دراسة تأثير التداخل الثلاثي (التآكل – الكلال – الزحف) على عمر الفولاذ الكربوني (A106 Gr-B) المستخدم في أنابيب النفط

Rp-Investigation of triple interaction effect (corrosion-fatigue-creep) on life of carbon steel (A106 Gr-B) used in oil pipelines.pdf

In some applications, material may be subjected to an interaction of fatigue-creep, and corrosion fatigue, as well as an effect of triple interaction (corrosion-creep-fatigue), and here it is known as the triple fatigue interaction (TFI).
This study investigated dry fatigue and the effect of interaction (corrosion and creep) with fatigue to determine fatigue life for bending stress regimes of both constant and variable amplitude at (R=-1) using a high cyclic fatigue technique on specimens made of carbon steel alloy (A106 Gr-B) at elevated temperature (350°C) with some specimens immersed in Heavy Fuel Oil (HFO) to achieve pre-corrosion.
Under constant amplitude loading, tests of dry fatigue (DF), creep-fatigue interaction (“C” _”r” FI), corrosion-fatigue interaction (CFI), as well as triple fatigue interaction (TFI), were performed to construct an S-N curve in laboratory conditions, and the same tests were performed again under variable amplitude loading to evaluate the cumulative fatigue damage in the laboratory conditions.
The results observed that fatigue life of the specimens exposed to a corrosive environment, creeping, or dual corrosion/creep under constant amplitude loading and variable amplitude loading was greatly decreased. It was discovered that at constant amplitude loading for (“C” _”r” FI) gave a reduction percentage in fatigue life of (31.95%) compared to pure fatigue, while (CFI) gave a lower reduction percentage (of 44.41%) than the previous case, and (TFI) gave the highest reduction percentage (63.17%) of the remaining two cases.
Under experiments with variable amplitude loading, the fatigue life is predicted using the Modified Fatigue Interaction Model (MIFM). When compared to models based on the Miner concept, the suggested model shows less variation and yields better representative results. The suggested model agrees well with experimental findings and accounts for the effect of the loading sequence. Estimated results from the MFIM are found to be in good agreement with the compared experimental data.