腐蚀疲劳过程中裂尖阳极溶解对裂纹扩展的作用

在模拟腐蚀疲劳裂尖介质中,分别用铂丝和40CrNiMo钢为辅助电极测定了在不同拉伸速率下中温回火的40CrNiMo钢的腐蚀电流密度i_(a)与应变速率、塑性应变量的关系,其结果为:利用疲劳裂纹尖端应变的弹塑性有限元计算,得到腐蚀疲劳裂尖阳极溶解引起的裂纹扩展与△K的关系,结果表明:中温回火的40CrNiMo钢在3.5％NaCl水容液中裂尖阳极溶解对腐蚀疲劳裂纹扩展的直接贡很小,阳极溶解的主要作用是影响为裂尖断裂区氢致开裂提供氢原子的阴极过程。

THE EFFECT OF ANODIC DISSOLUTION AT CRACK TIP ON CRACK GROWTH CORROSION FATIGUE

The relationship between corrosion current density (i_a)and strain rate ((?)) as well as plastic strain (ε_p) was measured for 40CrNiMo steel tempered at moderate temperature in the simulated medium of corrosion fatigue tip by employing Pt-wire and 40CrNiMo steel respectively as auxiliary electrode under various tensile rates. The result of which is shown as following: i_a=K_1·(?)_e~A+K_2·(?)~B[1-exp(-ε_p] The analysis of elasto-plastic finite element to the strain at fatigue crack tip was carried out in order to obtain the relationship of crack growth rate induced by anodic dissolution at crack tip of corrosion fatigue with △K. The result showed that the direct contribution of anodic dissolution at crack tip to the crack growth of corrosion fatigue in 3.5% NaCl aqueous solution was very little for 40CrNiMo steel, the major effect of anodic dissolution was to affect the cathodic process at crack tip which supplies hydrogen atoms for hydrogen induced cracking in the fracture process zone of corrosion fatigue.