基于有限元的螺栓弯曲强度分析方法

应用MSC/NASTRAN有限元分析软件,对螺栓弯曲强度进行了分析,通过与工程计算结果的对比,证明有限元模型和有限元分析方法是准确可靠的。     

一种多串口和以太网转换方法的研究

嵌入式系统中普遍应用RS232串口进行调试通信，但RS232串口在复杂的综合化航电处理平台中的应用却有诸多不便，而通过以太网却无相关问题。鉴于当前大多数成熟应用都需要通过RS232进行通信，设计了一种新型接口模块，实现了将多个RS232串口协议数据转换为以太网协议数据的方法。实践表明，方法能很好地应用在复杂的综合化航电处理环境中，简单方便，不影响用户调试习惯，值得推广应用。     

Preparation of bimodal grain size 7075 aviation aluminum alloys and their corrosion properties

The bimodal grain size metals show improved strength and ductility compared to traditional metals; however, their corrosion properties are unknown. In order to evaluate the corrosion properties of these metals, the bimodal grain size 7075 aviation aluminum alloys containing different ratios of coarse(100 μm in diameter) and fine(10 μm in diameter) grains were prepared by spark plasma sintering(SPS). The effects of grain size as well as the mixture degree of coarse and fine grains on general corrosion were estimated by immersion tests, electrochemical measurements and complementary techniques such as scanning electron microscope(SEM) and transmission electron microscope-energy disperse spectroscopy(TEM-EDS). The results show that, compared to fine grains, the coarse grains have a faster dissolution rate in acidic NaCl solution due to the bigger size,higher alloying elements content and larger area fraction of second phases in them. In coarse grains,the hydrogen ions have a faster reduction rate on cathodic second phases, therefore promoting the corrosion propagation. The mixture of coarse and fine grains also increases the electrochemical heterogeneity of alloys in micro-scale, and thus the increased mixture degree of these grains in metal matrix accelerates the corrosion rate of alloys in acidic NaCl solution.     

机电液压设备控制软件系统构架探讨

分析了机电一体化设备软件系统的需求特点.探讨了实用的控制软件系统构架和设计方法.提出了实时控制系统软件的开发工作流程和测试过程.     

英语翻译教学与能力训练的探索

在英译汉训练中，加强英文单词的辨析和理解，提高英语的分析能力是表达原著内容的基础；只有了解英语文化背景，掌握常用的翻译技巧，才能提高汉语水平使译文达意通顺。     

舰尾流环境中载机纵向QFT/TECS控制系统设计

为了消除舰尾流对载机着舰过程产生的影响,同时完成低动压状态下飞行速度与高度的解耦工作,基于定量反馈理论/总能量控制理论(QFT/TECS)设计了纵向着舰控制系统。针对着舰过程中数学模型所具有的不确定因素及舰尾流对下滑航迹的影响,以载机高度变化率为控制对象,使用定量反馈理论结合推力补偿系统进行了内回路鲁棒控制律设计。外回路控制律设计是以总能量控制理论为基础,通过粒子群优化算法对待调控制参数进行寻优,进而实现了对高度、速度等参数的精确控制,完成了载机纵向着舰轨迹与速度的解耦工作。仿真结果表明,该控制律在拥有较强的鲁棒性的基础上具有良好的解耦控制能力,实现了载机着舰段的高度与速度的解耦控制,明显提高了载机对着舰轨迹的跟踪能力,可满足不确定条件下载机的着舰要求。     

焊缝补强方式对大直径贮箱箱底承载性能影响

基于有限元法研究了典型10 m级直径贮箱箱底焊缝在双面对称补强、内表面补强及外表面补强三种情况下的内压承载性能。数值计算采用二维对称平面模型,考虑了筒段和短壳真实边界条件及焊缝对承载能力的影响,构建的考虑材料塑性的非线性数值分析模型准确地获得了贮箱箱底内外表面经向应力。结果表明:顶盖和瓜瓣焊缝区域是箱底的薄弱位置,使用内压下,双面对称补强的加强区内外表面经向应力差较小,结构均未进入塑性,单面补强的加强区内外表面经向应力差远大于双面对称补强,局部进入塑性,且外表面补强的加强区最大和最小经向应力差相对于内表面补强分别增加了9.7%和27.2%,变形不协调；设计内压下,箱底内外表面均有局部进入塑性,材料塑性对内外表面经向应力差有一定的缓解作用,能够显著缓解内外表面应力差造成的附加弯矩；双面对称补强优于内表面补强,内表面补强优于外表面补强,单面补强易产生附加弯矩,不利于箱底的均匀承载和变形协调。该研究结果指导了大直径贮箱箱底结构的优化设计。     

芳纶纤维对EPDM绝热层力学行为的影响

研究了芳纶纤维长度和用量变化对三元乙丙绝热层力学行为的影响。结果表明,随着芳纶短纤维用量增加和长度增大,绝热层的抗拉强度和伸长率均呈下降趋势,初始模量呈上升趋势,而且平行压延方向的变化程度明显大于垂直压延方向。此外,芳纶纤维明显改变了绝热层平行压延方向的拉伸应力-应变曲线形态,而且随着纤维用量增加和长度增大,绝热层的应力屈服点和初始模量逐渐提高,但最大拉伸应力和应变逐渐降低。     

空间可展桁架结构等效动力学模型研究进展与展望

随着航天重大工程的逐步实施，桁架式空间可展结构正朝着大型化、轻量化和多功能等方向发展，该类桁架结构具有周期性、大柔度、构型复杂等特点。为满足大型空间结构的高精度、高可靠性要求，其动力学建模、非线性振动与振动控制等问题越来越复杂且难于处理。因此，大型空间可展结构的等效连续体建模成为研究热点。本文着重介绍大型空间可展桁架结构等效动力学建模的研究现状，综述了等效动力学建模的研究对象、方法及已取得的成果，提炼出等效动力学建模和与之相应的非线性振动与振动控制研究领域中亟待深入研究的关键科学问题。     

Control of a Spherical Robot: Path Following Based on Nonholonomic Kinematics and Dynamics

This paper presents the controller design for the path following of a spherical mobile robot,BHQ-1.Firstly,a desired velocity for the reference path is deduced from the kinematic model,which cannot be transformed into the classic chained form.Secondly,a necessary torque for the desired velocity is obtained based on the dynamic model.As to the kinematics,a one-dimensional function is selected to measure the two-directional tracking error,and the velocity of rolling forward is reasonably assumed to be constant;therefore the multiple-input multiple-output (MIMO) system is transformed into a single-input single-output (SISO) system.As to the dynamics,both exact dynamics and inexact dynamics with modeling error as well as bounded unknown disturbance are taken into account,based on which a proportional-derivative (PD) controller and a sliding mode controller with adaptive parameters are proposed respectively.Finally,convergence analysis and simulation results are provided to validate these controllers.