Experimental Study on Fatigue Properties of Q420 Bridge Steel in a Deicing Salt Corrosion Environment in Western China

The corrosive environment in the western region will adversely affect the fatigue performance of bridges. In order to determine the influence of the corrosion environment in western China on the fatigue failure of bridges, this paper simulated corrosion environment characteristics in northwest China, conducted alternating corrosion and high-cycle fatigue experiments on Q420 bridge steel, and used Origin (2019b 64Bit) to fit S-N curves of specimens with different corrosion periods to study the influence of corrosion damage in western China on their fatigue properties. Based on the damage theory, the corrosion fatigue failure degree of Q420 bridge steel was analyzed, and the crack propagation law was revealed by microscopic scanning of the fracture. The findings indicate that the damage to Q420 bridge steel progressively worsens with more prolonged corrosion exposure in the deicing salt conditions of western China. The 60-day corrosion resulted in a rust rate ηs of 2.17% and a corrosion rate K of 1.413 mm/a. The fatigue life of Q420 bridge steel is significantly affected by the coupling of stress level and corrosion damage. After 60 days of corrosion, the specimen’s fatigue limit decreases by 12.28%, which accelerates the fatigue property degradation rate of the specimen. The damage index effectively represents the internal damage behavior of materials under corrosion fatigue conditions. Fatigue damage escalates as the corrosion period extends, and the number of fatigue bands decreases, with the stress corrosion threshold σth diminishing by 1.77%, 3.55%, 4.61%, and 6.38% across various corrosion durations. The research results are significant for the fatigue failure prediction and reliability analysis of Q420 bridge steel in a deicing salt corrosion environment in western China.