In this paper, a stepped copper microcolumn array was fabricated based on the micro-electroforming process of THB–151N photoresist. In order to solve the problem of difficult development of 20 μm micro-blind hole and film retention at the bottom during THB–151N photoresist development, a submerged bidirectional megasonic assisted development method was proposed. The influence of megasonic power density and aspect ratio of micro-blind hole on mass transfer process of developer was simulated. The megasonic power density and aspect ratio of micro-blind hole were optimized, and the megasonic assisted development was studied experimentally. At the same time, aiming at the poor verticality of sidewall of the micro-blind hole due to inappropriate exposure dose of THB–151N film，the effect of exposure dose on the verticality of sidewall of the micro-blind hole was discussed by lithography experiment，the empirical equation of preferred exposure dose and film thickness was fitted. On the basis of the above technological methods and experimental study, 4×6 stepped copper microcolumn arrays with a height of 300 μm, overall aspect ratio of 15∶1 and minimum side length of 20 μm were fabricated.
Titanium alloy sheet products are widely used in aviation, aerospace, marine, shipbuilding and other national defense fields. The manufacturing technology of titanium alloy sheet is still not fully matured though it has been continuously broken through and improved over the years. In this paper, the status of titanium alloy sheet manufacturing technology is summarized. The rolling process of sheet metal is introduced, the progress and problems are analyzed emphatically. The rolling technology and microstructure characteristics of different titanium alloys (α titanium alloy, α + β titanium alloy and β titanium alloy) are compared by reviewing the process of cold rolling and pack ply-rolling. The key process and common problems in the rolling process of titanium alloy sheet are clarified and specific solutions are put forward. Finally, the research focus and development direction of titanium alloy sheet rolling technology in China are prospected.
As the engine technology of the third industrial revolution, selective laser melting (SLM) has broken through the manufacturing limit of traditional processing technology and provided the possibility for the structural design and manufacturing of high-performance components in aerospace, medical, automotive and other fields. Lattice structure has been widely used in various disciplines due to its high specific strength, high specific stiffness, low coefficient of thermal expansion and high specific surface area. Based on SLM technology, combined with the innovative manufacturing mode of material-structure-performance integration, lattice structure has become an effective solution for lightweight, highperformance and multi-functional design and manufacturing proposed by multidisciplinary fields at this stage. In this paper, the types of SLM-manufactured lattice structure, process synergy and design optimization methods are introduced in detail. The mechanical properties and energy absorption capacity of the lattice structure are analyzed; The applications of several typical functional lattice structures in aerospace, medical and automotive fields are described, and their future development in engineering applications is prospected.
During selective electron beam melting (SEBM) process, powder particles are negatively charged by the electron beam causing coulombic interactions, which is easy to cause the powder scattering and smoking phenomenon. This phenomena can lead to problems such as electron gun discharge, unstable beam current, uneven powder spreading, etc., which in turn will cause process instability and stop processing. In order to expand the application scope of SEBM process, based on the interaction characteristics between the electron beam and the powder, the mechanism and factors for the formation of powder smoking were analysed and summarised in terms of powder characteristics and process parameters. Based on the ways to reduce the electrostatic force between powders, from which measures to prevent powder smoking were summarised, further directions for basic research on powder smoking in SEBM were described. This is to provide a reference for the long-term work stability, reliability improvement and quality enhancement of SEBM.
Friction stir additive manufacturing (FSAM) as a novel solid-state additive manufacturing technology, can be effectively utilized to fabricate high-performance components without evaporating the elements of aluminum – lithium alloy. Self-constrained friction stir additive manufacturing was proposed to prepare the multi-layered structural components made of aluminum – lithium alloy strips. The results show that the well interlayer metallurgical bonding was obtained due to the sufficient material flow. The grain sizes and distribution of the precipitates in each additive manufactured layer were primarily influenced by thermal-mechanical effects. Those layers worked by less stirring pass showed more precipitates and higher microhardness, attributed to less thermal-mechanical effects. The additive manufacturing thickness of single layer is 1 mm, and the additive manufacturing rate is 200 mm/min. The microhardness reached 126.8HV (79.3% of 2195–T8 aluminum-lithium alloy). The corrosion resistance of the additive manufacturing zone was better than that of the base materials due to the solid solution of Cu elements.
Based on different additive manufacturing building directions, four groups of Ti–6A1–4V primitivecubic (PC) lattice samples fabricated by selective laser melting (SLM) with various relative densities were investigated for the effects of the building directions on the mechanical properties of the lattice structures. The mechanical properties were obtained by numerical simulations and uniaxial compression tests, and the microscopic morphology of the samples defects was analyzed. The results show that the manufacturing defects caused by different building directions will change the effective Young's modulus in different directions and failure mode of the lattice structure. The specimens with low relative densities collapsed layer by layer randomly, and the high-density lattice structures collapsed by the diagonal shear failure. The lattice structure strut defects caused by SLM increased with the increase of the angle between building direction and the struts, and the defects lead a decrease in effective Young's modulus. The manufacturing defects of the low-density lattice structures were more sensitive to the building direction, and due to the internal defects of additive manufacturing, the simulation results based on the homogenization theory are higher than the experimental values.
