航空发动机状态监控和故障诊断系统

 本文从世界各航空公司采用和研制该系统的情况,和我国民航维修工作的现状及发展提出了研究此系统的必要性,对发动机参数趋势分析和气路分析以及发动机振动分析进行了较全面的讨论,提出了研究的途径和基本模型及所要达到的目的。     

疲劳裂纹起始扩展门槛值的研究

 1.疲劳裂纹起始扩展门槛值(△K_(th))的概念 人们通常提到的疲劳裂纹扩展门槛值△K_(th)是在裂纹扩展过程中不断下降△K,使裂纹扩展不断减慢,直至停止扩展时所对应的△K值。它由降K程序测定,试验方法见文献。达到△K_(th)时裂纹前缘塑性区很小,在厚度和应力比一定的条件下,△K_(th)是材料常数。然而,在构件承受变幅交变载荷作用时,某级载荷使裂纹尖端产生应力强度因子K_(fmax),对应     

Effects of Machine Tool Configuration on Its Dynamics Based on Orthogonal Experiment Method

In order to analyze the influence of configuration parameters on dynamic characteristics of machine tools in the working space, the configuration parameters have been suggested based on the orthogonal experiment method. Dynamic analysis of a milling machine, which is newly designed for producing turbine blades, has been conducted by utilizing the modal synthesis method. The finite element model is verified and updated by experimental modal analysis (EMA) of the machine tool. The result gained by modal synthesis method is compared with whole-model finite element method (FEM) result as well. According to the orthogonal experiment method, four configuration parameters of machine tool are considered as four factors for dynamic characteristics. The influence of configuration parameters on the first three natural frequencies is obtained by range analysis. It is pointed out that configuration parameter is the most important factor affecting the fundamental frequency of machine tools, and configuration parameter has less effect on lower-order modes of the system than others. The combination of configuration parameters which makes the fundamental frequency reach the maximum value is provided. Through demonstration, the conclusion can be drawn that the influence of configuration parameters on the natural frequencies of machine tools can be analyzed explicitly by the orthogonal experiment method, which offers a new method for estimating the dynamic characteristics of machine tools.     

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).     

An intelligent control method for a large multi-parameter environmental simulation cabin

The structure and characteristics of a large multi-parameter environmental simulation cabin are introduced.Due to the diffculties of control methods and the easily damaged characteristics,control systems for the large multi-parameter environmental simulation cabin are diffcult to be controlled quickly and accurately with a classical PID algorithm.Considering the dynamic state characteristics of the environmental simulation test chamber,a lumped parameter model of the control system is established to accurately control the multiple parameters of the environmental chamber and a fuzzy control algorithm combined with expert-PID decision is introduced into the temperature,pressure,and rotation speed control systems.Both simulations and experimental results have shown that compared with classical PID control,this fuzzy-expert control method can decrease overshoot as well as enhance the capacity of anti-dynamic disturbance with robustness.It can also resolve the contradiction between rapidity and small overshoot,and is suitable for application in a large multi-parameter environmental simulation cabin control system.     

高超声速电离绕流中电子密度的静电探针测量方法研究

高焓激波风洞是开展高超声速电离绕流研究的重要地面模拟设备。在中科院力学所JF-10高焓风洞上通过新的破膜技术获得了稳定运行的试验状态,利用施加高频扫描电压的静电探针来探索模型边界层内的电子密度测量方法研究。为解决高频扫描时线路由于RC特性所带来的噪音干扰问题,针对测试环境发展了新的探针电路。结果表明：新型探针电路大大降低了线路干扰噪音,能够有效测量模型边界层内的电子密度分布规律。     

燃烧室热力计算的一种新方法

本文根据燃气轮机燃烧室热力计算的“非迭代精确法”原理,推导了使用液体或气体燃料的燃气轮机.蒸气轮机联合循环研究中几种燃烧室热力计算的通用公式,并从两个不同角度,将其与国内常用的“等温焓差法”进行对比分析,揭示了它们之间的内在联系.     

LC4铝合金厚板在复杂应力应变状态下的断裂机制

 <正> 一、引言 把铝合金厚板直接加工成整体构件,用作飞机大梁壁板等结构,是现代飞机设计和制造过程中的一项先进技木。我国目前也在开始进行这方面的研究。由于在整体构件上不可避免地要打孔、开槽或加工有其它形式的截面突变部位,材料实际所承受的应力应变状态比较复杂。为保证这类整体构件的安全可靠及最佳的使用性能,需要对厚板的断裂行为有所了解。因此,本文将在试验室条件下以LC4铝合金厚板在复杂应力应变状态下的断裂机制进行考察。     

显微组织对Al-Mg-Si合金断裂行为的影响

 <正> The hardness, tensile strength and fatigue properties of an Al-Mg-Si alloy were measured in this paper. The microstructures were observed using a transmission electron microscope. The tensile and fatigue fractures were studied by scanning electron microscopy. The results show that the microstructure affects the fracture behavior of the alloy markedly. The alloy exhibits dimpled fracture in UA and OA conditions, and mixed fracture with dimples and intergranular rupture in PA condition. The fatigue cracks were developed with the features of the alloy in UA condition. The cracks were developed with the second stage mode and the striations could be seen on the surface of the fractures for the alloy in PA and OA conditions. But the intergranular fracture and facets could also be seen in the crack initiation area at these conditions.     

DO 28非线性多点模型的建立及其参数估计

 本文建立了DO 28试验机的非线性六自由度多点数学模型。该模型考虑了飞机运动的高度非线性,螺旋桨、机翼、尾翼空气动力特性,改进的推力计算,风场干扰以及飞行试验数据一致性检验和校正。与一点模型相比,该模型能更准确地描述飞机的运动,更适合飞机的参数估计。