ALTERNATIVE CONSTRUCTION FOR BODY SUBASSEMBLIES AND MODEL VARIANTS.

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

Beam

2119

2128

:beamsFloor

LLLRQ

LLLRQ

R

R

BSQQ R910

:ceRear valan

221102

:Sideframes

hLLQQX

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

FFSRT

014 PPRF

TLS

L

L

LRP

LPLR

FF

F

2

1

2

14

241

:Habout Moment

FF S

T

L

L

L

LRP

2

1

2

11 11

FRP 1

TBL

L

B

SPP

BPSP

F

F

2

143

34

Assgnmnt

Frontal Structures – Grillage Type Frontal Structure With Torque

Tubes

11

1

LRM

RP

F

F

Missing or Flexible Shear Web in Inner Fender

Missing Shear Web in Inner Fender: Upper Rail Direct to A-pillar

baaRR

RRR

babRR

F

F

F

2

21

1

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

02

02

02

XRLZ

ZRLX

RRU

MwP

MwP

MwP

2/2

0

0

1

31

21

bQM

wQcQ

wQaQ

z

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