中波红外光学材料的研究现状和发展趋势

随着红外制导导弹速度的提高,对红外光学材料的性能要求越来越高.本文综述了导弹用中红外光学材料白宝石、尖晶石、氟化镁、氮氧化铝等的光学性能、机械性能、性能价格比、应用及其发展现状和发展趋势.     

多自应力模态索穹顶结构的几何构造分析

索穹顶结构是发展和推广Fuller张拉整体结构思想后唯一实现的一种新型大跨空间结构,它的几何构造分析是一项非常重要的工作。本文在对一般空间杆件体系的分类、自应力模态和机构位移模态研究的基础上,从索穹顶结构特有的杆件拓扑关系入手,提出了单位整体可行预应力这一新概念,并最终解决了多自应力模态下该体系稳定性判定问题;通过对若干类型索穹顶结构的几何构造分析,得出了一些对结构设计有用的结论。     

超声速长波红外整流罩材料研究进展

采用长波红外制导的超声速导弹具有极佳的军事应用前景,但高速飞行的导弹整流罩会承受较高的气动冲击以及砂蚀、雨蚀,极易出现结构和光学性能失效,因此选择与服役环境相匹配的整流罩材料至关重要.基于上述应用现状,本文综述了目前主要研究的几种长波红外整流罩材料,对其光热理化性能及应用前景进行了分析,同时对几款整流罩材料或结构的发展方向进行了展望,旨在为超声速长波红外整流罩的选材提供技术参考.     

Conformal optical system design with a single fixed conic corrector

A conformal optical system refers to the one whose first optical surface conforms to both aerodynamic and imaging requirements. Appropriate correction is required because a conformal dome induces significant aberrations. This paper intends to explain that an effective solution to the easy-fabrication conic surface corrector compensates aberrations induced by a coaxial aspheric dome. A conformal optical system with an ellipsoid MgF₂ conformal dome, which has a fineness ratio of 2.0, is designed as an example. The field of regard angle is pm 30 degrees with a pm 2 degree instantaneous field of view. The system's ultimate value of modulation transfer function is close to the diffraction limit, which indicates that the performance of the conic conformal optical system with a fixed conic corrector meets the imaging requirements.     

Experimental and numerical study on formability of friction stir welded TWB sheets based on hemispherical dome stretch tests

In order to investigate formability performance and also to obtain guidelines for the stamping process design of friction stir welded TWB (tailor welded blank) sheets, the hemispherical dome stretching test was experimentally performed and the results of the base and friction stir welded samples were compared. Also, in order to better understand the experimental results, numerical analysis was performed. In this work, five automotive sheets, 6111-T4, 5083-H18, 5083-O aluminum alloy, dual-phase steel (DP590) and AZ31 magnesium alloy sheets were considered by (friction stir) welding the same materials. To represent mechanical properties for the numerical analysis, the non-quadratic orthotropic yield function, Yld2000-2d, was utilized for the aluminum alloy and DP590 sheets, while the Cazacu anisotropic/asymmetric yield function was applied for the AZ31 sheet considering different hardening behavior in tension and compression.     

红外窗口和整流罩材料研究现状与发展趋势

介绍红外窗口的三个综合性能评价因子:热破裂品质因子、光畸变品质因子、抗热冲击品质因子;并用它们评价了氟化镁、尖晶石、氮氧化铝、蓝宝石、硫化锌和硒化锌、金刚石等主要的红外窗口和整流罩材料;综述其国内外的研究现状,并对其未来的发展趋势发表了自己的观点.     

超声速红外长波光学整流罩设计技术研究

红外光学整流罩的性能直接影响超声速飞行器的成像质量和探测性能.本文提出了一种基于硫化锌材料的整流罩设计方法,详细讨论了材料选择、外形尺寸、厚度、镀膜、与壳体连接方式等问题,分析了试验验证对整流罩设计的重要性.     

Experimental study of wind loads on cylindrical reticulated shells

The cylindrical reticulated shell structures without side walls, which are normally arranged in pairs, are usually used as dry-coal sheds in a thermal power plant. The wind loads of these shells do not exist in standards or codes. Therefore, this study investigates the mean and fluctuating wind loads on a cylindrical reticulated shell with a rise-to-span ratio of 0.39 through a series of wind tunnel tests. The characteristics of the wind pressures on the upper and lower surfaces and the net pressures are presented. The results show that the wind direction and another shell structure significantly affect the wind loads on the principal shell. The most unfavorable wind direction is around 30°, whereas the effects of the wind field and the height of the coal stack are small. The surfaces of the shells are divided into nine blocks, and the block mean and fluctuating (rms) pressure coefficients suitable for engineering applications are given as references for wind load codes.     

基于应变响应敏感性的单层球面网壳冗余度分析

冗余特性是结构鲁棒性的重要组成部分,也是复杂系统的安全性和传力路径可靠性的体现。如何对结构构件冗余度进行定量评价是目前结构工程界尚未定论的问题之一。本文借鉴P.C.Pandey方法,并将其推广应用到大跨空间网格结构,基于结构应变响应对构件单元截面面积的敏感性提出静力作用下的结构构件冗余度评价方法,从理论上以数值方式量化结构构件冗余度,并通过对三个球壳结构算例的冗余度分析说明该方法在空间结构体系中的有效应用。算例结果表明,结构构件冗余度能够反映构件在结构中的重要性,低冗余度构件是结构的关键构件。采取措施加固低冗余度构件可以有效提高结构整体刚度、结构稳定极限承载力,但在改善结构缺陷敏感性方面则视具体情况而定。     

锅仔片表面指纹检测方法

锅仔片是薄膜开关、微型开关等电子元件中的关键部件之一,具有接触平稳、导通性强、回弹稳定、手感俱佳的几大优点;在锅仔片的生产过程中,不可避免地会被人的手指接触到,并留下指纹和油脂,导致锅载片加快氧化,影响其寿命,对主体产品的质量留下了隐患;因此,锅仔片的质量检测是提高主体产品竞争力的重要环节;目前,生产企业大多采用的检测法是人工目视检测法,该方法效率低,且容易误判;为了提高生产效率,提出了基于机器视觉的锅仔片表面指纹检测方法;该方法通过利用广义霍夫变换对目标进行定位、提取目标的灰度共生矩阵和支持向量机分类识别,实现了锅仔片质量的自动检测,并给出了该方法的工作流程;实验结果证明,该方法取得了良好的效果,具有一定的实用价值和推广价值。