Fracture Mechanism of GCr15 Steel in Very High Cycle Fatigue

Fracture mechanism of GCr15 steel in very high cycle fatigue was studied in rotating bending.Based on the observation of fracture surface,the analysis of fracture mechanics and the simulation with FRASTA method,the initiation and propagation mechanisms of interior cracks were explained and the model of granular bright facet (GBF) formation mechanism was proposed.The test results show that the interior fracture of GCr15 steel was induced by the nonmetallic inclusion in the subsurface of material,the GBF was formed in the vicinity around the inclusion,and the entire interior crack exhibited typical appearance characteristic of “fish-eye”.The interior crack was the typical characteristic of very high cycle fatigue failure.The stress intensity factor range ΔKGBF about 4-6 MPa·m1/2 was the critical parameter of controlling interior crack propagation.The majority of the very high fatigue life was possessed by the formation progress of GBF.