According to the actual size parameters, the finite element model (FEM) of friction stir welding (FSW) was established, and the FEM was updated by experiments. The FSW of the 2A14-T6 high-strength aluminum alloy was simulated under a reasonable welding process parameter range, and the welding process parameters with good simulation effect were determined. The test was carried out under the same parameters, and the axial force of the FSW tool and temperature of the workpiece measuring point were collected. The comparison between the simulated data and the experimental data is reasonable, indicating the correctness of the FEM. The microstructure analysis of the welded joint shows that the grain size in the upper part of the weld nugget was smaller than that in the middle and lower parts, and there are obvious boundaries of grain size in each region of the joint. The hardness of the joint in the upper layer is higher than that in the middle and lower layers, and the minimum Vickers hardness value of the joint appears near the interface between the thermo-mechanically affected zone and the heat-affected zone on both sides of the weld. Tensile testing shows that the strength coefficient of the joint reaches 82.5% under this process parameter, and the sample breaks at the intersection of the material flow during stretching. After analyzing the final mechanical properties of the joint, we found that a degree of aerospace application can be achieved. Under this parameter, the welding test was carried out on the top cover of the rocket fuel tank. Firstly, melon valve welding, which is relatively difficult in welding conditions, was carried out, and a high-quality joint with good surface and no defects was obtained.

The impact phenomena of solid micro-particles have gathered increasing interest across a wide range of fields, including space debris protection and cold-spray additive manufacturing of large, complicated structures. Effective motion monitoring is essential to understanding the impact behaviors of micro-particles. Consequently, a convenient and efficient micro-particle motion monitoring solution is proposed based on continuous single-frame multiple-exposure imaging technology. This method adopts a camera with excellent low-light performance coupled with high-frequency light-emitting diode (LED) flashes to generate short interval illumination. This technology can, in theory, achieve 1 million effective frames per second (fps) and monitor particles as small as 10 microns with speeds up to 12 km/s. The capabilities of the proposed method were validated by a series of micro-particle motion monitoring experiments with different particles sizes and materials under varying camera configurations. The study provides a feasible and economical solution for the velocity measurement and motion monitoring of high-speed micro-particles.

The modal analysis of a satellite sailboard finite element model is carried out to accurately investigate the response of a satellite sailboard in a complex loaded space environment through simulation. The basic excitation vibration test of the satellite sailboard is used to perform model matching and a correlation test. Appropriate design variables are selected through sensitivity analysis. Modal analysis data and vibration table excitation test response data are used to modify the finite element model. After optimization, the orthogonality of the simulated vibration mode and experimental vibration mode is good. The low‐order frequency errors in the simulation model are less than 5%, the high‐order errors are less than 10%, and the modal confidence MAC values are above 0.8. The modal frequency and mode shape are closer to the experimental modal frequency and mode shape, respectively. The simulation and test acceleration response of the modified finite element model of a honeycomb panel are compared under the two conditions of sine sweep and random vibration. The acceleration response curves of reference points are consistent, and amplitude and frequency errors are within acceptable limits. The model updating effect is evident, which provides good reference for research on satellites and other aerospace products.

Angular contact ball bearings are widely used in the multiple rotor system, such as gear box, machine tool spindle, and aero-engine rotors. The support stiffness is very important to the vibration of shafting. In order to obtain the dynamic stiffness, a numerical simulation method for dynamic stiffness of angular contact ball bearings is presented. By means of LS-DYNA software, the displacement and stress curves of the bearing’s different components are obtained successfully, and then, the dynamic stiffness of bearing under certain working conditions also can be calculated. The maximum envelope radius of the inner ring of the measured bearing can be taken as the relative displacement change value of the inner and outer rings of the bearing. To obtain the dynamic stiffness, the test strategy for dynamic stiffness of the angular contact ball bearings is introduced. The experimental results show that the equivalent dynamic stiffness increases with the increase in the preload of measured bearing under certain conditions. The simulation result coincides with the experiments well. The research work can provide the basis for the design and dynamics analysis of the bearing rotor system and have important engineering significance to improve the service performance of angular contact ball bearings.

Referring to the ultrasonic vibration effect on casting, welding and laser cladding, the paper demonstrates the feasibility that it can be also used in Laser Metal Deposition(LMD)of titanium alloy to protect the defects such as crack,pore and oxidation and refine the grain size and improve the distribution uniformity of solidified structure.So the paper applies ultrasonic vibration system to fabricate the functionally graded materials(FGMs) samples and analyses its effect on the specimen microstructure and mechanical property by experiments.The results show that ultrasonic vibration can suppress the formation of pore、refine the grain and make the TiC hard phase more homogeneous in the FGMs parts, which is also indicated by the microhardness tests