复合材料缝合预制体的研究

缝合技术作为复合材料预制体成型的主要方法,在航空领域应用广泛。临缝、链式缝合和锁式缝合是缝合技术中较为常用的3种缝合方式,不同的缝合方式对缝合复合材料预制体的渗透特性和压缩特性产生的影响不同。同时缝合参数包括针距和行距对缝合复合材料预制体的渗透特性和压缩特性会也产生不同的影响。本文通过试验分别研究了临缝、链式缝合和锁式缝合3种缝合方式以及不同的针距和行距对缝合复合材料预制体渗透特性和压缩特性的影响。试验结果表明,缝合预制体的渗透率均大于未缝合织物的渗透率,且链式>锁式>临缝,链式缝合预制体随着缝合针距的增加,渗透率显著增大,临缝预制体的渗透率随行距的增加而减小;缝合预成型体厚度压缩率的大小关系为：临缝>链式>未缝合;链式缝合预制体的厚度压缩率随着缝合密度的增加而增加;临缝的压缩率随着针距的增大而减小。     

复合材料层合结构开口的非对称补强研究

中心开口的碳纤维复合材料层板的插层铺设非对称补强进行了孔边应力集中、应变分布、层间应力、损伤和强度特性的实验研究和理论分析,结果表明,本文采用的插层铺设非对称补强方式与顺序铺设补强方式相比,具有明显优异的补强效率,并能达到或超过对称补强的效率。     

复合材料迭层板孔边应力集中分析

采用平面４节点等参元方法，研究含中心圆孔复合材料迭层板孔边应力分布规律，对比分析了边距、铺层、材料性能常数、外载等因素对孔边应力集中的影响。     

缝合单层板弹性常数的计算与分析

建立了缝合单层板弹性常数分析模型,通过考虑缝线穿过纤维时产生的弯曲并假设近似正(余)弦曲线,计算T700/QY8911缝合单层板的有效弹性常数,并将其与未缝合模型比较,总结了各缝合参数(行距、针距、缝线半径)对有效弹性常数的影响,为分析缝合层合板弹性常数提供了依据。     

受弯曲对称复合材料层板的层间应力分析

本文引伸了受均匀拉伸复合材料层板自由边界效应问题的准三维有限元理论,分析了受弯曲（±45）_s角交层板与正交对称层板中的应力响应。着重讨论了层板自由边附近及层间界面上的应力分布。与受均匀应变拉伸下的应力分布相比,受弯曲对称复合材料层板中的层间应力分布有许多不同的特点。本文的分析结果将有助于理解在复合载荷下复合材料层板的破坏模式与破坏过程。     

复合材料缝合结构的力学性能及湿热效应

试验研究了国产复合材料缝合结构的吸湿特性、基本力学性能及湿热效应，层板缝合后的吸湿量大约提高30％左右，弯曲强度下降20％左右，层间剪切强度提高大约20％；吸湿对缝合结构的性能影响不大，仅对压缩强度有15％左右的影响；高温严重影响缝合及未缝合结构的性能，特别是压缩性能，对缝合层板的影响大于未缝合层板，在170℃高温下，未缝合层板压缩强度保持率为17．8％，而缝合层板仅为14．6％，设计高温环境使用的缝合结构应特别注意。研究结果可供结构设计参考。     

含孔复合材料层合板孔边应力集中的近似计算

针对含圆孔有限大复合材料层板的应力集中间题,提出一种计算孔边应力分布及应力集中系数的方法:先利用经典层板理论,将复合材料层合板化归为各向异性板;再将各向异性板等效转换为一偏轴拉伸的单向纤维层板;最后利用含圆孔偏轴单向板的孔边应力计算公式来分析一般铺层层合板孔边应力集中情况.根据所推导的含孔有限宽度复合材料层合板应力集中系数的表达式,分析讨论了板宽/孔径比、铺层比例、铺层方式、材料性能参数等因素对孔边应力集中的影响.     

