应力作用下点蚀损伤发展特点的理论分析

Theoretical Research on the Pitting Damage Growth Characteristics under Stress

根据现场挂片试验下点蚀发展速度规律和应力对腐蚀电流的加速效应,提出了应力作用下点蚀速度和点蚀坑形状变化规律的微分方程,并通过数值方法进行求解。分析发现,应力作用下腐蚀速度更快;点蚀坑的形状受应力影响,通常在垂直于主应力方向上腐蚀更快,可能逐渐形成垂直于主应力的扁平型点蚀坑甚至发展成为裂纹;应力必须要达到一定数值才会对腐蚀速度有明显的影响,对于304不锈钢半球形点蚀损伤,残余应力达到180 MPa就可能引起点蚀坑迅速发展成裂纹。

Based on the law of pitting corrosion development speed and the accelerating effect of stress on corrosion current in the field coupon test,the differential equations of pitting corrosion speed and pit shape change law under stress were proposed and solved by numerical methods.Analysis results indicated that the stress could accelerated the pitting corrosion rate,the shape of pitting pits was affected by stress.Corrosion perpendicular to the principal stress axis was faster than others,pitting pits might gradually form flat pitting pits perpendicular to the principal stress,or even develop into cracks.Moreover,the stress could not have a significant effect on the corrosion rate until increased to a certain value.As for the hemispheric corrosive pits damage of 304 stainless steel,they would change to crack rapidly when the residual stress was greater than 180 MPa.