圆钢管截面极限强度受随机分布点蚀的影响研究

提出一种随机分布点蚀损伤的模拟方法,模拟点蚀在构件表面的随机生长过程,并建立了随机态点蚀损伤圆管截面的有限元分析模型;设计了三个受不同腐蚀深度点蚀损伤的圆管构件,并开展轴压试验,利用试验结果校验有限元模型的计算精度;在多种腐蚀情形下(点蚀强度和腐蚀深度变化),研究点蚀分布模式变化引起的极限强度退化及其变异性;比较随机分布点蚀模型与传统腐蚀模型(规则分布点蚀和均匀腐蚀)在计算强度和结构失效行为方面的差异。研究结果表明,点蚀的随机分布模式会引起显著的极限强度变异,且蚀坑深度越大,强度变异越大,蚀坑分布造成的强度极差与强度均值相比达到5%;随机分布点蚀相比于传统腐蚀模型,除了引起更为严重的强度削减,还会改变结构的破坏模式。提出的随机点蚀损伤的模拟方法,可替代昂贵的构件试验,应用于评估点蚀损伤圆管截面的极限强度,增强评估结果的可靠性。

Study on impact of randomly distributed pitting on ultimate strength of steel tubular sections

This paper presents a numerical method to simulate random pitting corrosion, focusing on the process where pitting randomly initiates and grows on the surface of steel tubular section. Finite element (FE) models of the tubular sections with random pitting corrosion were constructed in terms of the validation of computing accuracy on the FE models against compressive loading tests of three tubular members with artificial pitting corrosion. The reduction of ultimate strength and strength variation were studied under various corrosion scenarios accounting for the changes in pitting intensity and pit depth. This was followed by the exploration into the disparities in calculated strength and failure behavior between diverse corrosion models such as the random pitting, regular pitting and general corrosion. The simulated results show that the random pitting distribution results in a remarkable variation of ultimate strength, and the deeper the pit depth, the larger the strength variation, with an xmax-xmin about 5% of the mean strength. Compared with the existing corrosion models such as the regular pitting and general corrosion, the random pitting corrosion leads to the transition of failure mode besides a larger reduction of ultimate strength. The proposed method to simulate the random pitting corrosion proved to be able to take the place of the expensive experiments, and to assess the ultimate strength of the tubular member with random pitting damage, improving the reliability of the assessment results.