Graphene reinforced resin matrix composites have low density and excellent electromagnetic wave absorption properties, and are highly promising radar stealth absorbing materials. However, traditional graphene absorbing composite materials have complicated processes, making it difficult to prepare and manufacture complex structures. As an artificial electromagnetic medium, metamaterial is designed based on the electromagnetic properties of the material, and can realize the design of high-performance metamaterial absorber (MMA) through the design of unit cell structure, and can achieve the integrated manufacture of resin matrix MMA functional structure, taking advantages of rapid prototyping for complex structural parts using 3D printing technology. The research progress of the absorbing properties of graphene reinforced resin matrix composites and 3D printing metamaterials is emphasized. A 3D printed graphene reinforced polylactic acid composite gradient metamaterial absorbing structure based on wood pile structure is proposed. In the 4.5–40GHz band, this structure has an ultra broadband microwave absorption performance of 35.5GHz (reflection loss below –10dB).
The development level of aviation precision manufacture technology has already become one of the important signs to weigh the comprehensive strength and the development of science and technology of the country. With the fast development of mechanical processing, electronics and electrics, automatic control and information techniques, the aviation precision manufacture technology, which is on the basis of these techniques, has made an unprecedented leap forward, new technologies, new processes and new products have been emerging. At the same time, with the increase of precision and performance in techniques and products, the demands for precision measurement of key parameters are growing. However, for devices in aviation manufacturing, many requirements cannot be met by the traditional measuring methods. The laser feedback effect is a phenomenon where the laser emitted from the laser is reflected or scattered by the surfaces of the targets and returns back into the laser cavity, modulating the intensity, polarization state, and the phase of the laser. In the precision measurement field, the laser feedback effect has the advantage as high sensitivity, which can measure noncooperative targets such as black, rough, cylindrical, micro or liquid targets; compact structure and easy alignment; high resolution and traceability to the laser wavelength. By using the laser feedback effect, precision measurement of aviation product can be carried out, realizing the precision locating and monitoring of real time working condition, which plays an irreplaceable role in improving the precision of aviation manufacturing and promoting the development of the industry.
The projection position of tube axis should be calculated accurately when the tube axis is measured using stereo vision. Previous methods for measuring tube axis approximate the centerlines of image contours as the axis projection. This assumption exists errors. In order to obtain the exact projection position of tube axis and to improve the measurement precision of tube axis, the proposed method studied the imaging characteristics of tubes. Firstly, a perspective projection model for any cross section of tube was established to explore the geometric relationship between the contour points of the cross section and their corresponding projection points on space axis. Furthermore, a way to locate the precise projected position on image planes of points laying on axis was presented. A binocular vision system was constructed to measure an aerospace tube. Compared with classical approaches, the repeatability accuracy of the proposed method is same as the former, while the measurement accuracy of the presented method increased by 14.5% on average due to precisely calculating the projection position of axis. It is shown that the proposed method is correct in calculating the projection position of tube axis and can effectively improve the measurement precision of tube axis.
Aiming at the high precision machining for weak rigid parts of aircraft, the digital measure technologies including collaborative calibration for robot milling system, edge extracting and reverse modeling of skins, and positioning correction of end-effector were developed. Based on the above measure of edge machining allowance and on-line correction of machining process, the measurement error of skin edge was 0.1mm and end-effector positioning error was no more than 0.2mm for skin, cover and panel of aircraft. The digital collaborative measure in this paper meets the requirements of digital measurement for advanced aircraft manufacture, improves level of automatization and digitization for skin and panel milling of aircraft, and accelerates the progress from handwork assembly to intelligent assembly.
Aiming at the assembly rework and repair problems caused by the poor assembly precision in assembly process of large aircraft fuselage components, the quality control technology for key assembly procedure of aircraft based on preassembly precision analysis is proposed. Firstly, the actual coordinate information of key control characteristic points (KCCPs) of components or in-process assembly parts is preprocessed, including coordinate system transformation, data compensation, data integration and format conversion. Then, according to the assembly process and measured data, an assembly procedure precision model based on measured data is established to perform the pre-assembly precision analysis. Finally, taking the fuselage panel assembly as an example, the laser tracker is used to obtain the measured information of the three-dimensional coordinates of KCCPs, and the processed data are used as the input deviation of the assembly precision prediction model for preassembly precision analysis, so as to realize the quality control of the fuselage panel.
