Deng Hailong, Li Wei, Zhao Hongqiao, Sakai Tatsuo
School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China.
College of Mechanical Engineering, Inner Mongulia University of Technology, Hohhot 010051, China.
Materials (Basel). 2017 Sep 14;10(9):1084. doi: 10.3390/ma10091084.
Axial loading tests with stress ratios of -1, 0 and 0.3 were performed to examine the fatigue failure behavior of a carburized Cr-Ni steel in the long-life regime from 10⁴ to 10⁸ cycles. Results show that this steel represents continuously descending characteristics with interior inclusion-induced failure under = -1, whereas it shows duplex characteristics with surface defect-induced failure and interior inclusion-induced failure under = 0 and 0.3. The increasing tension eliminates the effect of compressive residual stress and promotes crack initiation from the surface or interior defects in the carburized layer. The FGA (fine granular area) formation greatly depends on the number of loading cycles, but can be inhibited by decreasing the compressive stress. Based on the evaluation of the stress intensity factor at the crack tip, the surface and interior failures in the short life regime can be characterized by the crack growth process, while the interior failure with the FGA in the long life regime can be characterized by the crack initiation process. In view of the good agreement between predicted and experimental results, the proposed approach can be well utilized to predict fatigue lives associated with interior inclusion-FGA-fisheye induced failure, interior inclusion-fisheye induced failure, and surface defect induced failure.
进行了应力比为-1、0和0.3的轴向加载试验，以研究渗碳Cr-Ni钢在10⁴至10⁸次循环的长寿命范围内的疲劳失效行为。结果表明，该钢在应力比为-1时呈现出连续下降的特性，失效由内部夹杂物引起；而在应力比为0和0.3时，呈现出双重特性，失效由表面缺陷和内部夹杂物引起。拉应力的增加消除了压缩残余应力的影响，并促进了渗碳层表面或内部缺陷处的裂纹萌生。细晶区（FGA）的形成很大程度上取决于加载循环次数，但可以通过降低压应力来抑制。基于对裂纹尖端应力强度因子的评估，短寿命范围内的表面和内部失效可以用裂纹扩展过程来表征，而长寿命范围内伴有FGA的内部失效可以用裂纹萌生过程来表征。鉴于预测结果与实验结果吻合良好，所提出的方法可很好地用于预测与内部夹杂物-FGA-鱼眼诱发失效、内部夹杂物-鱼眼诱发失效以及表面缺陷诱发失效相关的疲劳寿命。
