Linear Friction Welding (LFW) of Aircraft Structural Components in High Strength Aluminium Alloys

Linear friction welding (LFW), a solid state welding process, can produce high weld quality in a wide range of metallic alloys. The technique was pioneered for joining aeroengine blades to disks and has progressed through to production for such parts. It is significant that the process has gained acceptance in the production of aeroengine components and this is a testament to the quality and performance of the welds in a challenging application.

Recent attention has focussed on the development of alternative, cost effective, high quality manufacturing routes for airframe components both in titanium and aluminium alloys.The main driver here is that many structural parts consume large quantities of material to produce the final machined component. An outstanding example of this is wing rib manufacture, where up to 96% of the original billet required is machined away. If, as predicted, 25,000 single aisle aircraft will be produced in the next 20 years, then it is estimated that around $8.5 billion worth of high strength aluminium alloy will have been reduced to scrap just for wing rib components.

A series of rectangular plates can be linear friction welded at right angles to the edge of an aerofoil section plate, to form the basic I-beam shape of a wing rib. Welding efficiencies of up to 90% can be achieved just for wing rib components. This rib preform requires much less machining to final shape compared to current practice. This novel approach could significantly reduce the cost of wing and other airframe structures manufacture and is attracting a great deal of industrial interest. Examples will be shown of recent work in this area at TWI and the future potential of the approach will be discussed.