EFFECT OF PRE-ACCUMULATED PLASTIC STRAIN ON STRESS CORROSION CRACKING AND FATIGUE LIFE OF STEELS; EXPERIMENT AND MODELING
Amir AbdelmawlaGrand Ballroom B
Steel structures may experience localized plastic strains, arising from wide range of service anomalies. Regions of accumulated plastic strain are more prone to accelerated stress corrosion cracking and reduced fatigue life. In this work, we systematically analyzed the intergranular corrosion (IGC) under combined oscillatory mechanical loading and active electrochemical environment in a specially designed experimental apparatus. Loading cycles were design to mimic both the low amplitude high frequency vibration loads and the low frequency-high amplitude structural duty cycles. Electrochemical potentials were maintained for active dissolution in moderately alkaline carbonate-bicarbonate solutions and under pre-accumulated plastic strain of 0-4%. We observed grain boundary softening, directly arising from vacncies formed by silicon oxidation. Triangular wedges were formed and correlated with the level of the accumulated plastic strains and the load profile. A three-dimensional elasto-plastic continuum damage mechanics model is developed to account for both, the pre-accumulated plastic strain, and the induced elasto-plastic fatigue strains to accelerate the evolution of damage accumulation. Upto 90% of life reduction is observed with 4% of pre-accumulated plastic strain. These findings can be used to advance the understanding of the combined effect of damage and corrosion on the remaining fatigue life of energy materials.