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The dynamic mechanical properties of metallic materials have been extensively investigated at the macro-scale in terms of deformation mechanisms, strain rate strengthening, and fracture mechanisms. However, the dynamic mechanical properties affected by size effects at micro/meso-scales have rarely been investigated. To explore the size effects on the dynamic mechanical properties at micro/meso-scales, the experiments of quasi-static compression and SHPB were carried out using oxygen-free, high-conductivity (OFHC) copper with different geometrical and grain sizes. The experimental results show that the quasi-static and dynamic mechanical properties of OFHC copper are affected by size effects at micro/meso-scales. In particular, OFHC copper exhibits strain rate strengthening effects at the micro/meso-scales, and the presence of micro-cracks was observed in the SHPB experimental specimens. The J-C constitutive model based on the surface layer model is proposed and the analysis of the average relative error of the modified model and the original constitutive model is performed. Finite element analysis was carried out based on the modified J-C model and the original model, and the results show that the modified J-C model was in good agreement with the experimental results.

The research on pollution flashover characteristics of insulators under low air pressure is of great engineering application value and scientific significance for carrying out altitude correction research and formulating relevant standards in the field of external insulation of power transmission and Transformation Engineering in ultra-high altitude areas. It provides an important reference for the construction of power transmission projects and railway project in high altitude areas. AC pollution flashover tests of QBG-25/16 and QBG-25/20 insulators at high altitude and low air pressure were carried out in a large-scale multi-function artificial climate chamber. The results show that when the altitude is 1000m∼5500m and the salt density is 0.1∼0.15mg/cm2, the pollution flashover voltage of insulators decreases with the decrease of air pressure, and the pollution flashover voltage of insulators decreases with the increase of salt density; the flashover voltage of insulators with different insulator structures is affected differently by air pressure; the characteristic index n of air pressure decreases with the increase of pollution degree, and the characteristic index n of air pressure also decreases Affected by insulator type.

Accurate analysis of the resin filling process into the mold cavity is necessary for the high-precision fabrication of moth-eye nanostructure using the ultraviolet nanoimprint lithography (UV-NIL) technique. In this research, a computational fluid dynamics (CFD) simulation model was proposed to reveal resin filling behavior, in which the effect of boundary slip was considered. By comparison with the experimental results, a good consistency was found, indicating that the simulation model could be used to analyze the resin filling behavior. Based on the proposed model, the effects of process parameters on resin filling behavior were analyzed, including resin viscosity, inlet velocity and resin thickness. It was found that the inlet velocity showed a more significant effect on filling height than the resin viscosity and thickness. Besides, the effects of boundary conditions on resin filling behavior were investigated, and it was found the boundary slip had a significant influence on resin filling behavior, and excellent filling results were obtained with a larger slip velocity on the mold side. This research could provide guidance for a more comprehensive understanding of the resin filling behavior during UV-NIL of subwavelength moth-eye nanostructure.