A fatigue crack growth model with mean stress effects

A fatigue crack growth model with mean stress effects has been developed for low and intermediate values of the stress intensity factor range ;A model has been proposed by Kujawski and Ellyin (1) which account for stress ratio R effects on the fatigue crack growth behaviour at low and intermediate values of the stress intensity factor range. The fatigue failure criterion adopted within the "process zone" was based on the product of stress range and plastic strain range, and the effect of the mean stress ;The present model was developed in order to improve the predictions of the crack growth rate values for low and intermediate stress intensities for all values of R. This was achieved by adopting a fatigue failure criterion based on the total cyclic strain energy density as a damage parameter to describe the fatigue fracture process within the "process zone".;A new equation for the calculation of the total cyclic strain energy density is introduced, based on the calculation of the elastic component of the total cyclic strain energy density.;The predictions of the proposed model were compared with experimental data, and with the results obtained by Kujawski and Ellyin's model.