飞机钣金特征自动化建模技术研究

为了实现飞机钣金工艺几何特征的自动化设计,对传统的飞机钣金特征建模方法进行了研究,提出了飞机钣金特征自动化建模技术,基于知识与特征设计,开发了飞机钣金特征自动化建模系统,实现了钣金几何特征的快速自动生成,提高了飞机设计效率。     

Training of the maintenance personnel to prevent failures in aircraft systems

The aircraft maintenance process plays a vital role in aviation safety. The quality of the maintenance process and the qualifications of the aircraft maintenance personnel are important factors in the safety of aircraft.In this study the aircraft maintenance training model has been developed by especially taking in to account the EASA Part 66 regulations. The progression of the aircraft maintenance personnel training was investigated and suggestions to improve training process were given so as to prevent failures in aircraft systems.     

Systematic synthesis of R-L and C-D immittances using single CCIII

We present a systematic approach to the synthesis of R–L (resistor–inductor) and C–D (capacitor–frequency-dependent negative resistance) configurations by using a single third-generation current conveyor (CCIII) and a minimum number of passive elements. All the simulated immittance values can be orthogonally adjusted, there are no requirements for any certain element matching or cancellation constraints. The test filter circuits, constructed with the derived R–L immittances, are used to verify the theory by HSPICE simulations. The simulation results corroborating all our theoretical predictions are incorporated in the work. This methodology can be extended to the immittance synthesis based on different active elements.     

Hydraulic System Component Storage with Military Hydraulic Fluids

In the military aerospace community, most hydraulic fluid pumps and components are currently being stored in rust inhibited fluids containing barium dinonylnaphthalene sulfonate (BSN). Fluids containing barium are hazardous waste after use, with expensive disposal, and have caused operational problems in aircraft hydraulic systems including helicopters and fighter aircraft. In this program, bearings and pistons were stored in jars containing both operational hydraulic fluids (MIL-PRF-83282, MIL-PRF-87257, and MIL-PRF-5606) and rust-inhibited hydraulic fluids containing BSN (MIL-PRF-46170 and MIL-PRF-6083). In addition, hydraulic pumps were filled with MIL-PRF-83282, MIL-PRF-87257, and MIL-PRF-46170. Hydraulic pumps were not filled with MIL-PRF-5606 or MIL-PRF-6083 because these hydraulic fluids are being phased out of military aerospace applications as operational and storage fluids, respectively. Jars, containing bearings and pistons, as well as hydraulic pumps, were stored for up to three years in a laboratory environment to determine if operational fluids would protect them from rusting during storage. After each year, the bearings, pistons, and pumps were inspected for corrosion. At the end of three years of storage, pumps were endurance tested using fresh operational fluid, MIL-PRF-83282. The bearings, pistons, and pumps showed no rusting for the duration of storage with either operational or storage fluids. The pumps stored with the operational fluids, MIL-PRF-83282 and MIL-PRF-87257, were in better condition than the pump stored with the rust-inhibited fluid. The operational hydraulic fluids, MIL-PRF-83282 and MIL-PRF-87257, provided excellent protection against rusting during storage.

     

现代飞机数字化设计制造流程

讨论了飞机数字化设计制造的工作模式及流程,为实现产品设计、工装设计和工艺设计过程的并行和协同夯实基础,并在工作内容、参与人员、工作手段和结果形式等方面与传统的飞机研制过程进行详细对比分析。基于并行和协同工作方法,使得原来概念和初步设计、详细设计、工艺审查和图纸发放、工艺准备、生产准备、产品制造等流程变为现在的并行产品设计和产品制造2环节。提出飞机产品设计制造项目管理精益化理念,并在某型现代飞机的研制过程得到应用,实践证明生产效率明显提高。     

飞机发动机尾喷口调节片断口的电子显微分析

利用扫描电子显微镜及附带的能谱分析仪对飞机发动机尾喷口调节片断口进行了微观分析研究。结果表明:调节片边缘的损伤特征以磨损为主,而中部则以接触疲劳为主,疲劳裂纹易在微动区产生。根据上述结果讨论了促使疲劳裂纹萌生的因素,即循环应力和摩擦力引起材料表层塑性变形,以及磨损破坏了材料表面的完整性,造成裂纹尖端应力集中效应。     

