Torsional Corrosion Fatigue Process of an Annealed Carbon Steel S 45 C. Comparison with Rotating Bending Corrosion Fatigue Process.

Abstract

The corrosion fatigue process under cyclic torsion was investigated in annealed carbon steel. The results obtained were as follows. (1) During the fatigue process in laboratory air and salt water at the high stress amplitude region, slip bands appeared on the smooth specimen surface and cracks initiated from some of these slip bands. These cracks propagated in the direction of the specimen axis at mode II and thereafter branched and propagated in the direction inclined 45° to the specimen axis at mode I. (2) During the corrosion fatigue process at the low stress amplitude region, cracks initiated at corrosion pits and directly propagated in the direction inclined 45° to the specimen axis at mode I. (3) In torsional fatigue tests, the decreasing rate of fatigue strength due to the corrosive environment was smaller than that of rotating bending tests. (4) Differences in the initiations and growth behavior of corrosion pits between the torsional corrosion fatigue test and the rotating bending corrosion fatigue tests were not observed.