2219-T87/T852铝合金异质接头力学性能弱化及断裂机制

开展了航天贮箱用2219-T87和2219-T852铝合金变极性钨极氩弧焊接研究,通过拉伸试验确定了接头力学强度薄弱区,对接头焊缝晶粒特征、晶界偏析及强化相分布等微观组织分析,阐明接头力学性能弱化及断裂机制。结果表明,接头在-196℃低温条件下平均抗拉强度为314 MPa,平均延伸率为5.68%,接头力学强度薄弱区为2219-T852侧熔合区。在拉伸过程中,接头背部焊缝打底层边缘首先发生起裂,沿熔合区向上扩展,最终断口呈现混合断裂模式。微观组织分析表明,在接头力学强度薄弱区,组织为非均匀过渡混合晶粒特征,晶界偏析造成的沿晶共晶相呈粘连网状分布,基体强化相大量溶解与粗化,共同导致了接头强度和塑性的显著下降。     

Corrosion Properties of Light-weight and High-strength 2195 Al-Li Alloy

The intergranular corrosion and exfoliation corrosion of 2195 Al-Li alloy treated by multi-step heating-rate controlled aging (MSRC) are studied. The corrosion features of 2195 Al-Li alloys which are respectively treated by high-temperature nucleation MSRC (H-M) and low-temperature nucleation MSRC (L-M) are contrasted. And the corrosion mechanism of 2195 Al-Li alloy is also discussed from the viewpoint of microstructure (types, distribution, etc.) of the strengthening phase. The results show that 2195 Al-Li alloy after H-M is more susceptible to intergranular corrosion and exfoliation corrosion than that of alloy after L-M. The degree of intergranular corrosion increases with the increase of predeformation amount and the surface parallel to the rolling direction is more prone to exfoliation corrosion. The main reason of intergranular corrosion and exfoliation corrosion is the for-mation of corrosion galvanic couples among T1 phase, ?θ’ phase and grain boundary precipitate-free zones (PFZ).     

图C4k∪pn的优美性

证明了圈C4k是优美交错图，证明了路Pn是优美交错图。证明了由圈C4k与路Pn粘接而成的图C4k∪Pn是优美图，也是交错图，并给出了图C4k∪Pn的优美标号。     

直升机悬停回转时尾桨载荷计算研究

本文推导了直升机尾桨线性和非线性的静、动力分析方法,从理论上推导出直升机尾桨叶在悬停回转时的运动学及动力学之间的关系,并对Z11型机悬停回转状态下尾桨叶载荷进行了计算。     

静电悬浮微加速度计高灵敏度电容检测通道设计

高灵敏度电容式位移检测是实现静电悬浮微加速度计闭环测控的关键技术之一.针对微加速度计径向悬浮检测的特点及指标要求,设计了高灵敏度、高精度电容式微位移检测通道.该通道主要由前置RC隔离网络与C/V转换、高共模抑制比差动放大器、二级运放、二阶压控电压源有源带通滤波、相敏解调(含模拟乘法器与四阶Butterworth低通滤波...     

现代战争的航空维修保障对机务人员的挑战

从现代战争的特点和需要出发,从航空装备维修保障科学高效的角度出发,研究和探讨了作为活动主体的高素质航空机务人员所必须具备的基本特征。     

基于FTA的飞机空调组件关断的故障分析

为迅速准确地确定飞机空调系统故障源,提高航线排故效率,针对B737飞机空调组件关断的故障,介绍了故障树建立的依据和方法,引入最小割集概念定性分析主要的故障模式;在综合考虑空调系统历史故障数据、零部件的可靠性、维修实践经验和部件更换方便性等信息的基础上,列出了排故顺序和排故措施,最后根据各类事件发生的概率,利用结构函数定量分析了顶事件发生的概率;所建立的空调系统故障树可迅速准确地确定故障源,在实际的航线排故过程中已得到了初步验证。该故障树对于排除空调系统各个子系统的故障也具有一定的参考价值。     

飞机起落架载荷谱实测与编制方法

飞机起落架载荷谱实测时,应变计粘贴位置的选择是载荷谱实测的基础,然而起落架结构复杂,可供选择粘贴应变计的位置十分有限,因此研究并给出了起落架载荷谱实测时选择的典型测试切面,以为其他起落架载荷谱实测提供重要参考.根据实测载荷-时间历程,依据起落架受力特点对其进行了典型任务段的划分,分别对各个任务段进行载荷谱的编制.针对某...     

Operation of a Rotary-valved Pulse Detonation Rocket Engine Utilizing Liquid-kerosene and Oxygen

The pulse detonation rocket engine (PDRE) requires periodic supply of oxidizer, fuel and purge gas. A rotary-valve assembly is fabricated to control the periodic supply in this research. Oxygen and liquid aviation kerosene are used as oxidizer and fuel respectively. An ordinary automobile spark plug, with ignition energy as low as 50 mJ, is used to initiate combustion. Steady operation of the PDRE is achieved with operating frequency ranging from 1 Hz to 10 Hz. Experimentally measured pressure is lower than theoretical value by 13% at 1 Hz and 37% at 10 Hz, and there also exists a velocity deficit at different operating frequencies. Both of these two phenomena are believed mainly due to droplet size which depends on atomization and vaporiza-tion of liquid fuel.     

飞机载荷机构特性曲线的自动检测

基于飞机飞行品质和装备科学保障的基本要求,提出了载荷机构特性曲线自动检测的原理方案,研制了相应的通用性自动检测仪,并成功地实现了载荷机构特性曲线的实时自动检测。检测结果准确可靠,为分析飞机操纵系统品质提供了直接的参考依据,对提高飞机操纵的可靠性、安全性和维修保障性具有重要意义。