有限元法在42英寸多枪彩色显像管玻壳设计中的应用

由于多电子枪显象管玻壳是一个变厚度组合壳体，很难用板壳经典理论进行求解，所以在设计九电子枪彩管玻壳时用有限元方法预先知道该玻壳的应力分布，通过修改设计参数，使九电子枪彩管玻壳能满足强度要求，在设计玻屏时采用非均匀有理B样条的曲面分析方法，锥体采用四条组合的非均匀有理B样条曲线旋转一周得到，本设计实现了玻屏表面外形和曲率变化及玻壳结构设计的全参数化，提高了玻壳的设计效率，本还给出了计算玻壳外型的公式和一些技术参数。计算机仿真结果表明：42英寸九电子枪彩色无支撑CRT的玻壳既能满足强度要求，又具有好的视觉效果。     

有理曲面的截面设计方法

本文在分析张量积有理B样条蒙皮面曲面方法不足的基础上,给出了用截面外形设计原理构造有理蒙皮曲面、回转曲面及扫掠曲面的方法,并提出了对G~1连续的有理曲线进行重新参数化使其达到C~1连续的方法。文中的实例表明用该方法能够产生满足设计要求的参数曲面。     

有理B样条方法的工程应用

1946年,Schoenberg发表了长篇文章讨论等距节点的逼进问题,最早提出了B样条的概念。二十余年后,Riesenfeld研究了B样条逼近在计算机辅助几何设计中的应用,并于1973年发表了博士论文。随即B样条曲线曲面在几何设计中获得了广泛的应用。翌年,Versprille完成了“有理B样条在计算机辅助设计中的应用”的博士论文,首先研究了有理B样条问题。由于有理B样条方法的独特优点,已为若干系统如SDRC公司的GEOMOD、波音公司的系统以及Evans＆Sutherland公司的PS300智能图形终端等采用,但公开发表的文献很少。为了进一步完善我们正在发展的三维造型系统,使其具有更强的造型功能,并能精确表达园锥曲线、曲面,我们对有理B样条方法作了初步研究,并设计了试验程序。本文根据我们的研究成果依次阐述有理B样条的特点,有理B样条曲线曲面的表达和形状控制,有理B样条曲线和有理Be＇Zier曲线的转换,最后简述当前正在进行的研究。文中也涉及Versprille曾经研究过而很少应用的若干问题。     

用八级场参数表示的九级像差公式及分析

给出了用八级场参数表示的九级像差系数。并对其在超大屏幕彩管开发和生产中解决屏边缘失会聚问题的作用进行了理论探讨     

用八级场参数表示的九级像差公式及分析

给出用八级场参数表示的九级像差系数，并人在超大屏幕彩管开发和生产中解决屏边缘失会聚问题的作用进行了理论探讨。     

B样条曲面为基础的计算机辅助工业包装设计探讨

本文在论述工业包装设计中应用非均匀有理B样条曲面的化越性后,介绍了一个工业包装CAD系统,阐述了工业包装设计中精细艺术曲面造型的两种新方法,从而开拓了计算机图学在工业包装设计中的应用前景.     

逆向工程中曲面重构技术的介绍

首先简单的讲解了逆向工程的概念,在此基础上介绍了逆向工程曲面重构技术中的基本知识点和曲面重构技术的以三角Bezier曲面为基础的曲面构造技术的基本知识以及B-Spline(B样条)或NURBS(非均匀有理B样条)曲面为基础的曲面构造基本知识。     

基于NURBS的PDE曲面构造法研究及应用

由非均匀有理Ｂ样条曲线曲面给定边界条件，用偏微分方程来构造曲面，以参数“ａ”控制其整体形状，本文分析其思路原理及过程，并列举了在ＣＡＤ上的应用，最后分析了优缺点。     

显象管玻壳的有限元分析和防爆质量的无损检测法

本文用有限元法研究了显象管玻壳的应力和位移分布。由于显象管玻壳是一种变厚度的组合壳体,很难用板壳经典理论进行求解,传统的玻壳强度分析主要依靠电测法。玻壳设计应用有限元法可以使玻壳在设计阶段就可预知应力与位移分布情况,便于修改设计,这样就可缩短设计制造周期和提高经济效益。文中给出了用有限元法和电测法得到的应力分布图。二者结果比较吻合。根据玻壳在大气压力作用下的位移值和防爆钢带箍紧后玻壳的位移性质,提出玻壳防爆质量的无损检测法,其优点是弥补传统的抽样引爆方法的缺陷,应用新方法玻壳无须引爆,减少了玻壳成品的损耗,大大降低了玻壳成本,而且便于玻壳逐个检验,提高了显象管的防爆质量,建议推广应用。     

