| Because of S690 steel's comprehensive mechanical properties,it was widely used in offshore platforms,such as the moveable legs.The offshore platforms were easily to generate corrosion fatigue fracture and the corrosion fatigue crack growth behavior was significantly affected by the corrosion effect of seawater,the cyclic loading and the constraint effect of the structure.Therefore,to study the effects of the seawater,?35?K0,R and the constraint on the corrosion fatigue crack growth behavior of S690 steel,the fatigue crack growth rate tests in air and seawater were conducted and the crack length was measured by direct current potential difference?DCPD?.What's more,with the fracture morphology,the mechanism of the corrosion fatigue crack growth behavior of S690 steel in seawater was analyzed.And the mechanism of the constraint effect on the corrosion fatigue crack growth behavior of S690 steel was explored.The main research results were as follows:The fatigue crack growth rate in seawater was dramatically accelerated by anodic dissolution?AD?and hydrogen induced cracking?HIC?.In the stable stage of crack growth,the crack growth rate in seawater was about 4 times faster than the one in air.And the corrosion fatigue crack growth rate of S690 steel in seawater decreased with the reduction of?35?K0.What's more,there was almost no disparity of the crack growth rates when different stress ratios were applied.Meanwhile,the constraint effect on the corrosion fatigue crack growth rate was small at the beginning of the crack growth,but the constraint effect increased with the crack growth,and 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. |
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