The effect of weld geometry and residual stresses on the fatigue of welded joints under combined loading

A mathematical model is developed to predict the overall effect of the influencing weld geometry parameters such as (e.g. weld toe radius, weld toe undercut, flank angle, plate thickness, misalignment) and residual stresses on the fatigue strength and fatigue life of butt-welded joints subjected to combined loading (tensile and bending). The concepts of linear elastic fracture mechanics (LEFM), finite element analysis (FEA), dimensional analysis technique (DAT) and superposition approaches have been used for the modelling. It has been found that the co-influence effect of weld toe-undercut with other butt-weld geometry parameters is very significant. The reduction of fatigue life and fatigue strength, in comparison to that of flush-ground welded plate, caused by the introduction of a weld toe undercut is twice that for a welded joint without an undercut. The combined loading condition resulting from misalignment can significantly reduce the fatigue life and fatigue strength of butt joints by 10-60% subject to misalignment levels of 5-50% (ratio of axial eccentricity to plate thickness of 0.05-0.5), respectively. The effects of both compressive and tensile residual stresses are incorporated successful in the model. The mathematical model is satisfactorily verified by experimental data. (C) 1998 Published by Elsevier Science S.A. All rights reserved.