Fatigue-Strength Distribution of Carbon Steel in Corrosive Environments

The influence of corrosive environment on the fatigue-strength distribution was studied for a carbon steel. A standard deviation of the fatigue strength at 107 cycles increased to three halves in mild aqueous environments such as ion-exchanged water, as compared with that in laboratory air, and it decreased to a half in severe environments such as synthetic seawater. In laboratory air, the fatigue life varied mainly due to the scatter of crack initiation. In mild aqueous environments, many cracks initiated uniformly on the specimen surface in an early stage and grew at a similar rate, and the difference in time to the coalescence of cracks caused the dispersion of fatigue life. However, in severe aqueous environments, localized crack-initiation occurred in the corroded region, and the fatigue life or the fatigue strength scattered less because of the easiness of the coalescence of growing cracks.