Effects of Hammer Peening on Fatigue Performance of Roof and U-Rib Welds in Orthotropic Steel Bridge Decks

The effects of hammer peening on the fatigue performance of roof and U-rib welds in orthotropic steel bridge decks were studied by fatigue testing and finite element analysis simulation. Eight specimens of roof and U-rib welds were manufactured. The changes in weld geometry and microstructure after hammer peening were measured by the reverse mold and metallographic test. The effects of hammer peening on fatigue life were compared. Through the use of finite element models, the stress and deformation after hammer peening, and the effects of hammerhead radius and hammer depth were investigated; operational suggestions regarding hammer peening were also proposed. The results indicated that hammer peening reduced the geometric mutation of welds and generated a stratiform microstructure near the surface. The fatigue life of roof and U-rib welds increased significantly after hammer peening. The influence depth of residual compressive stress induced by hammer peening increased as the hammerhead radius increased, while the maximum compressive stress decreased without changes to its distribution. The principal stress and influence depth of the applied compressive stress increased with increasing hammer depth as well. The Hammer peening parameters of a 4 mm hammerhead radius and a 0.5 mm hammer depth were suggested.