The edge effect of the electric field in the assembled inertial switch electroforming will disturb the uniform distribution of the power lines between the anode and the cathode. This leads to the problem of poor uniformity of electroforming layer thickness, which prolongates the production cycle. In order to shorten the production cycle of the assembled inertial switch, the megasonic is introduced into the microelectroforming process in this paper. The slider structure has the worst electroforming uniformity in the assembled inertial switch. This paper focuses on how to improve the microelectroforming layer uniformity of the slider structure. Firstly, the current density distribution and layer thickness distribution in the process of electroforming process are simulated by COMSOL finite element analysis software. The simulation results indicate that, compared with the electroforming process without megasonic, the thickness of microstructure obtained by megasonic-assisted electroforming is more uniform. With the increase of megasonic power density, the layer thickness uniformity is better. Secondly, on the basis of simulation, megasonic-assisted electroforming experiment is carried out. Compared with the electroforming process without megasonic, the thickness uniformity of the megasonic-assisted microelectroforming with simultaneous left and right vibration and power density is 2.4 W/cm² is improved by 51.78%. The simulation results are basically consistent with the experimental results. According to the above research results, the assembled inertial switch with the size of 20 mm×20 mm and the height of 900 μm is made by introducing the simultaneous left and right vibration megasonic with the power density of 2.4 W/cm² into the microelectroforming process. The switch meets the design requirement. Compared with the microelectroforming process without megasonic, the manufacturing time of the assembled inertial switch made by megasonic-assisted microelectroforming is reduced by 25%.

In the process of aircraft assembly, it is often necessary to finish the large diameter intersection hole. The large diameter of the intersection hole and the poor manufacturability of the material lead to large cutting force and large vibration during processing, and the initial holes between different lugs is not concentric, which leads to uneven force of the tool and easy deviation, and the complex assembly and hole making operation environment leads to the difficulty of using large processing equipment. At present, the main processing method is to use automatic feed drill for chambering and reaming. The hole making efficiency is low, and there are many kinds of tools used and the cost is high. Helical milling is a new hole making method in the aerospace field. In the processing of large diameter holes in difficult to machine materials, it has better hole making quality and efficiency than the traditional drilling, chambering and reaming processes. Especially in the chambering process, the helical milling tool will not be biased by the initial hole, with obvious advantages. Based on the portable helical milling equipment, the reaming and finishing test of large-diameter intersection holes was carried out, the dimensional accuracy of the machined holes and the surface quality of the hole wall are tested, and the integrity of the hole wall surface is further studied. The results show that the accuracy of hole size is better than ± 0.05 mm, and the hole wall roughness is better than R_a1.6 μm, which verify the feasibility of using the helical milling method to achieve the precision machining of intersection holes for aircraft assembly.

For wire electrical discharge machining (WEDM) with semiconductor characteristics, including superhigh-thickness cutting, ultra-fine wire cutting, metal matrix ceramic composite cutting, etc., a theoretical system of EDM with semiconductor characteristics is proposed. The performance of semiconductor characteristics is that the workpiece, wire or both have non negligible resistance, which cannot be treated as equipotential in traditional WEDM. The machining characteristics of high-speed WEDM with semiconductor characteristics are analyzed, and the reasons for the failure of traditional WEDM servo control methods are explained. A method based on current pulse probability detection with higher identification is proposed to judge the machining status between electrodes. To achieve stable cutting for a long time, different servo control strategies should be employed for the positive and negative traveling direction to adapt to the processing conditions with obvious differences in reciprocating traveling-wire mode.

