16802 matls selection

7/28/2019 16802 Matls Selection

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Requirements for Automotive

Body Materials


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Summary of Requirements of Body Materials

1. Performance Factors (strength, stiffness, ductility, toughness,

impact properties, density)

2. Manufacturing Factors (ease of formability, joinability and

surface finishing, volume of production)

3. Cost Factors (raw materials costs, manufacturing costs, cost of

change, in-service costs, end-of-life costs)4. In-service Factors (ease of repair, availability of repair sites,

corrosion resistance, fatigue resistance)

5. Environmental Factors (resource availability, pollution during

primary and secondary processing, recyclability, end-of-life

disposal)

6. Miscellaneous Factors (legislation, fashion, customer

perception, etc.)


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Comparison of Tensile Properties

210 210

70

45

121.5

300

450

300

240

70

40

0

50

100

150

200

250

300

350

400

450

500

MildSteel(DC05)

HighStrengthSteel

(HSLA350)

AlalloyAA6111

MgAlloyAZ91

SMC(polyester-

25%glass)

Polypropylene

(PP)

Youngs Modulus, E (GN/m3)

Tensile Strength, TS (MN/m3)


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4

7.8 7.8

2.7

1.8 1.8

0.9

0

1

2

3

4

5

6

7

8

9

MildSteel

(DC05)

HSLA350

AlalloyAA6111

MgAlloyAZ91

SMC(polyester-

25%

glass)

Polypropylene

(PP)

Den

sity,r

(g/cm3)

Comparison of Density


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5

27 27 26 25

72

40

60

110

130

4045

0

20

40

60

80

100

120

140

M

ildSteel(DC05)

HighStrengthSteel

(HSLA350)

AlalloyAA6111

MgAlloyAZ91

S

MC(polyester-

25%glass)

Polypropylene

(PP)

Specific Modulus (E/ )

Specific Strength (TS/ )

Comparison of Specific Tensile Properties

r

r


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6

690810 800

15

3440

3030

11201010

3830

2140

1840

0

500

1000

1500

2000

2500

3000

3500

4000

4500

MildSteel(DC05)

CoatedDC05

HighStrengthSteel

SteelScrap

6XXXAlalloy

5XXXAlalloy

Alalloysegregated

scrap

Alalloynon-

segregatedscrap

Mgcastingalloy

SMC(glass-

polyester) P

P

Price(/tonne)

Approximate Costs of Automotive Body Alloys


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0

10

20

30

40

50

60

70

80

90

100

Mild Steel

(DC05)

Hot Dip

Galvanised

DC05

5XXX

Al Alloy

6XXX

Al Alloy

AZ91C

Mg Alloy

AZ91E

Mg Alloy

(purer)

Relative Corrosion Performance

Approximate Relative Rates of Corrosion

in Automotive Metals (Mild Steel = 100)


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Materials Trends

0

10

20

30

40

50

60

70

80

1975 1980 1985 1990 2000 2005

C

ontributiontoVeh

icleWeight(%)

Steel

Elastomers

Plastics

Aluminium

Other

Materials

used inGerman

Passenger

Cars


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Why Steel?

Readily available

Relatively cheap Excellent combination of strength, stiffness and ductility

Good sheet formability

Clear fatigue limit

Joining technology is well known Finishing technology is well known

Design with steel is well known

Why not Steel?

High density

Poor corrosion resistance


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Types of Automotive Steels

Mild Steel:

Cold Rolled, Low Carbon Steel Hot Rolled, Low Carbon Steel

High Strength Steels:

High Strength, Low Alloy (HSLA) or Microalloyed Steel Dent Resistant Steels (Bake Hardening steel,

Rephosphorised Steel)

Dual Phase (DP) and Complex Phase (CP) Steel

Martensitic Steel

Transformation-Induced Plasticity (TRIP) Steel


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High Formability

Mild Steel (DC06)

Complex Phase Steel (CP900)

Microalloyed Steel (H 350 LA)

200

400

600

800

1000

1200

TrueStress,s(

MPa)

Hot Rolled Mild

Steel (DD11)

Bake HardenableSteel (H 260 BD)

Dual Phase Steel (H 300 X)

Martensitic Steel (MS 1100)

TRIP Steel (TRIP 700)

Properties of Automotive Steels

(before bake)(after bake)

0.05 0.10 0.15 0.20 0.25

True Strain, e or

0.30


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0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

HRMildSteel

DC05

BakeHardened

Rephosphorised

HSLA

DualPhase

TRIP

Martensitic

RelativeCos

t(DC05=1)

Relative Costs of Automotive Steels


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10

20

30

40

50

200 300 400 500 600 700 800

Elongation(%)

Tensile Strength (MPa)

Relationship between Ductility and

Strength in Automotive Steels

900 1000

Direction

of development


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Typical Modern Useage of High Strength Steels

MS

MS

MS

MS

MS

MS

MS

MS

MS

BH BH

BH

(iso)

MS

IFMS

IF

IF

B256 (New Fiesta) - 45% HSS, 55% MS(MS = Mild Steel, IF = Interstitial-Free Steel, BH = Bake Hardening Steel)


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Why Aluminium Alloys? Readily available

Low density (2700 kg/m3, cf. 7800kg/m3 for steel)

High specific strength (strength:weight ratio)

High specific stiffness (when thickness effect taken into account)

Corrosion resistant (but.)

