Atomic-Scale Insights into Damage Mechanisms of GGr15 Bearing Steel Under Cyclic Shear Fatigue

Alternating shear stress is a critical factor in the accumulation of damage during rolling contact fatigue, severely limiting the service life of bearings. However, the specific mechanisms responsible for the cyclic shear fatigue damage in bearing steel have not been fully understood. Here the mechanical response and microstructural evolution of a model GGr15 bearing steel under cyclic shear loading are investigated through the implementation of molecular dynamics simulations. The samples undergo 30 cycles under three different loading conditions with strains of 6.2%, 9.2%, and 12.2%, respectively. The findings indicate that severe cyclic shear deformation results in early cyclic softening and significant accumulation of plastic damage in the bearing steel. Besides, samples subjected to higher strain-controlled loading exhibit higher plastic strain energy and shorter fatigue life. Additionally, strain localization is identified as the predominant damage mechanism in cyclic shear fatigue of the bearing steel, which accumulates and ultimately results in fatigue failure. Furthermore, simulation results also revealed the microstructural reasons for the strain localization (e.g., BCC phase transformation into FCC and HCP phase), which well explained the formation of white etching areas. This study provides fresh atomic-scale insights into the mechanisms of cyclic shear fatigue damage in bearing steels.