Stress corrosion cracking of high-strength steel: influence of cyclic residual stresses

This paper analyzes the influence of cyclic residual stresses (generated by fatigue pre-cracking) on the stress corrosion behaviour of high strength pearlitic steel subjected to localised anodic dissolution and hydrogen assisted cracking. The effects of crack-tip plastic straining and residual stresses of a compressive nature, generated by fatigue loading, are elucidated by using both a simple theoretical estimation and a high-resolution numerical modelling of the near-tip stress-strain field during the previous cyclic loading and the posterior monotonic loading. It is shown that cyclic crack tip plasticity improves the stress corrosion behaviour of the steel in the two regimes of cracking. In the respective cases, the effects are supposed to be due to accelerated local anodic dissolution of-the cyclic plastic zone (cumulative damage region) producing chemical crack blunting or to the delay of hydrogen entry into the metal caused by compressive residual stresses, thus increasing in both cases the fracture load in aggressive environment.