遥感图象几何校正的有限元法

本文介绍了在选好地面控制点后,按最优原则自动构成三角形网。建立三角单元的仿射变换,求出仿射变换系数。为了避免计算仿射系数可能失败,对边框及三角形的长边进行了适当分割。几何校正时,采用了行列式的判断条件及漂浮法的判断技巧,防止了判断失误,提高了运算速度。文中还提出几何校正边界的一种处理方法。     

用奇异有限元法计算正交各向异性复合材料平面断裂的应力强度因子

将复合材料平板视为正交各向异性平板，把正交各向异性平板裂纹顶点附近的位移展开式迭加在一般的等参数单元上，建立了用于复合材料平板应力强度因子计算的奇异元。并以所做出的公式，对正交各向异性板含单边裂纹和双边裂纹问题进行了计算分析，取得了较好的效果。     

Static strength analysis of dragonfly inspired wings for biomimetic micro aerial vehicles

This article examines the suitability of fabricating artificial, dragonfly-like, wing frames from materials that are commonly used in unmanned aircraft(balsa wood, black graphite carbon fiber and red prepreg fiberglass). Wing frames made with Type 321 stainless steel are also examined for comparison. The purpose of these wings is for future use in biomimetic micro aerial vehicles(BMAV). BMAV are a new class of unmanned micro-sized aerial vehicles that mimic flying biological organisms(like flying insects). Insects, such as dragonflies, possess corrugated and complex vein structures that are difficult to mimic. Simplified dragonfly-like wing frames were fabricated from these materials and then a nano-composite film was adhered to them, which mimics the membrane of an actual dragonfly. Finite element analysis simulations were also performed and compared to experimental results. The results showed good agreement(less than 10% difference for all cases).Analysis of these results shows that stainless steel is a poor choice for this wing configuration, primarily because of the aggressive oxidation observed. Steel, as well as balsa wood, also lacks flexibility. In comparison, black graphite carbon fiber and red prepreg fiberglass offer some structural advantages, making them more suitable for consideration in future BMAV applications.     

基于响应曲面的时效成形材料参数修正

为了提高时效成形中回弹现象的有限元仿真精度,使用均匀试验设计结合响应曲面设计的方法,建立了仿真误差对于材料参数的响应函数,求解出材料参数的修正解。以此法得到的仿真结果与试验结果相吻合。     

A hybrid lattice Boltzmann flux solver for integrated hypersonic fluid-thermal-structural analysis

In this paper, a hybrid Lattice Boltzmann Flux Solver (LBFS) with an improved switch function is proposed for simulation of integrated hypersonic fluid-thermal-structural problems. In the solver, the macroscopic Navier–Stokes equations and structural heat transfer equation are discretized by the finite volume method, and the numerical fluxes at the cell interface are reconstructed by the local solution of the Boltzmann equation. To compute the numerical fluxes, two equilibrium distribution functions are introduced. One is the D1Q4 discrete velocity model for calculating the inviscid flux across the cell interface of Navier–Stokes equations, and the other is the D2Q4 model for evaluating the flux of structural energy equation. In this work, a new dual thermal resistance model is proposed to calculate the thermal properties at the fluid–solid interface. The accuracy and stability of the present hybrid solver are validated by simulating several numerical examples, including the fluid-thermal-structural problem of cylindrical leading edge. Numerical results show that the present solver can accurately predict the thermal properties of hypersonic fluid-thermal-structural problems and has the great potential for solving fluid-thermal-structural problems of long-endurance high-speed vehicles.     

新一代航天电子系统现场总线及其应用

针对航天电子系统的特殊性，从航天电子系统现场总线技术的发展现状出发，结合现场总线技术的特点，分析了现场总线未来的发展方向。重点介绍了新一代航天电子系统现场总线——有限级联自动重构总线（FCARB）及其在某测量存储系统中的应用。测量存储系统可实现数据并发量10 M，时间同步精度750 ns，系统实时性260 ns。与传统的航天总线相比，新一代现场总线在自动重构、实时性、支持BIT模式、支持仪器总线等方面具有更高的性能，同时对用户更加友好，兼容性更强，能够适应高冲击、高动态等恶劣环境。     

Temperature effect on buckling properties of ultra-thin-walled lenticular collapsible composite tube subjected to axial compression

This paper seeks to outline the temperature effect on the buckling properties of ultra-thin-walled lenticular collapsible composite tube(LCCT) subjected to axial compression.The buckling tests of the LCCT specimens subjected to axial compression were carried out on INSTRON-500 N servo-hydraulic machine in dry state and at the temperatures of 25 C, 100 C and 80 C. The load–displacement curves and buckling initiation loads were measured and the buckling initiation mechanism was discussed from experimental observations. Experiments show that the buckling initiation load, on average, is only about 2.2% greater at the low temperature of 80 C than at the room temperature of 25 C due to the material hardening, demonstrating an insignificant increase in the buckling initiation load, whereas it is about 19.5% lower at the high temperature of 100 C than at the room temperature owing to the material softening, implying a significant decrease in the buckling initiation load. The failure mode of the LCCT in axial compression tests at three different temperatures can be reckoned to be characteristic of the buckling initiation and propagation around the central region until rupture. The finite element(FE) model is presented to simulate the buckling initiation mechanism based on the eigenvalue-based methodology. Good correlation between experimental and numerical results is achieved.     

A new approach on necking constitutive relationships of ductile materials at elevated temperatures

A new method is presented to determine the full-range, uniaxial constitutive relationship of materials by tensile tests on funnel specimens with small curvature radius and finite element anal-ysis (FEA). An iteration method using FEA APDL (ANSYS parametric design language) program-ming has been developed to approach the necking constitutive relationship of materials. Test results from SAE 304 stainless steel at room temperature show that simulated load vs displacement curve, diameter at funnel root vs displacement curve, and funnel deformation contours are close to mod-eled results. Due to this new method, full-range constitutive relationships and true stress and effec-tive true strain at failure are found for 316L stainless steel, TA17 titanium alloy and A508-III stainless steel at room temperature, and 316L stainless steel at various elevated temperatures.     

复合材料结构多钉连接设计、分析与试验技术

在理论研究的基础上,应用有限元法进行复合材料多钉连接的载荷分配,并通过有限元法预测连接孔的挤压强度,大大提高了分析的精度;同时利用非线性分析方法分析了复合材料对角接头多钉连接的强度,并通过试验进行了验证,为复合材料主承力结构连接强度设计、分析提供了依据,为复合材料在中、重型直升机上的应用提供了参考。