On the fatigue behaviour and design curves of friction stir butt-welded Al alloys

The advantages of the friction stir welding (FSW) process over competing fusion welding process for the welding of aluminium alloys have been clearly identified. One of the main advantages compared to conventional fusion welding processes is the improvement of fatigue strength, implying that structural reliability of friction stir welded components can be substantially increased. A major issue, however, is that no general overview is available to help structural designers in determining design strength values for friction stir welded joints or their dependence on material type or process parameters. During the last 10 years several studies have dealt with the issue of structural performance of friction stir welded joints (particularly in aluminium alloys). This paper collects available fatigue data on FSW of Al alloys and statistically analyses these deriving a first set of reference fatigue curves. It is envisaged that a comparison of the reference curves obtained with the design curves given by design standards or recommendations (concerning conventional joining techniques) can assist, at the design stage, thereby giving a quantitative comparison of the influence FSW technology on structural dimensioning and design.