中文摘要：

对带有单边裂纹的40GrNiMo金属薄板试件进行了脉冲放电在线止裂实验研究。在超强脉冲电流作用瞬间，单边裂纹尖端熔化、裂尖钝化，曲率半径增加了2～3个数量级，并在裂纹尖端处产生热压应力场，达到了遏制裂纹扩展的目的。止裂前后裂纹前缘的微观组织对比分析发现，止裂后裂尖处组织更加均匀细小，且裂尖处Cr原子数量增加，其他元素与Cr生成更多的合金组织，得到强韧性均高的微观组织，提高了止裂后构件的力学性能。

英文摘要：

The study of crack preventing using pulse current discharge was carried out in 40GrNiMo specimen with edge crack. On the moment of super pulse current discharge, the edge crack tip melt and dulled whose circle radius increased 2-3 quantitative level, the thermabstress field also formed around the crack tip. The goal of crack arrest was achieved. The contrast analysis results of microstructure before and after crack preventing indicates： the microstructure becomes more even and compact and the quantity of Cr atom increases at the crack tip, more alloy structure forms comprised of Cr with other elements. The high strength-toughness microstructure is gained around crack tip after current discharge, the mechanical performance of metal component is improved.