Fatigue safety estimation of eh690 high-strength steel and welded joints in extreme marine environments

This study investigates the EH690 high-strength steel base metal and its welded joints under neutral salt spray tests simulating extreme marine atmospheric conditions. The research systematically examines the evolution of surface morphology under different corrosion durations and its influence on fatigue performance, with the stress concentration factor applied to quantify the effect of corrosion pits. A total of 18 base metal and welded joint specimens were subjected to corrosion exposures of 240, 480, and 960 h. The corrosion behavior was evaluated using mass loss measurement, 3D morphology scanning, and fatigue tests. Results show that with prolonged corrosion time, the surface roughness of the base metal increases significantly, and the fatigue life decreases drastically under high stress ratio. Moreover, at the weld toe, the corrosion notches deepen and the notch radius decreases, leading to aggravated stress concentration and more severe fatigue degradation. Based on experimental data, an S-N prediction model incorporating surface roughness and the stress concentration factor was developed, and a fatigue life assessment method applicable to corroded EH690 base metal and welded joints was proposed. This study provides a theoretical basis for the anti-corrosion fatigue design of such materials in marine environments.