A physically-based model for the prediction of long fatigue crack growth in Ti–6Al–4V

Abstract

A physically-based model is presented for the prediction of fatigue crack growth in Ti–6Al–4V. The model assumes that the crack extension per cycle is directly proportional to the change in the crack-tip opening displacement, during cyclic loading between the maximum and minimum stress intensity factor. The extent of irreversibility is also assumed to exhibit a power law dependence on the effective stress intensity factor range. A simple power law equation is then derived for the prediction of fatigue crack growth as a function of the effective stress intensity factor range. The model is validated for fatigue crack growth in the near-threshold, Paris and high-Δ K regimes. The fatigue crack growth mechanisms associated with the parametric combinations of stress intensity factor ranges and maximum stress intensity factor are then summarized on fatigue mechanism maps. Mechanistically-based fatigue crack growth relationships are thus obtained for the prediction of fatigue crack growth in the near-threshold, Paris and high-Δ K regimes.