Modeling of the in-service degradation of steels of cargo seaport structures under the laboratory conditions

We study the influence of the duration of high-cycle loading on the complex of mechanical characteristics of low-strength steels specifying their structural strength. We distinguish three stages of cycling characterized by well-pronounced regularities in the behavior of the properties of these steels. It is shown that, in the first stage, the fatigue-sensitive characteristics of steels vary almost identically: their hardness somewhat increases, whereas the relative elongation and impact toughness decrease. The microcracks appearing and propagating in the second stage affect only the impact toughness of the metal: it becomes almost twice lower. After the formation of a macrocrack in the third stage, the subsequent cycling almost does not affect the mechanical characteristics of steels. It is shown that high-cycle fatigue is responsible for changes in the state of the metal similar to those observed for the steels of cargo port structures in the course of their long-term operation. Thus, it can be used for the simulation of in-service degradation of the mechanical properties of steels under laboratory conditions.