The uniaxial tensile test, linear expansion coefficient test of a modified epoxy resin in the ambient temperature range from -35℃ to 120℃, and the impact test at room temperature were carried out to explore its mechanical and thermal characteristics under temperature change environment. The constitutive model of the material suitable for temperature change environment is deduced, the numerical calculation is carried out in MATLAB, compared with the relative tested curve, and the obtained constitutive model is applied to the modeling calculation in ABAQUS and the results are verified. The results show that the modified epoxy resin has better strength, stiffness, impact toughness and lower coefficient of linear expansion than common epoxy resins such as E-44, E-51 and EPON e863. The material is suitable to be used as the matrix of spaceborne electronic component potting module. The proposed empirical constitutive model can obtain the stress-strain relationship of the material at any temperature in the range of -35℃~120℃ through interpolation, and can be directly used in relevant damage analysis and life prediction of electronic component potting module. The research method and derivation results have engineering reference value.
Due to the wind resistance which acts on the main reflector of large rotary mesh antenna, the correct balancing result of satellite antenna is difficult to be gotten in the ground dynamic balancing test. In order to solve this problem, the dynamic balance method of large rotary mesh antenna which is under the influence of wind resistance in both low pressure environment and standard atmospheric pressure environment on the ground is studied. Based on the theoretical analysis and the experimental data of two-dimensional flow around circular cylinder, a new method of the large rotary mesh antenna wind resistance calculation is proposed, according to the CFD analysis of the three dimensional flow field. Through the dynamic equivalent method, the distributed wind resistance acted on the main reflector of the mesh antenna in the rotating state is equivalent to the principal vector and principal moment of the action point in each quadrant, and then transformed into the eccentric mass on the distribution plane. It provides a feasible and innovative way to estimate the influence of wind resistance on the dynamic balance accuracy of large mesh antenna, so as to compensate the wind resistance effect. Combined with the ground dynamic balancing requirements of a certain type of satellite mesh antenna, the whole finite element model of the mesh antenna is established, the simulation of ground dynamic balancing test is carried out, and the influence of wind resistance on the ground dynamic balancing results of the antenna is analyzed in this study, which provides important data for compensating the influence of wind resistance and ensuring the on-orbit balancing accuracy of the antenna.
The CeO2 catalyst is commonly utilized in diesel particulate filter (DPF) to promote soot regeneration. It is necessary to give a particular attention to the performance of hydrothermal aging and the effect on DPF regeneration characteristics. Based on the fixed-bed test bench, the gas and particle emission characteristics of carbon black oxidation following hydrothermal aging and sieving treatment of CeO2 are investigated under a 3% water concentration condition. CeO2 is subjected to characterization and analysis combined with X-ray Photoelectron Spectroscopy (XPS), Electron Spin Resonance Spectroscopy (ESR), and Scanning Electron Microscopy (SEM). The results indicate that the addition of fresh CeO2 proves beneficial in improving the oxidation efficiency (η) of carbon black, reducing CO emission and the total average particle number (PN). Meanwhile, CO2 emission rapidly increases. After hydrothermal aging, the average particle size and agglomeration degree of CeO2 increase, resulting in an increase in lattice defects and bulk oxygen vacancies. The reduction of surface oxygen vacancies plays a dominant role in the catalytic oxidation process of carbon black, leading to a decrease in η and CO2 emission, while CO increase; And the contact mode between CeO2 and Printex-U (PU), as well as alterations in the microstructure of CeO2, consequently contributing to hindering particle movement and reducing total PN. Furthermore, the sieving treatment of catalyst increase particle emission, but significantly promote the η and reduce harmful gas CO. This research establishes a theoretical and experimental foundation for enhancing the hydrothermal stability of catalysts and controlling particle emission at the DPF outlet.
The ratcheting effect of the liner wall structure in the thrust chamber of liquid rocket engine under cyclic load is studied, and its service life is predicted. Firstly, the 3-D heat transfer analysis of the wall of the thrust chamber is carried out while explaining the mechanism of its "dog room" failure. Based on the results of the heat transfer analysis, the stress-strain evolution of the structure under cyclic load is analyzed by nonlinear plane strain finite element method. According to the finite element analysis results, the ratcheting effect of the liner wall structure is described and the ratcheting damage is calculated. The low cycle fatigue damage is calculated by using modified Morrow model, and the creep damage is also calculated using Norton model. Finally, the total damage of thrust chamber liner wall is calculated by using Miner linear cumulative damage law and the thermomechanical fatigue life of the structure is estimated. The result shows that the middle point of the lower surface of the liner wall will fail first, and the calculated service life is 33 times, which is good agreement with its actual service life. In the total damage of the weak point, ratcheting damage, creep damage and low cycle fatigue damage account for 52%, 32% and 16% respectively, indicating that the ratcheting effect is the main reason for the failure of the thrust chamber structure. The research results of this paper provide important engineering reference for the structural optimization design and rapid life prediction of regenerative cooling thrust chamber of liquid rocket engine and the future reusable aerospace power.
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