Standards and Specifications for Friction Stir Technologies

To initiate the establishment of industry standards and specifications for friction stir technologies, a proposal was made to the Aerospace Metals and Engineering Committee (AMEC) of SAE to coordinate the drafting of AMS specifications for friction stirred materials and joints.  The proposal was accepted and preliminary work of formulating a road map was begun.  This work is also being coordinated with the Emerging Technologies Working Group (ETWG) of the Metallic Materials Properties Development & Standardization (MMPDS) to further support the establishment of a procedure for developing design data for airframe structure.   This program consists of two thrust areas.  The first program is a path independence initiative for butt joints produced by friction stir welding (FSW) and is based on the observation that many aluminum alloys have been joined with a wide variety of weld tool designs.  Therefore, an unspecified number of tool designs are expected to make equally sound joints with independently developed process windows.  Any advantage one tool may have over another is expected to be evident primarily in terms of productivity, i.e. welding and processing speeds. The second program involves qualifying friction stir spot welds for lap joints as integral fasteners. Individual “spots” are evaluated similar to conventional fasteners such as rivets.  Integral fasteners are fabricated in place (in situ) using the parent material that is normally discarded during drilling for installed fasteners.  In both static and dynamic tests, properly designed FSSW joints are proving superior to rivets because of favorable residual stresses and the elimination of the stress concentration associated with a rivet hole.  To promote the transition of these technologies to the shop floor, end effectors for producing swept FSSW are being developed for use with robots, machining centers, etc.