Generalized SCF Formula of Out-Of-Plane Gusset Welded Joints and Assessment of Fatigue Life Extension by Additional Weld

The existing S-N curves by effective notch stress to assess the fatigue life of gusset welded joints can result in reduced accuracy due to the oversimplification of bead geometries. The present work proposes the parametric formulae of stress concentration factor (SCF) for as-welded gusset joints based on the spline model, by which the effective notch stress can be accurately calculated for fatigue resistance assessment. The spline model is also modified to make it applicable to the additional weld. The fatigue resistance of as-welded and additional-welded specimens is assessed considering the geometric effects and weld profiles. The results show that the error of SCFs by the proposed formulae is proven to be smaller than 5%. The additional weld can increase the fatigue life by as great as 9.4 times, mainly because the increasing weld toe radius and weld leg length lead to the smaller SCF. The proposed series of S-N curves, considering different SCFs, can be used to assess the welded joints with various geometric parameters and weld profiles.

Numerical analysis of the fatigue behaviour of friction stir welded joints in aluminum bridge decks

<p>Friction stir welding (FSW), a relatively new welding technique, has been widely used in the aero- space and manufacturing industries, showing superior mechanical and durability properties. How- ever, its application in civil engineering is very limited due to the absence of appropriate standards and quality control guidelines. FSW appears to be a promising welding solution for the fabrication of vehicular bridge decks made from aluminum extrusions, with a potential to reduce distortions and improve fatigue properties. The fatigue behaviour of common FSW joint types such as the butt FSW has extensively been investigated and documented in literature. However, certain practical configurations such as the butt-lap joint used in the fabrication of extruded aluminum bridge decks have rarely been studied, especially in the area of fatigue performance. In this context, the present research provides first an overview on the welding process of typical aluminum friction stir welded bridge deck extrusions presenting the butt-lap configuration. Then, the fatigue behaviour of butt- lap FSW joints is assessed using the effective notch stress (ENS) approach. The effect of geometrical features on the fatigue behaviour of butt-lap FSW joints is numerically investigated also by the ENS approach.</p>