Environmental barrier coating (EBC) is a surface protection layer established between the service environment and the engine material to prevent or reduce the environmental erosion of the engine. Mullite is regarded as an important material for environmental barrier coating due to its good high temperature resistance, chemical compatibility， oxidation resistance and thermal conductivity. The preparation process of nanostructured mullite feedstock was studied, and the purpose was to prepare nanostructured feedstock with good sphericity, smooth surface, good fluidity and high density. This paper uses nano Al2O3 and nano SiO2 as raw materials, and uses spray drying and solid phase sintering methods to prepare nanostructured mullite feedstock. The microstructure and morphology of feedstock at different heat treatment temperatures were studied by means of X-ray diffractometer and scanning electron microscopy. The experimental results show that the sphericity of solid-phase sintering at 1300 ℃ + 150 min is consistent with the sphericity of the feedstock obtained by spray drying, and the surface is relatively smooth, with fewer defects, the particle size of the feedstock is about 60 μm, and the grain is nano structure.
The material of satellite rocket connecting belt is TB2 titanium alloy, which has strict requirements on surface quality. A novel method of electrochemical – electrochemical mechanical polishing of TB2 titanium alloy was proposed, the thickness of adhesive layer of TiCl4 near workpiece surface is controlled by mechanical action. A tool with consolidated abrasive was designed and a electrochemical mechanical polishing system was established. Experiments were carried out to investigate the effects of different combination modes of electrochemical polishing and electrochemical mechanical polishing on surface quality, and the influences of typical process parameters such as voltage, tool rotation speed and feed rate on surface quality. Finally, under the conditions of machining voltage 25 V, tool rotation speed 100 r/min and tool feed speed 30 mm/min, a smooth surface with surface roughness Ra0.031 μm and Sa0.082 μm was obtained after alternating electropolishing and electrochemical mechanical polishing for 15 times. The continuous polishing of TB2 titanium alloy sheet parts was realized.
In the assembly process of complex products based on augmented reality, the location of augmented reality equipment is the core of the real-time integration of virtual guidance information and assembly site. The traditional positioning method based on label or pre-built offline assembly matrix model has the problems of low compatibility between assembly task and visual positioning, and poor robustness and stability of single visual positioning. The fusion of vision and inertial measurement unit (IMU) can improve the positioning accuracy and robustness, and effectively improve the assembly quality and efficiency of complex products. In this paper, a positioning algorithm based on the fusion of binocular vision and IMU is proposed. This algorithm extracts image features through point and line features. The binocular camera and IMU are jointly calibrated, and the point and line features are extracted and matched by ORB and LSD line end fusion. The pose error fusion model of visual-inertial fusion based on point and line features is established by means of tight coupling of vision and IMU. By comparing the experiments of VINS-Fusion, PL-VIO algorithms and IPL-VIO algorithm improved in this paper, the absolute displacement and rotation error of the IPL-VIO algorithm in structured scene is smaller than that of the original algorithm, and the structured scene information is more abundant, which can be applied in AR assembly field with weak texture, and provide stable and reliable pose data for augmented reality assembly platform.
The connection of aircraft structural parts is mainly mechanical connection. The position accuracy and surface quality of the connection holes are important to the service life and safety of the aircraft. The intelligence, automation, and flexibility of hole-making equipment directly affects the quality, efficiency, and the cost of aircraft manufacturing. However, the domestic research and application of automated hole-making equipment is still at a relatively early stage and has not been put into use on a large scale. Therefore, the development of such equipment is of great significance and a crawling hole-making robot was developed, and the motion of the developed crawling hole-making robot was calculated and analyzed using the spin method. First, calculate the degree of freedom of the crawling holemaking robot’s posture adjustment and correction movement, and then solve the robot’s posture adjustment and correction movement, and analyze the movement characteristics of the robot during the movement, laying the foundation for the future control system design.
As a typical difficult-to-machine material, beryllium material is mainly processed by turning, but beryllium material is harder and more brittle, which often has local fractures and sharp edge chipping defects; Cutting force is an important factor that affects tool wear and processing quality, predicting the cutting force of turning beryllium materials is of great significance to the selection of cutting parameters. Based on the semi-empirical prediction formula of mechanical analysis, this paper establishes a thermal-mechanical coupling-based cutting force prediction model for beryllium turning, and conducted experimental verification. The result shows that the predicted value of the model fits well with the experimental value, and the overall error is 10.79%, the error range is 2.96% – 20.53%. The change mechanism of tool wear and surface roughness under different cutting parameters is analyzed, which provides a certain theoretical reference for beryllium turning processing.
