316L不锈钢具有良好的力学性能和很强的耐腐蚀能力，因此在航空航天、舰船、工业生产、核电等各领域被广泛应用。不锈钢材料长期在腐蚀环境服役，受腐蚀介质和外加应力等复杂工况的影响，容易出现应力腐蚀开裂等问题，导致结构材料的失效，造成不可挽回的经济损失。本文以316L不锈钢为研究对象建立电化学-化学缝隙腐蚀模型和裂尖力学-电化学耦合模型，研究316L不锈钢在NaCl溶液中缝隙腐蚀过程中化学物质的变化规律，并分析腐蚀产物膜形成前后不同位移载荷和裂纹宽度作用下裂纹尖端的力学变化，进一步分析腐蚀产物膜厚度对裂尖力学的影响，得到了裂纹扩展速率与裂尖应变梯度的定量关系。主要研究内容有： (1) 在COMSOL软件中模拟316L不锈钢在NaCl溶液中的缝隙腐蚀，分析了缝隙腐蚀对溶液性能的影响；通过计算缝隙内各种化学物质的输运以及化学和电化学反应，对溶液中各种离子成功地进行了高精度的数值模拟。结果得到O2、Cl-、Fe2+、H+等各种离子在缝隙中的分布。 (2) 基于裂纹缝隙腐蚀电化学模型，对腐蚀产物膜的形成进行定量表征；基于吸湿膨胀理论，用腐蚀产物膜的膨胀模拟腐蚀产物膜的生长过程，计算无位移载荷时，不同氧气浓度下的腐蚀产物膜致应力；研究不同载荷以及不同裂纹宽度时腐蚀产物膜对裂尖力学的影响。 (3) 根据菲克定律建立固体力学与物质扩散的计算模型，分析腐蚀产物膜形成前后裂纹尖端的应力应变；分析腐蚀产物膜形成后不同裂纹宽度以及不同腐蚀产物膜厚度对裂纹尖端应力应变的影响；以滑移溶解理论和Ford-Andresen模型为基础，采用裂尖应变梯度替代裂尖应变率的分析方法，研究得到裂纹扩展速率随裂尖应变梯度的改变所导致裂尖力学特性的变化规律。

316L stainless steel has good mechanical properties and strong corrosion resistance, so it is widely used in various fields such as aerospace, ships, industrial production, and nuclear power. Stainless steel materials are in service in a corrosive environment for a long time. Affected by complex working conditions such as corrosive media and externally applied stress, problems such as stress corrosion cracking are likely to occur, leading to the failure of structural materials and causing irreparable economic losses. In this paper, 316L stainless steel is taken as the research object to establish an electrochemical-chemical crevice corrosion model and a coupled model of crack tip mechanics and electrochemistry. The variation law of chemical substances during the crevice corrosion process of 316L stainless steel in a NaCl solution is studied, and the mechanical changes at the crack tip under different displacement loads and crack widths before and after the formation of the corrosion product film are analyzed. Furthermore, the influence of the thickness of the corrosion product film on the mechanics at the crack tip is analyzed, and the quantitative relationship between the crack propagation rate and the strain gradient at the crack tip is obtained. The main research contents are as follows: (1) Simulate the crevice corrosion of 316L stainless steel in a NaCl solution in the COMSOL software, and analyze the influence of crevice corrosion on the properties of the solution. Through calculating the transport of various chemical substances within the crevice as well as the chemical and electrochemical reactions, a high-precision numerical simulation of various ions in the solution is successfully carried out. As a result, the distributions of various ions such as O2, Cl-, Fe2+, and H+ within the crevice are obtained. (2) Based on the electrochemical model of crack crevice corrosion, the formation of the corrosion product film is quantitatively characterized. Based on the hygroscopic expansion theory, the growth process of the corrosion product film is simulated by the expansion of the corrosion product film. The stress induced by the corrosion product film under different oxygen concentrations without displacement load is calculated. The influence of the corrosion product film on the crack - tip mechanics under different loads and different crack widths is studied. (3) Establish a calculation model of solid mechanics and substance diffusion according to Fick's law, and analyze the stress and strain at the crack tip before and after the formation of the corrosion product film. Analyze the influence of different crack widths and different thicknesses of the corrosion product film on the stress and strain at the crack tip after the formation of the corrosion product film. Based on the slip dissolution theory and the Ford-Andresen model, adopt the analysis method of replacing the crack tip strain rate with the crack tip strain gradient, and conduct research to obtain the variation law of the mechanical properties at the crack tip caused by the change of the crack tip strain gradient with the crack propagation rate.

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