Experimentally validated dwell and cyclic fatigue crack nucleation model for α-titanium alloys

(a) Statistically equivalent polycrystalline Ti-7Al model showing the Schmid factor contour plot, (b) cross section showing stress and Nye tensor fields around a critical soft-hard grain pair after 2824 cycles of dwell loading at Pmax = 100%Y.S., (c) number of cycles to crack initiation under dwell (black) and cyclic loading (grey) and Pmax varying from 85%Y.S. to 100%Y.S. Circles and error bars: experimental mean and fracture-mechanics-estimated bounds of nucleation life. Squares and diamonds: calibrated and predicted number of cycles to nucleation, respectively.497