The butt welding experiments were carried out using double-pulsed variable polarity gas tungsten arc welding (VP–GTAW) process with 4mm 2219–T87 high strength aluminum alloy as base metal, and ER2319 Al–Cu wire and ER5087 Al–Mg wire as filler wire, respectively. The microstructure and mechanical properties of welded joints were investigated. The results show that double-pulsed VP–GTAW process has benefits on refining grain size and improving mechanical properties. The maximum tensile strength and elongation can be achieved when the frequency of low-frequency pulse frequency is 2Hz. The tensile strength and microhardness of the 2219 aluminum alloy welded joints using Al–Mg wire are superior to that using Al–Cu wire with similar plastic property. The maximum tensile strength is 328MPa, which is 72% of base metal. The microhardness of weld zone is above 100HV. Fracture pattern of all welded joints is mixed fracture of brittle and ductile.

      The SiC fiber reinforced β21S composites (SiCf/β21S) were prepared by foil–fiber–foil (FFF) method. The foils were obtained by cold rolling and annealing treatment, and the fiber cloth was obtained by computer controled filament winding machine. The consolidation process of FFF was calculated by finite element analysis software, and the optimum process parameters were determined. SiCf/β21S composites were prepared under the optimum conditions, the hot isostatic pressing process parameters were 830℃ , 860℃ /120MPa/2h, and then heat treated in vacuum environment at varied temperature for 0h, 9h, 25h, 49h. The microstructure of SiCf/β21S composites and metal matrix were analyzed after the vacuum heat treatment, the microstructure evolution and kinetics of interfacial reaction layer were investigated. The ribbed skinning part of SiCf/β21S composite was fabricated by the combination of foil–fiber–foil method and hot isostatic pressing process. The microstructure and properties of SiCf/β21S composite part were tested and analyzed.

      The fatigue life of the riveted structure greatly depends on the meso-cracks around the hole and the crack expansion. Furthermore, the riveting process parameters have significant effect on the initiation and growth of the mesocracks. It is analyzed that how these parameters affect the mesoscopic quality of the areas around the hole in this paper. There are three parameters used to describe the mesoscopic structure around the hole. Here MR represents the fillet radius of the area where the panel touches the riveting head and rod. MD and Md are both the parameters for the plastic layer thickness around the hole. The effects of some riveting process parameters on the above three characterization parameters for the meso-structure around the hole are researched respectively, including riveting force, riveting process time and upper riveting cavity. This study helps to polish up the quality of the meso-structure through adjusting riveting process parameters, and get further improvements on the fatigue performance of the riveted structure.

      Numerical method can effectively solve the problem of mechanics in engineering practice. According to the basic process of finite element numerical analysis, the numerical research on the composite joints from several aspects is summarized: finite element modeling, load analysis, post-processing analysis. The factors affecting the joining strength of composite materials are reviewed, and some research of finite element method for strength and fatigue life of composite joint under hygrothermal conditions are enumerated. Finally, future research on mechanical problems of composite joint is discussed.

      Uniaxial tensile test was used to test the unidirectional tensile strength of the composite plate with penetrating hole damage and the bolted-repaired joints plate containing the penetrating hole damage, and the bolted-repaired composite plate with the damage of the penetrating hole was evaluated. The effect of repair was analyzed, and the failure load, failure mode, and stress distribution of the bolted-repaired composite plate structure containing the damage of the penetrating hole were analyzed. The test results show that: The typical failure modes of the composite plate with penetrating hole damage and the bolted-repaired composite plate with penetrating hole damage are transverse tensile failures; compared with non penetrating hole damage plate, the recovery rate of tensile strength of the repair plate with penetrating hole damage reaches 44.2%; the strain readings indicate that the patch can be relieve the load at the edge of the damage hole of the plate, thereby increasing the tensile strength of the structure effectively.

