Constraint effect of corrosion fatigue crack growth behavior in S690 high strength steel

S690 high strength steel was widely used in offshore platforms because of its comprehensive mechanical properties. Corrosion fatigue fracture was easily formed at the offshore platforms, while corrosion fatigue crack growth behavior was significantly affected by seawater corrosion, cyclic loading and constraint effect of the structure. Therefore, the fatigue crack growth rate tests in air and seawater, combining with fracture morphologies analysis, were conducted to investigate the constraint effects of the corrosion fatigue crack growth behavior in S690 high strength steel. The results indicated that the fatigue crack growth rate in seawater was dramatically accelerated by anodic dissolution and hydrogen induced cracking. Meanwhile, the constraint effect on the corrosion fatigue crack growth rate increased with the crack growth. The corrosion fatigue crack growth rate was closely related to the constraint increment before and after the crack growth and the constraint of the structure.