removal rates.     

A high order finite element for completely incompressible creeping flow

A finite element method for simulating the creeping flow of an incompressible material is presented. The method allows for (1) a quadratic approximation of the velocity field, (2) material incompressibility everywhere within an element and (3) the ability to follow the flow through large changes of the material boundaries. A candle slowly bending under its own weight is simulated for illustrative purposes.     

A computational approach for multi‐scale analysis of heterogeneous elasto‐plastic media subjected to short duration loads

The asymptotic expansion homogenization (AEH) approach has found wide acceptance for the study of heterogeneous structures due to its ability to account for multi‐scale features. The emphasis of the present study is to develop consistent AEH numerical formulations to address elasto‐plastic material response of structures subjected to short‐duration transient loading. A second‐order accurate velocity‐based explicit time integration method, in conjunction with the AEH approach, is currently developed that accounts for large deformation non‐linear material response. The approach is verified under degenerate homogeneous conditions using existing experimental data in the literature and its ability to account for heterogeneous conditions is demonstrated for a number of test problems. Copyright © 2004 John Wiley & Sons, Ltd.     

The effect of water soluble salts on the nucleating ability of the Agl-AgBr-Cul system

Experiments have been done to determine the extent to which the nucleating ability of 50: 25: 25 mol% composition of Agl, AgBr and Cul fusion material is influenced by the presence of soluble salts. Using a bulk freezing technique, the freezing nucleation temperatures are measured for each salt combination with the nucleant, at salt concentrations of 0.01, 0.1 and 0.5 M. For this, 21 soluble salts have been considered. These salts are found, in general, to increase the supercooling to varying amounts depending upon the salt type and the concentration. But NaCl, at 0.01 M concentration significantly improved the nucleation ability of the material and the nucleation temperature was found to be as high as –0.35° C. The combination of chlorides as well as some sulphates are found to exhibit a decrease in nucleation activity of the material.     

Werkstoffkenngröße „Zeta“ — ein praxisrelevantes Kriterium zur Charakterisierung des Zähigkeits/Festigkeits-Verhältnisses

Strength and toughness are one of the most important properties describing materials. A material in addition a construction part, need to have a certain strength, providing enough resistance against the impact of environmental forces and moments. On the other hand often a high ability of plastic deformation for instance during the process of chipless forming is required. The resistance during the process of chipless forming is required. The resistance against the impact of outer forces and the resulting deformations is determined by static and dynamic material testing. This article outlines briefly the required testing methods and rates their ability to describe the strength-toughness-relation. It’s shown, that the material parameter “zeta” meets all the expectations in describing the strength-toughness-relation concerning a wide range of materials such as steel, steel casting, cast iron materials (GG, GV, GTW, GTS, GGG), copper-, aluminum-, magnesium-alloys and also polymeric materials (for instance thermoplastic polymers).     

导电沥青混凝土及其功能特性研究进展

为系统掌握国内外有关导电沥青混凝土的研究现状,通过调查现有导电沥青混凝土的添加材料、路用性能、功能特性、影响因素等,对比不同导电材料制备沥青混凝土的电导率特征,总结导电沥青混凝土的功能特性及其电导率影响因素。结果表明:国内外主要采用石墨、碳纤维、钢棉作为导电材料制备导电沥青混凝土,石墨对沥青混凝土的电导率提升效果最佳,碳纤维可提高沥青混凝土的路用性能;同时,导电沥青混凝土具有明显的压敏特性,感应加热可增强沥青混合料的抗疲劳性能,通电加热可快速提高沥青混凝土的温度,导电沥青混凝土的电导率主要受空隙率、环境温度、电极类型的影响。     

增材制造智能材料研究现状及展望EI北大核心CSCD

增材制造技术自问世以来成为拓展多学科发展、实现多学科研究融合以及联结材料与产品的关键性技术,该技术颠覆了传统加工设计和制造理念,同时也是实现智能制造的重要方法。智能材料是对环境具有感知、可响应、自修复和自适应的一类材料。将智能材料与增材制造技术有机结合,可实现具有感受外部刺激或环境激活的三维智能器件的一体化制造。智能材料增材制造技术被广泛应用于个性化医疗、柔性电子和软体机器人等领域。本文对增材制造中所涉及的智能材料进行综述,介绍通过增材制造方法对金属类、高分子类和陶瓷类智能材料所带来的优势及面临的问题。增材制造技术作为实现设计、材料和结构有机融合的有效手段,将成为推动智能材料发展的关键。     

