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选用合格多股的铜包铝导线和劣质的单股铜包铝导线制备一次、二次短路熔痕和火烧熔痕,以金相法为基础,采用常用的三种浸蚀剂研究该种导线熔痕的浸蚀方法,观察每种熔痕的金相组织晶粒和气孔特征。分析发现:HF浸蚀剂浸蚀效果最好,一次短路熔痕、二次短路熔痕和火烧熔痕的金相组织呈现出了有别于铜、铝导线熔痕的特征。区别于铜包铝导线二次短路熔痕,一次短路熔痕的金相组织最显著的特征是晶粒以细小的胞状晶、柱状晶为主,且组织中气孔数量相对较少。二次短路熔痕多数晶粒为粗大的胞状晶和柱状晶,存在大气孔,且分割晶界。与铜、铝导线火烧熔痕不同,铜包铝导线火烧熔痕的晶粒不以等轴晶为主。 相似文献
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通过对火灾中铜导线熔痕的组织结构进行X射线衍射仪分析,找出了铜导线一次短路熔痕、二次短路熔痕、火烧熔痕在物相组成、晶面取向和晶格畸变等参数的特征规律,建立了铜导线熔痕组织特征的技术鉴定方法,为火灾物证鉴定提供定量技术依据。 相似文献
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模拟火灾现场形式,利用火灾痕迹物证综合试验台,制备多股铜导线的一次短路熔痕,设计自然冷却、水激冷却等不同冷却环境,通过金相显微镜观察其金相组织,同时,进行10次同条件实验,进行横向比较,判断金相显微组织呈现出来的稳定性,利用IPP图像分析软件,对实验采集结果进行定量分析,归纳金相组织的量化指标.实验结果表明,火灾现场电器元件短路时间、火场温度、导线冷却方式均可对多股铜导线的一次短路所形成的短路熔痕金相显微组织的微观形态产生一定影响.通过横向比较分析实验数据,进行数学建模归纳运算,排除干扰因素条件,得到的多组实验数据的金相显微组织形态具有极其一致的相似性和稳定性. 相似文献
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Composite panel stability can easily be improved by using vertical male beads. In this paper, new methods of stabilizing techniques used for the panels, webs and ribs of composite structures are studied. A parametric study is performed to assess the effects of important design considerations such as, bead length, number of beads, bead radius, bead depth and bead spacing on the initial buckling load of the panels. The results show that, there is an optimum bead spacing for each panel containing more than one bead which can be estimated using a simple equation. Integration of vertical beads with a length of less than 0.5 times the panel's length has no significant effect on the buckling load. There are no significant changes on the buckling loads of the beaded panels with bead depths greater than 0.6 times the bead radius. In this investigation, the instability of the nose and main ribs of a light airplane wing structure made of woven E-glass material and stiffened by P.V.C foam core and vertical male beads are also studied using experimental methods. The experimental results show that we can easily improve the buckling capability of the panels and webs by using vertical male beads instead of sandwiched construction. It is estimated that this would cause a weight reduction of about 50% and a manufacturing time reduction of about 50%. 相似文献
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以TiO2-BaO—SiO2-Al2O3系统的玻璃作为高折射率玻璃微珠的材料,研究了玻璃的组成对玻璃折射率的影响,玻璃的性能和成珠工艺对微珠的性能影响。通过对微珠的回归反射特性进行分析,指出了微珠的应用前景。 相似文献
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通过添加Cu(NO3)2溶液的方式,在中压压敏电阻基础料中引入杂质元素Cu,测试其电性能并分析影响机理。得出:Cu元素在压敏电阻中无论哪种固溶形式,都是以受主态方式对压敏电阻的性能产生影响;随着Cu掺入量的增加,施主浓度Nd减小,但同时也引起晶界界面电子态密度Ns的减少,补偿了施主浓度的减少,从而使φB减少,非线性系数减小;随着Cu掺入量的增加,晶粒电阻增大,晶界电阻减小,使电压梯度上升,漏电流几乎不变,电容增大,残压比增大,通流能力和耗散能量能力变差;对比基料来讲,添加Cu元素之后漏电流是下降的;建议在生产过程中,Cu掺入量(质量分数)最好不要超过8×10-6,最大不要超过20×10-6。 相似文献
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通过保护电器在预期短路电流作用下,在约定时间内切断TN系统单相接地短路故障时,导体温升值的计算与分析发现:可以采用绝缘导体允许最高工作温度,作为短路时电阻的计算温度;通过保护线因为热稳定问题殃及相线绝缘的分析发现:保护线线芯最小截面应不小于相线截面的0.7倍。 相似文献
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The Ni(2+) accumulation in batch mode from diluted solutions by gel beads of gellan gum (GG), alginate, kappa-carrageenan, agar, agarose, silica gel, polyacrylamide and two mixtures of GG+agar was investigated. All polymeric materials studied accumulated Ni(2+), but gel beads of GG were stable, easily obtainable and showed the highest Ni(2+) accumulation. The pH of the Ni(2+) solution was not critical for Ni(2+) accumulation. Accumulation of metals Cu(2+), Co(2+), Ni(2+), Pb(2+), Cd(2+) and Zn(2+) by GG gel beads reached the equilibrium after 24h. The removal of Pb(2+) and Cu(2+) from the aqueous solution was very efficient, with maximum metal uptake (q(max)) of 0.85 and 0.75 mmol/g dw GG, respectively. The general q(max) sequence was Pb>Cu>Ni approximately Zn=Co>Cd. In an equimolar metal mixture sorption experiment a clear reduction in accumulation was observed, except for Pb(2+) (30%). Heavy metals were desorbed with 100mM sodium citrate. 相似文献
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近年来国内输配电线路引发森林草原火灾风险越来越高。为探究低压架空裸导线引发火灾的特性和机理,本文搭建了380/220 V低压架空裸导线模拟实验平台,开展了树枝短接线路实验、两相线路相间接触短路实验,并对线路穿越林区与树木接近处经常出现短路熔痕的现象进行了实验和仿真分析。结果表明:正常树枝和雨水浸湿后的树枝短接线路,不会发生放电打火现象,也无温升和泄漏电流产生。两相线路相间接触短路,放电产生的喷溅熔珠掉落至地面温度较低,不足以引燃地面的可燃物。结合近年低压线路火灾原因调查结果分析,线路过流保护开关对低压线路引发的火灾有显著预防作用。线路穿越林区与树木接近处的短路熔痕,可能为大风大雨天气下树枝短接线路放电产生。所做研究可为低压线路火灾原因调查和防范提供技术参考。 相似文献