冷加工对316L不锈钢裂尖力学特性的影响

Effect of cold working on mechanical properties at crack tip of 316L stainless steel

采用弹塑性有限元软件的子模型技术,研究了核电压力容器高温水环境中冷加工程度对316L不锈钢应力腐蚀裂纹尖端应力应变状态和断裂参量的影响,并结合316L不锈钢在不同冷加工程度下屈服强度、杨氏模量、硬化指数和偏移系数的变化规律,对比冷加工程度对微观裂纹尖端应力腐蚀开裂速率的影响,发现冷加工程度不同,材料的力学参数不同,进而影响应力腐蚀裂纹尖端Mises应力、等效塑性应变、拉伸应力、拉伸应变的分布状态和裂尖J积分变化规律。结果表明:不同冷加工程度引起316L不锈钢材料力学性能的变化会改变应力腐蚀裂纹裂尖应力应变状态和断裂参量的分布规律,当应力强度因子一定时,随着冷加工程度的增大,应力腐蚀裂尖Mises应力增大,而裂尖的等效塑性应变减小,同时应力腐蚀裂尖的拉伸应力随着冷加工程度的增大而增大,而拉伸应变随着冷加工程度的增大而减小,裂尖J积分随着冷加工程度的增大而增大,冷加工程度的增加在一定范围内加剧了高温高压水环境中316L不锈钢应力腐蚀开裂速率。

The effect of cold working degree on stress and strain state and fracture parameters at stress corrosion cracking tip of 316 L stainless steel in high temperature water environment of the nuclear pressure vessel was studied by sub-model technology of elastic plastic finite element method. It combined with the change rule of yield strength,Young＇s modulus,hardening exponent and yield offset of 316 L stainless steel under different cold working degree,and compared the influence of cold working degree on stress corrosion cracking rate at micro crack tip. It is pointed that the degree of cold working is different,and the mechanical parameters of the material are different,which will further affect the Mises stress,equivalent plastic strain,tensile stress,tensile strain distribution and the J integral rule of crack tip. The results indicate that the change of mechanical properties of 316 L stainless steel caused by different cold working degree can change the distribution rule of stress and strain state and fracture pa-rameter in stress corrosion crack tip. When the stress intensity factor is certain,the Mises stress in stress corrosion cracking tip increases with the increase of the cold working degree,and the equivalent plastic strain in the crack tip decreases with the increase of the cold working degree. At the same time,the tensile stress in stress corrosion cracking tip increases with the increase of the cold working degree,and the tensile strain decreases with the increase of the cold working degree. The J integral at the crack tip increases with the increase of cold working degree. The increase of cold working degree aggravates the stress corrosion cracking rate of 316 L stainless steel to a certain extent in high temperature and high pressure water environment.