LY12CZ板材冷挤压强化孔边残余应变场变化初探

 用实测方法初步探讨了ＬＹ１２ＣＺ板材冷挤压强化孔边残余应变场在３种不同交变应力幅作用下的衰减变化情况。结果表明：沿与作用应力垂直且过孔中心的轴线,孔边切向残余应变分量符合幂函数分布规律；在交变载荷作用下,当孔边实际最大应力小于材料屈服极限时,残余应变场在一定次数循环载荷作用下,会有一个突变性衰减变化,而且距孔边距离越近,衰减程度越严重。     

复合材料层板多钉机械连接强度计算方法

提出了一种适于设计计算使用的复合材料层板多钉机械连接强度分析方法。该方法将复合材料板多钉机械连接强度分析问题化为求解各向异性体弹性理论中的复势函数边值问题,以Faber级数和最小二乘边界配置技术为工具导出了孔边应力的级数解表达式。选用的孔边特征曲线上的点应力失效判据避开了孔边接触、材料非线性、大位移、刚度减缩等复杂且难以验证的强度摸拟计算过程。计算方法与试验符合性较好。文中还详细探讨了铺层比例、排距等设计参数对钉载分配、挤压强度的影响规律。     

复合材料层板多钉机械连接强度计算方法

提出了一种适于设计计算使用的复合材料层板多钉机械连接强度分析方法。该方法将复合材料板多钉机械连接强度分析问题化为求解各向异性体弹性理论中的复势函数边值问题,以Faber级数和最小二乘边界配置技术为工具导出了孔边应力的级数解表达式。选用的孔边特征曲线上的点应力失效判据避开了孔边接触、材料非线性、大位移、刚度减缩等复杂且难以验证的强度模拟计算过程。计算结果与试验结果符合较好。还详细探讨了铺层比例、排距等设计参数对钉载分配、挤压强度的影响规律。     

The effect of inlet conditions on the flow and heat transfer in multiple rotating cavity with axial throughflow

This paper discusses experimental results from two different build configurations of a heated multiple rotating cavity test rig.Measurements of heat transfer from the discs and tangential velocities are presented.The test rig is a 70% full scale version of a high pressure compressor stack of an axial gas turbine engine.Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air.Tests were carried out for a range of non-dimensional parameters representative of high pressure compressor internal air system flows(Re up to 5×106 and Rez up to 2×105).Two different builds have been tested.The most significant difference between these two build configurations is the size of the annular gap between the(non-rotating) drive shaft and the bores of the discs.The heat transfer data were obtained from thermocouple measurements of surface temperature and a conduction solution method.The velocity measurements were made using a two component,LDA system.The heat transfer results from the discs show differences between the two builds.This is attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity.There are also significant differences between the radial distributions of tangential velocity in the two builds of the test rig.For the narrow annular gap,there is an increase of non-dimensional tangential velocity V/Ωr with radial location to solid body rotation V/Ωr=1.For the wider annular gap,the non-dimensional velocities show a decrease with radial location to solid body rotation.      

Research on Auto-detection for Remainder Particles of Aerospace Relay Based on Wavelet Analysis

Aerospace relay is one kind of electronic components which is used widely in national defense system and aerospace system. The existence of remainder particles induces the reliability declining, which has become a severe problem in the development of aerospace relay. Traditional particle impact noise detection (PIND) method for remainder detection is ineffective for small particles, due to its low precision and involvement of subjective factors. An auto-detection method for PIND output signals is proposed in this paper, which is based on direct wavelet de-noising (DWD), cross-correlation analysis (CCA) and homo-filtering (HF), the method enhances the affectiv-ity of PIND test about the small particles. In the end, some practical PIND output signals are analysed, and the validity of this new method is proved.     

Preparation of Highly Dispersed Antimony-doped Tin Oxide Nano-powder via Ion-exchange Hydrolysis of SnCl4 and SbCl3 and Azeotropic Drying

Antimony-doped tin hydroxide colloid precipitates have been synthesized by hydrolysis of SnCl4 and SbCl3 using: (1) an ion-exchange hydrolysis to remove chlorine ions, and (2) isoamyl acetate as an azeotropic solvent to obviate water. The obtained dried powder is of high dispersivity without any need for further grinding. The size and dispersivity of the final particles are investigated with the aid of TG-DTA, BET, XRD and TEM. After having calcined, the antimony-doped tin oxide nanopowder possesses a tetragonal rutile structure with high dispersivity, uniform particles and low hard agglomeration.     

Effects of Mo on the Microstructure and Hydrogen Sorption Properties of Ti-Mo Getters

The effects of Mo on the microstructure evolution, porosity and hydrogen sorption properties of Ti-Mo getters are investigated in this work. The results show that the addition of Mo prolongs the densification process of Ti-Mo getters and results in a significant amount of sintered pores. With the Mo content increasing, the porosity of getters firstly increases reaching the maximum value as it at- tains about 7.5wt.%, and then drops. At the room temperature, the hydrogen sorption property of getters increases progressively with the Mo content increasing, but the tendency is not very clear before its content lies below 2.5wt.%. When the Mo content achieves about 7.5wt.%, the hydrogen sorption property proves to be the best. The discussion is made about the above mentioned phenomena inclusive of hydrogen sorption properties of getters under different activation conditions (from 500-750 ℃).     

