Fatigue strength assessment of as-welded and HFMI treated welded joints according to structural and local approaches

High-frequency-mechanical-impact (HFMI) is a post-weld treatment for improving the fatigue strength of welded structures, by introducing compressive residual stresses, localized strain hardening and enlarged weld toe radii. The Peak Stress Method (PSM) is extended for the first time to the fatigue strength assessment of HFMI treated steel joints, by means of a dedicated analysis procedure and new fatigue design curves. Experimental data generated from joints tested under uniaxial loading, both in the as-welded and HFMI treated conditions, have been taken from the literature and have been successfully analysed by using the PSM and the structural hot-spot stress (SHSS) approaches.