Improving fatigue performance of fillet weld roots using soft metal insertion

This study investigates the effect of soft metal insertion on the fatigue performance of fillet weld roots under bending-shear coupled loading. Previous research demonstrated that bonding-assisted welding improves fatigue strength, but issues such as epoxy combustion limited its application. To address this, zinc sheets were inserted between steel plates to establish zinc-steel bonding. Fatigue tests and numerical analyses were conducted on specimens with and without zinc insertion. Results indicate that zinc insertion significantly reduces fatigue stress at the weld root, extending fatigue life by approximately 70 % in some cases. However, the instability of zinc-steel bonding led to variations in fatigue strength among specimens. Finite element analysis using the effective notch stress (ENS) and equivalent displacement (ED) methods confirmed that zinc insertion reduces weld root stress and deformation by nearly 90 %. Both methods demonstrated similar accuracy in evaluating fatigue strength, but the ED method showed better alignment with the experimental results. This study demonstrates that zinc insertion effectively enhances the fatigue strength of fillet weld roots, providing a promising approach for improving welded joint durability. • Zinc insertion ensures better and more stable welding quality than epoxy insertion. • Zinc insertion improves fillet weld root fatigue strength under bending-shear loads. • Soft metal bonding effectively reduces weld root stress and deformation. • Equivalent displacement method accurately evaluates weld root fatigue strength.