基于C-B样条的三角形和四边形曲面生成

文章给出了基于C-B样条的由网格数据产生三角形和四边形曲面片的方法,C-B样条是由基底函数{sin t,cos t,t,1}导出的一种新型样条曲线,它可以克服现在正在使用的B样条和有理B样条为了满足数据网格的拓扑结构而增加多余的控制点,求导求积分复杂繁琐,阶数过高,从而讨论其连续拼接时增加了困难等缺点,如何将它推广成曲面就成为一个重要问题。作者利用边-顶点方法构造插值算子,再将这些算子进行凸性组合,将C-B样条曲线推广成三角形曲面片和四边形曲面片,它可以用于CAD的逆向工程中散乱数据的曲面重构。     

多孔薄膜荫罩热变形的有限元仿真设计

荫罩的热变形使电子束产生着屏偏移 ,进而导致了色纯变坏。本文采用大型软件ANSYS对 1 5英寸荫罩进行了热变形的有限元仿真 ,从而得到了电子束的着屏偏移。建立了包括阴极射线管 (CRT)里所有部件的完整的有限元模型。荫罩被建为无孔连续薄壳的模型 ,对它的表面导热系数和表面弹性模量作了等效的计算。考虑了弹簧片的预应力以及弹簧片和销钉的连接。这样可使我们的分析模型更接近真实情况。本文给出了 50 0、1 0 0 0、1 0 0 0 0s时的热变形和电子束着屏偏移。分析表明 :电子束着屏偏移的最大值发生在 50 0s左右。利用这种分析方法及研究结果可指导新型荫罩的设计和研制。     

双峰式显示管的特点及电路设计

双峰式显示 (像 )管由一个小尺寸的后锥和一个较大的显示屏构成 ,后锥上附有两个装着电子枪的管颈 ,它采用低熔点玻璃粉封接工艺制成一个完整的显示管。与常规的显示管相比 ,双峰式显示管可具有进深小 ,分辨率较高和畸变失真较小等一些良好的特性。它也是多枪结构扁平显示管的经典模式之一。双峰式显示管采用了两组相互独立的磁偏转系统 ,因此它显示的整幅图像是由两幅单元图像拼接而成。在双峰式显示管的应用中 ,研究的主要内容之一是如何消除存在于单元图像之间的黑白接缝。本文简要介绍了双峰式显示管的基本结构及特点 ,并探讨了它的电路设计 ,该设计可有效地消除或减小单元图像之间的黑白接缝     

Probability of Failure of Sylgard-Mounted Optical Lenses in Head-Up Display During Thermal Cycle Testing

Lenses made from optical glass do not have a single characteristic strength. The strength of any optical glass is highly dependent on the area under stress and its surface finish. The nominal design strength of manufactured glass is typically in the 6.9–70 MPa range. This study presents an analysis of measured strain data and an approach to quantify the failure probability of optical lenses that are used in head-up display systems for aircraft applications when these lenses are subjected to accelerated thermal cycling. The thermal cycling produces thermal stress within the elastomerically mounted optical lens of the head-up display. We used a combination of experimental methods and finite element modeling to determine the thermal strain in the optical lens. The thermal strain values that were obtained using these methods were validated and were found to be in a cumulative distribution. This cumulative strain provides a quantitative estimate of the effects of thermal stress in the optical lens. We then determined the failure probability using Weibull parameters.     

Tensile strength of glass fibres with carbon nanotube–epoxy nanocomposite coating

A study has been made of a concept of ‘healing’ coatings applied onto the brittle fibre surface to reduce the stress concentrations and thus to improve the reinforcing efficiency in a composite. Coatings made from neat epoxy and carbon nanotube (CNT) reinforced epoxy nanocomposite were applied onto the individual glass fibres as well as rovings. It is shown that the 0.3 wt.% CNT–epoxy nanocomposite coating gave rise to a significant increase in tensile strength of the single fibre for all gauge lengths, better than the neat epoxy coating. The results on glass fibre roving also indicated a clear beneficial effect of nanocomposite impregnation on tensile strength. The rovings impregnated with the CNT nanocomposite exhibited a more uniform strength distribution and higher strengths than those impregnated with the neat epoxy. The changes in prevailing failure mechanisms influenced by the epoxy and nanocomposite coatings have been identified.     

