Effects of FDM-3D printing parameters on mechanical properties and microstructure of CF/PEEK and GF/PEEK

Fused deposition modeling (FDM) has unique advantages in the rapid prototyping of thermoplastics which have been developed in diverse fields. However, although great efforts have been made to optimize FDM process, the mechanical properties of printed parts are limited by the weak interlamination bonding as well as the poor performance of raw filaments used, such as acrylonitrile butadiene styrene (ABS), polylactic acid (PLA). Adding fibers into thermoplastic matrix and preparing high-performance filaments have been indicated to enhance the properties of fabricated parts. Recently, heat-resistant polyetheretherketone (PEEK) and its fiber reinforced composites were proposed for FDM process due to overcoming the limitation of equipment and process. However, few researches have been reported on the effects of FDM-3D printing parameters on the mechanical properties of fiber reinforced PEEK composites. Therefore, 5wt% carbon fiber (CF) and glass fiber (GF) reinforced PEEK composite filaments were prepared respectively in this study. The effects of various printing parameters including nozzle temperature, platform temperature, printing speed and layer thickness on the mechanical properties (including tensile strength, flexural strength and impact strength) were surveyed. To analyze the microstructure and failure reasons of printed CF/PEEK and GF/PEEK samples, the tensile fractured surfaces were investigated via scanning electron microscope (SEM).     

航空发动机叶尖径向间隙静电监测方法

提出航空发动机叶尖径向间隙静电监测方法,分别对叶尖荷电在点电荷与电荷分布条件下的静电感应过程建立数学模型,得到感应电荷量与叶尖径向间隙值、叶尖周向位置及叶尖电荷分布的关系。设计并搭建叶尖径向间隙静电监测模拟实验台,提取时域特征参数并分析叶尖径向间隙值及叶尖局部曲率对静电水平的影响。数学模型计算结果表明:①感应电荷量与叶尖径向间隙及叶尖相对传感器的径向位置绝对值呈负相关;②感应电荷量与叶尖所带电荷量呈正相关,且与电荷密度分布有关;③感应电荷量与叶尖尺寸及传感器尺寸有关。实验结果表明静电信号方均根值和整流平均值与叶间径向间隙值呈负相关,与叶尖局部曲率呈正相关,其结果与理论模型相符。      

制造工程中的质量管理模式特性探讨

研究遵循对过程进行闭环管理的思想,依据制造系统设计的质量管理的一般机理和实用方法,在对质量模式中软件硬件系统因素进行分析的基础上,推论出制造工程的管理组织所建立的经济简单质量管理体系应为与其工程活动和规模持续相适应的基本特性。     

子系统性能参数变化对飞控系统稳定性的影响

分析子系统（元部件）性能指标超差对飞控系统总体性能的影响，是实际工程提出的一项重要研究课题。本文基于分层递阶的分析思想，采用灵敏度分析技术和仿真实验相结合的手段，研究了子系统性能参数的不确定性对飞控系统稳定性的影响，得到了一些有价值的分析结果。     

电弧喷射推力器内部工作过程研究综述

对电弧喷射推力器及其内部工作过程特性作了简要介绍,分析了内部工作过程对其性能的影响并对有关实验与理论研究作了概述。电弧喷射推力器内部流动具有过程复杂剧烈,空间狭小,非平衡性强烈等特点。目前在实验上,采用气动方法、静电方法、光谱方法以及激光方法等获得了内部及外部（羽流）流动过程的多种综合参数和流场参数;理论上已建立了能初步反映化学不平衡、热力学不平衡等较为复杂物理过程的数值模型,为全面认识电弧喷射推力器内部工作过程机制提供了有效的手段。     

再入参数调整对登月航天器返回再入特性的影响

首先分析了再入参数调整对登月航天器返回再入运动特性的影响;然后利用自主编制的仿真软件,对再入参数调整的影响进行了仿真分析;最后在深入分析仿真结果的基础上,研究了再入参数变化对航天器再入过载、航程、飞行时间及落点散布等的具体影响规律,为后继进一步开展载人月球飞行相关任务的分析设计提供了有益参考。     

Phobos-Grunt: Russian sample return mission

As an important milestone in the exploration of Mars and small bodies, a new generation space vehicle “Phobos-Grunt” is planned to be launched by the Russian Aviation and Space Agency. The project is optimized around a Phobos sample return mission and follow up missions targeted to study some main asteroid belt bodies, NEOs and short period comets. The principal constraint is use of the “Soyuz-Fregat” rather than the “Proton” launcher to accomplish these challenging goals. The vehicle design incorporates innovative SEP technology involving electrojet engines that allowed us to increase significantly the mission's energetic capabilities, as well as highly autonomous on-board systems. Basic criteria underlining the “Phobos-Grunt” mission scenario, scientific objectives and rationale including Mars observations during the vehicle's insertion into Mars orbit and Phobos approach maneuvers, are discussed and an opportunity for international cooperation is suggested.     

碳纤维陶瓷基复合材料的磨削加工研究进展

综述了磨削参数、纤维方向、不同加工方式以及其他因素对磨削力和表面质量的影响规律;总结了不同加工方式下的碳纤维陶瓷基复合材料的磨削机理;展望了碳纤维陶瓷基复合材料磨削加工的研究方向。     

基于改进PSO算法的导弹控制参数优化

研究了将粒子群算法(PSO)应用于空对空导弹控制参数自动设计的方法,解决导弹控制参数手工设计中遇到的困难与问题.标准PSO算法在导弹静稳定工作点参数优化中表现出良好性能,但在静不稳定工作点优化时容易限入局部最优,因此引入遗传算法(GA)的杂交思想对标准PSO算法进行了改进,以扩大解空间的范围.仿真结果表明:改进后的PSO优化算法具有更强的全局搜索能力,获得的参数能够满足给定的性能指标,并且可以节省大量的设计时间,具有很高的工程应用价值.     

富燃料推进剂燃烧产物粒度参数的激光衰减法测量

介绍了激光衰减法测量粒子参数的基本原理.搭建了激光衰减法测量高铝含量富燃料推进剂实验系统,解决了燃烧环境下粒度测试的光学介入问题,对高铝含量富燃料推进剂中粒子参数进行测量,对所得的凝相燃烧产物进行电镜分析,并对电镜照片进行分析处理,计算出燃烧后凝相产物平均粒径,验证了激光衰减法测量粒子参数的可行性和合理性.