Moist particle electrolyte electrochemical mechanical polishing (MPE-ECMP) is an emerging technology that has difficulties in obtaining high-surface quality workpieces. In order to solve this problem, the contact characteristics of the workpiece and electrolyte particles were investigated, and the discrete element simulation software Altair EDEM was used to explore the influence of workpiece inclination angle and speed on the number of contacts and contact force. The results show that when the inclination angle is 30°, the contact number between electrolyte particles and the workpiece per unit time is the largest, and the tangential force is the largest, which is 3.38 mN. The tangential force is the smallest at 90°, 1.21 mN. As the rotational speed of the workpiece increases, the number of electrolyte particles in contact with the workpiece per unit of time becomes less, and the normal and tangential forces of electrolyte particles in contact with the workpiece tend to increase. When the polishing potential (vs. Hg/Hg2SO4) is 0.8 V and the workpiece is tilted at 30° for 1 h, the surface roughness is reduced from Sa433.51 nm to Sa22.43 nm, and the surface roughness is reduced by 94.8%. The results demonstrate that the adjustment of workpiece tilt angle and rotational speed can effectively improve the polishing accuracy of MPE-ECMP, the reduction of surface roughness is jointly determined by the number of contacts and contact force, and EDEM can effectively simulate the flow characteristics of electrolyte particle motion, which lays the foundation for further research of MPE-ECMP.

Based on the characteristics of micro electrical discharge machining (EDM), the modular design of control system of micro-EDM has been carried out, and the experimental platform of magnetic field assisted EDM system has been built. The human–computer interactive (HCI) operation interface was developed based on LabWindows/CVI environment. The micro-EDM drilling experiments were conducted to verify the stability of the micro-EDM machine. The experiment of single pulse EDM showed that the discharge duration increases with the increase of magnetic induction intensity. With the increase of magnetic induction intensity, the diameter of the crater and volume of the material removal has increased, the depth of the crater has decreased. The experiment of micro hole machining shows that proper external magnetic field can improve the performance of EDM significantly. When magnetic induction intensity is 0.3 T, the magnetic field can increase the rate of material removal whereas reduce the surface roughness. Material removal rate growth will be more obvious when the volume fraction of SiC_p/Al is larger. Compared with no magnetic field, material removal rate of SiC_p/Al composites with 65% volume fraction increased by up to 96.85%.

The stability of the welding process is an important factor determining the quality of the weld seam, and the welding spatter and weld surface morphology are direct manifestations of the stability of the welding process. In order to obtain a stable aluminum alloy laser–arc hybrid welding (LAHW) process, this study used high-speed photography to count the number of welding spatters and analyze the weld surface forming quality. A comprehensive qualitative evaluation of the stability of the welding process was carried out. Combined with the fundamental principles of laser welding and arc welding, the mechanism of reducing spatter and stabilizing the welding process is discussed. Under the present experiment condition, the welding spatter could be reduced by appropriately increasing the Ar shielding gas flow, arc length, distance between the center of laser beam and wire tip or decreasing the electromagnetic contraction force of the arc. The LAHW spatter suppression mechanisms are that: Firstly, the preheat effect of laser enlarges front welding pool which stabilizes metal transfer; Secondly, the optimized processing keeps reasonable force of arc on molten drop. The stable LAHW process contributes to the success of industrial application.

The laser welding is a high-efficiency joining technique with high energy density, narrow heat affected zone and small workpiece deformation. However, problems still exist in laser welding, such as high cooling speed, cracks, pores, etc. Spatters and pores were effectively inhibited by adding suitable gas or using oscillating laser. The joint defect was reduced and the welding process stability was effectively improved by using arc assisted laser welding. Laser welding assisted by ultrasonic, magnetic and electric fields can improve joint performance by refining grain, reducing element segregation and crack sensitivity. The review on laser welding was summarized from three perspectives, namely process optimization, auxiliary heat source and auxiliary energy field. Finally, problems existing in the research of energy field assisted laser welding were analyzed and its development prospect was forecasted.

The effect of B/Y composite trace addition on the solidification process and microstructure of high temperature titanium alloy was studied. The microstructure evolution process of high temperature titanium alloy at different deformation temperatures is analyzed. The tensile properties at room temperature and 650 ℃ were tested. The results show that the micro-composite addition of B/Y leads to component undercooling during the solidification of high temperature titanium alloys, forming chain-like TiB reinforcing phases wrapped in β grain boundaries and rare earth oxide particles dispersed in the grain boundaries and within the grains. The original β grains are refined, the movement of β grains boundaries is inhibited, and the aspect ratio of the α lamella precipitated in the crystal is reduced. After single step axial deformation at different temperatures, there are inhomogeneous microstructures at different positions of the hightemperature titanium alloy cake blank. The TiB reinforcement phase promotes the spheroidization of the secondary α phase. The results of mechanical properties and the analysis of the tensile properties show that the deformed alloy in the twophase zone has a good strong plastic matching, and the tensile strength of the high temperature titanium alloy at 650 ℃ is significantly improved after the B/Y composite addition.