Evaluation of the basic formulations for the cumulative probability of brittle fracture with two different spatial distributions of microcracks

The random distribution of microcracks in terms of their size, shape, orientation and spatial location has direct impact on the cumulative probability of brittle fracture induced failure, with the effect of spatial distribution being rarely explored. Recently, two weakest link theory‐based formulations for the cumulative probability of brittle fracture induced failure have been proposed for the spatial distribution of microcracks obeying the Poisson postulates and the uniform distribution, respectively. This work compares these two new formulations with the currently commonly adopted one built on the Poisson postulates under both the uniform and the non‐uniform uniaxial loading conditions. It is concluded that under general loading conditions involving non‐uniform stress states, the existing formulation is equivalent to or closely approximate to neither of the two new formulations thus should be discarded, because of its inaccurate derivation. The new formulations are featured with unique symmetry or self‐similarity in their expressions. Their capability in revealing the size effect or the scaling law of failure is highlighted and validated by a set of published uniaxial and biaxial flexural strength data of brittle material.     

Adhesion of glassy arsenic sulfide to quartz glass

Adhesion between As₂S₃ glass and quartz glass has been studied by a uniform pull-off method. The pull-off stress for the adhesion of glassy As₂S₃ to quartz glass has been determined as a function of temperature in the temperature range 110–190°C. The results demonstrate that, in the case of As₂S₃ glass, the adhesion strength increases exponentially with increasing test temperature and exceeds 2500 kPa at the glass transition temperature. We have studied how the adhesion strength is influenced by the contact temperature and time, tension test temperature, and quartz glass surface roughness.     

Effect of surface finish on strength degradation of glass ceramics

The processing of components manufactured from ceramics, such as machining, induces cracks on or beneath the surface leading to strength degradation. Usually, four-point bending tests are used for measuring the strength of ceramic materials. In this paper, a new approach is proposed to evaluate the loss of strength due to machining. First, beam specimens of glass ceramics are prepared by milling. The surface profile of representative areas of the specimens is determined using a laser profilometer. The surface topography of the representative area is reconstructed to characterize the surface irregularities after machining. A finite element program is then employed to analyze the stress distribution on a rough surface of a beam in four-point bending. A performance index—the stress concentration factor, is introduced to quantify the effect of surface irregularities on determining the critical crack depth related to the machining-induced damage. The flexural strength of machined ceramic specimens is predicted using the fracture mechanics. The strength degradation is compared with the experimentally determined values. A close correspondence between the predicted and measured strength is observed. The potential of using a computer-based evaluation to study the strength degradation of glass ceramics by machining induced surface damage has been established.     

Effects of particle size of treated CRT funnel glass on properties of cement mortar

Over the last decade, new types of display technologies have increasingly replaced cathode ray tube (CRT) displays leading to an increase in the disposal of discarded old CRT monitors and TV sets. The present study is a further development of our previous work to explore the effects of using different size fractions of crushed CRT glass as 100 % substitution of sand in cement mortar. A range of cement mortar mixes were prepared and the tests conducted included table flow (fluidity), mechanical strength, drying shrinkage, alkali–silica reaction (ASR) expansion and toxicity characteristic leaching procedures. Generally, the results obtained for the CRT glass-based cement mortars were comparable to those of the beverage glass mortars except the hardened density due to the presence of lead in the CRT glass. Decreasing the particle size of the CRT glass led to a decrease in fluidity, compressive strength and water absorption. However, the use of finer glass particles slightly improved the flexural strength and reduced the risk of expansion due to ASR due to its pozzolanic reaction. The experimental results indicated that treated CRT glass can be utilized as 100 % replacement of sand in cement mortar regardless of its particle size.     

Usefulness of cathode ray tube color displays in chromaticity-discrimination experiments

Chromatic-discrimination thresholds have been determined by use of a CRT color monitor that simulates aperture and object observation modes. The results were compared with earlier ones [Appl. Opt. 35, 176 (1996)] that were obtained under the same experimental observation conditions with different devices. The differences found between the results obtained with the CRT monitor and with visual colorimeters are of the order of magnitude of interobserver variability (9%). However, greater differences were found between results for CRT monitors and for illuminated samples, which could be attributed to suboptimal distribution of the samples in color space. The current results support the usefulness of CRT color monitors in new chromatic-discrimination experiments.     

真空荧光显示屏玻板的选用

真空荧光显示屏的外壳通常用浮法玻璃做成，要求有足够的强度。本文从材料力学角度出发，分析真空荧光显示屏的外壳所受的剪切应力，吸收他人的经验，并根据自己的试验，确定真空荧光显示屏中浮法玻璃的容许剪切应力。