商用飞机热塑性聚氨酯防潮胶带的研制

探究了国外某产品与军用防腐膜HP8714在关键技术指标水蒸气透过量及12 s垂直燃烧的性能,并以乙酸乙酯EAC为胶黏剂溶剂研究了胶黏剂种类及含量对防潮胶带性能的影响。结果表明,HP8714的热塑性聚氨酯原料A198FR可作为高性能阻燃热塑性聚氨酯防潮胶带的树脂原料,并以A198FR为树脂原料,确定压敏胶YY16为最适宜胶黏剂,优选YY16/EAC配比为75/25,并通过第三方测试验证所有指标。     

环氧树脂固化工艺条件对YBCO超导带材临界电流的影响

为了研究固化条件对超导带材临界电流的影响,采用电测法实验测量了多种固化工艺条件下YBCO高温超导带材的临界电流。分析得到热处理温度140℃时,超导带临界电流出现明显退化,温度越高退化越明显;超导带临界电流随着固化时间的延长而降低,处理温度越高,随时间下降的幅度越大,并从超导体钉扎效应的角度对实验结果进行了初步的分析。     

Long multifilament Bi-2223 Ag-sheathed superconducting tapes and solenoids

Multifilament Ag-sheathed BiPbSrCaCuO (2223) superconducting tapes containing 49 filaments were fabricated by the powder-in-tube route and the roll-anneal process. The transport critical current densityJ _c was 1.3×10⁴ A cm^–2 at 77 K and 7×10⁴ A cm^–2 at 4.2 K in self-field. A 12-m-long tape was used to construct superconducting solenoids (50, 28, and 14 mm internal diameters) generating dc fields 380–1070 G at 4.2 K. Measurements of the variation ofJ _c with field (0–1.6 T) and bend strain (0–5%) are used to explain the performance of the solenoids. The critical bend strain of tapes was about 1.5%.     

Evaluation of turbulent forced convection of non-Newtonian aqueous solution of CMC/CuO nanofluid in a tube with twisted tape inserts

The present paper investigates the turbulent flow and heat transfer of non-Newtonian aqueous solution of Carboxymethyl cellulose (CMC) and CuO nanoparticles in a plain tube and also tube with twisted tape inserts. The aqueous solution of CMC and CuO/CMC nanofluid show a shear-thinning (pseudo-plastic) rheological behavior, resulting in a higher viscosity than that of water. The consistency index and the power law index are evaluated based on available experimental data. The single phase approach with temperature dependent thermo-physical properties is applied to simulate the nanofluid flow and heat transfer. Simulation results are presented at different nanoparticle concentrations and twisted tape ratios. Only an axial flow is identified in the plain tube whereas both axial and swirl flows are detected in the tube with twisted tape inserts. The turbulence kinetic energy in the tube with twisted tapes is significantly higher than that in the plain one, which is useful for non-Newtonian fluid with higher viscosity. Also, the temperature fields in the tube with twisted tapes are disturbed relative to those in the plain one, due to stronger turbulence intensity and better fluid mixing. Higher amounts of nanoparticles concentration and lower twist ratios, giving maximum values of total efficiency, display the advantage of using non-Newtonian nanofluid in the tube with twisted tape inserts rather than non-Newtonian base fluid in the plain one.     

基于粘性胶带的缠绕捆扎机构设计

针对一种新型胶带捆扎机构,分析了其对柔性塑料袋的缠绕捆扎过程;引入断裂力学概念,基于断裂能量释放机理,建立了胶带剥离的力学模型;研究了胶带剥离速度与剥离力关系,得到了实现胶带缠绕捆扎所需的最小驱动力;最后,对弹簧支座位置进行了优化,使捆扎机构在最小驱动力条件下,能够实现对成束后塑料袋的捆扎。     

自动铺带铺层贴合形成机制

探讨了自动铺带工艺过程中相邻铺层界面间的贴合形成机制,将铺层界面间贴合过程建模为树脂补片在平行板之间挤压流动从而浸润界面的过程。指出在树脂流体黏度一定的情况下,树脂对界面浸润效果越好,则界面贴合能力越强。利用流体力学理论推导出树脂流体对界面浸润效果的计算公式,并分析了铺放压力、铺放速度等因素对浸润效果以及贴合能力的影响,提出以剥离力作为量化铺层间贴合能力的指标。在自行研制的自动铺带工艺参数实验平台上进行了一系列实验,实验结果表明,铺层间贴合能力随铺放速度增大而变差,随铺放压力、模具温度、压辊半径增大而变强,这一规律验证了所提出的树脂流体对界面浸润效果计算公式的正确性。     

LTCC流延生瓷带的力学性能

选择邻苯二甲酸二丁酯(DOP)和聚乙二醇(PEG)作为复合增塑剂,采用流延法制备生瓷带。研究复合增塑剂中PEG和固含量对浆料黏度及生瓷带力学性能的影响。结果表明,复合增塑剂的增塑效果优于单组分增塑剂。随着PEG含量的增加,生瓷带拉伸强度减小,断裂伸长率先增大后减小;生瓷带的拉伸强度和断裂伸长率随固含量的升高而降低。当增塑剂中w(PEG)为30.0%～70.0%,w(固含量)为86.5%～87.3%时,生瓷带拉伸强度约为1.94MPa,断裂伸长率约为12.07%。     

煤矿主提升胶带输送机改造技术

主要介绍了东峡煤矿主提升胶带输送机的改造依据及设计构思、实施过程以及解决的技术关键.主提升胶带输送机在不增加带强、带宽的基础上,保证皮带机运行的安全系数的前提下,增加了皮带机总功率,提高了带速,增加了运输能力,达到了预期目标.     

一种新型视频判读方法的辨析与探讨

利用录像和视频处理技术以及单片机原理,设计了一种新型智能判读系统,提出了一种新型的判读方法,即通过录像测量靶场光测仪器脱靶量的先进方法(简称视频判读).它把电视实时测量和事后判读的优点结合起来,代替了当前通用的胶片半自动判读仪。新型判读方法的研究成功,是胶片半自动判读的重要补充和发展,提高了靶场光电测量的效率,改变了靶场数据处理的面貌,推动电视测量的发展及新一代光电自动经纬仪的诞生。     

Ceramic green tape extrusion for laminated object manufacturing

Al₂O₃ and SiC green tapes with 0.2 mm thickness used for LOM (laminated object manufacturing) were prepared from a 75 wt.% ceramic suspension in a LDPE based organic vehicle followed by extrusion. Rheological characterization of the alumina and SiC suspensions were studied. TG-DTA analysis was carried out in air and microstructures were examined by SEM.