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对含单边裂纹的40CrNiMo钢构件进行脉冲放电止裂,分析了脉冲放电止裂后结晶区、相变区和基体区的显微硬度变化.结果可知,止裂后的裂纹尖端变得圆钝,曲率半径增大,应力集中得到消除,有效地阻止了裂纹的继续开裂;结晶区晶粒得到细化,相变区晶格畸变及位错密度增大导致塑性变形抗力增大,两者的显微硬度得到了不同程度的提高.应用Eshelby等效夹杂原理对脉冲放电止裂后单边裂纹尖端发生组织转变的相变应力进行了理论和数值计算,最终获得相变应力的计算方程;采用ANSYS有限元软件对于含单边裂纹构件脉冲放电止裂进行数值模拟,验证体积变化和屈服强度变化对相变应力的影响.最后,简述了含单边裂纹构件脉冲放电止裂技术对于异种材料焊接裂纹的止裂修复工程应用.“,”The pulse current discharge was applied to 40CrNiMo gear steel with unilateral crack for arrest-strengthening effect,and the change of microhardness in crystalline region,transformation area and matrix was analyzed.Result shows that after the discharge,the crack tip becomes blunt,the radius of curvature increases,the stress concentration is eliminated,and the propagation of fracture is effectively prevented;the grain of crystalline region is refined and the plastic deformation resistance of transformation area is improved by lattice distortion and dislocation density increasing,and microhardness of the above two regions increases in different degrees.The transformation stress for the organization transition occurred in the tip of unilateral crack after pulse current discharge was theoretically and numerically calculated by the equivalent inclusion method of Eshelby,and the calculating equation of transformation stresses was obtained.The crack arrest process of pulse current discharge for parts with unilateral crack was simulated by ANSYS,which verified the effect of yield strength change and volume change to transformation stress.Finally,The engineering application of crack arrest by using pulse current discharging to metal component with unilateral cracks was briefly introduced.