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

摘要

The effects of positive stress rations 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 1/100 offset procedure is shown to collapse " closure corrected" low stress ratio data with the "closure-free" high stress ration data. A three parameter multiple regression model is developed for the prediction of the fatigue crack growth rate as a function of stress ratio, crack closure and stress intensity factor range for Ti-6A1-4V.