Despite radical changes in the focus of the aerospace industry, TWI's activities within the sector continue to provide some of the key drivers for the business. It is from these drivers that the work in our diverse Technology Groupsis generated. This article gives a brief description of just a few of the new developments TWI is working on.
Arc welding
One of the main concerns when using arc welding is the occurrence of distortion in welded parts. TWI's current developments in Low Stress No Distortion (LSND) welding have shown that this technique significantly reduces the level ofdistortion as a result of welding. The process involves spraying liquid CO 2 onto the back face of the weld to rapidly cool the weld metal immediately behind the weld pool.
Friction welding
Friction stir welding of aluminium alloys has prompted a lot of interest within the aerospace industry. Boeing originally employed the technique in the Delta II rocket, launched in 1999, which had a friction stir welded interstagemodule. A subsequent model incorporated three friction stir welded fuel tanks. The process is being looked at to replace riveting in the floor of the Lockheed Martin C130J and Boeing C17 military transport aircraft, and in thedevelopment of integrally stiffened skin panels for the Eclipse 500 business jet.
Linear friction welding has found industrial application in aircraft engine manufacture, where it has proved to be an ideal process for joining turbine blades to discs (blisks). One of the current issues under investigation is thejoining of single crystal nickel alloys to polycrystalline discs.
Electron beam welding
Electron beam welding has long been favoured in the aerospace industry for its ability to make precision, low distortion welds under clean vacuum conditions. Less well known is the potential to control and manipulate the electronbeam for other materials processing tasks. Electron beams can be split and deflected away from the weld hundreds of times a second to perform other operations on the workpiece (such as preheating ahead of the weld pool) without therisk that the weld pool will react to the changing heat source.
Non-Destructive Testing (NDT)
TWI has been involved in a number of large European NDT projects to support the aerospace industry. ROBAIR involves the development of a robotic system for the inspection of aircraft wings and fuselage. NANOSCAN concentrates on NDTtechniques for the detection of defects in composite materials.
The expansion of TWI through the Technology Centre South Yorkshire will directly benefit the aerospace industry. We expect state of the art friction stir welding and laser welding equipment to be commissioned by early 2004, thanksto support from the European Regional Development Fund and Yorkshire Forward. Much of the work carried out at this facility will have an aerospace focus.
If you would like to find out more about TWI aerospace activities, e-mail aerospace@twi.co.uk