Recyclable (but.)

Finishing technology is well known

Why not Aluminium Alloys? Expensive (~2000/tonne, cf. ~400/tonne for mild uncoated steel)

Limited formability Design with Aluminium is less well understood

No fatigue limit

Different joining technologies need to be employed


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Principal Aluminium Alloys

Aluminium Association (AA) grades:1XXX >99%Al

2XXX Al-Cu Past use in US, for closures

3XXX Al-Mn4XXX Al-Si Castings (4XX)

5XXX Al-Mg Structural sheet & extrusions

6XXX Al-Mg-Si Skin sheet & extrusions

7XXX Al-Zn Skin sheet & extrusions

8XXX Al-X


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Design ImplicationsBody-in White (BIW) options:

Monocoque

Spaceframe

Hybrid


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COMPOSITES

DEFINITION: A UNIFIED COMBINATION OF TWO

OR MORE PHYSICALLY DISTINCT AND

MECHANICALLY SEPARABLE MATERIALSPROVIDING A COMBINATION OF PROPERTIES

THAT CANNOT BE ACHIEVED IN THE ORIGINAL

CONSTITUENTS.


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NOTE THAT THEY WOULDNORMALLY BE USED IN LOW-

VOLUME CAR PRODUCTION

(


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REINFORCED POLYMERS

FOR AUTOMOTIVE BODY

APPLICATIONS? VERY LOW DENSITY MAKING CARS FASTER AND

FUEL EFFICIENT

HIGH STRENGTH AND HIGH STRENGTH TO

WEIGHT RATIO CAN BE ACHIEVED

LOW-COST MOULDS CAN BE MADE

PROCESS SKILLS LEVELS CAN BE LEARNTQUICKLY

DIIFFERENT TYPES OF FIBRES ARE AVAILABLE

(KEVLAR, CARBON, GLASS) GIVING DIFFERENT

PROPERTIES

Wh t t i l ti i t t i


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What material properties are important in

choosing frame material? First, there are three

types of material properties:

Physical - Density, color, electrical conductivity, magnetic

permeability, and thermal expansion.

Mechanical - Elongation, fatigue limit, hardness, stiffness, shear

strength, tensile strength, and toughness.

Chemical - Reactivity, corrosion resistance, electrochemical

potential, irradiation resistance, resistance to acids, resistance to

alkalis, and solubility.


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Chassis Materials

STEEL ALUMINUM


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Titanium

Titanium has an association with space tech, and isregarded by many people as an "ultimate" material.

It has a density roughly half that of steel, and also a

little over half the stiffness value. It's a similar

situation with regards to ultimate and yieldstrengths.

Only alloynot raw

MAGNESIUM


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MAGNESIUM

Magnesium is the lightest metal that's likely to beused in a vehicle chassis, with a density about

quarter that of steel. This weight advantage helps to

compensate for the fact that it's strength and rigidity

is below even aluminium, and with careful design canbe used to build a light, stiff structure.

Currently, the use of magnesium in vehicles is

generally restricted to cast shapes for mountingbrackets, braces and so on, though several

manufacturers are working on using magnesium

sheet and extruded sections where possible.


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fibreglass

Raw plastics do not have anywhere near enough stiffness to beused for structural components in cars. If strands of glass are

added to the mixture, though, their properties improve

remarkably. This gives you a Glass Fibre Reinforced Plastic

(GFRP or GRP), most commonly referred to as fibreglass.

Traditionally, fibreglass has been used for specialist applications

like sports cars most of all, and is often used in conjunction with a

separate chassis or subframes rather than alone. Even if a

bodyshell is made to be a stand-alone fibreglass structure, metal

inserts are still usually used to spread the load at mounting pointsetc.


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CARBON FIBRE:

Carbon Fibre Reinforced Plastic The key to this is that, unlike fibreglass, where the

strands are pretty much random, carbon fibre uses a

woven matt of fibres - this is what gives it it's

distinctive appearance.

use of carbon fibre tends to be restricted to large,

reasonably flat panels (such as roof panels and

bonnets), where the best "bang for buck" weightsavings can be found.

16802 matls selection

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