Evaluation of Hardness Distributions around Fracture Surface in Induction-Heated SUJ2 Steel after Rotating Bending Fatigue Test

Induction-heated carbon steel is used in various mechanical parts and the fracture mechanism from internal cracks is still being investigated. In order to explain the fracture mechanism of an induction-heated SUJ2 steel bar specimen, we investigated Vickers hardness distributions around the fracture surface after a rotating bending fatigue test. We found an area which is defined as the transition area near the fracture surface whose HV values decreased about 150 HV and this area was formed by the fatigue crack during the rotating bending fatigue test.