基于ANSYS的齿根应力和齿面变形的合理分析

根据齿轮啮合原理,准确求出复杂的齿廓曲线;采用MATALB—APDL混合建模方法,创建精确的齿轮有限元模型。在不同网格密度等级下,分别对齿轮的齿面变形、齿根应力分布进行分析。对照经验公式的计算结果,得出如下结论：在齿轮数值模拟中,由于有限元软件计算中舍入误差的存在,网格划分合理与否将直接影响仿真程度的高低;网格密度等级对齿面最大变形的仿真结果有较大影响,而对齿根应力影响甚微。     

导弹用非金属材料贮存期评估技术及应用

非金属材料的老化是影响导弹贮存可靠性的重要因素之一。本文针对导弹用非金属材料,介绍了国内外关于贮存期评估技术研究的现状和应用,总结了非金属材料的典型老化模型和寿命评估方法,分析预测了非金属材料贮存期评估技术的发展方向。     

混合线性/非线性状态空间模型的边缘Rao-Blackwellized粒子滤波法(英文)

本文提出了边缘 Rao-Blackwellized 粒子滤波器(marginal Rao-Blackwellized particle filter, MRBPF)算法,算法融合了 Rao-Blackwellized 粒子滤波器(Rao-Blackwellized particle filter , RBPF)算法和边缘粒子滤波器(marginal particle filter, MPF)算法。算法中状态被分为线形和非线性两部分,分别用 MPF 和卡尔曼滤波器(Kalman Filter)进行估计。地形辅助导航(terrain aided navigation, TAN)的仿真结果表明,与 RBPF 相比,提出算法的非线性状态估计的误差均方根(root mean square error, RMSE)和误差方差分别降低了约 29%和 96%,独立粒子数提高了约80%,获得了更好的收敛结果。分析表明,现有RBPF是MRBPF的一个特例。     

民用飞机翼梢小翼多约束优化设计

采用Lagrange乘数优化方法,约束升力系数和机翼翼根弯矩,通过修改机翼 翼梢小翼组合体的结构外形,减小机翼的诱导阻力和形状阻力,提高机翼的展向效率和升阻比的大小。成功的实例设计结果表明,本文方法对民用飞机机翼-翼梢小翼的设计具有应用价值。     

基于引导线的涡轮气冷叶片伸根建模方法

发动机涡轮气冷叶片伸根段是复杂的过渡曲面,设计过程繁琐.针对伸根段的几何结构特征,提出了基于引导线的伸根过渡曲面建模方法,由伸根段边界条件生成引导线,使用最小能量法优化引导线,以此为基础完成伸根段的建模,实现了指定高度截面面积修改.开发了伸根段参数化建模模块,提高了叶片设计效率,并为航空发动机复杂过渡曲面参数化建模提供参考.     

基于湿热老化试验的NEPE推进剂贮存寿命预估

用NEPE推进剂进行湿热加速老化试验获得了推进剂在不同湿热老化条件下抗拉强度和弹性模量随老化时间的变化规律,建立了推进剂湿热老化失效物理模型,并提出了将弹性模量作为失效判据预估推进剂贮存寿命的方法。分别用抗拉强度和弹性模量作为失效判据,对推进剂贮存寿命进行估算。结果表明：将弹性模量作为失效判据预估NEPE推进剂贮存寿命的方法可行。     

Influence of processing and external storage conditions on the performance of envelope materials for stratospheric airships

Envelope materials are extremely vital for stratospheric airships, which are widely used in numerous applications. The influence of processing as well as the storage and utilization conditions on the performance of envelope materials has been studied systematically for the first time. Results show that the performance of envelope materials depends largely on the hot-pressing temperature and the flexing during processing. The tensile strength of samples dropped to 289.1 ± 8.0 MPa from 346.6 ± 9.3 MPa when pressed at temperature above 180 °C and helium leakage appeared. The outer layers would be worn off when flexed no matter by manual or machine, resulting in dramatic increase of helium permeability and even leakage as well as varying decrease of mechanical properties. Hence, suitable hot-pressing temperature and limitation of flexing as little as possible during processing are essential to obtain products with suitable properties. Besides, the storage and utilization conditions are also critical to the properties of envelope materials. Both naturally aged samples in outdoor storage on ground and samples recovered from actual flight on stratospheric airship exhibited reduced mechanical properties and even helium leakage due to excess solar irradiation, ozone concentration and energetic particles interaction compared with those stored indoors. The weatherability of envelope materials should be further strengthened in the next few years. This research could provide a theoretical guidance for actual practice.     

Influences of characteristic parameters on starting-up process of an arcjet thruster

Arcjet thruster has been a widely used electrical propulsion technology on GEO satellites since 1993. In its long history of technical development and commercial application, lifetime verification of an arcjet thruster is always one of the most important and expensive tasks. Considering that the main life limitation of an arcjet thruster is electrode ablation and a significant share of the total ablation happens in its starting-up process, the starting-up process is studied with arc voltage signals. Through interpretation of arc voltage signals, the transfer process of the arc root on the anode surface is identified, and ΔT (the duration of the arc root transfer process) is suggested to be a characteristic parameter for fast evaluation of lifetime assessment and design optimization for an arcjet thruster. With this criterion, the influences of typical parameters on the starting-up process are established through comparison with a benchmark parameter. According to experimental results, an increase of the gas flow will obviously reduce ΔT, while a smaller swirl aperture and a longer throat channel do not have a remarkable correlation with ΔT. Moreover, with a sample of a smaller throat diameter to increase the flow velocity, a reduction of ΔT is achieved. Meanwhile, the modifications also affect the stability of arcjet thruster operation, which is also discussed.     

正互反矩阵一致性的充要条件

本文论述了正互反矩阵一致性的充要条件，并给出了证明。     

周边式桁架可展开天线的形面调整

本文针对周边式桁架可展开天线进行了基于优化方法的网面调整。以纵向调节索调节力的大小为设计变量，网状反射面的均方根误差为目标函数，应力和频率为约束条件，建立了形面调整的优化数学模型，并用遗传算法对网面调整进行了优化、仿真。数值结果表明：基于优化方法的网面调整是可行的，对工程应用具有一定的指导意义。