Additive manufacturing is an effective way to solve the manufacturing problems of aeronautical complex structural parts. Firstly, the principle and characteristics of additive manufacturing technology and its application in aeronautical field are introduced. Furthermore, the challenges faced by additive manufacturing technology in terms of material mechanical properties and surface quality are discussed deeply. Moreover, it is pointed out that additive and subtractive hybrid manufacturing and advanced finishing technology are effective approaches to the improvement in surface quality and accuracy of aeronautical complex structural parts. The advantages of abrasive flow machining with high processing accessibility in the precision polishing of aeronautical complex structural parts are highlighted, and important researches of maintaining the precision of parts while improving the surface quality are recommended.

    Micron-scale surface accuracy and nano-scale surface roughness, as well as the processing interference, path limitation, tool wear, and inefficiency caused by their surface structure, restrict the application of complex surface optical components seriously. In order to solve it, the ultra-precision grinding of the typical complex surface optical components was investigated systematically. A variety of on-machine precision truing for diamond grinding wheels was proposed, and the corresponding ultra-precision grinding technologies were presented. As the results, the single crystal silicon aspheric surface with the roughness R_a of less than 5nm, the form accuracy PV of less than 527nm/140mm; the sapphire conformal window with the form accuracy PV of less than 2.5μm/50mm; the binderless tungsten carbide micro-structured surface with the roughness R_a of less than 70nm was obtained by ultra-precision grinding.

    Investment casting has been used in the aerospace military equipment, civil aviation and commercial aerospace area during the industrial development. In this paper, its research and development status in superalloy, titanium alloy, aluminum alloy and magnesium alloy were discussed in detail, and the research results of BIAM in recent years were mainly introduced. Different process characteristics among the investment technology and additive manufacturing, semi-solid forming, injection molding and other new process technologies were analyzed, meanwhile the development direction and research hotspots in the future were expected.

    A high speed and small volume pneumatic polishing device was designed in order to solve the problem that using large volume and low speed of motorized spindle in traditional grinding. The bearing’s load capacity is analyzed by theoretical calculation, and the simulation model of the device is established by the finite element analysis (FEA) software. The static and dynamic characteristics of the device, such as stiffness, natural frequency and critical speed, are analyzed and checked. On this basis, the polishing experiment was carried out with flexible resin grinding tools, and the polishing characteristics of the device were preliminarily studied. The surface roughness of the workpiece is reduced to Ra1.395μm after polishing. The results show that the device can be used for high precision polishing.

    To explore the relationship between cutting force, vibration and surface roughness is of great significance to predict surface roughness. In this paper, the 64 all-factor experiments of milling 45 steel were conducted with the control variable method of three factors and four levels of cutting speed v, feed per tooth f_z and cutting depth a_p. The main cutting force, axial force, radial force and vibration were measured on line, and the corresponding average value, standard deviation and RMS values of cutting force were obtained. At the same time, the two-dimensional surface roughness R_a, three-dimensional roughness average S_a and RMS S_q were measured off-line. Then five distribution functions such as Normal distribution, Exponential distribution, Gamma distribution, Weibull distribution and Cauchy distribution were used to fit the sample data. The optimal distribution function was determined by AIC criteria, and the unknown parameters were estimated by maximum likelihood method. The five Copula functions such as Gaussian Copula, t-Copula, Frank Copula, Gumbel Copula, and Clayton Copula were used to fit the related structural forms between milling force, vibration, and roughness, and the optimal Copula function was selected according to the AIC criteria and the parameters are determined. Deriving from the optimal Copula function, the Kendall rank correlation coefficient τ was chosen as the evaluation index to analyze and compared the overall relativity between milling force and surface roughness. A mixed Copula function was constructed to analyze the tail correlation between milling force and surface roughness.

    The uniformity of material removal of aspheric polishing process using bonnet is studied in this paper. The influence of rotational velocity of bonnet and workpiece on distribution of material removal is analyzed according to Preston Law and a series of fix polishing experiments are conducted. Accordingly, a uniform material removal method is proposed by modifying contact time and optimizing feed rate of polishing bonnet. The quartz aspheric polishing experiment shows that form error keeps stable and the high-frequency of PSD decreases dramatically. It means that the method proposed in this paper leads to material removal in a uniform way.

    The bolt connection is the main way of mechanical connections for aero-engine. The traditional torque method causes a large pre-tightening error, which reduces the connection quality to some extent. Therefore, the key connection structure of an engine low-pressure turbine disk and shaft is taken as subject, which is combined with the traditional torque method and the advanced angle method. For the first time, in the domestic engine assembly, the “torque control + angle monitoring” method is applied, and the intelligent tightening system is developed. Taking use of high precision of the pre-tightening force by angle method, when the torque is accurately applied, the rotation angle of nut is monitored to adjust to ensuring the precise control and the uniformity of the joint rigidity, and the structural connection quality of the engine is improved, which is going to provide technical means for subsequent process co-design of engine and solutions to engine assembly inconsistencies.

    The linear friction welding (LFW) experiment of solid-solution strengthening Ni-base superalloy GH3044 was carried out. Microstructural examination of the joint showed that both in the weld zone (WZ) and thermomechanically affected zone (TMAZ) the grains are refined significantly and the streamlines are formed due to the rearrangement of carbides. The tensile strength of the joint is comparable to that of the base metal (BM). The EBSD results show that the joint microstructure undergoes mainly discontinuous dynamic recrystallization during LFW, accompanying with a part of continuous dynamic recrystallization and static recrystallization. As a consequence, the low-angle grain boundaries (LAGBs) increase sharply while the twin grain boundaries decrease drastically in the joint. The TMAZ has more LAGBs than WZ, because strong microtexture forms in the TMAZ while more sufficient recrystallization occurs in the WZ.

    The tool wear is serious in the process of machining difficult-to-machine materials. The tool wear will directly lead to the change of milling force. Therefore, a milling force model considering the flank wear of ball end milling cutter is proposed. In this model, the milling force is decomposed into shear force produced by the shear effect of the rake face, and the friction force and pressure of the flank surface. Taking the axial position angle of the cutting edge of the micro element as the parameter, the milling force model considering the wear of the flank surface is established, and think that the axial milling force of the cutter is not affected by the friction effect. Finally, the cutting tool wear experiment and milling force experiment show that the experimental results are consistent with the predicted results, and verify the correctness of the milling force model is verified. It provides effective guidance for optimizing the technological process and improving the surface quality.

    In order to improve the load capacity of spindle support and enhance the working performance of precision machine tool, the hydrostatic spherical gas bearing was chosen as the research object. The bearings were set up in different forms of latitudinal or longitudinal grooves. The axial load capacity of bearings with radial and axial eccentricity was researched by CFD theory. The relationship between axial load capacity and geometric dimensions of latitudinal and longitudinal grooves was analyzed. It is found that the latitudinal grooves can homogenize the gas pressure in bearing clearance and slow down the speed of pressure reduction to improve axial bearing capacity. Through the pressure homogenization and dynamic pressure effect, the longitudinal grooves can increase the pressure of gas film flow field and improve the load capacity and stiffness of bearing. The axial load capacity of hydrostatic spherical gas bearing is greatly influenced by the width of latitudinal grooves and the depth of longitudinal grooves. Increasing the width of latitudinal grooves or the depth of longitudinal grooves can improve the axial load capacity faster in a certain range. It would provide reference for application of gas bearing in heavy load situations to research the influence of forms and geometric dimensions of the latitudinal and longitudinal grooves on the axial load capacity.