Experimental analysis of S–N curves of welded joints with different fatigue life extension approaches

The fatigue life extension approaches played an important role in ensuring the safety of marine engineering structures. This study conducted an in-depth analysis of the S–N curves of welded structures under different service environments and different fatigue life extension approaches, and found that the comprehensive life extension process of welding toe polishing and coating (the fatigue life was extended by 15–33 times compared to untreated samples) was the most significant approach under dry air medium environment. The comprehensive life extension process of welding toe polishing and coating (the fatigue life was extended by 10–25 times compared to untreated samples) was the most significant approach under salt spray corrosive medium environment. Moreover, the S–N curve and related parameters of welded joints of semi-submersible platform under different environmental media conditions and different combinations of fatigue life extension approaches were studied in depth, which had important guiding significance for practical life extension tools of jacket platform T-joints in practice.