为了进一步认识机械应力对交联聚乙烯(XLPE)电缆中水树生长的影响,研究了XLPE薄片试样在不同温度下受机械应力作用时的水树生长特征.对XLPE试样采用冷扎孔和热扎孔两种方式制造针孔缺陷,并对试样进行加速水树老化实验.利用偏光显微镜观测未老化试样针孔周围XLPE材料的形态,并通过显微镜观测老化试样中的水树形态.结果表明:热扎孔试样中存在明显倾斜的应力纹,且热扎孔老化试样中存在和应力纹形态相似的倾斜生长的水树枝.基于高聚物在不同温度下的力学响应特性,温度升高时XLPE材料的屈服强度降低,在较小的机械应力作用下发生取向,进而导致倾斜的水树枝出现.
To further understand the influence of mechanical stress on the water tree propagation in XLPE cables, the water tree propagation characteristics in XLPE sheet samples which subjected to mechanical stress at different temperatures were investigated. Pinhole defects were made in XLPE sam-ples by cold-insertion and heat-insertion, respectively. Then the samples were conducted accelerated water tree ageing experiments. The morphology around the pinholes in the unaged XLPE samples was observed by polarizing microscope, and the water trees in the aged samples were observed by microscope. The results show that there are obvious inclined stress strips in the heat-insertion samples, and there are also inclined water tree branches in the heat-insertion aged samples, which are similar to the stress strips. According to the mechanical response characteristics of polymer at different temperatures, the yield strength of the XLPE materials decreases with the increase of temperature, and the XLPE materials ori-ent under the impact of small mechanical stress, which results in the formation of inclined water tree branches.
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