A new (ΔK+Kmax)0.5 driving force parameter for crack growth in aluminum alloys

In this paper, a new mechanical driving force parameter for long- and short-crack growth rate correlation is proposed. This new parameter, (ΔK+Kmax)0.5, does not utilize disputable crack closure data, instead it is calculated as a geometric mean of the positive part of the applied stress intensity factor (SIF) range, ΔK+, and the corresponding maximum value of the SIF, Kmax. The proposed parameter correlates fairly well the R-ratio effects on the threshold condition and fatigue crack growth rate at the low and intermediate stress intensities for six aluminum alloys investigated.