局部随机点蚀下圆管截面极限强度退化规律

针对构件外表面局部区域遭受随机点蚀损伤的圆管截面,考虑点蚀随机特性的影响,建立包含点蚀坑细节的精细有限元模型;在多种腐蚀强度下,研究局部腐蚀的点蚀区分布位置(沿轴向和周向分布位置变化)及其形状(点蚀区长度和宽度独立或联合变化)影响轴压极限强度退化的规律;并比较局部随机点蚀与局部均匀腐蚀引起构件极限强度退化的差异。研究结果表明,尽管局部随机点蚀与最大初始几何缺陷的耦合作用会使极限强度的退化趋于严重,但是总体而言点蚀区分布位置变化对圆管极限强度的退化没有显著的影响。此外,同等腐蚀体积和腐蚀面积下,相比于长窄式局部腐蚀,短宽式局部腐蚀会引起更严重的极限强度退化,在严重腐蚀情形下后者导致的强度退化会高出25.5%;相比于局部均匀腐蚀,局部随机点蚀会导致更剧烈的极限强度退化,其不利影响可高出20.7%。

Degradation law of ultimate strength of tubular sections with random pitting corrosion in local region

Finite element (FE) model of tubular section, locally corroded in the external surface due to random pitting corrosion, was constructed with the detail of individual pit to reflect the random nature of pitting corrosion. Influences of location and shape of corroded region on ultimate strength degradation were studied under variant levels of corrosion intensities. In the numerical models for strength assessment, the location of corroded region altered along the length or hoop direction of tubular section. Whereupon the shape variation was the result of independent or combined change in the length and width of the corroded region. In view of the effects on the reduction of ultimate strength, comparisons were performed between two types of localized corrosion damage such as the localized random pitting and uniform corrosion. The results obtained show that the localized random pitting tends to cause more serious strength degradation when it is located on the region with the maximum initial geometrical imperfection. However, overall, there is no significant difference in the strength degradation due to the location variation of the corroded region. In addition, in the case with the same loss of corroded volume and area, the locally pitted area with a smaller length and a larger width causes a decrease of ultimate strength, larger than that with a larger length and a smaller width, up to 25. 5% for the severe corrosion case. And the localized corrosion in the form of random pitting results in a strength reduction likely up to 20. 7% larger than the uniform one.