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is that traditional welding processes are difficult to control within the strict tolerances and safety
margins required by the aeronautic industry. New welding processes such as FSW are successfully
"New Trends in Welding in the Aeronautic Industry," P.F. Mendez and T.W. Eagar,
2nd Conference of New Manufacturing Trends, Bilboa, Spain, November 19 - 20, 2002. 6
addressing this issues. The welding fraction of cost is likely to increase significantly in the next
few years as these new processes expand to replace rivets.
Despite the low fraction of costs related to welding in the aerospace sector, we realize that each
airplane and rocket produced have enormous welding costs if we analyze the welding costs per unit
produced, as shown on Table 1. On average, the welding cost of each airplane is $100,000 and the
welding cost of each rocket is about $500,000. In contrast, a car typically carries $100 of welding
costs.
Table 1
Welding expenditures per unit manufactured
Total welding
expenditures [7]
Units produced in a
year
Welding expenditures
per unit
automotive $2.5 billion 30 million ~$100
aeronautics $200 million 2,500 ~$100,000
space $50 million 100 ~$500,000
The welding cost is driven principally by labor and materials. The labor fraction of costs for the
aeronautic/aerospace industries is around 80%, the highest for all industries, a reflection of the
highly qualified personnel required to design and implement welds of such high integrity. This cost
is likely to see a significant reduction as welding becomes ubiquitous in airplanes; in fact, laser
welding is a cheaper joining process than riveting. Despite the advanced materials used in airplanes
and rockets, materials and consumables constitute only 13% of the cost of welding airplanes and
22% for rockets.
Latest developments
Laser welding
Laser welding in airplanes is a reality with orders in place for the Airbus A318 and A380. The
lower panels of the fuselage of the A318 are the first ever to include laser welding. These panels
are manufactured in Saint-Nazaire (France) and Nordenheim (Germany). The welding machines at
this last location were supplied by the Spanish company M. Torres. Compared to automatic
riveting, laser welding reduces joining time by half, taking only one minute to weld 8 m of
stringers, and has proven gains in weight and manufacturing costs. It is also less sensitive to
corrosion than rivets.
"New Trends in Welding in the Aeronautic Industry," P.F. Mendez and T.W. Eagar,
2nd Conference of New Manufacturing Trends, Bilboa, Spain, November 19 - 20, 2002.
7
Figure 7
Conventional design with the stringer riveted to the skin plate (left) and design adapted for laser
welding without rivets (right)[8].
Friction Stir Welding
The application of FSW to aeronautics has happened faster than we expected, being the primary
joining method for the Eclipse 500, a six-person, twin-engine jet. FSW is also planned for the next
generation external tank in the Space Shuttle, and it is being considered for the Airbus A380, where
rivets have already been replaced by laser welds in several places. What enabled this rapid growth
of FSW was the introduction of an automatically retractable pin tool developed by Jeff Ding, a
welding engineer at NASA's Marshall Space Flight Center, and Peter Oelgoetz, of Boeing.
The rapid progress of FSW might influence materials selection. Revolutionary materials, such as
the Glare composites -alternating layers of aluminum alloy and glass fiber-reinforced epoxy- used
in the Airbus 380 cannot be friction stir welded. It is possible that the advantages of FSW outweigh
those of the composite, as future designs shift to the use of high-performance aluminum alloys,
previously considered unweldable.
Figure 8
Friction stir welding process and retractable pin tool[9, 10]
The Eclipse 500
This airplane, which flew for the first time in August 2002, is the first to incorporate FSW to join
structural components. The use of FSW is innovative, being applied to lap joints instead of the
traditional butt joints. These lap joints are used over 65 percent of the aluminum-alloy structure in
the cabin, aft fuselage, wings and engine mounts. Common locations for FSW lap joints include
attachment points of ribs and stringers to wing skin eliminating 65% of the riveted joints or about
8
30,000 rivets. Rivets will still be used in tail components that have skins thinner than 0.040”, and
in longitudinal fuselage joints that will see high structural loads. These continuous welded joints
have about three times the static strength offered by a single row of rivets, and a fatigue strength at
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