Influence of Laser Remelting Treatment on Fatigue Performance of Steel Structure Welded Joints

As a crucial method for connecting steel structures, welding plays a vital role in ensuring structural integrity, and the fatigue performance of welded joints directly affects the overall safety of steel structures. To enhance the fatigue performance of welded joints in steel structures, this study proposed the use of laser remelting treatment on the welded joints. For this purpose, this study conducted high cycle fatigue tests on the as-welded joints and laser remelting treated welded joints of Q355 steel plate butt welding. The stress levels for high-cycle fatigue tests were determined through tensile tests on as-welded joints. Fatigue fracture surface analysis was conducted using scanning electron microscopy (SEM). Based on the experimental results, stress-life (S-N) fatigue curves were fitted for both the as-welded joints and the laser-remelted welded joints, and the results were compared with standard fatigue design curves specified in relevant codes. The experimental results show that laser remelting treatment can change the location of fatigue fracture in welded joints, prevent failure at the weld toe and thereby significantly improve the fatigue life of welded joints, with an average increase of 244% to 499%. The fatigue fracture analysis show that there were mainly ratchet crack sources and a few subsurface crack sources in the as-welded joints, and there are mainly corner crack sources and edge crack sources in the laser remelted joints; the fatigue performance design curves provided by the American Steel Structure Code ANSI/AISC360-22, European Code EN 1993-1-9:2005, and Recommended Method for Offshore Steel Structure Design DNV-RP-C203 can be applied to the fatigue performance of as-welded joints, while these curves tend to be conservative for laserremelted welded joints.