Week 3

Question 1

Typical BIW weight saving if replacing steel with aluminium or carbon fibre composites?

Answer 1

Aluminium replacement: ~30% saving; carbon fibre composite replacement: ~50% saving

Question 2

Give examples of platform sharing within VW Group.

Answer 2

Golf Mk IV, A3, TT, Octavia II, Touran etc. shared A-platform BIW base.

Question 3

What strength range does the lecture cite for steel blanks used in mass BIW manufacture?

Answer 3

Steel blanks of various grades about 140 MPa to 900 MPa are laser welded together.

Question 4

Which BIW elements are critical for crashworthiness?

Answer 4

Front chassis rails, sills, A- and B-pillars, cross-car beam, tunnel – typically made from HSS/AHSS.

Question 5

Function of the transmission tunnel?

Answer 5

Longitudinal stiffness + torsional strength; channels drivetrain/exhaust.

Question 6

BIW resonant frequency benchmark (typical range)?

Answer 6

Benchmark 38 Hz; range 34–45 Hz.

Question 7

What are the three longitudinal crash tests considered in BIW design?

Answer 7

IIHS front 40 % ODB, Euro NCAP front, FMVSS 301 rear 70 % ODB.

Question 8

Follow-on programmes after ULSAB.

Answer 8

ULSAB-AVC (2001) and Future Steel Vehicle (FSV 2013) – demonstrated multi-phase steels and TWB integration.

Question 9

Advantages of TWB in BIW.

Answer 9

Weight reduction by thinning low-stress zones, material cost saving, fewer parts → simpler assembly, optimised crash behaviour.

Question 10

Typical BIW mass benchmarks (ULSAB vs modern).

Answer 10

ULSAB ≈ 270 kg (1996) → modern ≈ 310 kg (2014) due to stricter crash standards.

Question 11

What design principle separates the passenger cell from crumple zones?

Answer 11

Rigid high-strength safety cell + ductile front/rear zones to absorb energy.

Question 12

List key BIW components that must appear on a standard exam sketch.

Answer 12

Front chassis rail, strut tower, A/B/C pillars, sill, floorpan, transmission tunnel, instrument panel beam, cross-car beam, cant rail, header rail

Question 13

Joining method used in steel BIW and why?

Answer 13

Resistance spot welding – fast, repeatable, suitable for coated steels.

Question 14

BIW torsional stiffness benchmark (with glass) and typical range?

Answer 14

~11,500 Nm/deg with glass; range 8,000–14,500 Nm/deg.

Question 15

Define a tailor-welded blank.

Answer 15

Two or more steel sheets of different grade or thickness laser-seam-welded into one blank before pressing.

Question 16

What was the ULSAB project and its relevance?

Answer 16

UltraLight Steel Auto Body (1998) – industry collaboration showing advanced HSS BIW design and manufacture; foundation for modern AHSS usage.

Question 17

Two lateral and one vertical load cases?

Answer 17

IIHS side impact, FMVSS 214 pole impact, FMVSS 216 roof crush (4× strength-to-weight ratio).

Question 18

Bending stiffness-to-mass (Cb/m): typical values?

Answer 18

Average 45; range 25–60 (N/m)/kg.

Question 19

What is the “platform” concept and why used?

Answer 19

A different BIW can
use platform components (drivetrain, seats, electrics etc) enabling the manufacturer
to reduce development and tooling costs across a product range

Question 20

Define the three volume categories.

Answer 20

Mass volume
Over 250,000 per annum
Unitary BIW/ Advanced steels

Mid volume
Below 50,000 per annum
Materials: Multi material: steel, aluminium, composite

Niche/Low volume
Less than 10,000 per annum
Materials: carbon composite, aluminium, steel

Question 21

Why can low-volume vehicles use expensive materials?

Answer 21

Tooling costs spread over fewer cars → justify hand lay-up carbon or bonded aluminium structures to reduce mass without press investment.

Question 22

Why is the process capital-intensive?

Answer 22

High automation, large press tools (> £50 M A-class tools), expensive robotic lines – viable only at > 250 k units/yr.

Question 23

Example of multi-material BIW.

Answer 23

JLR XE – 251 kg BIW (66 % Al + 34 % steel); BMW 7-Series Carbon Core.

Question 24

Give five examples of steel types and properties

Answer 24

Mild: 140/270 (YS/UTS)
HSLA: 350/450 (YS/UTS)
DP: 700/1000 (YS/UTS)
TRIP: 450/800 (YS/UTS, high ductility)
MS: 1250/1500 (YS/UTS)

Question 25

Three biggest BIW marks risks to forget?

Answer 25

Omitting front rails / tunnel on sketch, not naming steel grades, forgetting TWB definition.

Question 26

Benchmark torsional stiffness targets?

Answer 26

11 500 Nm/deg with glass installed (8 000–14 500 range).

Question 27

Function of sills (rockers)?

Answer 27

Transfer crash loads; provide side-impact strength and torsional rigidity.

Question 28

Map regions of a BIW to typical steel grades.

Answer 28

Front rails + B-pillars = DP/TRIP/AHSS; roof rails = HSLA; crumple zones = mild/ductile steel.

Question 29

Innovative manufacturing approach by Tesla.

Answer 29

Tesla developed a highly innovative “Giga press” solution for large chassis components. The giga press is actually a large high-pressure aluminium die-casting process to manufacture one-piece front and rear end structures (up to 80kg) with a cycle time of 80-90 seconds.

Question 30

Alternative joining methods for aluminium.

Answer 30

Riveting, adhesive bonding, TIG welding (due to Al oxide layer and conductivity).

Question 31

Raw-material cost comparison (approx £/tonne).

Answer 31

Steel ≈ £383; Al ≈ £1 340; Carbon ≈ £12 900.

Question 32

What “current technology” point is stated about laser welds in Class A areas?

Answer 32

Technology enables exposed laser welds in Class A surface finish areas; laser-welded coil is a derivative process

Question 33

What is AHSS and its advantage?

Answer 33

Advanced High-Strength Steel – Uses highly complex chemical compositions and multi-phase microstructures created by controllef heating and cooling processes. AHSS grades contain signficant alloying and two or more phases yield high strength + ductility, enabling weight reduction and crash energy management.

Question 34

Typical press and output data?

Answer 34

JLR Halewood Press Shop – 10 automated lines (600–1000 t); ~ 700 panels / h, 25 million / yr.

Question 35

What does BIW stand for and what stage of manufacture does it represent?

Answer 35

Body in White – the welded steel shell before painting or adding closures/interior

Question 36

Torsional stiffness-to-mass (Ct/m): typical values?

Answer 36

Average 44; range 30–60; most 40–50 (Nm/deg)/kg

Question 37

Typical sheet thicknesses used across BIW?

Answer 37

0.6–2.0 mm depending on stress and function.

Question 38

List the 6 main steps in mass-volume BIW manufacture.

Answer 38

(1) Steel coil → blanks (140–900 MPa, 0.6–2 mm) (2) Laser/TWB welding (3) Press forming 3D panels (4) Robotic fixturing (5) Resistance spot welding sub-assemblies (6) Final BIW assembly in jigs.