Prediction models of intrinsic fatigue threshold in metal alloys examined by experimental data

A comprehensive study is carried out on the models for predicting the intrinsic threshold value for fatigue crack growth (FCG) in the absence of closure effects. The models reviewed and commented in this paper are based on different approaches, such as the models based on the mechanical properties of the materials and the so-called dislocations models. In particular, the model proposed for the first time in 1985 by one of the authors of the present paper, which is based on tensile and cyclic properties of the material, cyclic plastic zone size parameter and the minimum amount of physically possible crack advance (the inter-atomic spacing or Burgers vector) is revisited and compared with other models, through assessment of theoretically predicted values against more recent experimental data obtained in different types of metal alloys. It is shown that, once the appropriate material parameters are available, this model can give more accurate prediction results than other models.