Numerical investigation of a crash test of a composite helicopter subfloor structure

Composite energy-absorbing aircraft structures are being studied within a European Commission research programme (CRASURV – Design for Crash Survivability). One of the aims of the project is to evaluate the current capabilities of crashworthiness simulation codes for modelling future composite primary structures. In this paper, a detailed analysis is presented of a generic module of a composite helicopter subfloor structure, subjected to crash loading. The analysis is performed with the explicit finite element code PAM-CRASH and is compared with the results of a drop test. It has been found that pre-test simulations with only coupon data as input are capable of providing a reasonable overall representation, but to closely match the behaviour of the test, a significant amount of post-test work is required. The calibration of the post-failure material properties proved to be more crucial than the behaviour up to initial failure. The representation of fabric materials was found to be inadequate and a new fabric material model is under development as a result. The importance of modelling frictional effects was highlighted, and a mesh density study showed the model to be robust over a range of mesh densities.     

航空发动机磨损在线监测的能谱数据处理方法研究

对用于航空发动机磨损在线监测的能谱数据处理方法进行了研究。介绍了基于同位素Ｘ射线荧光法的滑油磨损在线监测系统的组成及工作原理,通过对所获得能谱数据进行平滑、剥谱、寻峰、峰净面积计算、浓度插值计算等处理,就可以实现杂质浓度的自动检测。文中担子一种函数拟合寻峰方法,实现结果表明,这种方法具有算法简单、运算速度快等优点,特别适合于在线监测的能谱数据处理。     

An investigation of the repetitive failure in an aircraft engine cylinder head

Cylinder head (CH) failures in aircraft piston engine may have serious or fatal consequences to the safety of the crew and the aircraft. Moreover, when failure becomes undoubtedly repetitive and critical resulting in loss of aircraft, destruction of properties, and first and foremost loss of human lives, the cause of the failure requires to be investigated using a scientific approach. Therefore, the aim of this study is to investigate and identify the root cause of a repetitive premature failure in an aircraft engine CH.The piston engine of the training aircraft Utva-75 has malfunctioned during the flight due to the cracking of its aluminum cast CH. It has been the second engine failure of this type of aircraft due to the cracking in the CH in a very short span of time. From the visual examination of the mating fracture surfaces, it has been possible to observe typical beach and ratchet marks indicating the occurrence of fatigue failure. The crack has initiated from multiple origins located on the inner flange fillet on the exhaust side of the CH. Further examinations by using scanning electron microscopy as well as energy dispersive spectroscopy and metallography have shown that the fatigue had promoted from pre-existing material defect due to a high concentration of shrinkage pores at the initiation crack site and can be most likely associated with the manufacturing process of casting. The stress analysis of the cylinder assembly, carried out by means of finite element analysis, has also confirmed that the crack origin was located at the most stressed area of the cylinder assembly i.e. on the inner flange fillet of the exhaust side of the CH.This case study, together with the other recently reported, has definitely confirmed the repetitive and therefore systematic problems with the CH of air cooled, horizontally opposed, aircraft piston engines.     

Experimental evaluation of fault diagnosis in a skew-configured UAV sensor system

This paper presents an experimental evaluation of a hybrid fault detection and isolation scheme against three successive faults in skew-configured inertial sensors of an unmanned aerial vehicle (UAV). An additional small and low-cost inertial measurement unit is installed with a skewed angle to a primary inertial measurement unit. A parity space method and an in-lane monitoring method are combined to increase system tolerance to the occurrence of multiple successive faults during flight. The first and second faults are detected and isolated by the parity space method. The third fault is detected by the parity space method and isolated by the in-lane monitoring method based on the discrete wavelet transform. Hardware in-the-loop tests and flight experiments with a fixed-wing UAV are performed to verify the performance of the proposed fault diagnosis scheme.