USE OF FRICTION STIR WELDING ON MAIN LANDING GEAR BAY INSTEAD OF RIVETED JOINTS
Friction Stir Welding is a solid phase joining process commonly used in the aluminum industry. Contrary to fusion welding processes, FSW allows welding of 7xxx and 2xxx alloys, frequently used in aeronautic industries. Repeatability and low cost are the main qualities which make FSW a good candidate to replace riveted assemblies on aircraft structures. The removal of fastened assemblies should enable substantial weight and cost savings.
The typical junction area of primary structure is riveted for commercial aircraft. These junctions are sized by fatigue and damage tolerance criteria, due to pressurization loading, with single-shear or double-shear geometries, and potential overlap.
The use of FSW is a solution for critical junctions due to its capability for achieving high mechanical properties. Two welding configurations are possible: butt joint welding and lap joint welding. Due to corrosion requirements, butt joint welding is the best configuration.
In order to optimize the $/kg cost for weight savings, tailoring of properties is key in the design of future aircraft. A large alloy portfolio of products, including conventional alloys and Airware® (Aluminum Lithium technology), allows for combinations which maximize value in a weight/cost driven environment.
The Friction Stir Welding technology opens new opportunities for best performance assemblies, including dissimilar material joints. Through close collaboration between the airframer and the material supplier, specific process routes can be developed for complex structural parts achieving the performance targets.
The main challenge is to prove the viability of FSW through development of an industrial process which takes account of certification and cost aspects. This includes no defects in the welded area maintenance capability and no destructive testing.
Keywords: FSW, Riveted junction, Main Landing Gear Bay, Primary structure