As a new solid state additive manufacturing technology, friction stir additive manufacturing is developed based on friction stir welding. For the re-stirring and re-heating phenomena in friction stir additive manufacturing, both experimental and numerical methods are used for analysis. Monte Carlo method is used to calculate the microstructural evolutions. The precipitate distributions are calculated by the developed precipitate evolution model. The hardness distributions on different additive manufactured layers are then calculated. Experimental data is compared to show the validities of the numerical models. Results indicate that different grain sizes and morphologies can be found due to the existences of restirring and re-heating. The variations of particle numbers and mean radii of precipitates on different layers, caused by different temperature histories, can lead to the different mechanical properties. The mechanism for the generation of different mechanical properties in different layers are explained by numerical simulations in combination with experimental validation.

    4D printing is a kind of additive manufacturing which uses 3D printing to make the printed structure have the function of responding to external stimulus, shape changing or performance changing. The processes of 4D printing technology, such as 4D printing based on shape memory materials, 4D printing based on biomimetic composite structures and 4D printing based on field-driven smart structures, are summarized. The problems of existing 4D printing technology, such as discontinuous deformation process, difficult to prepare and difficult to realize controllable deformation, are analyzed. The 4D printing strategy for composites with continuous fibers reinforced is proposed, and the 4D printing of arbitrary deployable surface structure is realized by controlling the deformation of composites. Finally, the potential applications of 4D printing technology in aerospace, bio-medicine and soft robots are analyzed.

    Metamaterial structure has important scientific research value and extensive application prospect in military stealth and camouflage, communication, security and medical imaging owing to the ability of manipulating the phase and propagation mode of electromagnetic wave and acoustic wave precisely. The research is one of the hotspots in the field of international academic and engineering. Generally speaking, the research on metamaterial structure in the world has greatly promoted its development of lightness, broadband, high performance and practicality. However, the interdisciplinary research of manufacturing technology and electromagnetics, acoustics, physics, materials and other disciplines should be further focused. It is necessary to accelerate the exploration of the way of manufacturing metamaterial structure in a large scale, and promote its rapid development towards application. In this paper, the application status of additive manufacturing technology in manufacturing metamaterial structure is summarized, and the research progress of metamaterial structure functional devices is discussed. We also discuss and prospect the future development trend about metamaterial structure.

    Micro-and Nano-scale 3D printing is a new frontier in additive manufacturing. It has been used in various fields including the aerospace industry, tissue engineering, MEMS, new materials (metamaterials, lightweight materials, smart materials, composite materials), new energy, flexible electronics, printed electronics, micro/nano optical devices, soft-body robots, etc. This paper presents a novel micro-and nano-scale 3D printing developed by our research group which is named the electric-field-driven jet deposition based micro-and nano-scale 3D printing technique. The recent progresses and significant results of this technique are described. In addition, five typical cases are introduced. The electric-field-driven jet deposition based micro-and nano-scale 3D printing provides a new and prospect solution for micro-nano scale 3D printing and micro-and nano manufacturing, and shows a high potential in industrial applications.

    Selective electron beam melting technique (SEBM) is a kind of metal additive manufacturing technique using electron beam as heat source, can form high–performance metal parts with complex shapes. It has been widely applied in aerospace industrial, biomedical application, automobile manufacturing and other fields. The basic principle of selective electron beam melting technique is briefly introduced, the microstructure and properties of different materials produced by selective electron beam melting technique are reviewed, and the numerical simulation methods of SEBM process and the application of SEBM technique are also summarized in this paper. Finally, some problems to be solved in forming quality of selective electron beam melting technique are pointed out and its development trend is forecasted.

    The 4043 aluminum alloy thin–wall was manufactured by arc additive manufacturing (AM) process with forced water cooling constraint, and the macro–appearance and microstructure of AM specimens were studied. The results revealed that the verticality of the sample and the surface forming precision were improved. The average grain size decreased from 25μm to 12μm when the water cooling constraint was used, and the grain size was obviously refined. When the water cooling constraint device was applied, the 4043 aluminum alloy lateral wall was directly in contact with the restraint device, and the heat quickly dissipated. Therefore, the columnar grain grew in a certain angle. The hardness decreased from the bottom to the top of the AM specimen, and the average value of hardness increased from 48HV without restriction to 58HV. The horizontal grain distribution was cellular grain on both sides, central region was columnar grain, and the hardness of central region was lower than that of both sides.

