1.0wt％Li对Al-Zn-Mg-Cu合金时效硬化的影响

对含1.0wt%Li和不含Li的5.6wt%Zn,1.9wt%Mg,1.6wt%Cu,0.3wt%Er合金在110℃,120℃和160℃进行单级时效,并对含Li的铝合金进行110℃ 5h+160℃ 40h两级时效。由于合金中Li对GP区的抑制作用,与不含Li合金相比,含Li合金的单级时效硬化效果差。双级时效时,含Li铝合金具有较好的强化硬化效果,这与形成了η′相和T′相有关。     

飞机结构雷电防护试验符合性验证

简要阐述了飞机结构雷电防护验证试验的种类、主要试验参数和试验规范,并具体介绍了复合材料平尾、整体油箱口盖、复合材料翼梢小翼和复合材料方向舵等飞机典型结构件的雷电防护试验方案设计     

温度对浮环密封泄漏特性的影响

为揭示不同温度工况下浮环密封封严间隙的变化过程,采用有限单元法和CFD进行了数值计算,并结合试验研究,获得了不同封严气体温度下浮环密封的封严间隙.数值计算得到的泄漏量与试验结果的最大偏差为13.1％,最小偏差为-5.05％,偏差的标准差≤7.23％.数值计算结果与试验结果一致.揭示了不同封严气体温度下封严间隙的变化过程...     

新型浮动式收敛袋型密封动力特性与自适应同心性能数值研究

提出新型浮动式收敛袋型密封结构,建立新型收敛袋型密封与传统迷宫密封多频椭圆涡动动力特性求解模型,研究转速、进出口压比及偏心率对新型收敛袋型密封与传统迷宫密封浮动同心力的影响,对比分析涡动频率对新型收敛袋型密封与传统迷宫密封动力特性系数的影响,基于有效刚度系数定量分析浮动密封的自适应同心性能.研究结果表明:随着转速、进出...     

The Potential of GOCE in Constraining the Structure of the Crust and Lithosphere from Post-Glacial Rebound

Glacial Isostatic Adjustment (GIA) due to Pleistocene glaciation and deglaciation has left clear imprints in the present-day geoid. The solid-earth models that are commonly used in simulating these geoid anomalies usually have the upper layer (crust/lithosphere) elastic. While this is a good approximation for oceanic lithosphere, it is over-simplified for many continental crustal areas, of which some are submerged at continental margins. At many places, these continental areas have a lower crustal zone that has low viscosities. Also at the top of the mantle (asthenosphere) such zones with low viscosities can exist. Modeling results show that, due to their shallowness and due to the laterally non-homogeneous water load, these low-viscosity layers induce discernible signatures in the high-harmonic steady-state components of the geoid. These patchlike patterns have typical length scales ranging from about 100 – 1000 km, and typical magnitudes of 1 cm – 1 m, depending on, a.o., depth and width of the low-viscosity zone, viscosity and shoreline geometry. Complications in correlating GIA modeling results with observed geoid anomalies might arise from uncertainties in isostatic corrections (topography and non-uniform composition of crust and lithosphere) and from other non-GIA related contributions to the observered anomalies. The characteristic forms of the patterns might assist in separating the various contributions to the observed geoid anomalies. This can be illustrated for the Adriatic coast of Italy, where the best fit to the spatial sea-level curve pattern is provided by a combination of GIA and regional plate tectonics. This revised version was published online in August 2006 with corrections to the Cover Date.     

Analysis of the variability of temperature gradient in the ocean frontal zones based on satellite data

AVHRR MCSST data for the periods 1982–2000 (mean weekly data) were used to calculate mean gradient fields in the ocean for different periods of time. Three-month averaged sea surface temperature gradients (SSTG) and their mean seasonal variations have been studied for 25 points in the large-scale oceanic fronts zones. Major oceanic fronts in the Atlantic and Pacific have been identified and compared in literature. In the North Atlantic and Pacific, the areas under study were the North Polar Front and Subpolar Fronts. In the South Atlantic and Pacific we studied the region of the Antarctic Circumpolar Current (ACC) and the fronts formed by this current, known as the South Polar Front, and the Subantarctic Front. SSTG were also calculated for El Niño (Southeast Pacific) and Benguela Current (Southeast Atlantic).     

面向铺放工艺的预浸料剥离仿真与试验验证

为系统建立可表征刚度与黏性的预浸料剥离模型,构建探针、拉伸与剥离相结合的试验验证系统。首先,设计用于预浸料的移动悬臂剥离装置,完成各工艺参数下预浸料黏性和动态刚度的90°剥离试验测定,并建立剥离仿真模型;然后,通过探针试验获取黏性参数,采用内聚力模型定量表征黏性参数;接着,通过拉伸、压缩试验测定预浸料的正交各向异性力学参数,连同探针试验获得的黏性参数一同输入到剥离模型中,在各个工艺参数下黏性和刚度的仿真结果与试验值吻合程度良好;由于仿真与试验揭示剥离脱辊现象会影响剥离力测定值,因此研究脱辊现象及其机理,发现将导辊半径设计在3~7 mm内,可减弱脱辊程度、提高剥离试验的准确性。为系统测定并表征预浸料黏性及刚度、预浸料建模、开展自动铺放仿真等提供了参考。     

飞机雷电防护

雷电是一种危险现象,但是到目前为止还没有一种技术能够防止飞机遭受雷击。本文分析了雷电造成的危害,并论述了飞机结构设计应该为雷电流提供低阻抗的通路。对于对雷击放电敏感的部位和部件,必须根据其自身的重要性采取适当的雷电防护措施,以尽可能减少雷电对飞机的损害。最后介绍了为确保雷电防护措施的可靠性而进行的验证试验方法。     

等离子体接触器对空间站充放电的影响

针对采用100V高压电池阵的空间站结构体带电现象,提出采用等离子体接触器进行主动电位控制方案,根据此方案建立包含接触器的空间站充放电等效电路模型,研究等离子体接触器对空间站充放电过程的影响及空间站结构因素对接触器钳位效果的影响,从而了解等离子体接触器与空间站悬浮电位的耦合特性。结果表明,无论空间站处于“快速充电”还是“正常充电”情况,等离子体接触器均能有效将空间站悬浮电位钳制在合理范围内。空间站结构因素中,电池阵暴露导体面积对接触器钳位过程影响较大,结构体暴露导体面积和结构体等效电容的影响可忽略。     

复杂结构件数控加工浮动装夹自适应控制方法

为了减小复杂结构件数控加工产生的变形,满足装夹自适应调整需求,基于浮动装夹加工原理提出了浮动装夹自适应控制方法,研究了基于CAN(Controller Area Network)总线的浮动装夹系统通信、零件受力和变形的监测与检测、基于OPC(OLE for Process Control)的机床状态监测、数控机床和夹具协同控制等关键技术,开发了浮动装夹自适应控制系统。此系统在航空制造企业进行了实际加工应用验证,能够实现装夹自适应调整,满足工业应用需求。