      Bolted rabbet joint structure is commonly used in aero-engine, and bolt pre-tightening force is usually dispersed after assembled under the current process technology, which can aggravate the unsteadiness of mechanical properties. This paper analyzes the Von Mises equivalent stress of the joint interface and stiffness of the bolted rabbet joint structure with FEA software ANSYS Workbench. Five levels of bolt pre-tightening force dispersion were set up by engineering experience, then a group of pre-tightening forces were randomly generated for each of the dispersion level to simulate the pre-tightening force in engineering condition. The stress distribution of joint interface, the axial stiffness, the radial stiffness and the torsional stiffness were calculated, and related mathematical relation curves were plotted. Finally, the influence rules of bolt pre-tightening force dispersion on the bolted rabbet joint structure were summarized which can provide a theoretical reference for the control of bolt pre-tightening force dispersion.

      Automatic drilling technology has been widely used in the assembly of aerospace product. With the further application of automatic drilling, the problem of insufficient capacity or model feedback errors occur when the traditional laser normal-leveling methods were used in the complex curved surface structures and intensive fastener arrangements. Aiming at this problem, this paper proposed a contact leveling device and some related process tests and analysis experiments were also conducted. The experimental results indicate that the contact leveling device are still effective to meet the final quality requirements under special conditions.

      In current work, two key techniques in laser fine surface processing—laser cleaning and laser polishing—are introduced in the improvement of material surface quality and performance. On the one hand, laser cleaning technique was used to remove the oxide layer on commercial aluminum alloy (5A06) surface. Results reveal that oxygen content on the laser treated surface is significantly decreased, improving the welding quality and avoiding the formation of porosity in fusion zone. On the other hand, laser polishing process is carried out on the laser-based additive manufactured titanium alloys (TC4 and TC11), showing that as-received Ti-based alloys with surface roughness more than 5μm can be reduced to less than 1μm through laser polishing process. Meanwhile, phase transformation occurs on the laser polished Ti-alloy surfaces, which brings great enhancement of microhardness and wear resistance. Finally, it was furtherly discussed on the composite laser treatment on Ni–Ti shape memory alloy (SMA) surface by combining laser cleaning and polishing technologies.

      The subject discussed the method of generating trajectory line of regular shape and irregular shape space surface. By means of the finite element powerful free meshing technique, the regular meshing of the surface was generated in the CAE environment, and the node position information was extracted to establish the trajectory line. On the basis of the trajectory of the laying track, the theoretical gap of the tubular piece was deduced, and the mechanical model of the roller and the cylindrical mold was simulated by the nonlinear contact finite element method. Get the best rolling pressure and the laying parameters change rule, by adjusting the parameters of the fiber laying to make gap to reach the allowable range, which establishes foundation to improve the quality of fiber laying and accuracy.

     Aerospace monolithic component was composed of different typical characteristics, the research on the machining properties of the monolithic component can be implemented by studying the machining properties of typical structure characteristics, respectively, and then combining characteristics to study the correlation of characteristics. Virtual machining is an important simulation method to study the machining process. In this paper, the machined part, which was made up of typical
features, was constructed in virtual environment. The two high performance machining strategies of high feed milling and high cutting depth milling were applied to machining simulation experiments, respectively. The experimental results show that the main cutting force, cutting power and material removal rate under high feed milling strategy are obviously less than that of high cutting depth milling strategy, and the specific energy consumption of high feed milling strategy has obvious mutation point at the corner characteristic. It is found that the material removal rate of high feed milling strategy has a large deviation from the theoretical value due to the frequently up and down of the feed speed at the corner characteristics.

      In order to improve the quality of the aircraft final assembly, shorten the manufacturing cycle of aircraft assembly, reduce the manufacturing cost, the paper researched the modeling method of aircraft virtual assembly ergonomics simulation and the analysis method of ergonomics simulation, according to the characteristics of the final assembly process. And the ergonomic simulation technology of the aircraft final assembly is applied based on the 3DExperience software.