Physically short fatigue crack growth from notch described by plasticity-corrected stress intensity factor

• Published in: International journal of mechanical sciences 2020-06, Vol.176, p.105544, Article 105544
• Main Authors: Meng, Li, Yang, Menghao, Chen, Xiuhua, Hu, Yandong, Feng, Miaolin
• Format: Article
• Language: English
• Subjects: Notch; Physically short fatigue crack; Plastic zone size; Plasticity-corrected stress intensity factor; V-shaped behavior
• ISSN: 0020-7403; 1879-2162
• DOI: 10.1016/j.ijmecsci.2020.105544

•V-shaped behavior for physically short FCG was eliminated with PC-SIF by numerical analysis.•Effect of plastic zone from notch root on fatigue crack growth rate was studied in detail.•Ratio of PC-SIF range to stress intensity factor range was determined by power functions.•Two type specimens made of two steels were analyzed with different load ratios, notch radii, and notch depths. When a physically short fatigue crack propagates from a notch root, the crack growth rate shows a “V-shaped” behavior; i.e., the rate firstly decreases and then increases as the crack propagates. In this study, a plasticity-corrected stress intensity factor (PC-SIF) is applied to describe the effects of both notch's plastic zone and crack-tip's plastic zone in ductile materials under cyclic loading. Experiments in previous study for disk-shaped compact tension (CT) specimens made of 1070 steel with different notch sizes and load ratios, as well as single-edged specimens made of low-carbon steel with U-shaped notches, are examined by numerical analysis in present paper. The V-shaped curves of fatigue crack growth data can be summarized by straight lines if the PC-SIF range is applied which considers the influence of plastic zone near the notch roots. The plastic zone near the notch root plays an important role in the V-shaped behavior for the physically fatigue short crack, and the evolution of the plastic zone is discussed in detail. The ratio of PC-SIF range to the stress intensity factor (SIF) range was fitted by the power functions and the fitting expressions before and after the turning point of the V-shaped curve exhibit a significant difference. [Display omitted]