In-plane corrugated cosine honeycomb for 1D morphing skin and its application on variable camber wing

A novel 0-Poisson’s ratio cosine honeycomb support structure of flexible skin is proposed. Mechanical model of the structure is analyzed with the energy method, finite element method (FEM) and experiments have been performed to validate the theoretical model. The in-plane characteristics of the cosine honeycomb are compared with accordion honeycomb through analytical models and experiments. Finally, the application of the cosine honeycomb on a variable camber wing is studied. Studies show that mechanical model agrees well with results of FEM and experiments. The transverse non-dimensional elastic modulus of the cosine honeycomb increases (decreases) when the wavelength or the wall width increases (decreases), or when the amplitude decreases (increases). Compared with accordion honeycomb, the transverse non-dimensional elastic modulus of the cosine honeycomb is smaller, which means the driving force is smaller and the power consumption is less during deformation. In addition, the cosine honeycomb can satisfy the deform- ing requirements of the variable camber wing.     

石墨烯/聚合物纳米复合材料研究进展

介绍了近年来石墨烯改性聚合物和功能化石墨烯改性聚合物纳米复合材料的研究现状。其中,在石墨烯改性聚合物方面,主要论述了石墨烯改性聚乙烯(PE)、聚丙烯(PP)、聚苯乙烯(PS)以及聚苯胺(PANI)纳米复合材料的制备方法和性能改善;在功能化石墨烯改性聚合物方面,主要论述了二苯基甲烷二异氰酸酯(MDI)、十八烷基胺(ODA)、氯化铝(Al Cl3)等对石墨烯的修饰以及改性后的石墨烯对聚合物的影响。最后,对石墨烯/聚合物纳米复合材料的潜在应用和发展前景做出了展望。     

不同热处理工艺下激光增材制造TC4钛合金组织与性能研究进展

由于激光增材制造(Laser Additive Manufacturing,LAM)TC4钛合金加工成形过程的特殊性,导致该合金在力学性能上存在明显的各向异性,同时韧性、疲劳性能不能很好地满足使用要求。从材料组织与力学性能之间的关系出发,介绍了不同热处理工艺对激光增材制造TC4钛合金组织与力学性能的影响,指出了当前激光增材制造TC4钛合金热处理研究中存在的问题,并为后续激光增材制造TC4钛合金的热处理研究提供思路与方向。     

固体推进剂动态力学行为研究进展

从动态力学表征、损伤机理、动态断裂和动态本构4个方面,对固体推进剂动态力学行为进行了综述。分析表明,动态力学实验重点关注固体推进剂的初始弹性模量、屈服应力、强度等参数,填充颗粒破裂是动态损伤的主要形态,动态断裂主要集中动态起裂研究,并对3类动态本构模型性进行了评述。在此基础上,梳理了下一步研究的重点,认为深化实验研究、力学数值模拟和含损伤热粘-超弹性动态本构模型将是下一步研究的重点。     

铝合金可回抽搅拌摩擦焊接头组织和性能

针对8 mm 厚2219 铝合金进行可回抽搅拌摩擦焊工艺试验,详细分析了回抽过程中搅拌针运动

轨迹、不同回抽位置的接头组织形态及力学性能。结果表明:搅拌针的运动轨迹是焊接速度与搅拌针相对于轴

肩回抽速度的合成运动轨迹,并呈现出一定的线性关系。回抽结束处和回抽起始处的接头组织形貌为典型的

常规搅拌摩擦焊接头,位于中间回抽区域的焊接接头可以认为是100% 焊透的焊接接头与“相同直径的轴肩+

(100% ~0%) ×L 的搅拌针”形成的焊透深度逐渐变浅的常规搅拌摩擦焊接头复合形成的。接头力学性能测

试结果表明:回抽结束处的性能最高,回抽起始处的性能次之,中间回抽区域的力学性能最低,并且随着回抽距

离的逐渐增加,中间回抽区域的力学性能逐渐增加。不同回抽位置的搅拌摩擦焊接头均呈现出典型的韧性断

裂形貌。

     

Semi-analytical investigations of the long term evolution of the eccentricity of Galileo and GPS-like orbits

This paper aims at investigating the stability over 150 years of a very large number of trajectories in the Medium Earth Orbit (MEO) region, near the orbits devoted to radionavigation such as the Global Navigation Satellite Systems (GNSS like GPS, Glonass, Galileo, COMPASS).     

重装空投动力学分析与控制方案研究

针对重装空投任务,基于拉格朗日分析力学,建立了货物在机舱内滑行阶段飞机-货物两体系统的动力学模型.给出了一种控制补偿方案,用以抵消或削弱货物运动对飞机的影响.通过数值仿真,观察货物运动和飞机运动之间的耦合关系,分析了牵引伞尺寸对飞机和货物运动参数的影响.仿真结果表明,所给出的控制补偿方案能够有效改善飞机飞行品质,提高飞...     

The gauge-generalized Gyldén–Meshcherskii Problem

The Gyldén–Meshcherskii Problem (GMP) extends the classical two-body problem of Newton and Kepler by considering time-varying gravitating masses, an important extension of the two-body problem for modeling cometary motion and cosmological phenomena. In this paper, we consider the GMP in a specialized setup, the setup of gauge theory. We show that the variational equations, modeling the effect of the mass time variation on the orbital elements, can be derived by fixing a gauge of a particular form that is different from the Lagrange gauge. Thus, the orbital elements modeling the effect of a time-varying secondary mass are non-osculating. This implies that the trajectory of a celestial body whose mass is continuously changing cannot be approximated by a series of Keplerian orbits. Finally, we provide the first-order averaged equations written in terms of non-osculating elements.     

求解流体力学反问题的数学方法及应用

流体力学反问题是一类重要的非线性问题，这类问题在工程中有广泛的应用，如过坝水流问题，给定流量的射流和翼型设计问题。由于这类流动求解区域不确定，导致问题的非线性特征，使数值计算十分困难，本文将以亚、跨声速翼型设计问题为例，提出了一种求解流体力学反问题的新方法。     

Analysis Approach to Durability Based on Material Initial Fatigue Quality and S-N Curve

Based on probabilistic fracture mechanics approach, a new concept of material initial fatigue quality (MIFQ) is developed. Then, the relation between S-N curve and crack propagation curve is studied. From the study, a new durability analysis method is presented. In this method, S-N curve is used to determine crack growth rate under constant amplitude loading and evaluate the effects of different factors on durability and then the structural durability is analyzed. The tests and analyses indicate that this method has lower dependence on testing, and higher accuracy, reliability and generality and is convenient for application.