海洋大气环境下桥梁钢结构持力腐蚀机理及多尺度多物理场模拟方法

Corrosion of bridge steel structures in marine atmospheric environment is affected by both global and local environment conditions as well as the mechanical states of their components, thus corrosion of steel structures is a coupling effect at macroscopic scale and mesoscopic scale. However, most current researches on corrosion of bridge steel structures still focused on single scale level, and no recognized multi-scale simulation theory has been formed yet. In this project, the local distribution of chloride ions on steel surfaces with different cross-sections will be studied by multi-physics simulation methods and field tests, and the shape distribution coefficient of chloride ion concentration will be established. At the same time, salt spray accelerated corrosion tests of standard steel samples will be carried out under the condition of load-bearing state. Corrosion mechanism under load-bearing state will be clarified and the equation of load-bearing coefficient will be established according to the metallographic analysis results. Considering the shape distribution coefficient and the load-bearing coefficient, an atmospheric corrosion model at macroscopic scale will be established based on stochastic theory and a pitting corrosion model at mesoscopic scale will be proposed based on neural network technology and cellular automata. Finally, stochastic process based multi-scale corrosion simulation theory of bridge steel structures in marine atmospheric environment will be formed.

海洋大气环境中桥梁钢结构的腐蚀程度受构件所处的宏观与局部腐蚀环境、构件的力学状态等因素影响，钢结构腐蚀是宏观效应与介观效应耦合作用的结果。然而当前国内外针对桥梁钢结构的腐蚀研究仍停留在单一尺度层面，尚未形成公认的多尺度模拟理论。本课题首先利用试验和数值模拟方法，研究多物理场耦合作用下氯离子在不同断面形式的钢构件表面的局部分布规律，并建立氯离子浓度体型分布系数的表达方程。设计标准试件持力状态下的盐雾加速腐蚀试验，通过盐雾加速腐蚀试验并结合金相分析，阐明持力状态对钢构件腐蚀的影响机理，并建立持力补偿系数的表达方程。最后，考虑氯离子浓度体型分布系数及持力补偿系数，建立海洋大气环境下桥梁钢结构大气腐蚀宏观尺度的随机数学模型，发展基于神经网络技术与元胞自动机的介观尺度点蚀坑演化三维数学模型，最终形成基于概率的海洋大气环境中桥梁钢结构腐蚀多尺度模拟理论。

海洋大气环境中桥梁钢结构的腐蚀程度受构件所处的宏观与局部腐蚀环境、构件的力学状态等因素影响，具有显著的多物理场耦合特征。为阐明钢结构的持力腐蚀作用机理并建立有效的腐蚀预测手段，本课题首先基于计算流体动力学的基本理论，模拟了单箱断面和双箱断面表面的氯离子局部分布规律，并针对来流风速、断面高度、离海岸距离和空气盐浓度折减系数进行了参数分析。其次，设计了钢构件的持力腐蚀试验装置，通过开展一系列盐雾加速腐蚀试验并结合超景深三维显微镜观测分析，阐明了持力状态对钢构件腐蚀的影响机理，建立了不同外力水平下钢构件的均匀腐蚀和点蚀概率模型，明确了构件极限强度与腐蚀程度之间的定量关系。再次，完善了点蚀坑涌现的三维元胞自动机理论，建立了在广域范围内能同时考虑点蚀坑萌发和发展两个过程的元胞自动机概率模型。最后，采用相场方法对腐蚀失效开展了一系列分析，建立了能有效描述构件均匀腐蚀和点蚀演化规律的相场预测模型，利用该模型可以实现腐蚀由活化控制向扩散控制的自动转化；在此基础上，通过在相场模型中引入力学控制方程并考虑钝化膜破损—阳极溶解—再钝化过程以及Gutman力—电化学耦合方程，建立了能够描述点蚀演化—点蚀向裂纹转化—裂纹扩展失效全过程的应力腐蚀开裂相场模型；进一步地，引入了极化动力学的基本理论，建立了考虑多物质传输的应力腐蚀开裂精细化预测模型，该模型可有效捕捉腐蚀演化过程中电解质溶液内的各类复杂力学、化学、电化学过程及其耦合效应。