Efficacy of the Stationary shoulder Tool for Modifying the Heat Input During Friction Stir Welding

In the work to be presented here the intent is to take advantage of the simplicity of the stationary shoulder heat source to improve our understanding FSW heat sources in general.  The nature of the heat source is probed by performing several series of welds with both stationary shoulder and conventional FSW tools.  Critically, (1) the stationary and conventional shoulder tools have identical or nearly identical probe geometries and (2) identical process parameters, tool rotation rate and welding speed, are used for both stationary and conventional shoulder welds. In both the stationary and conventional shoulder welding, the z-force is controlled to produce good quality welds however, in the stationary shoulder welding the z-force has minimal importance in determination of the heat input. Critical findings include that: (1) total heat inputs and weld temperatures may, under some conditions, be almost identical for otherwise similar (probe geometry and weld parameters) stationary and conventional shoulder welds, (2) similarity between the stationary and conventional shoulder heat inputs depends to some degree on the gage welded and on the particular alloy. As might be expected, stationary and conventional shoulder heat inputs tend to be more similar for thick plate and less similar for thin plate (in some cases).