GKN Aerospace has delivered the first production examples of an entirely new process for creating complex curved titanium structures. The delta pressure forming process is now being used to make the advanced cone-shaped titanium exhaust systems for the Boeing 747-800 airliner. The unit is lighter and more durable.
The process will also provide an effective method to create the complex shapes required for extremely rugged items such as engine inlet lips and inner barrels, thrust reverser inner fixed structures and exhaust nozzles and plugs. It has been developed by GKN’s operation in Santa Ana, California.
GKN’s proprietary resistance welded and diffusion bonded “Soundwich” technology produces flat panels of titanium honeycomb sandwich with excellent noise suppression qualities. These panels are then formed to the shape of the final product using the company’s drape creep forming technique.
In this process, the flat panel is draped around a die in a vacuum furnace at temperatures well above 1,000 degrees F with static weights attached to the ends of the panel. This creates a straight cylindrical or conical shape. Until now there has been no practical means of forming these panels into complex parts with compound curves.
Delta pressure forming begins with a cylindrical honeycomb barrel formed with an improved drape creep forming process that uses a roller system in place of static weights. The cylindrical barrel is inflated into a die to create the required compound curvature.
The operation is conducted in a vacuum furnace at temperatures exceeding 1,500 degrees F and the inflation pressure is provided by inert argon gas. Sophisticated forming analyses and special tooling features ensure the honeycomb core and the face sheets are not damaged during the process.