IHS ESDU Fatigue propagation behaviour of short cracks in titanium alloys. 92023

ESDU 92023 discusses the different propagation behaviour of short and long cracks; short cracks often do not display a threshold value of stress intensity factor range and propagate at higher rates than long cracks. The difficulties of calculating the stress intensity factor for short cracks are explained. Experimental data extracted from the literature for crack growth rate in air under constant amplitude loading are presented graphically against stress intensity factor range for 7 alloys (IMI 318, IMI 685, Ti-4Al, Ti-6Al-4V, Ti-6Al-2Sn-4Zr-6Mo, Ti-8Al, Ti-8.6Al). All the curves are derived from a number of tests except that some data for IMI 318 and Ti-8.6Al relate to individual cracks. Details of the alloy, heat treatment and mechanical properties are included, and the experimental arrangement for each set of data is indicated. For IMI 318, IMI 685 and Ti-6Al-4V, data for short and long cracks are compared. The effect of stress ratio is shown for Ti-8Al (values of 0.1 and 0.5) and for Ti-6Al-4V (values of 0 and -1).