In the present work, rotating bending fatigue tests have been carried
out to investigate the fatigue strength of plain and circumferentially
notched specimens of Ti-6AL-4V alloy. The purpose of this work is to
evaluate fatigue strength and notch sensitivity under different stress
concentrations . The notch radius of specimens changes from m (plain
specimen) to 1.3, 0.4, 0.2, and 0.1 mm. The fatigue cracks initiate by
approximate 25% of cycle ratio in the cases of p= 1.3 and 0.4 mm while
the fatigue cracks initiate by approximate 15% in the case of p = 0.2
mm. The notch sensitivity of Ti-6AL 4V alloy is higher Ahan that of
cast iron, and lower than that of steel material. The non-propagating
micrwcracks at the specimen surface are not existed for not only the
plain specimen but also for all of the notched specimens including plain
specimen under fatigue limit by N = 1 X 10' cycles.