316L奥氏体不锈钢因具有良好的力学性能和优异的耐腐蚀能力，被广泛应用于航空航天、舰船、工业生产、核电等领域。但是以不锈钢为材料的结构在长期服役于腐蚀环境时，受腐蚀介质和外加应力等复杂工况的影响下，会出现应力腐蚀和氢致断裂等问题，导致材料和结构的损伤失效，造成不可挽回的经济损失。本文以316L奥氏体不锈钢为研究对象，通过建立相场断裂模型，分析外加载荷和氢共同作用下不锈钢裂尖区域的氢扩散行为及其引起的裂尖力学场变化，并结合弱键理论对氢致断裂行为进行模拟，本文的主要研究内容如下：

（1）通过建立裂尖氢扩散的计算模型，分析氢在不锈钢内部的扩散与分布情况，以及不同载荷、不同温度、不同裂纹深度对氢扩散的影响，从而研究氢分布与应力-应变的关系。并且对316L奥氏体不锈钢进行电化学充氢，通过拉伸试验结果研究氢进入金属后对其材料力学性能的影响。

（2）建立了包含固体力学和物质扩散过程的316L不锈钢相场断裂模型，并在COMSOL中建立多物理场耦合计算模型，研究材料的裂纹扩展，得到了外加载荷对氢的再分布的影响，结合氢脆弱键机制，建立氢扩散-内聚力耦合模型研究了316L奥氏体不锈钢的断裂行为。

（3）基于菲克定律，推导力学与氢扩散耦合公式，通过建立裂尖力学与氢扩散以及弱键机制耦合数值模型，研究裂尖氢向静水压集中位置聚集、氢进入金属后对材料的作用规律；通过分析氢进入金属后对裂尖区域的应力应变的影响，模拟氢对裂纹扩展速率的影响，并且考虑了不同载荷、裂纹深度对裂纹扩展速率的影响。

316L austenitic stainless steel is widely used in aerospace, shipbuilding, industrial production, nuclear power and other fields due to its good mechanical properties and excellent corrosion resistance. However, when the structure with stainless steel as the material is in a corrosive environment for a long time, under the influence of complex working conditions such as corrosive media and external stress, problems such as stress corrosion and hydrogen-induced fracture will occur, resulting in damage and failure of materials and structures, causing irreparable economic losses. In this paper, 316L austenitic stainless steel is taken as the research object. By establishing a phase field fracture model, the hydrogen diffusion behavior in the crack tip region of stainless steel under the combined action of external load and hydrogen and the change of the mechanical field at the crack tip are analyzed. Combined with the weak bond theory, the hydrogen-induced fracture behavior is simulated. The main research contents of this paper are as follows:

(1) The calculation model of hydrogen diffusion at the crack tip was established to analyze the diffusion and distribution of hydrogen in stainless steel, as well as the effects of different loads, different temperatures and different crack depths on hydrogen diffusion, so as to study the relationship between hydrogen distribution and stress-strain. The 316L austenitic stainless steel was electrochemically charged with hydrogen, and the effect of hydrogen on the mechanical properties of the material was studied by tensile test results.

(2) A phase-field fracture model of 316L stainless steel including solid mechanics and material diffusion process was established. A multi-physical field coupling calculation model was established in COMSOL to study the crack propagation of the material. The effect of applied load on the redistribution of hydrogen was obtained. Combined with the hydrogen fragile bond mechanism, a hydrogen diffusion-cohesion coupling model was established to study the fracture behavior of 316L austenitic stainless steel.

(3) Based on Fick 's law, the coupling formula of mechanics and hydrogen diffusion is derived. By establishing the coupling numerical model of crack tip mechanics, hydrogen diffusion and weak bond mechanism, the effect of hydrogen accumulation at crack tip to hydrostatic pressure concentration position and hydrogen entering metal on material is studied. By analyzing the influence of hydrogen on the stress and strain in the crack tip region after entering the metal, the influence of hydrogen on the crack growth rate is simulated, and the influence of different loads and crack depth on the crack growth rate is considered