Effect of scratch depth on high cycle fatigue behavior of Alloy 690TT stream generator tube

The effect of scratch depth on high cycle fatigue behavior of Alloy 690TT stream generator (SG) tubes was investigated by experimental characterization and numerical simulation. Results indicated that fatigue cracks initiated at the scratch root of the SG tube external surface. The effect of scratch depth on fatigue life mainly depended on the loading stress levels, which could be considered as an exponential relationship between the loading stress and scratch depth for a given fatigue life. The fatigue limit decreased with the increase of scratch depth and changed in a small range of yield strength.