无人火星取样返回任务关键环节分析

无人火星取样返回探测在科学成果获取和工程能力提升方面均具有重要意义,与国外已经多次实现的火星着陆巡视任务相比,其任务周期更长,技术风险更高。取样返回飞行方式决定了任务的系统顶层设计。通过对国外研究成果的对比论证,认为应当在火星轨道附近完成交会捕获与样品转移任务,因此需要采用2个不同功能探测器:一个完成火星捕获、样品转移收纳与火地返回;另一个完成火星大气进入、表面上升与样品投送。在此基础上对大气进入、起飞上升、火星轨道交会捕获、样品转移、地球再入等关键环节进行任务分析,论证主要技术难点和初步的可实现途径。     

考虑冲击缺陷的钛合金板的疲劳寿命预估

基于连续损伤力学理论,研究了含冲击凹坑缺陷的Ti-1023钛合金板的疲劳损伤问题。通过分析冲击损伤与疲劳损伤的共同作用以及应力场与损伤场的耦合作用,对含冲击凹坑的钛合金板的疲劳寿命进行了预估。首先,基于连续介质运动学理论,采用非线性动力学有限元分析软件进行冲击损伤的模拟,得到冲击凹坑处的残余应力场与塑性应变场。其次,根据塑性损伤方程,计算冲击凹坑局部的初始损伤场,并将其作为后续疲劳计算的初始条件。然后,采用Chaudonneret的多轴疲劳损伤力学模型建立损伤力学-有限元数值解法,以进行损伤演化过程的数值计算。最后,综合考虑残余应力场、塑性初始损伤和疲劳损伤的共同作用,对含冲击凹坑的钛合金板进行了疲劳寿命预估,并进行了相应的疲劳验证试验。结果表明,预估结果与试验结果相一致。所做研究为工程中采用损伤力学方法来预估含冲击损伤的结构的疲劳寿命提供了一种可行的方法。     

胚胎电子细胞中基因备份数目优选方法

分析现有胚胎电子细胞基因存储结构的基础上,考虑基因备份数目对自修复过程的影响,建立了可靠性模型;并根据存储结构的具体实现方式,建立了硬件消耗模型。以可靠性模型和硬件消耗模型为基础,通过分析可靠性、硬件消耗与基因备份数目间的关系,提出了一种基因备份数目优选方法。该方法根据目标电路的可靠性、硬件消耗设计要求,选择兼顾系统可靠性、硬件消耗的基因存储方式、基因备份数目及胚胎电子阵列规模,具有工程应用价值。通过某电路的基因备份数目的选择,对该方法进行了验证。      

借鉴航天规范编制经验推进航空规范编制工作

扼要说明了国防科工委推进编制"三大规范"工作的重要意义;阐述了"三大规范"在国防工业新产品开发和生产过程中的重要作用,并就航空工业系统如何推进"三大规范"编制工作提出了意见.     

子午修型对1.5级大子午扩张涡轮端区流动传热性能影响研究

大子午扩张涡轮由于子午型线扩张度较大,因而易导致端区边界层分离及热集中,针对这个现象,采用数值模拟方法,并采用正弦曲线对某型1.5级大子午扩张涡轮子午型线采取了8种修型方案,研究子午修型对于端区流动传热性能的影响。计算结果表明,子午修型可以有效地控制端区的分离流动,从而影响着通道涡与脱落涡强度及位置,也影响着端壁及叶片上热负荷分布。在本文研究条件下,振幅为三分之一叶片最大厚度的前凹后凸子午型线有效地减弱了脱落涡引起的损失,进而使整体总压损失减小6.06%,并可以减弱端壁及叶片传热集中,使叶片最大热负荷减轻21%。     

正攻角状态下尾迹对低压涡轮附面层的渗透及转捩的影响

为研究正攻角状态下尾迹对低压涡轮附面层的渗透以及转捩过程的影响,分别在设计攻角和+10°攻角下,对高负荷低压涡轮叶型的吸力面附面层流动进行了数值模拟与实验。数值模拟使用CFX软件,采用大涡模拟模型。结果表明+10°攻角下,尾迹对附面层转捩过程的促进作用比设计攻角下更为显著,这是由于正攻角下的尾迹中心射流与吸力面切向的夹角更大,使得尾迹扰动渗透入附面层的深度更深,尾迹放大Klebanoff条纹强度更强,尾迹诱导转捩起始位置更靠上游。     

