aluminium in commercial vehicles - European Aluminium Association

60 EUROPEAN ALUMINIUM ASSOCIATION ALUMINIUM IN COMMERCIAL VEHICLES CHAPTER VI
To save weight, the aluminium
beams in bending have to be
higher. An example will illustrate
this:
An aluminium beam shall have
the same deflection as an IPE
240 steel beam. The moment of
inertia and the mass of the IPE
240-beam are
I = 38.9 · 106 mm4 .
mass = 30.7 kg/m.
The aluminium beam must have
a moment of inertia of
I =116.7 · 106 mm4 to get the same deflection.
w
‰
b
h
t
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‰
‰ ‰
‰
If the height of the aluminium
alloy beam shall be 240 mm, this
will be satisfied by an I-beam of
I 240 x 240 x 12 x 18.3
which has a moment of inertia
and the mass of
I = 116.6 · 106 mm4 mass = 30.3 kg/m
If the height of the aluminium
alloy beam can be 300 mm, the
deflection criteria will be satisfied
by an I 300 x 200 x 6 x 12.9
which has a moment of inertia of
I = 116.7 · 106 mm4 and a mass =18.4 kg/m
which is a weight saving of 40%.
TABLE VI.1
An I 330 x 200 x 6 x 10 will have
a moment of inertia of
I = 117.3 · 106 mm4 and a mass = 15.8 kg/m
which give a weight saving of 49%.
These three different aluminium
beams will give the same deflection
as an IPE 240 steel beam. It will be
the shape and stability of the beam
that will determine the weight of
the beam. Table VI.1 shows the
beams and the weight savings.
Steel Aluminium Aluminium Aluminium
Moment in inertia in mm 4 38.9 10 6 116.6 10 6 116.7 10 6 117.3 10 6
E x I (N/mm 2 ) 8.17 10 12 8.16 10 12 8.17 10 12 8.21 10 12
h (mm) 240 240 300 330
b(mm) 120 240 200 200
w (mm) 6.2 12 6 6
t (mm) 9.8 18.3 12.9 10
Unit weight (kg/m) 30.7 30.3 18.4 15.8
Weight in %
of the steel beam 100 % 99 % 60 % 51 %