In the present study, Kachanov–Rabotnov continuum damage model has been employed to describe the steady state and tertiary creep deformation and damage behaviour of 316L austenitic stainless steel with different nitrogen contents of 0.07, 0.11 and 0.22 wt%, at 923 K. For all the nitrogen contents, the model appropriately predicts the creep strain–time data, creep rupture strain and rupture life. The model parameters such as characteristic strain and damage rates systematically decrease with the increase in nitrogen content. The derived iso-damage contours superimposed on creep strain–time data indicate that the evolution kinetics of strain, as well as damage, are unique at each applied stress level. For nitrogen added type 316L SS, the critical damage value (ωcr) at which creep failure takes place is found to be less than 1 and is in the range of 0.35–0.60. It is observed that the dominance of damage rate ( ω ˙ ) over the strain rate ( ε ˙ ) increases with increasing nitrogen content from 0.07 to 0.22% N for the steel. A direct correlation has been established between the creep rupture ductility and the ratio of strain rate to damage rate, i.e. ε ˙ / ω ˙ using the Kachanov–Rabotnov model for different nitrogen contents and stress levels.

中文翻译：

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连续介质损伤力学方法框架下氮变化对316L型蠕变变形和损伤行为的影响

在本研究中，采用 Kachanov-Rabotnov 连续介质损伤模型来描述 316L 奥氏体不锈钢在 923 K 下的稳态和三次蠕变变形和损伤行为，不同氮含量为 0.07、0.11 和 0.22 wt%。对于所有氮含量，该模型适当地预测蠕变应变-时间数据、蠕变断裂应变和断裂寿命。特征应变和损伤率等模型参数随着氮含量的增加而系统地降低。叠加在蠕变应变-时间数据上的导出等损伤等值线表明，应变的演化动力学以及损伤在每个施加的应力水平上都是独一无二的。对于加氮型 316L SS，发现发生蠕变破坏的临界损坏值 (ωcr) 小于 1，并且在 0.35-0.60 的范围内。据观察，损伤率 (ω ˙ ) 对应变率 ( ε ˙ ) 的支配地位随着钢的氮含量从 0.07% 增加到 0.22% N 而增加。对于不同的氮含量和应力水平，使用 Kachanov-Rabotnov 模型建立了蠕变断裂延性和应变率与损伤率之比，即 ε ˙ / ω ˙ 之间的直接相关性。