Further Study on the Crack Depth and the Low Temperature Embrittlement of a Carbon Steel Subjected to Corrosion Fatigue

Abstract

In the previous paper, the authors studied on the crack depth of a smooth specimen subjected to corrosion fatigue under a cycle frequency of 2300 c/min in saline, and the low temperature embrittlement of specimens having such corrosion fatigue cracks. In the present paper, the corrosion fatigue is given under a cycle frequency of 2300 c/min in tap water and 760 c/min in saline by repeated bending and also under 2300 c/min in saline by repeated twisting to make clear the influence of the crack depth on the embrittlement transition temperature of the materials subjected to corrosion fatigue under more extensive test conditions. The crack depth due to corrosion fatigue depends upon the damage of corrosion fatigue (k-1)/(kc-1), irrespective of the conditions of corrosion fatigue such as the intensity of corrosive, the nominal stress, the cycle frequency, and either under repeated bending or repeated twisting, where k represents the corrosion effect proposed by the authors and kc corresponds to k at the rupture time. The crack propagation rate under bending of the nominal stress σc is given as a function of the true stress σck acting on the root of the corrosion fatigue crack. The embrittlement transition temperature Tr of the specimens having these cracks rises with the square root of the crack depth and is in an exponential relation to (k-1)/(kc-1) under wide working conditions of corrosion fatigue.