Impact Fatigue Properties of Spheroidal Graphite Cast Iron

Abstract

  An impact fatigue test was carried out on spheroidal graphite cast iron using a Hopkinson bar type impact testing machine, which facilitates the measurement of the impact stress wave. The impact fatigue fracture mechanism of spheroidal graphite cast iron was also clarified. The results obtained ware as follows,
(1) When the applied stress exceeded the dynamic yield stress, the S-N diagram formed a curve which was affected by the stress duration time. The fracture surface was a mixture of cleavage fracture and ductile dimple destruction.
(2) When the applied stress was equal to the dynamic yield stress, the cleavage fracture surface rate was dependent on the fracture life (the generation stress), and was the lowest at 10-200 cycles.
(3) When the applied stress was below the dynamic yield stress, the S-N diagram formed a straight line, and no effects of the stress duration time were observed. The fracture surface was similar to the fatigue fracture surface, and the fatigue life was equivalent to the results of the axial load fatigue test.