电磁热效应止裂效果与电流通路尺寸关系的研究

RESEARCH ON RELATIONSHIP OF CRACK ARRESTING EFFECT USING ELECTROMAGNETIC HEAT EFFECT WITH DIMENSION OF CURRENT PATH

从理论、试验和数值模拟三方面研究利用电磁热效应技术对具有单边裂纹的导体进行止裂时 ,由于裂纹尺寸不同使得导体中电流通路尺寸不同 ,从而导致裂纹尖端的温度场、温度梯度场分布状态的不同。理论分析、试验研究和数值模拟结果均表明 :由于电流产生的焦耳热源的作用 ,能够在裂纹尖端处很小的范围内熔化形成焊口 ,遏制裂纹的扩展 ;导体中裂纹的长度 (即导体中电流通路尺寸 )是影响裂纹尖端温度场和温度梯度场的主要因素。

The technique of crack arresting is badly in need of current industry production and practice application. The preventing for a current conductor with a crack by the heat effect of the electromagnetic field is an effective method to extend its service life, to improve its security and reliability. The experiment study, theoretical analysis and numerical calculation are proposed for researching the different distribution of the temperature field and temperature gradient field near the crack tip in edge crack preventing inside a current carrying plate by electromagnetic heat effect under the different dimension of current path. Complex function is applied in theoretical analysis and the thermal electrical coupled theory applied in numerical simulation. Meanwhile, crack arresting experiments are also conducted by using a super density pulse current generator (model ZL 1) developed by authors. Theoretical analysis, experiment surveys and numerical calculations show that due to the heat concentration effect around the crack tip, small welded joints are formed by metal melting. The curvature of the crack tip will be increased by some orders of magnitude instantly and the stress concentration will be decreased remarkably. The superfine microcosmic structure was found around crack tip, so that the intensity, ductility and wearing capacity around crack tip have been promoted under the influence of superfine structure. Micro crack will be prevented and the spreading of the crack be arrested too. The dimension of current path is one of the main factors that effect the distribution of temperature field and temperature gradient field of crack tip.