金属波形膨胀节在六分量天平中的试验

为了探索弹性波纹管与内流式六分量天平的关联特性,在深入分析测力天平机理的基础上,采用测力台架与固定引气管路驻点式膨胀节软弹性连接方案.在载荷按刚度分配原则下,对膨胀节连接前、后天平输出信号的变化及天平控制体加压产生的附加力进行了对比分析,开展了膨胀节刚度、有效面积与测力平台的匹配性研究.试验结果表明:驻点式膨胀节的拉伸安装效果显著,为减少天平基准驻点漂移,提高测力系统的气动稳定性,有效面积的一致性一定要好,特别是整体横向刚度尽量小.      

某级压气机叶盘系统失谐振动关键因素研究

基于某级压气机叶片盘扇区,建立考虑非线性榫接触叶片盘有限元模型,应用提出的自由界面子结构-固定界面预应力模态综合超单元近似分析方法,并基于提出的围绕实验与有限元分析拟合出线性表达式的失谐参数识别方法,探究失谐关键因素对于叶盘系统振动的影响.结果表明,非线性榫接触不可忽略,提出的超单元法精度达到3.07%,满足要求.同时也表明,叶片平均频率、叶盘刚度比与频率转向对于失谐叶盘系统振动幅值、共振频率及应变能等参数均有一定影响.      

双线摆桨毂吸振器减振效率评估研究

建立了双线摆桨毂吸振器与旋翼和机体的耦合动力学评估模型,通过分析桨毂振动载荷作用下机体的振动响应,评估桨毂上安装双线摆吸振器的减振效率,分析了旋翼、机体模态特性对双线摆减振效率的影响。研究结果表明,双线摆桨毂吸振器的引入实质上是对耦合系统进行调频,旋翼桨毂载荷及量值是确定是否采取双线摆减振设计措施的重要前提。     

Testing the asymmetric cone model for halo CMEs using STEREO/SECCHI coronagraphic observations

Space weather is significantly controlled by halo coronal mass ejections (HCMEs) originating close to the central meridian and directing toward the Earth. Unfortunately, coronagraphic observations (especially for HCMEs) are subject to a projection effect which makes it impossible to determine the true radial velocity and width of CMEs. However, these parameters can be estimated by correcting for the projection effect using the asymmetric cone model (Michalek, 2006). A set of 20 CMEs, observed as halo events in the LASCO field of view and simultaneously as limb events in the STEREO/SECCHI field of view, are used to check the accuracy of the asymmetric cone model. For this purpose, characteristics of the considered CMEs (angular widths and radial speeds) measured in STEREO/SECCHI images are compared with those obtained by the asymmetric cone model. We demonstrate that the widths and speeds determined by both methods are very similar. Correlation coefficients for speeds and angular widths are 0.99 and 0.96, respectively. We have also shown that the projection effect is unpredictable and could sometimes be very significant (up to 100% of the velocity measured in the LASCO field of view). On average, the SOHO/LASCO projected speeds for the HCMEs are 23% smaller than the radial velocities obtained from the STEREO/SECCHI images.     

力限振动试验条件设计方法

给出了一种基于复杂二自由度模型的力限振动试验条件设计方法.该方法应用动态子结构法计算试验件结构和支持结构的模态有效质量和剩余质量,根据模态有效质量在频域上的分布情况确定不同频带内振动系统的复杂二自由度模型参数,结合支持结构激励条件给出试验件与支持结构接触面的力谱和加速度谱,在此基础上进行包络,得到力限振动试验剖面.仿真结果表明,由该方法给出的力限振动试验条件,与传统加速度试验条件相比,能更加真实地反应试验件的振动环境.      

NASA在声振领域研究的新成果

近年来在航天工业中声振已产生了许多重要进展。本文介绍了在NASA格伦研究中心所完成的工程项目中在声振领域取得的一些成果。     

小展弦比有限厚度舵面颤振特性分析

摘要： 舵系统是超声速再入飞行器机动飞行过程中对姿态进行控制的重要部件,其颤振特性分析是保证型号研制及飞行试验成功的关键环节.本文用当地活塞流理论对舵面颤振特性进行分析,首先建立舵系统动力学方程,确定舵面颤振临界边界计算方法,然后通过有限元分析和模态试验确定不同舵偏角度及不同加载量级组合工况下舵面模态参数,最后通过颤振分析确定舵面颤振临界参数,为舵系统结构方案设计及优化提供技术支撑.     

基于视线制导的空间交会停靠控制方法

空间交会停靠段的控制经常采用的一种方法是基于视线位置信息的平行接近法.对纵向控制中的非线性滑动模态控制方法进行了研究和改进,考虑了视线角对纵向控制的耦合作用,增加了耦合项,并进行了存在性和稳定性分析.对于横向和纵向同时协调控制,提出一种多变量互相耦合的非线性滑动模态视线制导控制方法,并对同时协调控制进行了存在性和稳定性分析.     

The scaler mode in the Pierre Auger Observatory to study heliospheric modulation of cosmic rays

The impact of the solar activity on the heliosphere has a strong influence on the modulation of the flux of low energy galactic cosmic rays arriving at Earth. Different instruments, such as neutron monitors or muon detectors, have been recording the variability of the cosmic ray flux at ground level for several decades. Although the Pierre Auger Observatory was designed to observe cosmic rays at the highest energies, it also records the count rates of low energy secondary particles (the scaler mode) for the self-calibration of its surface detector array. From observations using the scaler mode at the Pierre Auger Observatory, modulation of galactic cosmic rays due to solar transient activity has been observed (e.g., Forbush decreases). Due to the high total count rate coming from the combined area of its detectors, the Pierre Auger Observatory (its detectors have a total area greater than 16,000 m²) detects a flux of secondary particles of the order of ∼10⁸ counts per minute. Time variations of the cosmic ray flux related to the activity of the heliosphere can be determined with high accuracy. In this paper we briefly describe the scaler mode and analyze a Forbush decrease together with the interplanetary coronal mass ejection that originated it. The Auger scaler data are now publicly available.