大型反射面天线温度分布规律及变形影响分析

针对高频段大型反射面天线对电性能的高要求,必须降低太阳热辐射对天线的影响。先计算一天中太阳入射角度的变化规律,再基于I\|DEAS软件仿真,得到一天中各时刻天线反射面上的温度、热应力场、热变形分布,然后针对阴影对天线结构的重要影响,以“分点分段”的形式给出不同时刻温度在反射面上的分布及其影响程度和规律,为工程人员进行天线的温度补偿和结构优化提供了依据。     

Surface micro-texture on sapphire fabricated by laser ablation trajectory regulation

Fabrication of the surface micro-texture on the C-plane sapphire is undertaken by a355 nm Ultraviolet(UV) pulsed laser. The surface micro-textures of sapphire with different laser scanning line spacing ranging from 10 lm to 100 lm are obtained, where the selection range of scanning line spacing is controlled in the range of the groove width and plasma width to obtain a surface of high Peak-Valley(PV) value. A reasonable processing order is proposed to manufacture different types of surface micro...     

Integrated method for crater detection from topography and optical images and the new PH9224GT catalogue of Phobos impact craters

In a large majority of lunar and planetary surface images, impact craters are the most abundant geological features. Therefore, it is not surprising that crater detection algorithms (CDAs) are one of the most studied subjects of image processing and analysis in lunar and planetary science. In this work we are proposing an Integrated CDA, consisting of: (1) utilization of DEM (digital elevation map)-based CDA; (2) utilization of an optical-based CDA; (3) re-projection of used datasets and crater coordinates from normal to rotated view and back; (4) correction of the brightness and contrast of a used optical image; and (5) tile generation for the optical-based CDA and an assembling of results with an elimination of multiple detections, in combination with a pyramid approach down to the resolution of the available DEM image; and (6) a final integration of the results of DEM-based and optical-based CDAs, including a removal of duplicates. The proposed CDA is applied to one specific asteroid-like body, the small Martian moon Phobos. The experimental evaluation of the proposed CDA is done by a manual verification of crater-candidates and a search for uncatalogued craters. The evaluation has shown that the proposed CDA was used successfully for cataloging Phobos craters. The major result of this paper is the PH9224GT – currently the most complete global catalogue of the 9224 Phobos craters. The possible applications of the new catalogue are: (1) age estimations for any selected location; and (2) comparison/evaluation of the different chronology and production functions for Phobos. This confirms the practical applicability of the new Integrated CDA – an additional result of this paper, which can be used in order to considerably extend the current crater catalogues.     

基于人工神经网络的反射器型面精度预测

基于人工神经网络的预测方法,利用数量适当的有限元计算结果,建立人工神经网络模型,对反射器型面进行精度预测分析,得到在最小型面精度结果下的结构设计参数。计算结果显示训练好的神经网络模型能够较精确地预测格栅反射器的型面精度,节省计算时间,并且以型面精度最小为准则进行参数分析,能够指导反射器的结构设计。     

δ0.05mm薄钢带力学性能测试方法研究

研究了拉伸速率、试样类型、试样表面状态对δ0.05mm薄钢带力学性能测试的影响,通过数据对比,结果表明：拉伸速率对薄钢带的力学性能测试结果影响并不大,而试样的类型和试样的表面状态对力学性能测试结果有很大的影响;表面无缺陷的哑铃型试样可以满足检测要求,提高钢带检验一次合格率。     

利于翼型优化设计的超临界翼型参数化方法

为减少超临界翼型优化中的设计变量,消除优化结果的不光顺现象、保证C₂连续,在优化过程中控制翼型几何特性的变化范围,设计出了由4条首尾相接的有理Bézier曲线表示的超临界翼型的翼型参数化方法,该方法对翼型数据的参数化过程中主要运用了Bézier曲线拟合算法与SPSA(Simultaneous Perturbation Stochastic Approximation)优化算法,并在Bézier曲线拟合算法中使用了有别于常用方法的数据点参数选择方法.将这种超临界翼型参数化方法与优化算法结合便可实现翼型优化设计,其中的设计变量为21个,优化结果不仅光顺且满足C₂条件,通过设定设计变量变化范围便可控制相应的翼型前缘半径、上下弦最高最低点的位置与曲率、尾部契角等几何特征.      

Performance evaluation of creep feed grinding of γ-TiAl intermetallics with electroplated diamond wheels

This paper evaluates the performance of creep feed grinding γ-TiAl intermetallic (Ti-45Al-2Mn-2Nb) using electroplated diamond wheels. Firstly, a comparative analysis with the grinding results by using electroplated CBN wheels was conducted, mainly involving abrasive wheel wear behavior and maximum material removal rate below surface burn limit. It was found that the diamond wheel would produce much better grinding results including lower wheel wear rate and higher maximum material removal rate. Then the surface integrity obtained at different level of material removal rate was characterized with the utilization of the diamond wheel. The poor ductility of this γ-TiAl intermetallic material was found to have a marginal effect on the surface integrity, as no severe surface defects such as material pullout were generated during the stable wheel wear stage. For the involved operating parameters, a deformation layer was produced with ∼10 μm or more in thickness depending on the material removal rate used. Meanwhile, a work-hardened layer extending to more than 100 μm was produced with a maximum microhardness of above 520 HV_0.05 (bulk value 360 HV_0.05). The residual stress remained compressive, with a value of above −100 MPa and even up to −500 MPa for an elevated material removal rate. Shearing chip was the main chip type, indicating good wheel sharpness in the grinding process.     

Anhydrous based shear-thickening polishing of KDP crystal

Based on the special physical–chemical characteristics of optical crystal in the field of aeronautics, a new anhydrous based shear-thickening polishing (ASTP) method has been proposed to restrain deliquescence and to improve physical properties for KDP machining. The ultra-precision polishing of KDP crystal is completed by ASTP. A kind of anhydrous based thickening polishing slurry (ATPS) was proposed in our work, and high-performance rheological properties were determined to achieve the ASTP of KDP crystal. A material removal model of ASTP in KDP machining is established, followed by the verification experiment of the prediction model. The maximum error of the predictive model is only 9.8%, which proves the validity of the material removal model for KDP polishing. The polishing experiments were carried out on the polishing platform developed by ourselves. The results show that the new polishing method can polish 20 mm × 20 mm × 5 mm KDP crystal and obtain a super-smooth surface with a surface roughness of 1.37 nm and high shape accuracy. The surface accuracy of polished KDP crystal reaches up to 0.68λ (RMS). The experimental results show that the ASTP is a potential ultra-precision machining method for KDP crystal.     

基于特征的逆向工程数据分析

在CAD/CAM领域逆向工程是一门新兴的技术,对其进行初步研究,提出了在逆向工程中,零件特征数据的提取过程思路,以及实现初步建模的分析想法。     

过渡协调模式下机翼数学模型的建立

讨论了飞机制造模式由模拟量协调体系向数字量协调体系转化过程中出现的问题,重点研究了其中的关键技术,即飞机外形数字化模型的建立,主要包括理论图的分析与转化,外形数据的获取,翼型轮廓曲线的计算,外形曲面的重构以及误差检验等。上述建模过程遵循了原始设计意图,保证所建数模符合生产中使用的制造与检验依据,为定型飞机数字化建模提供了理论指导。