薄片状聚酰亚胺多孔材料的研究进展

综述了薄片状聚酰亚胺多孔材料的研究进展,主要介绍了薄片状的聚酰亚胺多孔材料的产品种类、研究单位、性能指标、应用情况及制备方法,并提出了目前对薄片状聚酰亚胺多孔材料研究存在的问题以及研究现状,展望了薄片状聚酰亚胺多孔材料在今后的研究方向和发展趋势.薄片状聚酰亚胺多孔材料,已经作为垫片用在宇宙飞船的多层隔热系统中,甚至会逐渐替代传统的多层隔热系统材料.     

Cutting force prediction for circular end milling process

A deduced cutting force prediction model for circular end milling process is presented in this paper. Traditional researches on cutting force model usually focus on linear milling process which does not meet other cutting conditions, especially for circular milling process. This paper presents an improved cutting force model for circular end milling process based on the typical linear milling force model. The curvature effects of tool path on chip thickness as well as entry and exit angles are analyzed, and the cutting force model of linear milling process is then corrected to fit circular end milling processes. Instantaneous cutting forces during circular end milling process are predicted according to the proposed model. The deduced cutting force model can be used for both linear and circular end milling processes. Finally, circular end milling experiments with constant and variable radial depth were carried out to verify the availability of the proposed method. Experiment results show that measured results and simulated results corresponds well with each other.     

Novel approach of crater detection by crater candidate region selection and matrix-pattern-oriented least squares support vector machine

Impacted craters are commonly found on the surface of planets, satellites, asteroids and other solar system bodies. In order to speed up the rate of constructing the database of craters, it is important to develop crater detection algorithms. This paper presents a novel approach to automatically detect craters on planetary surfaces. The approach contains two parts: crater candidate region selection and crater detection. In the first part, crater candidate region selection is achieved by Kanade-Lucas-Tomasi (KLT) detector. Matrix-pattern-oriented least squares support vector machine (MatLSSVM), as the matrixization version of least square support vector machine (SVM), inherits the advantages of least squares support vector machine (LSSVM), reduces storage space greatly and reserves spatial redundancies within each image matrix compared with general LSSVM. The second part of the approach employs MatLSSVM to design classifier for crater detection. Experimental results on the dataset which comprises 160 preprocessed image patches from Google Mars demonstrate that the accuracy rate of crater detection can be up to 88%. In addition, the outstanding feature of the approach introduced in this paper is that it takes resized crater candidate region as input pattern directly to finish crater detection. The results of the last experiment demonstrate that MatLSSVM-based classifier can detect crater regions effectively on the basis of KLT-based crater candidate region selection.     

翼柱型药柱内三维湍流流动仿真

应用Ｓｉｍｐｌｅ方法进行了固体火箭发动机燃烧室中的三维流动仿真。所考虑的物理因素如下：翼柱型药柱，三维加质不可压湍流，移动的燃面边界，燃气的热辐射等。方程为：三维连续、动量和能量方程，ｋ－ε湍流模型，三维热辐射通量方程等。为了处理燃面移动边界，提出了标记网格示踪技术。计算结果获得了固体火箭发动机燃烧室翼柱型药柱中三维流动的参数分布。同时，揭示了某些新现象和新规律：翼和柱通道间的几何匹配及其中的加质强度对流动参数有强烈的影响，甚至可能发生反向流动和旋涡；在一定条件下，翼通道下游附近可能产生明显的周向旋涡。     

16Co14Ni10Cr2Mo钢力学性能与应力腐蚀行为

研究了１６Ｃｏ１４Ｎｉ１０Ｃｒ２Ｍｏ钢不同温度回火５ｈ强度、冲击韧性、断裂韧性和应力腐蚀性能（在３．５％ＮａＣｌ水溶液中）。在５１０℃回火可以获得较高的强度，最高的断裂韧性及抗应力腐蚀性能，此时Ｋ＿（ＩＳＣＣ）可达，Ｋ＿（ＩＣ）为，屈服强度为１５８０ＭＰａ。应力腐蚀性能（ＳＣＣ）的改善主要与在较高温度回火，使Ｍｏ＿２Ｃ共格造成的应力下降，位错亚结构的恢复及碳化物的粗化，并导致氢的偏聚下降有关。     

两级涡轮三维无粘定常流场的数值模拟

采用三阶精度TVD格式和隐式近似因子分解方法, 求解了某型航空发动机两级低压涡轮的三维稳态流场。控制方程为欧拉方程组, 流动损失以分布体积力的形式加入到方程组中。动静叶之间的参数传递采用了一种新的周向平均模型, 基于连续流场的假设, 各列叶栅的进出口条件采用了新的给定方法。为了证实本文方法的可靠性, 与S2流面计算的结果进行了比较。      

救生伞收口性能分析

通过对ACESⅡ弹射座椅所使用的C－9伞收口速度补偿曲线的理论。分析了救生伞采用收口技术后,＿能在高速状态下降低开伞动载,在低速状态下不降低最低安全高度的原因;并对国产ＨＴＹ－4型弹射座椅装备了收口的救生－13型伞后的性能进行了估算。假如收口阻力特征等于210m2、收口时间等于10ｓ则在3000m高度上开伞动载将减小40％;并论述了收口阻力特征和收口时间选取的原则。     

叶轮机械气动声学频域分析

得到中弧线小弯度薄叶片叶轮机械声场的详细结果。讨论适用于近声场, 叶片的弯、掠等几何特征及运行条件也都在频域解中显式地表示出来。      

圆柱壳体上环形焊缝焊接变形的数值分析

用数值方法研究了圆柱形筒体间环缝及圆柱形筒体与法兰对接后环缝引起的焊接变形，并与试验进行比较，研究结果表明：圆柱形壳体间的对接环缝对法兰平面倾斜没有明显的影响；使圆柱形壳体的径向产生变形；圆柱形壳体与法兰对接环形焊缝将引起壳体的径向变形及法兰平面度的变化；采用纵向收塑力对圆柱形壳体间对接和圆柱形壳体与法兰对接两种环缝进行有限元分析是可行的。     

轴向受载的高速球轴承的拟动力学分析

提出了对仅受轴向载荷的高速球轴承进行拟动力学分析以掌握滚动元件运动特性的方法。首先确定了钢球和套圈的滚动速度以及套圈相对于钢球的滑动速度，建立了各滚动元件的润滑模型，阐述了建立高速球轴承运动特性分析基本方程的一般原理。通过求解这些基本方程可得到高速球轴承中各滚动元件的运动状态、受力情况、弹流油膜厚度和疲劳寿命，从而可确定高速球轴承不打滑的最小轴向力。