Abstract
Effect of zinc potential in sea water on fatigue life of notched specimen was examined using 80 kgf/mm2 grade high yield strength steel. Stress amplitude, stress ratio, and stress concentration factor of the notch were selected as factors affecting the above effect. Testing frequency was 0.5 Hz in sea water. The main results obtained are as follows:
1) The effect of zinc potential on fatigue life of notched specimen is less beneficial than that of smooth specimen.
2) The effect of zinc potential on fatigue life of notched specimen depends on stress amplitude, when R = 0.1.
(a) At a higher stress amplitude, fatigue life is shorter at zinc potential than at free potential.
(b) At a lower stress amplitude, fatigue life at zinc potential is comparable with that in air.
(c) At zinc potential, notched specimen fails at a stress amplitude lower than fatigue endurance limit in air.
3) Effect of zinc potential on fatigue life of notched specimen decreases with increase of stress ratio.
4) 1), 2), and 3) are explained by;
(a) decrease of crack initiation cycles at notch tip due to hydrogen evolution at zinc potential and
(b) increase of crack propagation cycles due to wedge effect at zinc potential in the early crack propagation stage.
