The Effects of Grain Size and Strain Amplitude on Persistent Slip Band Formation and Fatigue Crack Initiation

The maximum persistent slip band (PSB) width in cyclic loading is experimentally proven to be a material property in this paper. The dependence of the maximum PSB width on grain size, selected as a microstructural property of the material, is tested and reported. The effect of strain conditions, which conversely is not a material property of copper, is also included in the study. The results demonstrate that the maximum PSB width of annealed copper (grain size = 104.2 µm) is statistically the same within this class of grains, and is statistically larger than that of the stress-relieved copper (grain size = 14.2 µm). In contrast, the PSB width evolution is not sensitive to different strain conditions. These findings advance the fundamental understanding of how persistent slip band formation is influenced by variations in fatigue mechanical stimulus and metallurgical characteristics.