AN INVESTIGATION OF THE EFFECTS OF STRESS RATIO AND CRACK CLOSURE ON THE MICROMECHANISMS OF FATIGUE CRACK GROWTH IN Ti-6Al-4V

The effects of positive stress ratios on the fatigue crack growth behavior of a forged, mill-annealed Ti-6Al-4V alloy (with a duplex α + β microstructure) are discussed. Differences between fatigue crack growth rates at low and high stress ratios are shown to be due largely to crack closure. A 1% offset procedure is shown to collapse “closure corrected” low stress ratio data with the “closure-free” high stress ratio data. A three parameter...