In-Service Degradation of Structural Steels under Cyclic Loading

We analyze the characteristics of in-service degradation of structural steels under the conditions of cyclic loading and take into account that the process of degradation of steels has two stages. In the first stage, cyclic strain hardening is predominant. The second stage can be described as the intense development of microdefects dispersed in the bulk of the metal. We distinguish the influence of in-service cyclic loading on the complex of basic mechanical properties of steels important for their serviceability and on a broad range of the characteristics of fatigue strength. In the first case, these are the characteristics of brittle-fracture resistance and, in particular, impact toughness and crack resistance. In the second case, we deal with fatigue-fracture resistance. The indicated characteristics are determined for smooth specimens and specimens with cracks. We analyze the influence of corrosive hydrogenating media on the intensity of in-service degradation of steels under cyclic loading.