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To study the influence of multi-factors, such as long sunshine, sand erosion, and so on, in southern Xinjiang, we selected two kinds of composite insulators for the transmission lines in southern Xinjiang to study the aging characteristics of the umbrella skirt surface. The results of scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) show that the surface roughness of the umbrella skirt is high and there are a large number of micron inorganic particles. The skirt has the characteristics of low C/O element ratio and high Al element content. The results of thermogravimetric analysis and micro infrared test show that the aging depth of the Myli Line skirt after 19 years of operation is 160~190 µm and that of Yuhe Line 1 after 14 years of operation is greater than 180 µm. The plasma discharge method was used to simulate the corona discharge in the actual operation to accelerate the aging of the surface of the umbrella skirt and the hydrophobic recovery of the umbrella skirt was investigated. The results show that the temperature has a great influence on the surface hydrophobic recovery performance after plasma treatment. These results may provide some theoretical guidance and technical support for the selection, operation, and maintenance of composite insulators in Xinjiang. [ABSTRACT FROM AUTHOR]

• Corrosion fatigue behavior of SMATed AZ31B magnesium alloy is investigated. • Surface roughness increases and corrosion resistance decreases after SMAT process. • Fatigue resistances of SMAT and as-received samples are compared in NaCl solution. • Beneficial effect of SMAT in NaCl solution is pronounced at higher stress amplitude. • Mechanism of reduced fatigue life in corrosive environment is elucidated. Surface mechanical attrition treatment (SMAT) is considered as an effective technology to influence fatigue and corrosion resistance as these properties are largely related to surface structure and property. Despite the increasing number of studies that report the effects of SMAT on separate fatigue or corrosion behaviors, the impact of SMAT on fatigue property under corrosive environment is left unexplored. In this paper, the corrosion fatigue properties of AZ31B magnesium alloy before and after SMAT process are investigated. Hydrogen evolution tests and potentiodynamic polarization tests are carried out to obtain the corrosion resistance, and it is found that SMAT promotes corrosion rate. The surface roughness of SMATed specimen also increases, which accelerates corrosion rate. In terms of fatigue properties, the fatigue life of SMATed specimen is found to be higher, in both air and 3% NaCl solution. And the larger the size of stainless steel balls used during processing SMAT specimens, the longer the fatigue life. Under 3% NaCl corrosive environment, the beneficial effects induced by SMAT process gradually emerge with increasing stress amplitude during fatigue tests. Reduced fatigue life of SMATed specimen under corrosive environment is attributed to roughened interface between deformed surface layer and bulk material. Nevertheless, the crack initiation sites for SMAT specimens are the same in both air and NaCl solution, all located at the subsurface area. [ABSTRACT FROM AUTHOR]

A gradient nanocrystallined (NC) surface layer was generated on AZ31b magnesium alloy by means of surface mechanical attrition treatment (SMAT). The effects of strain rate and ball size on low cycle fatigue behavior of the SMATed samples were studied under strain-controlled mode. It is found that under the same strain rate, the fatigue life of the SMATed samples is significantly enhanced compared with the coarse-grained (CG) samples, and that the fatigue life of the SMATed samples treated with 3 mm balls is longer than that of those treated with 2 mm balls. The enhanced fatigue life of the SMATed samples is mainly attributed to the combined influences of compressive residual stress and NC surface layer suppressing the initiation of cracks. Meanwhile, for both the SMATed and the CG samples, the fatigue life increases with increasing strain rate, owing to the fact that high strain rate favors twinning activity and restricts dislocation slip, thus enhancing the fatigue crack resistance and prolonging the fatigue life. [ABSTRACT FROM AUTHOR]