Surface vs. interior failure behaviors in a structural steel under gigacycle fatigue: Failure analysis and life prediction

The failure behaviors of a structural Cr-Ni-W steel under gigacycle fatigue were investigated, and a life prediction method based on the crack growth was proposed. The discovery of two failure phenomena, including the coexistence of surface and interior cracks and the coexistence of multiple fish-eyes, verifies the possibility of competing failure. The developed interior crack growth model reveals the failure progress at a slow rate below 10^-10 m/cycle within the fish-eye induced by the inclusion or the inhomogeneous matrix area. The validity of the life prediction method is proved by the good agreement between the predicted and the experimental lives.