超声速燃烧数值模拟中的湍流与化学反应相互作用模型

高精度数值模拟有助于理解超声速湍流燃烧中湍流与化学反应的相互作用,可为发动机燃烧室等工程应用设计提供可靠的预测模型。除直接数值模拟外,目前在湍流燃烧应用中使用的大涡模拟和雷诺平均Navier-Stokes模拟均需要借助模型模化发生在湍流小尺度上的流动与化学反应过程对湍流大尺度运动的影响。现有的湍流与化学反应相互作用模型大致可分为:火焰面类模型和概率密度函数类模型,2类模型在不同的应用中各自具有优势和局限性。此外,现有模型大都基于低马赫数燃烧,而超声速燃烧中通常会伴随快速混合、局部熄火和再着火以及激波等复杂过程,这为发展其中的湍流与化学反应相互作用模型提出了更多的挑战。     

适于低轨卫星IP网络的单核共享树组播算法(英文)

为了解决低轨卫星IP网络中现有典型源组播算法的信道资源浪费问题,本文提出了一套单核共享树组播算法,即核心群合并共享树(CCST)和加权核心群合并共享树(w-CCST)算法。CCST 算法包括动态近似中心(DAC)选核方法和核心群合并组播路径构建方法。DAC方法专为周期、规律运动的低轨卫星网络提出,不需要复杂的星上计算。在核心群合并方法中,以核节点作为初始核心群,通过核心群和剩余组成员的最短路径方法逐步扩展直至整棵组播树构建完成,从而使得组播树的树代价最小,大大提高了网络的带宽利用率和组播传输效率。w-CCST 算法中所提出的加权因子可以调整树代价和端到端传播时延之间的折衷程度,因此,可以通过调整加权因子来适度增大树代价、降低端到端传播时延以支持某些端到端时延要求苛刻的实时组播业务。最后,与低轨卫星 IP 网络中典型算法进行了性能比较,仿真结果说明,CCST 算法的平均树代价比其它算法显著降低,w-CCST 算法的平均端到端传播时延小于 CCST 算法。     

Jet Vectoring Control Using a Novel Synthetic Jet Actuator

A primary air jet vectoring control system with a novel synthetic jet actuator (SJA) is presented and simulated numerically. The results show that, in comparison with an existing traditional synthetic jet actuator, which is able to perform the duty of either “push” or “pull”, one novel synthetic jet actuator can fulfill both “push” and “pull” functions to vector the primary jet by shifting a slide block inside it. Therefore, because the new actuator possesses greater efficiency, it has potentiality to replace the existing one in various appli- cations, such as thrust vectoring and the reduction of thermal signature. Moreover, as the novel actuator can fulfill those functions that the existing one can not, it may well be expected to popularize it into more flow control systems.     

Nonlinear Adaptive Slewing Motion Control of Spacecraft Truss Driven by Synchronous V-gimbaled CMG Precession

The slewing motion control of a truss arm driven by a V-gimbaled control-moment-gyro (CMG) is a nonlinear control problem. The V-gimbaled CMG consists of a pair of gyros that must precess synchronously. The moment of inertia of the system, the angular momentum of the gyros and the external disturbances are not exactly known. With the help of feedback linearization and recursive Lyapunov design method, an adaptive nonlinear controller is designed to deal with the unknown items. Performance of the proposed controller is verified by simulation.     

An SOR Implicit Time-accurate Scheme in Calculating Unsteady Flows

A new time-accurate marching scheme for unsteady flow calculations is proposed in the present work. This method is the combination of classical Successive Over-Relaxation (SOR) iteration method and Jacobian matrix diagonally dominant splitting method of LUSGS. One advantage of this algorithm is the second-order accuracy because of no factorization error. Another advantage is the low computational cost because the Jacobian matrices and fluxes are only calculated once in each physical time step. And, the SOR algorithm has better convergence property than Gauss-Seidel. To investigate its accuracy and convergency, several unsteady flow computa- tional tests are carried out by using the proposed SOR algorithm. Roe’s FDS scheme is used to discritize the inviscid flux terms. Un- steady computational results of SOR are compared with the experiment results and those of Gauss-Seidel. Results reveal that the numerical results agree well with the experimental data and the second-order accuracy can be obtained as the Gauss-Seidel for unsteady flow computations. The impact of SOR factor is investigated for unsteady computations by using different SOR factors in this algorithm to simulate each computational test. Different numbers of inner iterations are needed to converge to the same criterion for different SOR factors and optimal choice of SOR factor can improve the computational efficiency greatly.