Audi TT Coupé ´07 383, 2007 TT Coupe Service

Audi TT Coupé ´07 - Body

Self-Study Programme 383

Service Training

Audi-Space-Frame ASF® of the Audi TT Coupé

The development targets for the bodyshell of the Audi TT

With a weight advantage of 48 % over a comparable all-steel bodyshell, in addition to an optimised weight
distribution, the new composite aluminium-steel spaceframe body of the Audi TT marks yet another mile­stone in the development of modern Audi bodyshells.

Crash safety of the bodyshell is enhanced by means of load-bearing structures at the front end, sides and rear
end, with a heavy emphasis on pedestrian safety.

To ensure efficient volume bodyshell production, various new joining and production techniques are
employed.

The repair concept is based heavily on the well-known aluminium repair concept. However, of course, the
materials combination of aluminium and steel necessitated that new approaches be taken.

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NoteReference

The self-study programme teaches the design and function of new vehicle models,
new automotive parts or new technologies.

The self-study programme is not a repair manual!
All values given are intended as a guideline only and refer to the software version valid at the time of
preparation of the SSP.

For maintenance and repair work, always refer to the current technical literature.

Contents

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Punch riveting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Clinching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

MIG welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Resistance spot welding and MAG welding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Structural bonding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

New joining technique: solid punch riveting (Kerb-Konus riveting) . . . . . . . . . . 16

New joining technique: Flow Drill screwing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

New joining technique: aluminium laser welding . . . . . . . . . . . . . . . . . . . . . . . . . 18

Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Technological concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Contact corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Combination of steel and aluminium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Comparison of ASF concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Audi Space Frame of the Audi TT

Joining techniques and production processes

Bodyshell safety concept

Repair concept

Aluminium repairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Steel repairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Aluminium-steel repairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Workshop equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Qualification of aluminium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Head-on collision, side impact and rear collision . . . . . . . . . . . . . . . . . . . . . . . . . 26

Pedestrian safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Electromechanical rear spoiler

4

Dimensions

Audi Space Frame of the Audi TT

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Audi TT Coupé ’ 07 2,0 3,2 quattro

Transmission Manual gearbox S tronic Manual gearbox S tronic

Kerb weight without driver in kg 1260 1280 1410 1430

Max. perm. gross weight in kg 1660 1680 1810 1830

cw (rear spoiler extended) 0.3 0.3 0.31

Boot capacity in l 290 (700*) 290 (700*)

Max. power output in kW 147 (200 bhp) 184 (250 bhp)

vmax in kph 240 250

Acceleration 0-100 kph in s 6.6 6.4 5.9 5.7

Fuel consumption in l/100 km 7.7 7.7 10.3 9.4

* with the rear-seat back folded forward

5

Technological concept

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Aluminium castings

Sheet-aluminium parts

Aluminium extruded sections

Sheet-steel parts

Sheet-steel parts are used for the first time in the
ASF of the new Audi TT in addition to aluminium
castings, aluminium extruded sections and alumin­ium sheet-metal parts. Collectively, they make up
the body structure. Vehicle weight distribution has
been optimised by using sheet-steel parts in the
rear body section. This has a direct bearing on
sporting characteristics, such as driving dynamics
and acceleration as well as safety characteristics,
such as stopping distance and driving stability
In spite of the partial use of sheet-steel parts, the
total body weight of 277 kg, including attachments
such as doors and lids, is considerably less than
that of a comparable all-steel body.

Although the new TT has grown in size, the gross
weight of the vehicle has been reduced through the
use of the aluminium-steel bodyshell.

The body structure of the new Audi TT has higher
strength and 50 % higher torsional rigidity than its
predecessor.

6

Audi Space Frame of the Audi TT

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Contact corrosion

Aluminium has a passivating oxide surface layer
which protects the material underneath from corro­sion. This is why an unpainted aluminium part nor­mally does not corrode.

However, if there is contact between aluminium and
a metal higher up in the electrochemical series than
aluminium and if an electrolyte, such as salt water,
is present in this region, contact corrosion will
occur.

The greater the difference in potential, the greater
the contact corrosion. As aluminium is normally the
lesser noble metal, it degrades.

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Contact corrosion can only be prevented by taking
measures to stop the flow of electrical current
induced by the potential difference between
the two metals. This is best achieved by painting the
surfaces. However, the risk of corrosion is high even
if a tiny amount of paint damage occurs.

In the case of the Audi TT, the following anti-corro­sion measures have been taken:

– coating of all steel screws and fasteners such as

self-piercing rivets

– Galvanising of all sheet-metal parts (zinc and alu-

minium have a smaller potential difference than

steel and aluminium)
– Insulation by means of adhesive
– Sealing of aluminium-steel joints

Reference

For detailed information on contact corrosion,
please refer to Self-Study Programme 239 "Audi
A2 - Body" .

Schematic of contact corrosion with example

Contact corrosion

7

Joining steel and aluminium

Thermal joining processes such as MIG welding can
be ruled out because it is not possible by these
means to make a joint which has the requisite struc­tural and dynamic strength and will not result in
contact corrosion.

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Steel

Aluminium

One of the challenges for the development of the
Audi TT bodyshell was the attachment of the sheet­steel rear-end parts to the aluminium body assem­blies.

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Aluminium-steel connections

8

Audi Space Frame of the Audi TT

This is ensured by non-thermal joining of parts
using coated self-piercing rivets and special screws
in combination with bonding.

Special requirements are made with regard to the
strength and corrosion protection of the joints
between aluminium body parts and steel parts.

Adhesive bonding is the basis for the corrosion pro­tection of corrosion-susceptible aluminium/galva­nised steel joints in the bodyshell of the Audi TT.In
this way, the mating materials are superficially insu­lated, thus suppressing corrosion processes at the
point of contact. As a further measure, all compos­ite joints either sealed with PVC or coated with wax
preservative after the cataphoretic dip coating (KTL)
process.

Aluminium and steel joints with faulty corrosion pro­tection can exhibit much higher corrosion rates than
all-aluminium joints or all-steel joints.When making
aluminium-steel joints, therefore, highest standards
of quality must be maintained at all times during the
production process and in the service workshop.

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Adhesive

Adhesive

9

The aluminium sheet shown here exhibits severe
contact corrosion, which has resulted in mechanical
failure of the punch riveted joint.

This illustration shows clearly what effects contact
corrosion can have if adequate corrosion protection
is not provided. A this joint, the flange was sealed in
the bodyshell without using adhesive.

In this case, the aluminium sheet showed no dam­age due to contact corrosion after exposure to iden­tical environmental conditions.

By way of a comparison, this illustration shows the
same flange with an adhesive bond and sealing.

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Seal

Seal

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Seal

Adhesive

Seal

10

Audi Space Frame of the Audi TT

Comparison of ASF concepts

Audi A8 (2003 ➔)

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Aluminium castings

Sheet aluminium parts

Aluminium extruded sections

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Sill section Audi A8
Three-chamber extruded section

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A-post, Audi A8
Single-chamber extruded section