TC4板材组织特征与超声检测信号对应关系研究

在大厚度板材在轧制过程中,由于工艺控制不当易引起材料组织分布不均匀、粗大晶粒等问题,本文针对TC4轧制板材研究超声检测信号对材料内部组织分布的表征情况。结果表明,声波垂直于板材流线方向入射时,声衰减分布均匀;而平行入射时,声衰减分布极不均匀,呈条带状分布。为此,对引起不同声波衰减的截面进行组织分析,金相观察发现超声波衰减与材料内部α相的分布及形态有关：声衰减小的区域,材料内部等轴α相较多,晶粒细小,分布均匀;声衰减大的区域,α相被明显拉长。     

基于模糊理论的复合材料超声检测缺陷类型识别

本文以复合材料常见缺陷分层、孔隙、疏松的超声波检测缺陷信号为研究对象,选取缺陷波的时域及频域特征,考虑到各特征量之间的不可避免地存在耦合关系,而且对缺陷区分的重要性、敏感度也有很大的差别,采用加权多面体隶属度概念构造隶属函数,依据最大隶属原则进行模式识别,从而区分复合材料缺陷类型。     

基于P～t曲线的导弹火工品品质测试

为了提高导弹火工品的存贮安全性和使用可靠性 ,提出了一种基于P～t(压力 -时间 )曲线获取的火工品品质测试分析方案 ;利用凌华高性能数据采集卡PCI- 9112采集爆炸过程的瞬态压力信号 ,并在对采集到的信号进行频谱分析和在滤波的基础上提取出了火工品的特征参数 ,从而为火工品的品质评判提供了决策参考。     

虚拟仪器的超声检测系统在航空维修中的应用

为实现对海军琶机结构损伤的检测智能化,应用超声检测和虚拟仪器技术,研制了基于虚拟仪器的超声检测系统。应用该系统对某型进口直升机尾桨叶和某型运输机的螺栓进行了检测,结果表明仪器达到了设计要求,满足了航空维修无损检测需要。     

固体火箭发动机封头界面粘接相控阵超声检测技术可行性研究

固体火箭发动机封头部分的界面粘接状态目前还没有有效的检测方法,采用相控阵超声自动电子聚焦技术为该结构的检测提供了新思路.根据声线理论,研究等厚、不等厚壳体的界面粘接相控聚焦检测方式,得出相控聚焦具有较高的检测分辨率,同时也能解决不等厚壳体构件的界面粘接检测;对固体火箭发动机封头构件的粘接状态进行仿真分析,结果显示相控阵超声能很好地检测出构件的脱粘区域和大小,表明该检测方式在界面粘接检测方面具有广泛的应用前景.     

Grouping bi-chi-squared method for pulsar navigation experiment using observations of Rossi X-ray timing explorer

X-ray pulsar-based navigation is a revolutionary technology which is capable of providing the required navigation information in the solar system. Performing as an important pulsar-based navigation technique, the Significance Enhancement of Pulse-profile with Orbit-dynamics (SEPO) can estimate orbital elements by using the distortion of pulse profile. Based on the SEPO technique, we propose a grouping bi-chi-squared technique and adopt the observations of Rossi X-ray Timing Explorer (RXTE) to carry out experimental verification. The pulsar timing is refined to determine spin parameters of the Crab pulsar (PSR B0531+21) during the observation periods, and a short-term dynamic model for RXTE satellite is established by considering the effects of diverse perturbations. Experimental results suggest that the position and velocity errors are 16.3 km (3σ) and 13.3 m/s (3σ) with two adjacent observations split by one day (exposure time of 1.5 ks), outperforming those of the POLAR experiment whose results are 19.2 km (3σ) and 432 m/s (3σ). The approach provided is particularly applicable to the estimation of orbital elements via using high-flux observations.     

离心喷嘴声学相关热试验频率分析与计算

针对采用离心喷嘴的氢氧预燃室，基于高频脉动压力的热试验数据，对比了试验频率的变化趋势和与之相关的主要测试参数的变化规律，初步推测影响热试验频率的根本因素是离心喷嘴内部液膜的声速和燃烧室压力。发展形成了基于声学理论计算喷嘴频率的半经验公式，使用喷前压力和修正了的液氧温度查询声速计算的喷嘴频率。半经验公式的计算结果与试验实测频率吻合很好，分析认为类似管路声学频率计算的半经验公式同样适用于离心喷嘴。声学频率决定了离心喷嘴液膜主导表面波波长的初始值，主导表面波流动所受气体阻力随压力及液膜速度升高而增大使其波长减小，液膜一次破碎的频率升高，可能是热试验频率与燃烧室压力正相关的影响机制。     

芯材高度对三维中空夹芯复合材料低速冲击性能的影响

选取芯材高度分别为5、6、7 mm 的三维中空夹芯复合材料为研究对象,采用落锤式低速冲击试

验装置分别对上述材料进行8 J 能量的低速冲击测试,研究材料的低速冲击性能;利用Instron 3385H 型万能材

料试验机分别测试上述材料受到低速冲击载荷前后的压缩强度,研究材料受到低速冲击载荷后的压缩损伤容

限。结果表明:三维中空夹芯复合材料对低速冲击载荷比较敏感;随着芯材高度的增加,材料抗低速冲击性能

有所增加;低速冲击载荷使材料的剩余压缩强度大幅下降。

     

Derivation and validation of a similarity law for free-flight wind tunnel tests of parallel stage separation

Aiming at the safety problem of the stage separation of parallel reusable high-speed air vehicles, this paper studies the unsteady test method and focuses on deriving a similarity law of parallel stage separation free-flight wind tunnel tests. The new similarity law considers the influences of aerodynamic force and gravity on the motions of the two stages, as well as the influence of aerodynamic interference between the two stages on each other’s motion. From the perspective of multi-angle physical equations, the conditions to ensure that the two-stage separation trajectory of a wind tunnel test is similar to that of a real air vehicle are derived innovatively, so as to ensure the authenticity and credibility of wind tunnel test results. The similarity law is verified by an HIFiRE-5 air vehicle, and the separation trajectories of wind tunnel tests and the real air vehicle are obtained by numerical simulation. The research shows that the similarity law derived in this paper can ensure that wind tunnel free-flight tests have the ability to predict the two-stage separation characteristics of real parallel vehicles. By analyzing the separation trajectory curve of the typical state, it is found that the new method can ensure that the trajectory error of a wind tunnel test does not exceed 1%, which indicates that this method is credible. The establishment of the new method lays the foundation for subsequent wind tunnel tests and provides support for research on the safety of the stage separation of parallel reusable air vehicles.     

Ion thruster accelerator grid erosion mechanism under extreme conditions of cylindrical erosion and chamfer erosion

In this paper, the abnormal experimental phenomenon on barrel erosion under extreme working conditions in the ultra-long life experiment(>10000 h) of ion thruster ion optics is studied by the Immersed-Finite-Element Particle-In-Cell Monte-Carlo-Collision(IFE-PIC-MCC) method and the grid erosion evaluation model. The transport process of beam ions and Charge Exchange(CEX) ions in the grid system, and the characteristics and mechanisms of the aperture barrel erosion under extreme erosion condit...