    A multi-track finite element model was developed to simulate melt pool contours and the temperature field during selective laser melting (SLM) of 316L stainless steel powder under different scanning strategies. Considering, the thermophysical properties changes with temperature and the influence of latent heat of phase. The simulated temperature field was compared with experimental measurements results. Furthermore, the presented results established a correlation between the scanning path and the microstructure of SLM specimens. The simulation results showed that as the scanning tracks increase, the maximum temperature of melt pool rises slightly. The molten pool contains a large number of columnar crystals that grow vertically along the direction of the maximum temperature gradient. In addition, microscopic defects are more likely to occur at the junction between scanning islands, where the heat and stress are concentrated. Besides, the scanning strategy affects the microstructure and microhardness of SLM parts, and the part under the spiral strategy had finer grains and higher Vicker hardness than that formed under spiral-island strategy.

    Nickle-based powder superalloy FGH96 is regarded as one of ideal choices for the high-property turbine disk in an aero engine. In this paper, the FGH96 was laser melting deposited in four different scanning modes respectively. The purpose of this research is mainly to find out the effects of different scanning modes on microstructure, mechanical properties during laser deposited process. The results are shown as followed. The microstructure morphology of deposited layers is mainly epitaxially grown columnar crystal. Cracks are found in parallel scanning modes while none in zig-zag scanning mode. The main phases in samples are solid solutions, Laves phase and carbides. Sample made by parallel zig-zag mode with the same direction between layers has larger microhardness and the average is 389.3HV0.2. Its tensile strength is 1065.29MPa and the elongation is 28.17%. It has excellent mechanical properties and the fracture features of ductile fracture.

    In view of the characteristics of weak rigidity and easy deformation of parts during aircraft assembly process, an optimization method based on genetic algorithm for the clamping scheme of the weak rigid thin-walled parts of the aircraft is proposed. The objective of this method is to minimize the maximum deformation of thin-walled components caused by gravity external loads. A synchronous optimization model of clamping layout and clamping sequence is established. The maximum deformation of the thin-walled components under the clamping scheme is obtained through finite element simulation, and the optimization model is solved by genetic algorithm and finite element batch technology. Finally, taking the typical aircraft part long truss as an example, the feasibility and effectiveness of the method are verified.

     The high-frequency and high-precision machine tool motion axis location information can be used to fit the machining trajectory of the machine tool accurately, which is the foundation of dynamic error monitoring and dynamic machining accuracy evaluation. Aiming at the problem of acquiring high-frequency and high-precision machine tool motion axis location information, a method of high-frequency high-precision real-time acquisition for the motion axis of five-axis machine tool was put forward. This method based on gathering and analyzing the signal of the CNC servo system position loop for getting the high-frequency original position information. And then, compensate the linear errors and using homogeneous coordinates transformation which considers the rotary errors after the high-frequency original position information was transformed to coordinate values. The acquisition method was verified on a DMU 80P five-axis machine tool with Sinumerik 840Dsl system. The test indicates a conclusion that five-axis synchronous acquisition frequency reaches 1kHz, compared with the precision of the static location, linear axis acquisition precision reaches ±2μm and rotary axis acquisition precision reaches ±0.0025°.

    A high-aspect-ratio copper microchannel cooling device for radar was fabricated on metallic substrate based on the electrochemical deposition technique. In view of the problem of non-uniform thickness in making thick film with high-viscosity SU–8 photoresist, lapping and polishing techniques were applied to the unexposed SU–8 film to improve the thickness uniformity and the dimension error caused by air gap was also reduced. A novel method to measure the thickness of unexposed SU–8 film using refractive index was proposed and the refractive index of SU–8 photoresist at yellow sodium light was obtained by least square method. In order to overcome the failure in making high-aspect-ratio SU–8 film due to inappropriate exposure dose, the effect of exposure dose on the quality of the film was discussed by lithography experiment and the optimal parameter was 640mJ/cm2. SU–8 film with good quality was acquired and a copper microchannel cooling device was fabricated based on the above techniques and experiment. The width is 50μm, the height is over 250μm and the aspect ratio is over 5.