氧化铝短纤维增强ZL109铝合金复合材料的组织与性能的研究

本文以氧化铝短纤维为增强体,用挤压铸造技术制备了氧化铝/铝合金复合材料。研究了复合材料的组织与性能。研究结果表明,纤维在复合材料中分布均匀,与基体结合良好;氧化铝纤维有利于铝硅合金中硅相的非均质成核;和基体合金相比,复合材料具有更高的常温及高温强度、硬度和良好的耐磨性能,是一种性能优异的金属基复合材料。     

非稳定导热问题有限元算法的守恒条件及一种守恒格式

本文对非稳定导热问题的有限元算法的能量守恒条件进行了讨论。认为有限元之解有时出现反常、振荡的原因是对问题时空域的离散化未能使相应格式满足能量守恒原理。依据文中的分析,提出了一种以单元边长做为集中热容阵权因子的守恒格式。验算表明,其稳定、可靠、精度较高。     

基于三维模型定义技术应用的思考

MBD技术是一个新生事物,涉及到系统性问题,它的应用实施是一项长期、复杂而又艰巨的工作。需要考虑的问题不仅涉及技术方面,还有文化、管理、组织和生产方式等方面,只有解决好这些问题,才能充分发挥MBD技术的巨大效力,更好地为我国大飞机研制服务。     

锯齿形垫片成型模加工工艺

叙述了锯齿形垫片成型模的结构特点和工艺性,对模具加工工艺方法进行了分析、比较并确定了最佳方案。重点论述了加工模具工艺尺寸的计算过程,确定了模具加工的工序,并对采用手工铣床加工的锯齿形垫片的使用效果及效益进行了阐述。     

Experimental study of effect of post processing on fracture toughness and fatigue crack growth performance of selective laser melting Ti-6Al-4V

For Ti-6Al-4V, a titanium alloy increasingly used in aerospace structure, selective laser melting (SLM) is an attractive additive manufacturing technology, which is attributed to its complex construction capability with high accuracy and good surface quality. In order to obtain qualified mechanical properties, SLM parameters and post processing should be tailored for diverse service conditions. Fracture toughness and fatigue crack growth (FCG) behavior are critical characteristics for damage tolerance evaluation of such metallic structures, and they are affected by post processing technologies significantly. The objective of this study is to obtain the fracture toughness and fatigue crack growth behavior of Ti-6Al-4V manufactured by SLM, and to evaluate the influence of post-SLM thermomechanical treatment and surface machining. Fracture toughness and FCG tests were performed for SLM Ti-6Al-4V in three types of post processing status: as-built, heat treated and hot isostatically pressed (HIPed), respectively. Specimens with as-built and machined surface were tested. The microstructure and fractography were analyzed as well in order to investigate the relevance among manufacture process, microstructure and mechanical properties. The results demonstrate that as-built SLM Ti-6Al-4V presents poor ductility and FCG behavior due to martensitic microstructure and residual stresses. Both heat treatment and hot isostatic pressing improve the plane-stress fracture toughness and FCG performance considerably, while surface machining shows slight effect.     

美国载人航天步入后航天飞机时代

在纪念人类首次进入太空50周年的时候,回顾美国载人航天近30年的历程,不仅让我们看到了载人航天取得的辉煌成就,也让我们为载人航天发展的曲折和艰辛而感叹!     

空间机械臂运动控制的地面仿真验证技术

空间机械臂是在轨进行舱外巡检、航天员辅助出舱的关键活动机构,其在轨操作的运动过程需要在地面进行预先规划生成运动控制指令,再通过数字仿真与推演对运动控制指令进行验证,以确保机械臂操作全程的安全性和高效性.针对上述问题,本文主要从运动空间限制、运动速度限制和关节力矩限制等方面设计了地面仿真验证框架,提出了基于运动学与动力学...     

提高航空装备采购合同运行效率研究

针对航空武器装备订货合同制中涉及到的厂际间配套产品订货合同“两厂四方”模式在实际运行当中出现的一些问题进行探讨，通过订货合同管理工作实践，从经济理论和法律角度深入分析了产生问题的原因，并在此基础上提出了把市场调节与外部指导相结合，完善各方协作机制，细化合同内容等改进措施，旨在为提高航空武器装备订货合同制运行效率提供对策建议。     

涡轮的重复进气道的试验研究

用小型涡轮取代蓄电池和高压气瓶作为导弹上的辅助能源是明显地发展趋势.重复进气涡轮能较好地适应这种辅助能源系统的要求.本文研究了涡轮的不同形状的重复进气道,及其与喷嘴的匹配,不同的喷嘴出口角、流速等因素对损失的影响,给出了在所研究的条件下最佳形状的重复进气道、喷嘴和重复进气道的最佳匹配.     

Interactive Multi-objective Optimization Design for the Pylon Structure of an Airplane

The pylon structure of an airplane is very complex, and its high-fidelity analysis is quite time-consuming. If posterior preference optimization algorithm is used to solve this problem, the huge time consumption will be unacceptable in engineering practice due to the large amount of evaluation needed for the algorithm. So, a new interactive optimization algorithm-interactive multi-objective particle swarm optimization （IMOPSO） is presented. IMOPSO is efficient, simple and operable. The decision-maker can expediently determine the accurate preference in IMOPSO. IMOPSO is used to perform the pylon structure optimization design of an airplane, and a satisfactory design is achieved after only 12 generations of IMOPSO evolutions. Compared with original design, the maximum displacement of the satisfactory design is reduced, and the mass of the satisfactory design is decreased for 22%.