Methods for the Evaluation of Fracture and Strength of Pipeline Steels and Structures Under the Action of Working Media. Part D dagger. Influence of the Corrosion Factor

摘要

We generalize contemporary methods used for the evaluation of strength and fracture hazard of elements of pipeline structures with the use of approaches of fracture mechanics of materials, by taking into account specific features of influence of corrosive factors. The stages of initial corrosion damage to the metal and of the surface corrosion-fatigue cracking in pipeline steels are analyzed. We discover the influence of the chemical composition of the medium, frequency and stress ratio of the loading cycle, and the time of operation on their cyclic corrosion crack resistance. For the expert evaluation of the serviceability and fracture hazard of pipeline systems with corrosion cracklike defects, we propose to use special diagrams containing three characteristics zones: zone of safe operation, zone of operation with predicted development of the existing cracklike defects, and zone of brittle fracture hazard.