Fatigue analysis of cruciform welded joint with weld penetration defects

Abstract

For the fabrication of steel structures such as steel bridges, offshore structure etc, welding is nowadays considered as an efficient metal joining process. The type of fillet welded cruciform joint are widely used in construction of long spanned bridges with improved design and increased weld quality. However, the presence of geometrical discontinuities and metallurgical nonuniformities lead to crack initiations from different positions which are difficult to detect. Moreover, when these structures are subjected to repeated loading these cracks start propagating in different directions and lead to fatigue failure of welded structures. Also, the presence of locked in stresses and other factors affect the fatigue life and fatigue crack initiation. In the present work, the cruciform fillet welded joint with full and incomplete penetration were analyzed for both load types i.e load carrying and non-load carrying by using 3D fatigue FEM analysis. The experimental study of non-load carrying cruciform joint was also carried out. The effect of incomplete penetration depth, welding deformation, residual stresses and stress magnitude on fatigue crack initiation and fatigue life of fillet welded cruciform joints was investigated. Also, the S-N curves plotted for comparing with the results of hotspot stress and experiments. The results of 3D fatigue FEM analysis were compared with S-N curves recommended by IIW and DNV GL.