Page 546 - Automotive Engineering Powertrain Chassis System and Vehicle Body

Standard sedan (saloon) – baseline load paths C HAPTER 16.2

M XX

Q 1 MXX
Q 4 M XXC
MYY
M YYA
M XXB M YY
M XXA
P-AXIAL

A-pillar
A-pillar
bending
moments
P Axial

Fig. 16.2-17 Stresses in shared pillar.

Fig. 16.2-17). In this case the lateral load in each direction (f) The connection of the parcel shelf to the A-pillar is
P X and P Y must be accounted for. They will lead to another high stress area. This results from the high local
bending moments about two directions in the pillar. If the bending moment in the A-pillar due to force Q x1 . Simi-
pillar is sloped in one of these frames (e.g. the A-pillar in larly, in the standard sedan, the middle of the C-pillar
the sideframe) then there will also be an axial component will be highly stressed due to bending moments caused
of force in the member. These moments and axial forces by the ‘hat shelf’ end reactions Q x2 .
will cause a combined stress system in the pillar.
Therefore
16.2.3.7 Structural problems in the
M x y M y x P torsion case
s max: ¼ þ þ
I x I y A
16.2.3.7.1 The ‘faux sedan’
(e) A good load path from the inner fender upper A ‘closed box’ of SSSs is required in the passenger
booms to the sideframes, via the ‘parcel shelf’ is essential compartment to maintain an effective load path of ‘shear
(unless the booms are offset to connect directly to the panels’ to carry torsion.
sideframe A-pillar). Thus the parcel shelf must be stiff in If any one of the structural surfaces in the compart-
bending. It is a highly stressed component because of the ment is missing then the structure becomes an ‘open box’
high bending moments caused by forces P FT . and the shear panel load path for torsion breaks down.

0′ ′ 0′ ′
0′ ′
0′ ′ Q x1 0′ ′ 0′ ′ 0′ ′ 0′ ′ T
Q 3 0′ ′ 0′ ′ 0′ ′
0′ ′ 0′ ′ 0′ ′ 0′ ′
R NF 0′ ′
Q x1 0′ ′ 0′ ′
P 0′ ′ Q x1 Q x2 Q R 0′ ′
0′ ′ FT P
Q 3 R FT FT R NR
P FT R FT Q x1 Q 3 Missing
R FT 0′ ′ Q 7 R NR SSS
P FT Q 3 R NF
P FT
R FT Q 7 0′ ′
T P R NF P RT R NR
R FT FT P FT P RT
0′ ′ Q 7

R NF
Fig. 16.2-18 Faux sedan in torsion.

555