The shot velocity is the key factor to determine the performance of pre-mixed waterjet. The three-phase simulation model of a mixed jet was constructed by the CFD-DEM bidirectional coupling method. The VOF model was used for a gas-liquid phase and the volume fraction influence of a discrete phase was considered. The shot solid phase was modeled by the discrete element method under Lagrangian coordinates. The two-way coupling was realized through a special coupling interface, and the simulation value of shot velocity in a fixed position range of the exit was obtained. By using the particle image velocity (PIV) test system, the shot velocity at the corresponding position was measured. By comparison, the difference between simulation and testing results was less than 6%, implying correctness of the simulation model. The simulation results show that the larger the nozzle inlet pressure and nozzle outlet diameter, the greater the shot velocity; The larger the mixing ratio (volume fraction of shots), nozzle aspect ratio and nozzle cone angle, the smaller the shot velocity. This provides a theoretical basis for the subsequent formulation of a modification process.

Stack materials composed of carbon fiber reinforced polymer (CFRP) and titanium alloys are widely used in the aerospace field due to their excellent mechanical properties. In order to prolong the tool life, this paper adopted the center blowing, MQL (Minimum quantity lubrication), water-based coolant and liquid nitrogen cooling methods in the lowfrequency vibration assisted drilling experiment of CFRP/titanium alloy stacks to study the effects of these four cooling and lubrication methods on drilling temperature, axial force and tool wear. The results show that the machining temperature is the highest when center blowing is used, and temperature is the lowest when using liquid nitrogen; The thrust force is the largest when using liquid nitrogen, and is the smallest when water-based coolant is used; The tool life is the longest when using water-based coolant, reaching 66 holes, and the worst when using liquid nitrogen cooling, only 12 holes. The main forms of tool wear are adhesion wear and abrasive wear.

At present, the multi-material fusion 3D printing technology has a good application prospect for the development of short-life and low-cost small engines, such as the application of 3D printing functionally graded materials in the typical hot section parts of new-type turbine disk. In order to explore the influence of pore defects generated by 3D printing technology on the burst speed of turbine disk in aero-engine, the burst speed analysis of functionally graded material validation turbine disk was carried out based on the strain-based fracture criteria under the testing uniform temperature field of 500 ℃ and the real temperature field respectively. Our studies mainly focus on the influences of pore defect characterization parameters and related factors, such as porosity, the position of large pores located, the number of large pores, large-pore spacing and the distance between large pore and bursts initiation position on the burst speed of validation turbine disk. The results show that the random distribution of pore defects is not the only consideration for the performance analysis of 3D printed disk. The large pores distributed in the high-strain region (hazard section) will lead to a significant decrease in the burst speed of validation turbine disk, and the defects in the high-strain region, close to the predicted bursts initiation position, should be strictly controlled during 3D printing.

In order to solve the process problem of over-deformation caused by the release and redistribution of residual stress in the material removal process of large thin-walled casting guideway beam, the processing technology of guide beam parts was analyzed to realize the simplification of part model and substructure segmentation. At the same time, the surface residual stress measurement of the part blank was carried out, and the initial stress model of the part blank was successfully established. On this basis, the finite element simulation of part machining is carried out in combination with the actual machining process. The residual stress release caused by material removal during machining is simulated, and the residual stress redistribution law and machining deformation during machining are predicted. Summarize the finite element simulation results of the machining deformation of the parts, and propose a process plan to suppress the machining deformation of the parts. It is verified that the improved process sequence reduces the maximum deformation of the parts from 0.485 mm to 0.081 mm, which is reduced by 83.3%, and avoids the oversize of the parts during processing. At the same time, this plane is used as the benchmark for subsequent processing, which ensures the accuracy of subsequent processing and provides an effective theoretical basis for the optimization of production process.