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( material removal, welding, surface pattering, etc.) for the control of the heat input, in particular its reduction. The material changes are thereby substantially reduced in the so-called heat affected zone. By this, for instance, components in microelectronics allow themselves to be welded instead of soldered. However, developments are still very much in the early stages.

9.17.3 Hot topics Nanojoining technology, while still in its infancy, is starting to develop rapidly and will become a key technology in commercially viable manufacturing of nanodevices, nanosystems and nanoalloyed materials. Most current nanojoining work is on technological aspects, especially on developing new and modified processes to provide solutions for functional nanodevices and nanosystems. Work is, however, needed on fundamental aspects of nanojoining for the long term progress of this area. These include the mechanisms of joining at nanoscale, such as driving forces, oxide removal, surface roughness effects, the formation of chemical bonds and crystallographic orientations across the bondline, especially in dissimilar material combinations, and effects of joining on the functionality, whether physical, chemical or mechanical, of nanoscale building blocks. 9.18 Aerospace sector Airframes of commercial aircraft are primarily made of riveted Al-alloy skin and stringer construction and called “differential” or “built-up” structures. The manufacturing of these conventional riveted airframes is a very time consuming and expensive process. Aerospace industries have been exploring new technologies that have the potential to improve airframe design and fabrication processes, as well as reducing cost and weight. Knowingly, major aerospace industries have been intensely working on the development and technological implementation of advanced joining technologies (laser beam welding, LBW and friction stir welding, FSW) to replace the differential structures with welded integral airframe structures.

Figure 9.14 Laser beam welded Al-alloy fuselage part demonstrating LBW joints of skin-stringers (already flying) and skin-clip (future application) (Reproduced courtesy: AIRBUS)

Driven to higher and higher levels of performance, novel ways of fabricating structures in metallic and other material systems are of increasing interest. Such structures eliminate the cost and weight of conventional riveted structures and also provide improved aerodynamic performance, increasing fuel economy which is of increasingly critical interest. With the part count of a 747 being one million, half of these are rivets and other fasteners, mostly for the aerostructure. Partial or substantial elimination of these rivets and other fasteners dramatically reduces assembly time and lowers inventory cost. Development and use of advanced welding technologies associated to new aluminium alloys for the “ Integral Structure” or “Rivet-Free” Al-alloy airframes are considered as an innovative technology needed to achieve lighter and low cost metallic airframes. Currently, in some civil aircraft fuselages (including the

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Through Optimum Use and Innovation of Welding and Joining Technologies

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