Page 609 - Automotive Engineering Powertrain Chassis System and Vehicle Body

CHAP TER 1 8. 1 Design and material utilization

Fig. 18.1-31 Aston Martin Vanquish.
MIG welding process achieving synergistic effects by Elise), but incorporates a mixture of carbon fibre and
combining both joining processes. A hybrid welding seam aluminium extrusions in the floor/tunnel construction as
length of 4.5 metres is achieved per body. As well as the shown in Fig. 18.1-32.
hybrid welding seams there are also 2400 punch rivets, In addition to the tunnel the windscreen pillars are also
64 metres of MIG welding seams and 20 metres of laser carbonfibre bondedto the central structureto create a high
welding on each A8 body. Concerning the peripheral joint strength safety cell. A steel, aluminium and carbon fibre
on bolt-on panels, rollers secured to a robot arm bend the subframe carries the engine, transmission and front sus-
outer panel over the inner and create a strong joint with pension and is bolted directly to the front bulkhead. As can
the application of a hem-bonding adhesive. The doors, be seen above the doors are fabricated from aluminium
bonnet and tailgate are hemmed in this way and the incorporating extruded aluminium side impact beams.
wheel arch to side frame is similarly processed. Induction
curing is used to prevent movement between inner and
outer panels at the body-in-white stage. 18.1.8 Integration of materials
The new A8 body is shown alongside the original
version in Fig. 18.1-28 and a lot of development time and into designs
effort have obviously been expended in optimizing an
extremely efficient production process. The emphasis on 18.1.8.1 General
laser and MIG welding plus mechanical fastening appears
to have advantages over the ASVT technology where The above appraisal of designs shows how the choice of
adhesive application to structural joints must prove more material is paramount to achieving today’s objectives
of a challenge in terms of application and resulting con- and how this choice is widening. Having minimized the
sistency and durability. weight of a specific design and assuming the best ma-
terials have been specified, the next consideration is to
optimize material with regard to each link in the chain
18.1.7.5 Examples of hybrid material
of processing operations necessary to produce a func-
designs tional part, and each of these elements can strongly
influence the selection. For instance, complex parts
18.1.7.5.1 Aston Martin Vanquish
require maximum formability which requires a com-
The new Aston Martin Vanquish, 13 Fig. 18.1-31, contains promise with strength, realistically placing a maximum
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a mixture of innovative materials technologies in a low at around 300 N/mm proof stress, although for simple
volume model (350 units/year). A number of the skin sections such as door reinforcement beams levels of
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panels are pressed or superplastically formed from 1200 N/mm may be specified. The constraints im-
aluminium sheet. posed by local steelmakers may obviate certain grades
The body structure is mounted on an aluminium where for instance a bake-hardening or isotropic steel
bonded and riveted lower structure (similar to the Lotus is required, and a restricted choice of coating types

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