光学头罩超声速绕流流场光学传输效应风洞试验研究

在Ma=3连续超声速风洞中,开展了光学头罩绕流流场光学传输效应的风洞模拟试验方法研究,进行了现场振动测量与隔离,研制了专用试验装置,采用哈特曼传感器和剪切干涉仪两种手段进行了光学传输效应的试验测量。试验中,针对试验装置各部分的不同组合状态,进行了大量的测试,研究了试验装置有效性以及试验数据重复性,着重分析了探测光束的PV值与RMS值。结果表明：导流板可明显抑制风洞洞壁边界层干扰,试验装置与方法可行,对于连续式风洞中模型绕流流场光学传输效应测试有一定参考价值。     

开放式结冰条件模拟技术研究

在-1—-9℃的环境温度条件下,采用开放式结冰条件模拟技术可以为民机或军机发动机短舱防冰系统性能试验模拟出合适的结冰气象条件。采用气液两相喷嘴模拟水雾结冰环境时,所采用气体和液体的纯度是过冷水滴产生的先决条件,气液两相压差、风洞吹风速度和试验对象距离是影响结冰气象参数的关键因子。采用改造后的FM-100传感器可实现对结冰气象参数的实时测量。通过升降机构、小角度俯仰和万向轮等辅助结构设计,开放式结冰条件模拟系统可以满足不同试验对象的试验要求,可以适应不同风向的试验环境。具备非常广阔的推广应用前景。     

浅议大学生讲诚信

近年来诚信缺失普遍存在于社会生活各个领域,甚至影响到在校的大学生,因此加强高校自身诚信环境建设,加强对学生的诚信意识教育,完善社会信用评价体系,建立学生个人信用档案,使大学生树立诚信理念和准则,肩负起时代赋予的历史使命,具有十分重要的意义。     

粉末涂装系统的选择及维护

如果对粉末涂装系统技术或合作缺乏足够认识，生产不出高质量的产品，势必有被淘汰的一天。本文叙述了粉末涂料、喷粉设备、施工环境及设备使用维护等有关问题，以帮助使用者作出正确地选择。     

Impact effects from small size meteoroids and space debris

When the impact risk from meteoroids and orbital debris is assessed the main concern is usually structural damage. With their high impact velocities of typically 10–20 km/s millimeter or centimeter sized objects can puncture pressure vessels and other walls or lead to destruction of complete subsystems or even whole spacecraft. Fortunately chances of collisions with such larger objects are small (at least at present). However, particles in the size range 1–100 μm are far more abundant than larger objects and every orbiting spacecraft will encounter them with certainty. Every solar cell (8 cm² area) of the Hubble Space Telescope encountered on average 12 impacts during its 8.25 years of space exposure. Most were from micron sized particles.     

Comparative study between crack closure model and Willenborg model for fatigue prediction under overload effects

A comparative study is performed between a crack closure model and the Willenborg model, which can calculate the fatigue crack growth rate under the overload effects. The modified virtual crack annealing (VCA) model is briefly reviewed, which is based on the equivalent plastic zone concept. In this method, the retardation phenomenon is explained by the crack closure level variation, which is derived from the interactions between forward and reverse plastic zones ahead of the crack tip. As a comparison, the Forman equation in conjunction with the Willenborg model is also reviewed. The retardation phenomenon is described by directly modifying the stress intensity factor. It is known that the large plastic zone created by the overload can decelerate the fatigue crack growth rate until the crack grows beyond this region. A relationship between the plastic zone and the modified stress intensity factor is developed, which is a mathematical fitting equation instead of physical-based formulation. The experimental data in aluminum alloys are used to val-idate these two models. Overall, good agreement is observed between the model predictions and the testing data. It is noted that the approach based on modified VCA model can give more accurate prediction curves than the Willenborg model.     

A review of chatter vibration research in milling

Chatter is a self-excited vibration of parts in machining systems. It is widely present across a range of cutting processes, and has an impact upon both efficiency and quality in production processing. A great deal of research has been dedicated to the development of technologies that are able to predict and detect chatter. The purpose of these technologies is to facilitate the avoidance of chatter during cutting processes, which leads to better surface precision, higher productivity, and longer tool life. This paper summarizes the current state of the art in research regarding the problems of how to arrive at stable chatter prediction, chatter identification, and chatter control/suppression, with a focus on milling processes. Particular focus is placed on the theoretical relationship between cutting chatter and process damping, tool runout, and gyroscopic effect, as well as the importance of this for chatter prediction. The paper concludes with some reflections regarding possible directions for future research in this field.     

ANPyO Bi(III)含能配合物的合成、表征、热分解行为及其对高氯酸铵热分解的催化作用

合成了2,6-二氨基-3,5-二硝基吡啶-1-氧化物(ANPyO) Bi(III)含能配合物,采用FTIR、元素分析和XPS光电子能谱表征了含能配合物的结构.根据结构表征结果推测,ANPyO Bi(III)含能配合物的分子式为Bi(C5H4N5O5)3,金属离子与配体的配比为1∶3.其中,可能的配位方式为:每个配体ANPyO 2-位的氨基脱去一个氢原子,分别以NH和N→O结构单元中N原子和O原子与Bi(III)形成配位键.ANPyO Bi(III)含能配合物的撞击感度、摩擦感度和冲击波感分别为220 cm、36 kg和5.8 mm.采用TG-DTG和DSC测试考察了ANPyO Bi(III)含能配合物的热分解行为,配合物在50～450 ℃范围内热分解过程由一个吸热熔融峰和分解放热峰组成,相应的峰温分别为320.6 ℃和346.5 ℃,配合物热分解剩余残渣量为31.2％.同时,考察了配合物对高氯酸铵热分解的催化作用,并采用Kissinger法对纯AP和AP混合物热分解过程低温分解阶段和高温分解阶段的表观活化能和指前因子进行了计算.结果表明,ANPyO Bi(III)含能配合物可使高氯酸铵高温分解阶段和低温分解阶段的峰温提前63.6 ℃和63.1 ℃,表观活化能降低23.1 kJ/mol和61.5 kJ/mol,表观分解热增加339.3 J/g.可发现,ANPyO Bi(III)含能配合物对AP的热分解具有显著的催化作用.     

硼含量及横向取样对定向凝固Ni_3Al合金持久性能的影响

硼的添加增强了晶界的结合力 ,使合金相界面的位错组态改变 ,提高了持久断裂寿命 ;硼的添加细化晶粒 ,增加界面数 ,使持久寿命下降。Ni3Al定向凝固横向试样持久性能不稳定与取样位置有关     

固体推进剂生产厂环境现状评价

对某固体推进剂生产厂排放的有害物质进行了系统研究。确定了其“三废”排放以气态污染物为主，其次是废水。气态污染物又以苯乙烯排放量最大。采用综合指数法对厂区及周围大气环境进行评价分级，结果是，厂区周围500m以内为重污染区，2500m以外为清洁区。