钛合金加工中的安全问题

铋合金具有耐高温性能好、优越的抗蚀性、重量轻、与其他金属兼容等特点,因此,广泛被应用于制作各类先进客机的结构件和非结构件.但钛合金导热性差,切削加工时易产生粘刀现象,由此给钛合金的加工带来了一些麻烦.本文就钛合金加工过程中可能带来的着火、燃烧问题及其预防措施谈谈笔者的看法.     

为航天员树起安全屏障——航天动力技术研究院42所研制神舟九号飞船舱体密封件侧记

在首次载人交会对接任务中,3名航天员奔赴"太空之旅"。如何保障他们在神舟九号飞船内的生命安全格外引人瞩目。作为保障飞船内空气环境安全和航天员生命安全的飞船舱体密封件,则是整个飞船舱体结构密封的关键部件。由航天动力技术研究院42所生产的飞船舱体密封件在此次任务中将全程与航天员的生命安全相伴。由于外太空的环境复杂,要求密封件在高真空、高低温交变、紫外辐照、带电粒子辐照和原子氧等特殊的使用环境下不产生降解、老化和龟裂,始终保持可靠的密封性能。     

模型旋翼与全尺寸旋翼风洞试验结果的比较

本文介绍了旋翼原理样机4m模型旋翼在CARDC 8m×6m闭口风洞的试验结果与全尺寸旋翼在俄罗斯TSAGI T101开口风洞试验结果的比较.     

太阳能热推进系统效率分析

太阳能热推进采用小分子量气体作为推进剂可以获取800～900 s高比冲,但提高推进系统的换热效率是目前亟待解决的问题.本研究建立了太阳能热推进系统主要部件的基本分析模型,在利用有限单元法进行热分析的基础上,对系统在多种工况下的相关参数进行了计算,分析了各部件主要参数对提高太阳能热推进系统热效率和推进效率的影响,得出了系统效率在不同工作状态下的变化规律,并提出了提高系统效率的措施.     

非均匀入口与化学非平衡效应对尾喷管性能的影响研究

基于煤油燃料超燃冲压发动机尾喷管,对均匀入口和非均匀入口、冻结流动模型和化学非平衡模型下的尾喷管内流动进行数值模拟,采用两方程RNG k-ε湍流模型对三维NS方程组进行求解,获得非均匀入口与化学非平衡效应对尾喷管性能的影响。计算结果表明,尾喷管内流动非均匀性由尾喷管非对称膨胀和燃烧室出口非均匀等因素构成,尾喷管入口流动参数非均匀分布对尾喷管推力、升力及俯仰力矩均有影响,算例中非均匀入口使得尾喷管净推力相对于均匀入口增加了1.2%左右;尾喷管性能受化学非平衡效应的影响,非平衡流动模型下的其净推力计算结果相对于冻结流动模型增加3%~4%。     

Grinding performance evaluation of porous composite-bonded CBN wheels for Inconel 718

For high-efficiency grinding of difficult-to-cut materials such as titanium and nickel alloys, a high porosity is expected and also a sufficient mechanical strength to satisfy the function.However, the porosity increase is a disadvantage to the mechanical strength. As a promising pore forming agent, alumina bubbles are firstly induced into the abrasive layer to fabricate porous cubic boron nitride（CBN） wheels. When the wheel porosity reaches 45%, the bending strength is still high up to 50 MPa with modified orderly pore distribution. A porous CBN wheel was fabricated with a total porosity around 30%. The grinding performance of the porous composite-bonded CBN wheel was evaluated in terms of specific force, specific grinding energy, and grinding temperature, which were better than those of the vitrified one under the same grinding conditions. Compared to the vitrified CBN wheel, clear straight cutting grooves and less chip adhesion are observed on the ground surface and there is also no extensive loading on the wheel surface after grinding.     

Storage life of silicone rubber sealing ring used in solid rocket motor

It is urgent to carry out detailed research on storage performance of rubber sealing ring to get the criterion for its storage life. This paper acquires material ageing regularity by theoretical analysis and experimental confirmation. On this condition, failure mode and failure criterion of typical sealing structure is studied, and the failure mechanism is found. Thus by analyzing the stress distribution, the relationship between ageing state and sealing condition is established. Rationalization proposal is put forward and storage life of sealing ring is evaluated. The research mentionedabove has special reference to the design of sealing structures and can provide reference for prolonging their service life.     

消光漆在光学系统的国内外应用

简单地列举了国内外一些消光漆的应用情况,阐述了消光漆的消光性能指标的测定方法,同时对

国内外的一些消光漆的消光性能进行了比较。