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ALTERNATIVE CONSTRUCTION FOR BODY SUBASSEMBLIES AND MODEL VARIANTS

ALTERNATIVE CONSTRUCTION FOR BODY SUBASSEMBLIES AND MODEL VARIANTS. INTRODUCTION. Variations from the basic ‘standard sedan’ structure  2 levels: Body subassemblies Major subassemblies can take many different forms such as suspension mountings and passenger compartment

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ALTERNATIVE CONSTRUCTION FOR BODY SUBASSEMBLIES AND MODEL VARIANTS

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  1. ALTERNATIVE CONSTRUCTION FOR BODY SUBASSEMBLIES AND MODEL VARIANTS

  2. INTRODUCTION • Variations from the basic ‘standard sedan’ structure  2 levels: • Body subassemblies • Major subassemblies can take many different forms such as suspension mountings and passenger compartment • Vehicle model variants • Vehicle 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

  3. 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 reactions • Carried by the front or rear compartment bulkhead • Flange reactions • Taken by parcel shelves and floor

  4. In this lecture: • Alternative end structures at front & rear are considered • Variations are based on the standard sedan • All 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

  5. Rear Structures – Rear Suspension Supported on Floor Beam Normally for trailing arm & similar rear suspensions

  6. Load applied to the compartment • Q10, Q6,fig. 5.12 • Pass compartment • Bending, Q8, Q9

  7. 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

  8. line of action of strut, couple, torsion • vslc: brace • tlc: brace has same direction, stiff in shear add structure  assgmnt

  9. Frontal Structures – Grillage Type Frontal Structure For front suspension that is attached to the lower engine rails

  10. Assgnmnt

  11. Frontal Structures – Grillage Type Frontal Structure With Torque Tubes

  12. Missing or Flexible Shear Web in Inner Fender

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

  14. CLOSED INTEGRAL STRUCTURES • Different closed body configurations mounted on a common floor pan assembly will be discussed • Standard sedan floor is often used for: • Estate car • Hatchback • Rear structure experienced a little change • Extended for estate car • Shortened for hatchback

  15. 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 loads • Transfer forces to the sideframe

  16. Torsion load case must be treated differently than the standard sedan • Special care must be taken when analyzing the rear frame for estate/hatchback

  17. Estate Car/Station Wagon • Modern 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

  18. Hatchback • This 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 car • i.e. to transfer shear from roof to floor during torsion

  19. OPEN VEHICLE: bending load case The sidewalls are the major members carrying bending moment.Thus it needs extra care to stiffen the structure All edge loads are well supported by the components

  20. 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

  21. Torsion stiffening measures: • Adding in a torsionally stiff grillage • a) Cruciform braced members in the floor • b) Tubular backbone members • c) Full underfloor grillage structure

  22. Adding in torsion box-type members at the following areas: • a) luggage or engine compartments • b) region of engine bulkhead, parcel shelf and lower A-pillar • c) region under the rear seat or near fuel tank

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