On corrosion fatigue initiation from notches and the local corrosion fracture approaches

摘要

Corrosion fatigue emanating from semicircular notches is considered. The studies are focused on the relationship between stress field and electrochemistry in notches with the aim of understanding and prediction of the corrosion fatigue crack nucleation and growth behaviour from a notch surface. It has been done for typical corrosive active system "low strength carbon steel - 3%NaCl solution", where the electrochemical metal dissolution plays a dominant role. The semicircular notch is considered both as a stress concentrator and as local corrosion minicell. The early stages of corrosion fatigue at the notch bottom were determined and the existence of some critical crack density q{sub}* that causes an intensive crack coalescence and macrocrack creation has been shown. An expression predicting the formation on the notch surface of the characteristic density of corrosion fatigue cracks is derived as a function of the synergistic action of cyclic stress and the corrosion process.