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测量了A537钢在恒ΔK控制下单次拉伸超载对腐蚀疲劳裂纹扩展的影响,研究了阴极极化及自腐蚀条件下材料在3.5％NaCl水溶液中的超载延迟扩展规律与特点。结果表明:单次拉伸超载裂纹扩展延迟效应的作用距离大于塑性区尺寸。空气中与阴极极化条件下,超载后裂纹扩展过程由超载扩展、减速扩展与恢复三阶段组成,而自腐蚀条件下只有减速扩展与恢复两个阶段。与空气中的结果相比,阴极极化与自腐蚀条件下的裂纹扩展延迟幅度与延迟距离均明显减小。分析表明,塑性诱发裂纹闭合在腐蚀条件下的变化是造成超载后裂纹扩展规律变化的主要原因之一。
The influence of single tensile overload on the fatigue crack growth of A537 steel under constant ΔK control was measured. The law of delayed propagation of the material in 3.5% NaCl aqueous solution under cathodic polarization and self-corrosion was studied. The results show that the effect of the delayed extension of the single tensile overload crack is larger than that of the plastic zone. Under the condition of air and cathodic polarization, the crack propagation process after overloading consists of three stages of overload expansion, deceleration, expansion and recovery. However, under the condition of self-corrosion, there are only two stages of deceleration expansion and recovery. Compared with the results in air, the crack growth retardance and the retardation distance under cathodic polarization and self-corrosive conditions both decrease obviously. The analysis shows that the change of plastic-induced crack closure under corrosion conditions is one of the main reasons for the change of crack propagation law after overload.