Digital detection technology is an important guarantee for modern aircraft digital manufacturing. At present, laser tracker is the main digital measurement system widely used in the aviation manufacturing industry, and the iGPS measurement system is a new large-size space measurement system. This paper focuses on Hanzhong Aircraft Branch, AVIC Aircraft Co., Ltd. using two kinds of digital measurement system for the process of comparative testing and engineering verification, at the same time, conducts a preliminary analysis of both measurement systems by comparing the results. It is concluded that the iGPS measurement system has some advantages over the laser tracker, but the networking accuracy and measuring accuracy are slightly lower, which is restricted by the number of engineering launchers and product structure, and the layout of the digital assembly system, and the measurement accuracy will be further affected. iGPS is more suitable for the digital measurement environment, where the accuracy of measurement is relatively low, the range of measurement is large, and the efficiency of measurement is required to some extent.
Bolt connection is widely applied in aerospace structures. The bolted state of the structure is directly related to the safety and functionality of the equipment. The aircraft is faced with a variety of extreme environments such as vibration and impact in service, which will eventually lead to the phenomena of loose and slip of the bolted joints. Therefore, it is of great significance to monitor the connection state of the structure. This paper mainly reviews the research status and testing principle of bolt connection state testing technology. Firstly, the research status of bolted state mechanism is analyzed, which mainly includes the theory of joint surface microscopic characteristics and the theory of structural nonlinear dynamics. Then, the traditional direct measurement techniques of the bolted state are introduced, and its measurement accuracy and application limitation are analyzed. Finally, the principles of various types of the bolted state testing technologies based on response signals are reviewed, including vibration signal analysis method, electromechanical impedance method, acoustic elastic effect method, ultrasonic energy method and FBG sensor method. Their advantages, disadvantages and application range of the method are analyzed and the development direction is pointed out.
Graphene-reinforced 7075 aluminum alloy composites with different contents of graphene were prepared by spark plasma sintering (SPS). The structure and mechanical properties of the composites were investigated. Testing results showed that the hardness, compressive strength, and yield strength of the composites were improved with the addition of 1.0% graphene. A clean, strong interface was formed between graphene and the metal matrix via metallurgical bonding on the atomic scale. Harmful aluminum carbide (Al4C3) was not formed during SPS processing. Further addition of graphene (3.0%–5.0%) deteriorated the mechanical properties of the composites. The agglomeration of graphene plates was exacerbated with increasing graphene content, which was the main reason for this deterioration.
Double–wires+arc additive manufacturing (D–WAAM) system for Al–Mg–Si alloy using hybrid pulsedvariable polarity gas tungsten arc welding (HPVP–GTAW) process was established. When two different alloying wires (Al–5Mg + Al–5Si) were used, ternary (Al–Mg–Si) alloys with various compositions can be obtained by adjusting the wire feed speed of the two wires. Mechanical properties of the as-deposited and heat treatment Al–Mg–Si alloys were investigated. Microstructures of Al–Mg–Si deposits are mainly composed of columnar and equiaxed dendrite grains with non-uniform distribution characteristics. Mechanical properties of the as-deposited and heat treatment Al–Mg–Si alloys were investigated. Experimental results show that with the increase of the Mg/Si ratio, tensile properties of the as-deposited alloy increased, which were also nearly isotropic along the two directions. After heat treatment, tensile property of some specimens increased a lot but too much plasticity was loosed.
Contactless power transmission system is an important part of rotary ultrasonic processing system. The widely used fully coupled power transmission system obstructs automatic tool changing because of the interference of the structure. To solve this problem, a partially coupled contactless power transmission system was developed. Firstly, a partially coupled contactless power transmission model was established, which facilitates the design of the primary and secondary coil and their coil parameters. The electrical compensation of partially coupled contactless power transmission was studied in order to improve the efficiency of power transmission. Circuit compensation topology was designed based on a rotary ultrasonic machining system using giant magnetostrictive material. The effectiveness of partially coupled power transmission and its compensation was verified by experiments. The research shows that there is more magnetic leakage between the primary and secondary core for partially coupled system, and its power transmission efficiency and the vibration amplitude are slightly lower than that of the fully coupled power transmission system. With proper electrical compensation, the partially coupled power transmission can fully meet the requirements of the ultrasonic machining. For the GMM rotary ultrasonic machining system, the single-sided series compensation method can simplify the design of the system and ensure high power transmission capacity.
Machine parts in aircraft parts on the proportion gradually increased. The machining allowance of the traditional derivation method of blank size, shape part is partly insufficient or too large, resulting in scrap and waste phenomenon of rough machining. In this case, a optimization technology of parts based on laser scanning optimization design of blank is proposed, through fitting the blank point cloud and CAD model, machining allowance on each processing surface of blank parts is solved. Then the key point of the technology is studied. The machinability evaluation and optimization design of blank parts is completed combined with the part of a certain type of aircraft, and related applications have achieved good economic benefits.
