含埋藏裂纹构件脉冲放电相变应力分析

对带有圆形埋藏裂纹的40CrNiMo金属构件进行了脉冲放电止裂强化实验。通过对脉冲放电后裂纹尖端的宏观形貌、相变区域与基体区的化学成分及显微硬度进行对比分析,发现相变区的组织得到了细化,其显微硬度得到大幅度提高;应用含有热源的非齐次非稳态热传导方程、相变动力学及等效夹杂等理论推导出了裂尖相变区域的相变应力理论公式。结果表明,裂尖附近相变区域形成了相变压应力,验证了电磁热效应对埋藏裂纹的扩展起到抑制作用。

Analysis on Phase Transformation Stress after Pulse Current Discharging of Metal Component with Buried Crack

The circular buried crack of 40CrNiMo steel was arrested and strengthened by pulse discharging experiments. Comparative analysis with the changes in the macroscopic morphology, chemical composition and microhardness near the crack tip before and after the discharge was performed. Experimental results show that the microstructure and micro-hardness of transformation zone are improved greatly. The theoretical formula of phase transformation stress around crack tip is deduced using transient heat conduction equations, phase transformation kinetics and Eshelby equivalent inclusion. The compressive stress is generated in phase transformation zone, proving that electromagnetic heating effect plays a part in inhibiting crack propagation.