Solubility and susceptibility of carbonaceous quinoline-insoluble substances including mesophase material in the co-carbonization process

The solubility and susceptibility of carbonaceous quinoline-insoluble substances (QI) including mesophase material were studied in co-carbonizations with pitch-based materials by evaluating the homogeneity and the size of the anisotropic optical texture in resultant cokes. The efficacy of co-carbonization is attributed to the nature of both the Ql substance and pitch-based materials. The order of the modifying ability of the partner is CP-BSfa values and Rnus (number of naphthenic rings per structural unit)/Rtus (number of total rings per structural unit). The hydrogen donating ability of the pitch material may be the most important property able to modify the non-fusible QI. The order of ability to be modified of the QI substances (susceptibilty) is KPQI-EtBS>soft mesophase>hard mesophase>KPQI. These abilities appear to be related to their fusibility and dependent upon their chemical structure defined by their origin and heat-treatment history. The molecular weight (extent of condensation) and the hydrogen content (favourably naphthenic hydrogen) of the components may be the most important factors. This approval is relevant to the preparation of suitable carbon fiber precursors from Ql material including mesophase.     

TEM study of the FSW nugget in AA2195-T81

During friction stir welding (FSW) the material being joined is subjected to a thermal-mechanical process in which the temperature, strain and strain rates are not completely understood. To produce a defect free weld, process parameters for the weld and tool pin design must be chosen carefully. The ability to select the weld parameters based on the thermal processing requirements of the material, would allow optimization of mechanical properties in the weld region. In this study, an attempt is made to correlate the microstructure with the variation in thermal history the material experiences during the FSW process.     

Hypervelocity impact computations with finite elements and meshfree particles

The ability of computations to model characteristics of hypervelocity impact is demonstrated using an algorithm for the automatic conversion of distorted finite elements to meshfree particles. The Lagrangian formulation tracks material boundaries and properties without the errors typical in an Eulerian formulation as the material traverses large distances. A computation of a sphere impacting a bumper is shown to reproduce three regions in the debris cloud that are observed in tests: a front region composed of droplets of melted projectile and target, a middle region of fragmented projectile, and a back region of spalled projectile. Additional computations reproduce the observed traits that result from variations in the projectile shape and obliquity. The computation of a projectile impacting spaced plates demonstrates the ability of the method to model the damage to the rear plate of a Whipple shield for spacecraft protection.     

清代宫廷包装的结构设计

从包装材料及容装性、保护性和方便性几方面,用具体的图例介绍探讨了中国清代宫廷包装的结构设计.     

空间低轨长寿命飞行器用太阳电池复合互连材料的设计

空间太阳电池在低地球轨道工作时受到原子氧等的腐蚀,其互连材料的寿命决定了电池的寿命.为此,设计了一种Ag/Mo/Ag三层夹心结构的复合互连材料取代目前使用的纯Ag互连材料,选择耐原子氧腐蚀的Mo作为衬底材料,涂覆Ag薄膜以利于电阻焊接.采用线性规划思路优化求解复合材料各层厚度范围.通过有限元分析模拟了互连片与电池焊接后的应力和形变分布,验证了上述设计结果.根据设计结果实际制备出复合互连材料,经焊接验证其是可行的.     

Microwave processing: fundamentals and applications

In microwave processing, energy is supplied by an electromagnetic field directly to the material. This results in rapid heating throughout the material thickness with reduced thermal gradients. Volumetric heating can also reduce processing times and save energy. The microwave field and the dielectric response of a material govern its ability to heat with microwave energy. A knowledge of electromagnetic theory and dielectric response is essential to optimize the processing of materials through microwave heating. The fundamentals of electromagnetic theory, dielectric response, and applications of microwave heating to materials processing, especially fiber composites, are reviewed in this article.