客车铝合金车架设计与典型工况分析

应用轻量化材料如高强度钢和铝、镁合金等来替代普通钢制造汽车承载构件已成为发展趋势。本文以工业铝合金为材料设计了一种新型的轻型城郊客车车架,并建立有限元模型进行了多种典型工况的仿真分析。首先,基于CATIA进行了客车车架各零部件的设计,整体装配与校核;然后,通过简化模型、模拟连接等,在ANSYS Workbench中建立了合理的车架-悬架有限元模型;最后,模拟客车满载弯曲、制动等5种典型工况施加载荷与边界条件,进行有限元仿真,仿真结果表明该铝合金车架能够满足各典型工况的强度和刚度性能要求。      

Investigation of straightforward impedance eduction method on single-degree-of-freedom acoustic liners

In order to address the current aircraft noise problem, the knowledge of impedance of acoustic liners subjected to high-intensity sound and grazing flow is of crucial importance to the design of high-efficiency acoustic nacelles. To this end, the present study is twofold. Firstly, the StraightForward impedance eduction Method (SFM) is evaluated by the strategy that the impedance of a liner specimen is firstly experimentally educed on a flow duct using the SFM, and then its accuracy is checked by comparing the numerical prediction with the measured wall sound pressure of the flow duct. Secondly, the effects of grazing flow and high-intensity sound on the impedance behavior of two single-layer liners are investigated based on comparisons between educed impedance and predictions by three impedance models. The performance of the SFM is validated by showing that the educed impedance leads to excellent agreement between the simulation and the measured wall sound pressure for different grazing flow Mach numbers and Sound Pressure Levels (SPLs) and over a frequency range from 3000?Hz down to 500?Hz. The grazing flow effect generally has the tendency that the acoustic resistance exhibits a slight decrease before it increases linearly with an increase in Mach, predicted successfully by the sound-vortex interaction theoretical model and the Kooi semi-empirical impedance model. However, the Goodrich semi-empirical impedance model gives only a simple linear relation of acoustic resistance starting from Mach zero. Additionally, when the SPL increases from 110 to 140?dB in the present investigation, the acoustic resistance exhibits a significant increase at all frequencies in the absence of flow; however, the resistance decreases slightly under a grazing flow of Mach 0.117. It indicates that the SPL effect can be greatly inhibited when flow is present, and the grazing flow effect can be reduced partly as well at a relatively high SPL.     

Materials Experiment on Tiangong-2 Space Laboratory

During the China's Tiangong-2 (TG-2) flight mission, the experiments of 18 kinds of material samples were conducted in space by using a Multiple Materials Processing Furnace (MMPF) mounted in the orbital module of the TG-2 space laboratory. After the experiments of 12 kinds of samples of the first and second batches were completed successfully, astronauts packed and brought them back to the ground by ShenzhouⅡ spacecraft. By studying processing and formation on semiconductor and optoelectronics materials, metal alloys and metastable materials, functional single-crystal, micro-and nano-composite materials encapsulated in sample ampoules both in space and on Earth, we expect to explore some physical and chemical processes and mechanism of the materials formation that are normally obscured and therefore are difficult to study quantitatively on the ground due to the gravity-induced convection, to obtain the processing and synthesis technology for preparing high quality materials, and lead to the improvement and development of materials processing techniques on Earth, and also develop the experiment device and comprehensive ability for materials experiment in microgravity environment. This report briefly introduces the main points of each research work and preliminary comparative analysis results of 12 samples carried out by scientists undertaking research task.      

5G微基站环境下GNSS接收机性能及观测质量分析

我国已全面进入5G时代,为研究5G微基站电磁环境对全球卫星导航系统(GNSS)接收机工作性能及观测数据质量的影响,基于自主建设差分基准站的零基线观测数据,采用静态相对定位方法,通过观测数据质量分析、载波与伪距的双差残差序列、对比相对静态定位结果,综合评估5G微基站对GNSS接收机工作性能及观测数据质量的影响。实验表明：当前环境下,GNSS差分基准站及接收机处于近距离建设的5G微基站时,载波相位观测噪声变化范围为5cm,伪距观测噪声变化范围为15cm,零基线测试结果变化范围为1mm。在实验距离内,5G微基站对于GNSS接收机工作性能及数据观测质量影响较小,可以忽略。