奥氏体不锈钢和镍基合金等材料在核电高温高压水环境下的应力腐蚀开裂（SCC）是环境、材料和力学三者交互作用下的一种失效形式，也是影响核电结构安全的重要因素之一。为了了解裂尖力学因素对SCC扩展速率的影响规律，本文以氧化膜破裂理论为基础，以紧凑拉伸试样为研究对象，并以304L奥氏体不锈钢应力腐蚀裂尖形貌特征为主要依据，利用有限元法对由基体金属和氧化膜共同构成的SCC裂尖区域应力应变状态进行了详细分析，具体研究内容如下： (1) 将SCC裂尖简化为楔形裂尖和弧形裂尖两种形貌，并分析了氧化膜和基体金属相结合的SCC裂尖的应力应变状态，发现楔形裂尖氧化膜裂尖越钝，氧化膜裂尖应力越大，而基体金属裂尖应力越小。氧化膜破裂前最大应力出现在氧化膜表面上，最大应变值出在基体金属裂纹扩展方向两侧，基体上的应变和氧化膜上的应力应该是造成氧化膜破裂的主要因素。 (2) 分析了材料性能和裂纹扩展驱动力对裂尖区域应力应变分布的影响，发现氧化膜材料比基体金属材料对应力强度因子KI的变化更加敏感。基体金属的屈服极限和硬化指数对裂尖区域应力的影响较大，对应变影响较小，而基体金属的弹性模量对裂尖区域应力应变的影响恰恰相反。 (3) 根据应力腐蚀扩展速率预测模型，分析了不同氧化膜和基体金属材料力学参数以及不同裂纹扩展驱动力对应力腐蚀裂纹扩展速率的影响。研究结果表明除了裂纹扩展驱动力对SCC扩展速率有很大的影响外、裂尖基体金属和氧化膜的材料力学参数对SCC扩展速率也有很大的影响。

The Stress Corrosion Cracking (SCC) of the austenitic stainless steels and nickel-based alloys is one of the main failure in the high temperature environment of nuclear power plants, which is induced by the cooperation of environment, material and mechanics at the tip of SCC. To understand the effect of mechanical factors at the crack tip on SCC growth rate, based on oxide film rupture theory and a hypothesis of the morphology at the tip of SCC, the stress-strain state of the base metal and the oxide film at the tip of SCC of austenitic stainless 304L is analyzed and discussed by used of a compact tensile specimen and a commercial software ABAQUS. The main research works are performed as follows: (1) The SCC crack tip was simplified into two forms, i.e. wedged crack tip and arc crack tip, and the stress-strain state of the SCC crack tip concerning oxide film and base metal was analyzed. It was found that the blunter the wedged crack tip is, the higher the oxide film crack tip stress is, the lower the base metal crack tip stress is. The maximum stress appears on the oxide film surface before the oxide film ruptures, the maximum strain is on both sides of base metal crack extending direction. The strain on the base metal and the stress on the oxide film may be the main factors that cause the breaking of the oxide film. (2)The effect of material mechanical properties and the crack growth driving force to the stress and strain distribution of crack tip area has been analyzed, the stress intensity factor KI on the oxide film material is more sensitive than that on the base metal material. The yield strength and hardening exponent of base metal have large impact on the crack tip stress, and little impact on the strain, the impact of the base metal Young’s modulus is quite opposite. (3) Based on SCC growth rate prediction model, the effect of the different oxide film and base metal material mechanical f properties as well as different crack growth driving force on stress corrosion extend rate has been analyzed. It shows that, besides the crack growth driving force, oxide film and base metal material mechanical properties at SCC crack tip have a large effect on stress corrosion cracking growth rate.