Estimation of the fatigue limit of components made of Austempered Ductile Iron weakened by V-shaped notches

A fatigue model previously published in the technical literature has been applied to estimate the fatigue limit in presence of V-shaped notches. When the notch tip radius approaches reduced values, the model is based on the mode I notch-stress intensity factor. Conversely, when the notch tip radius is large, the classical approach based on the linear elastic stress concentration factor is matched. The resulting engineering design tool enables one to assess any kind of notch geometry, namely U-shaped and V-shaped notches of whatever notch tip radius and dimension. The well-known scale effect shown by the Kitagawa-Takahashi valid for cracks is included as a particular case. The fatigue model requires two material parameters, namely the plain material fatigue limit and the threshold range of the stress intensity factor for long cracks. The proposed fatigue design procedure has been applied to estimate the fatigue limit of round specimens and a gear made of austempered ductile iron grade 1050. Both specimens and the gears were characterised by the presence a V-notch having a 120° notch opening angle. Theoretical estimation were seen to be in fair agreement with the experimental fatigue test results.