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BAE Systems Airbus causes a stir

A friction stir welding process is being studied by BAE Systems for possible application to the manufacture of components for the forthcoming Airbus A3XX. The process enables metal components to be welded together instead of riveted, which saves time, money, and weight.

BAE Systems Airbus UK is studying a friction stir welding system.

The company explains that friction stir welding was invented and developed by The Welding Institute, an independent research and technology organization in the UK. The process involves the running of a welding tool between the pieces of metal that need to be joined. The tool spins at very high speeds, creating friction that heats the metal. Aluminum alloys may reach 450°C. As the tool moves along the joint, it softens the metal, causing it to become plasticated, which results in a high-strength weld. Friction stir welding, however, does not involve melting the metal. Therefore, the process overcomes the problems of traditional welding such as cracks or porosity.

In 1997, BAE developed a small-scale friction stir welding research program. Because it generated positive results, the company acquired a friction stir welding machine produced by UK company Crawford-Swift.

BAE is also using Knowledge Based Engineering (KBE) to speed A3XX development. KBE is, in essence, a software environment that allows a business to capture and retain engineers' and specialists' experience and knowledge, leading to time and cost savings. BAE has used it to "down select" wing designs for the A3XX within what it terms "revolutionary timescales" as well as achieve 50% cost savings in the engineering of key components and significant production savings. KBE integrates an object-orientated programming language with a geometric modeling tool controlled by encoded engineering "rules," according to BAE. This facilitates "generative modeling," which produces almost instantaneous new design data. This automation of the time-consuming element of design allows engineers to work on other projects, thus reducing both development and end product costs. KBE is now being successfully integrated with other design tools and manufacturing and materials research at the company. KBE and Design City, the tool that is at the heart of the Airbus wing aerodynamic design process, are able to interface and integrate the process, linking Navier-Stokes computer codes for aerodynamic prediction with new high-speed machine tools for wind tunnel A3XX model manufacture.

Airbus A3XX will carry 555 passengers in a typical configuration.

Airbus Industrie has said that an estimated 40% of the A3XX's structure and components will be manufactured from the latest generation carbon composites and advanced metallic materials because they are not only lighter, but offer improved reliability, maintainability, and ease of repair compared to traditional materials. The aircraft is described by Airbus as one of the first to have a carbon-fiber central wingbox, saving some l.5 tonnes compared to most advanced aluminum alloys. A monolithic carbon fiber reinforced (CFRP) design has been adopted for the fin box and rudder together with the horizontal stabilizer and elevators. The upper deck floor beams and pressure bulkhead will use CFRP, and the wing covers will be made from advanced aluminum alloys. The fixed-wing leading edge and secondary brackets in the fuselage (e.g., for fixing interior trim) are likely to be made from thermoplastics. The company is also considering the material's use for the ribs in the fixed leading edges of the vertical and horizontal stabilizers. The upper fuselage shell will use GLARE, a laminate with alternate layers of aluminum and glass fiber reinforced adhesive. Weight savings using this material is about 800 kg and has the added bonus of promising enhanced fatigue and damage resistance. Testing has demonstrated that an artificial crack subjected to thousands of flight cycles barely increased in size, according to Airbus. GLARE uses a hot-bonded manufacturing process but is repaired in the same way as standard aluminum.

In addition to the friction stir welding study by BAE Systems, several innovative manufacturing techniques have been selected by Airbus for the A3XX program, some of which will be applied initially to other aircraft programs. One of these is laser beam welding, which will be used to attach stringers of the lower fuselage shell as an alternative to traditional riveting. Again, the technique saves weight, but is also quicker. It takes only one minute to laser weld 8 m of stringers. It has a built-in automated inspection unit. The system obviates the need for fasteners, which may be a source of fatigue cracks and corrosion. The A318 will be the first Airbus aircraft on which laser beam welding will be used, starting next year.

Airbus has confirmed that the A3XX's hydraulic system will have a 5000-psi capability instead of the 3000-psi norm. Military aircraft currently use the higher pressure system. According to Airbus, this increased power is necessary to handle the A3XX's flying controls. The reduction in component size, connections, and piping not only lowers the weight of the aircraft by around one tonne, but also improves maintainability. The flight control system will feature a dual architecture consisting of hydraulic and electrical energy sources. The A3XX will get two hydraulic and two electrical circuits.

Knowledge Based Engineering (KBE) is used by BAE Systems Airbus.

Supply chain efficiency is crucial to aircraft manufacture, and BAE Systems Airbus is using Waer Systems' WaerLinx at its Broughton facility for the supply of nuts, bolts, and rivets to the wing assembly line. WaerLinx quickly matches supply to demand by pulling real-time data directly from the line. It provides information to anticipate usage and maintain warehouse stocks at optimum levels and links the logistics chain from manufacturer to the final point of use via the distribution network. WaerLinx is described as an advanced development of an IT system created by C.J. Fox, a UK company that specializes in the distribution of fasteners and other hardware to aerospace manufacturers. According to Waer Systems, some manufacturers have been frustrated by the log-istical challenges of managing high volume, low-cost parts from multiple suppliers because handling costs may exceed component unit costs. To overcome this, supply chain management systems must link the supplier and the manufacturer and rapidly match supply to demand.

Stuart Birch

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