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ALTERNATIVE CONSTRUCTION FOR BODY SUBASSEMBLIES AND MODEL
VARIANTS
INTRODUCTIONVariations from the basic ‘standard sedan’ structure 2 levels:
Body subassembliesMajor subassemblies can take many different forms such as
suspension mountings and passenger compartment
Vehicle model variantsVehicle model may be produced in a range of variants
E.g.: station wagon, hatchback, convertible, pick-up truck, etc.
Structural features are significantly different from sedan
ALTERNATIVE CONSTRUCTION FOR MAJOR BODY SUBUNITS
In standard sedan:
Suspension loads (RF & RR)Carried by the end structures
i.e. inner fender assemblies
Shear panel reactionsCarried by the front or rear compartment bulkhead
Flange reactionsTaken by parcel shelves and floor
In this lecture:Alternative end structures at front & rear are consideredVariations are based on the standard sedanAll discussions are in relation to the EXPLANATIONS OF TORSION AND BENDING LOAD CASES on the standard sedan
It is essential to configure the structure correctly. If not, local deficiencies might happen
This will lead to serious degradation of overall structure
Rear Structures – Rear Suspension Supported on Floor
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Normally for trailing arm & similar rear suspensions
•Q10, Q6, fig. 5.12
•Pass compartment
•Bending, Q8, Q9
Load applied to the compartment
Rear Structures – Suspension Towers at Rear
For strut type rear suspension
Need rear suspension towers
If it is closely built into the sideframe, hence Fig. 6.3
• line of action of strut, couple, torsion
• vslc: brace
• tlc: brace has same direction, stiff in shear add structure assgmnt
Frontal Structures – Grillage Type Frontal Structure
For front suspension that is attached to the lower engine rails
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Frontal Structures – Grillage Type Frontal Structure With Torque
Tubes
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Missing or Flexible Shear Web in Inner Fender
Missing Shear Web in Inner Fender: Upper Rail Direct to A-pillar
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CLOSED INTEGRAL STRUCTURESDifferent closed body configurations mounted on a common floor pan assembly will be discussed
Standard sedan floor is often used for:Estate carHatchback
Rear structure experienced a little changeExtended for estate carShortened for hatchback
Bending load case can be treated in the same way as before
Rear door frame for estate car will function in a similar way to the rear panel in standard sedan
The sill of the rear door will:Carry bending & shear loadsTransfer forces to the sideframe
Torsion load case must be treated differently than the standard sedan
Special care must be taken when analyzing the rear frame for estate/hatchback
Estate Car/Station WagonModern station wagon has a rear door that is near vertical & constructed in a single or near single plane
Can be treated as single SSS
Primary structural function in torsion case is to transfer shear from the roof panel to the floor
HatchbackThis style of body has caused particular structural problems
To minimize drag, hatchback rear frames are constructed with a sloping backlight with a short horizontal surface at waist height & a vertical surface between waist and rear bumper
No longer a plane structure but 3 planes
Structural function remains the same as estate cari.e. to transfer shear from roof to floor during torsion
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OPEN VEHICLE: bending load case
All edge loads are well supported by the components
The sidewalls are the major members carrying bending moment.Thus it needs extra care to stiffen the structure
OPEN VEHICLE: torsion load case
The open car suffers in the torsion case due to not having a closed box.This creates out-of-plane forces to the floor and thus breaks down the SSS
Torsion stiffening measures:1. Adding in a torsionally stiff grillage
a) Cruciform braced members in the floorb) Tubular backbone membersc) Full underfloor grillage structure
2. Adding in torsion box-type members at the following areas:a) luggage or engine compartmentsb) region of engine bulkhead, parcel shelf and lower A-pillarc) region under the rear seat or near fuel tank