Fatigue performance of aluminum butt joints under varying weld orientations, misalignments, and weld geometry effects

Abstract This study numerically evaluates fatigue tests on aluminum butt welds, focusing on alloys EN AW-5754 O/H111 and EN AW-6082 T6 with varying weld inclinations. A parametric finite element model is used to adjust weld parameters such as weld toe angle, weld toe radius, axial misalignment, and angular misalignment. The model is validated against strain gauge fatigue tests, and analytical stress concentration factors for weld geometry and imperfections are assessed. Finite element analysis shows good agreement with measured stresses for small imperfections, while larger ones significantly reduce stress ranges due to forced deformation to the midplane. Analytical stress concentration factors (using $$\lambda _{axial} = 3$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>λ</mml:mi> <mml:mrow> <mml:mi>axial</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:math> in the formula) tend to underestimate stress ranges for significant imperfections in EN AW-6082 T6 with axial misalignment. Maximum stresses occur for transverse butt welds on the bottom side and 45° welds on the top. Parameter studies explore weld toe angles up to 60° and radii up to 1.5 mm, revealing different stress behaviors along the weld length. Manufacturing imperfections, including axial misalignment up to 1 mm and angular misalignment up to 0.5°, are also examined, showing that axial misalignment significantly affects fatigue life, with transverse butt welds showing lower numbers of cycles until failure compared to a 45° weld arrangement.