LAUSR

Abstract This paper investigates the scale effect in relatively thin welded joints subjected to fatigue loading made of steel. In the scientific literature, the fatigue behaviour of arc-welded joints is usually divided into two groups: thick and thin joints. A cut-off thickness, typically in the range of 13–22 mm, was introduced; under such cut-off value, the design fatigue strength does not increase when the thickness is decreased. Despite this common approach, in this paper, the concept of cut-off thickness is revised and a numerical procedure is proposed, regardless of the thickness of the joint, by means of the implicit gradient method. Classical non-load-carrying and load-carrying cruciform joints made of steel are considered in the three-dimensional numerical analysis. Finally, the fatigue behaviour of joints two millimetres thick with a longitudinal or transversal stiffener was also analysed by means of the implicit gradient approach. The Woehler curve was evaluated in terms of the nominal stress of such a series and a good correlation was found with experimental data by using the numerical procedure optimised for thick welded joints.