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beam will be the most
stressed part and has to be very
carefully treated to avoid problems.
Generally good precautions
will be:
• It is of utmost importance to
avoid all welding or heat treatment
on, or near, the flanges.
• No welded or bolted attachments
to, or near, the flanges in
this area.
• No joining of the beams
and/or reinforcement of the
beams in this area.
• No sudden variation of material
thickness or properties in this area.
It is obviously mandatory to follow
the fabrication or shop
drawings, design manuals, welding
procedures, QA-manuals and
the designer’s guidance throughout
the whole fabrication
process.
Figures VI.17, VI.18 and 6.19 present
a few lifespan examples
depending on the geometry of the
Gooseneck (i.e. curvature radius).
One can see the increase in stress
level is approximately 70% and
the increased deflection (δ)
approximately 23%.
The consequence will be a relative
lifespan decrease of 50 %
PLAIN CHASSIS BEAM, R = 1000 mm (σmax = 43 MPa, δ = 5.3 mm)
FIGURE VI.17
PLAIN CHASSIS BEAM, R = 450 mm (σmax = 73 MPa, δ = 6.9 mm)
FIGURE VI.18
σmax = 43 MPa
σmax = 73 MPa
PLAIN CHASSIS BEAM, R = 300 mm (σmax = 85 MPa, δ= 7.5 mm)
FIGURE VI.19
σmax = 85 MPa
83
EUROPEAN ALUMINIUM ASSOCIATION
from the normal radius of 450
mm to 350 mm. As illustrated,
an increased radius of 1000 mm
will offer very low stresses and
demonstrates simply the importance
of smooth transitions.
8.2.2. Perforation
The fixture of the supporting legs
to the chassis beam will normally
be located at the highest stressed
area of the chassis beam, i.e. in
the gooseneck area. Hence a perforation
of the bottom flange by
boltholes must be avoided as
well as any welding on or near
the flange.
Figures VI.20 and VI.21 show the
consequence of perforating the
flange compared to the web in
this area.
The reduced relative lifespan will
be as much as >80% due to the
effect of stress concentration in
the perforated area of the flange.
For the situation with the perforation
through the web, the lifespan
will not be reduced. Both
examples show the importance
of a location away from the most
stressed area of the beam. If a
perforation through the flange is
inevitable, the location should be
as close as possible to the edge
of the flange (as far from the
web as possible). Note that
HOLE IN CHASSIS BEAM FLANGE, (ø = 20 mm): σmax = 102 MPa
FIGURE VI.20
σmax = 102 MPa
σ = 73 MPa
HOLE IN CHASSIS BEAM FLANGE, (ø = 20 mm): σmax = 73 MPa (on flange)
FIGURE VI.21
σ = 35 MPa
σmax = 73 MPa
84
ALUMINIUM IN COMMERCIAL VEHICULES CHAPTER VI DESIGN AND CALCULATION 84 | 85
required minimum distance from
the edge should be according to
actual standards, normally 1,5ø –
2,0ø depending on direction of
load, etc. Also note that local
bending capacity of flange must
be checked according to actual
location.
8.2.3 Welding
A fixture by welding in the web
area of the beam is a much-used
alternative to bolting, and will be
fully acceptable as long as welding
is avoided in or near the
flange (i.e. in the most stressed
area of the beam). Figures VI.22
and VI.23 illustrate the consequence
of welding on the flange
and on the web.
The lifespan reduction will be as
much as >90% in the case of the
fixture by welding on flange, due
to the effect of stress concentration
in the welded area of the
flange and the decreased material
properties due to heating.
The fixture by welding in the web
area will be of no effect to lifespan.
In both cases a geometrically
perfect weld is assumed. In real
life, imperfections are common
and therefore good workmanship
and after treatment of welds
must be considered.
FIXTURE BY WELDING ON FLANGE: σmax = 97 MPa
FIGURE VI.22
σmax = 97 MPa
σ = 73 MPa
FIXTURE BY WELDING ON WEB: σmax = 73 MPa (on flange)
FIGURE VI.23
σmax = 73 MPa
σ = 25 MPa
85
EUROPEAN ALUMINIUM ASSOCIATION
9. Special design issues
9.1. Tanks for the
transport of dangerous
goods - ADR
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