Wang Quanyi, Chen Yao, Liu Yongjie, Wang Chong, Li Lang, He Chao, Gong Xiufang, Wang Tianjian, Zhang Wei, Wang Qingyuan, Zhang Hong
School of Aeronautics and Astronautics, Sichuan University, Chengdu 610065, China.
Failure Mechanics and Engineering Disaster Prevention and Mitigation Key Laboratory of Sichuan Province, College of Architecture and Environment, Sichuan University, Chengdu 610065, China.
Materials (Basel). 2020 Aug 5;13(16):3444. doi: 10.3390/ma13163444.
Effects of the stress ratio on the very high cycle fatigue behaviors of 9%Cr turbine steel have been investigated at 630 °C. The experimental results show that the S-N curve has a continuous downward trend and has no fatigue limit with the increasing in the cycles at 630 °C. Meanwhile, according to the analysis of microstructure, there are two failure modes that were observed at different stress ratios (R = -1 and 0.1), including surface crack failure and internal crack failure, respectively. Besides, the theoretical threshold value of the crack growth is compared with the calculated value of the fracture surface. To decrease the difference between the threshold value of internal crack initiation and the corresponding theoretical value, a new model for the crack growth threshold of the interior-induced fracture at different stress ratios is proposed and discussed.
在630°C下研究了应力比对9%Cr汽轮机钢超高周疲劳行为的影响。实验结果表明，在630°C时，随着循环次数的增加，S-N曲线呈连续下降趋势且无疲劳极限。同时，通过微观结构分析，在不同应力比（R = -1和0.1）下观察到两种失效模式，分别为表面裂纹失效和内部裂纹失效。此外，将裂纹扩展的理论阈值与断口计算值进行了比较。为减小内部裂纹萌生阈值与相应理论值之间的差异，提出并讨论了一种不同应力比下内部诱发断裂裂纹扩展阈值的新模型。
