Equivalent crack growth model for correlation and prediction of fatigue crack growth under different stress ratios

•Equivalent crack growth model incorporates the effect of stress ratio.•Equivalent driving force yields same growth rate as combined effects of applied stress intensity range and stress ratio.•Curves of growth rate versus equivalent driving force for different R-ratios have common threshold.•The ratio of any two driving forces at two stress ratios is equal to the ratio of their thresholds.•Ratio of growth rates of two equivalent curves is a power function of the ratio of their threshold.