航天器热平衡试验技术评述

航天器热平衡试验是航天器研制过程中的一项重要试验。随着航天技术的发展,以及设计验证方法的改进,对航天器热平衡试验提出了新的要求。在总结以往实践的基础上,结合航天器的热控设计,根据既能满足设计验证的要求、又可以简化研制流程的原则,提出了存在的问题和研究重点。     

矢量喷管与发动机的共同工作研究

建立了轴对称矢量喷管的数学模型和带这种矢量喷管的发动机数学模型,研究了矢量喷管与发动机的共同工作,矢量喷管偏转角对高低压转子共同工作线的影响以及矢量喷管的几何尺寸对发动机共同工作线的影响。研究结果表明:对低涵道比涡扇发动机,矢量喷管偏转角较大时会引起低压转子共同工作线下移,矢量喷管的几何尺寸对低压转子共同工作线也有一定的影响。      

高同轴度精密零件的加工方法

高同轴度精密零件在精密加工中,用普通方法很难保证其同轴度精度要求。本文采用增加径向辅助定位面的方法,从而使被加工零件的轴向和径向定位误差得到误差补偿,较好地满足了同轴度要求。     

极区夏季中间层半日潮汐的VHF雷达观测

采用德国SOUSYVHF雷达观测数据,研究了极区夏季中间层半日潮汐的结构和变化特征.纬向和经向风的动态Lomb-Scargle谱表明,半日潮是中间层高度上占支配地位的波动,其谱峰对应的频率一般与1/12c·h-1有偏离,说明它们经常处在被扰动状态.稳定的半日潮振幅随高度增加而迅速增长,在87.9km高度附近达到饱和;经向分量的相位一般比纬向分量的相位超前π/4-π/2,从而水平扰动速度矢量端点随时间变化的轨迹显示出顺时针方向旋转的特征.半日潮汐特征参量在纬向和经向风中随时间的变化在基本趋势一致的基础上显示出一定程度的各向异性.      

纳秒激光脉冲宽度对2024铝合金损伤特性的影响

飞机激光除漆对2024铝合金蒙皮可能造成潜在的损伤,需探究激光参数变化对基体材料表面的作用规律,其中脉冲宽度对激光-材料作用与材料损伤特性具有重要影响。本文采用COMSOL Multiphysics软件模拟分析了不同脉冲宽度时激光作用铝合金表面的温升特性,并借鉴ISO 11254 1-on-1激光损伤阈值测试方法研究了脉冲宽度对铝合金损伤阈值的影响,进一步分析了不同脉冲宽度下的烧蚀凹坑微观形貌、直径与深度变化规律。结果表明：铝合金表面峰值温度随脉冲宽度增加而降低;脉冲宽度从150 ns增加到240和330 ns时,铝合金损伤阈值从9.96 J/cm²分别增加到11.24和12.66 J/cm²,当激光能量密度达到损伤阈值时,3μm厚氧化膜被完全损伤,破坏了铝合金表面完整性;烧蚀凹坑直径和深度随脉冲宽度增加而增加,深度受影响程度更大。该研究可为激光与材料作用的脉冲宽度选择提供一定的参考。     

骨架式压气机机匣仿真计算分析

为了实现通过改变压气机机匣材料、结构形式和加工手段,达到减轻压气机机匣质量的目标,依照骨架式结构设计思想,对某型压气机的机匣进行了骨架式结构的改进设计,即"桁架"式结构机匣,并针对这3种典型的结构机匣分别从静强度、模态和包容特性等角度进行了仿真计算和对比分析,得到了现阶段最优方案为圆形开孔机匣。结果表明:该类骨架结构可以实现在不影响机匣使用要求的前提下,将压气机机匣质量减轻10%~20%,有效提高发动机推重比。     

Multi-EAP:Extended EAP for multi-estimate extraction for SMC-PHD filter

The ability to extract state-estimates for each target of a multi-target posterior, referred to as multi-estimate extraction (MEE), is an essential requirement for a multi-target filter, whose key performance assessments are based on accuracy, computational efficiency and reliability. The probability hypothesis density (PHD) filter, implemented by the sequential Monte Carlo approach, affords a computationally efficient solution to general multi-target filtering for a time-varying num-ber of targets, but leaves no clue for optimal MEE. In this paper, new data association techniques are proposed to distinguish real measurements of targets from clutter, as well as to associate par-ticles with measurements. The MEE problem is then formulated as a family of parallel single-estimate extraction problems, facilitating the use of the classic expected a posteriori (EAP) estima-tor, namely the multi-EAP (MEAP) estimator. The resulting MEAP estimator is free of iterative clustering computation, computes quickly and yields accurate and reliable estimates. Typical sim-ulation scenarios are employed to demonstrate the superiority of the MEAP estimator over existing methods in terms of faster processing speed and better estimation accuracy.     

Anti-plane problem of four edge cracks emanating from a square hole in piezoelectric solids

By constructing a new numerical conformal mapping and using the Stroh-type for-mulism, an anti-plane problem of four edge cracks emanating from a square hole in piezoelectric solids is investigated. The explicit expressions of the complex potential function, field intensity fac-tors, energy release rates and mechanical strain energy release rate near the crack tip are obtained under the assumptions that the surfaces of the cracks and hole are electrically permeable and elec-trically impermeable. Numerical examples are presented to show the influences of the geometrical parameters of defects and applied mechanical/electrical loads on the energy release rate and mechanical strain energy release rate under two electrical boundary conditions.     

Enhanced wave and finite element method for wave propagation and forced response prediction in periodic piezoelectric structures

As a promising numerical tool of structural dynamics in mid-and high frequencies, the wave and finite element method (WFEM) is receiving increasingly attention and applications. In this paper, an enhanced WFEM has been developed with a reduced model and a new eigenvalue scheme. The reduced model is applicable for structures with piezoelectric shunts or local dampers;the new eigenvalue scheme can mitigate the ill-conditioning when the wave basis is calculated. The enhanced WFEM is applied to a thin-wall structure with periodically distributed piezoelectric mate-rials (PZT). Both free wave characteristics and forced response are analyzed and the influences of the suggested enhancements are presented. It is shown that if the control factors are properly cho-sen, these enhancements can improve the accuracy while accelerating the calculation. Resulting from the complexity of the application, these enhancements are not optional but imperative.     

多无人机绳索悬挂协同搬运固定时间控制

针对多无人机绳索悬挂协同搬运跟踪控制问题,设计了一种新的固定时间协同跟踪控制算法.首先,通过旋量分析,计算系统不同状态下的有效旋量空间,并根据静力学平衡计算系统在有效旋量空间约束下的拉力容许裕度.其次,在保证绳索张紧以及最大拉力约束的条件下,基于微分平坦性以及绳索拉力优化分配算法,规戈编队的期望跟踪轨迹.然后,基于Ud...