点蚀孔腐蚀钢构件力学性能劣化简化分析方法

Simplified analytical method of mechanical property degradation for steel members with pitting corrosion

点蚀是一种局部和剧烈的腐蚀形态,导致钢结构构件力学性能退化,突然之间发生事故,对结构整体造成安全隐患.本文针对具有点蚀孔腐蚀特征的钢构件,提出一种通过等效弹性模量定量评价其力学性能劣化程度的简化分析方法.依据周期喷雾复合试验数据,以锈蚀率和最大点蚀深度为基础,对点蚀孔深度、直径及分布情况作出适当假定;考虑涂层寿命的影响,以锈蚀率相等为原则建立人工加速腐蚀试验和海洋大气条件下Q235钢构件腐蚀情况的转换关系.建立考虑点蚀影响的有限元构件模型,通过轴向均布力作用下的构件变形确定海洋大气环境不同暴露时间下点蚀构件的等效弹性模量,提出点蚀构件力学性能劣化分析的实用计算方法.数值算例验证了上述采用等效弹性模量分析腐蚀构件受力性能方法的正确性;计算结果表明,在相同锈蚀率条件下,点蚀构件的等效弹性模量低于均匀腐蚀构件.

Pitting corrosion is a local and severe form of corrosion, resulting in degradation of the mechanical properties for structural members and security risks for the whole structures caused by sudden accident. A simplified analytical method for the quantitative evaluation of the mechanical properties of steel members with pitting corrosion resistance was proposed by equivalent elastic modulus. Based on experimental data, an analytical method was proposed to calculate the mechanical properties of members with pitting corrosion. In this method, some assumptions about the pitting depth, diameter and distribution were put forward. Considering the influence of the coating life, the relationship of corrosion status between in laboratory and in ocean atmosphere was established according to the same corrosion rate. Based on axial compression FEM model, the equivalent elastic modulus of structural members with pitting corrosion was obtained. Through curve fitting, practical method was proposed to obtain the mechanical properties of members in ocean atmosphere. A numerical example demonstrated the validity of the proposed method using equivalent elastic modulus to analyze the mechanical properties of pitting corrosion members. The calculated results indicate that, with the same corrosion rate, the equivalent elastic modulus of pitting corrosion members is lower than that of uniform corrosion members.