On the Crack Length and the Low Temperature Brittleness of a Carbon Steel Subjected to Corrosion Fatigue

Abstract

The lengths of the cracks formed by the corrosion fatigue in saline are studied on the smooth specimens or a carbon steel, and the effect or corrosion fatigue on the low temperature brittleness is discussed. The cracks occur at the early stage of the fatigue life and the cyclic rates of their propagation dl/dN depend on the true stress σ_ck repeated at the root of the crack, where k represents the notch effect of corrosion pits increasing with time. The transition temperature T_r°C of the specimens having the cracks caused by corrosion fatigue and the rate or its change with cycle ΔT_r/ΔN rise with increasins of cyclic ratio. It also rises according to the increase of square root of crack length l^1/2, having no relation to the nominal stress σ_c of the corrosion fatigue.