歼轰机挂架梁高强铝合金ZL205A优质铸件的研制

本文主要介绍了高强度铸造铝合金(ZL205A)大型复杂优质挂架梁铸件的研制情况。由于该铸件结构复杂,其轮廓尺寸既长又扁,非常易于变形,所以保证挂架铸件冶金质量和尺寸相对稳定难度较大。本文侧重论述了铸造工艺设计、模具特殊设计和激冷材料设置,以及ZL205A 熔炼和热处理等先进工艺的应用,使挂架铸件的机械性能和切取性能均达到了设计和使用要求,铸件产品的合格率达到了85%左右。     

New Cutting Force Modeling Approach for Flat End Mill

A new mechanistic cutting force model for flat end milling using the instantaneous cutting force coefficients is proposed. An in-depth analysis shows that the total cutting forces can be separated into two terms: a nominal component independent of the runout and a perturbation component induced by the runout. The instantaneous value of the nominal component is used to calibrate the cutting force coefficients. With the help of the perturbation component and the cutting force coefficients obtained above, the cutter runout is identified. Based on simulation and experimental results, the validity of the identification approach is demonstrated. The advantage of the proposed method lies in that the calibration performed with data of one cutting test under a specific regime can be applied for a great range of cutting conditions.     

波音飞机起落架减震支柱漏油故障分析与排除

近年来,相继发现波音飞机因为起落架减震支柱内、外筒的封严部分损坏造成减震支柱内的液压油外漏的现象。如果不能对这种故障进行妥善处置,轻者使飞机的减震性能降低,机内乘员感到颠簸,并可能损坏某些机     

制备预浸料的JFY—1静电粉末预浸机及其制备工艺

本文介绍了一种静电粉末预浸机及其制备工艺。这是一种将增强体通过树脂粉末带电的流化床，使树脂粉末沉积在纤维上而制备预浸料的新方法，该设备装有β射线仪，用微机闭环控制预浸料树脂含量，制备的碳纤维帘子布／ＰＥＥＫ预浸料控制精度可达±３％最大工作宽度３００ｍｍ。     

阿尔卡特DME／DVOR设备三种远程监控方案的设计与实现

本文以意大利阿尔卡特生产的FSD－40／45型DME测距器和DVOR4000型全向信标机为实例，对设备的I／O系统和监控软件作了分析，并结合数据通信知识设计了三种远程监控方案，为实现灵活地远程监控该设备提供了经验。     

航天飞机驮机空气动力学——航天飞机的空气动力学问题之七

根据美国航天飞机驮机空气动力学的研究结果,本文简要地介绍了轨道器/驮机空气动力学的高阶面元法理论计算,风洞模型试验,仿真和飞行试验。风洞模型试验是建立轨道器/驮机气动数据库的基础,仿真是确定分离程序和训练驾驶员的有效方法,飞行试验是轨道器/驮机的驮运、分离和进场着陆气动性能的最后验证。研究试验表明:飞行试验与风洞试验和仿真结果符合得较好。合理地改装现有大型运输机,可以较好地完成航天飞机轨道器的驮运和进场着陆试验任务。     

基于优化最小二乘支持向量机的襟翼趋势预测

将最小二乘支持向量机(LS-SVM)应用于飞机襟翼状态趋势研究。首先,通过分析飞机襟翼故障与襟翼动作耗时参数的关系,提出了利用动作耗时趋势来确定该系统未来状态的方法。然后,使用最小二乘支持向量机建立耗时回归预测模型,采用最终预报误差(FPE)准则确定回归模型嵌入维数,提出了自适应网格搜索法,优化最小二乘支持向量机的建模参数,从而实现比现有方法精度高,泛化性能好的预测模型。训练和测试样本取自飞行数据记录系统(QAR)中译码襟翼参数值。与神经网络模型的比较实践表明,该方法具有实用价值。     

微机控制梳棉机变频调速系统

本文介绍一种用于纺织机械——梳棉机的感应电机变频调速系统。变频调速器由MCS—51系列单片机控制。文章简要介绍了微机控制系统的硬件结构以及采用气隙磁通轨迹控制法产生三相脉宽调制波的基本原理,还介绍了两台电机速度跟踪的要求和实现方法。     

基于支持向量机的分类器设计

在支持向量机理论的基础上,打破了支持向量机的二类辨识传统,提出基于支持向量机的一类辨识理论,以它为基础设计基于一类辨识的一类分类器。     

多机并联火箭羽流流场及其底部热环境分析

For the problem that the plume flow field structure of a multi engine parallel rocket is complicated and the bottom thermal environment is extremely harsh, which may cause the failure of the engine structural components, the plume flow field and thermal environment at different altitudes are studied through numerical simulation. The result is compared with the measured results in flight which shows that when the rocket is flying at a low altitude, the plume of the engines do not interfere with each other. As the flight altitude increases, the plumes gradually expand and begin to interfere with each other, and finally there is an obvious backflow at the bottom of the rocket. The maximum heat flux at the moment of take off is basically the same as the measured value in flight. Before the backflow occurs, the heat flux mainly consists of radiant heat, the convective heat flow increases as the flight altitude grows, but it is also much smaller than the peak heat flow at takeoff. The result has certain guiding significance for the optimal design of engine structure thermal protection.