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Functional Properties of High Strength Steel in the Body in White

Markus PfestorfJacobus van Rensburg

BMW AG

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CONTENT

1. Introduction2. Acoustics3. Durability4. Stiffness5. Passive Safety6. Corrosion7. Cost Considerations8. Conclusion

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IntroductionDesign Philosophy

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IntroductionFunctional Requirements

Stiffness– Static– Dynamic– Torsion– Bending

Acoustics & Comfort–Noise-Vibration-Harshness–Sound Absorption Value–Impact Sound Reduction–Airborne Sound Isolation–Hollow Space Resonance

Service Life& Durability– Vibration Stability– Stress Cycle Diagram– Corrosion– Recycling

Passive Safety– Front Crash– Rear Crash– Side Impact– Over Roll, Others

Costs

Weight

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HS

S

High Strength Steel180 to< 300

AH

SS

Advanced High Strength Steel ≧ 300U

HS

S

Ultra High Strength Steel ≧ 600

LS

S

Low Strength Steel 140 to< 180

5xxx AlMg-Aluminum Alloys

(AlMg3,5Mn, AlMg4,5Mn0,4)

6xxx AlSi-Aluminum Alloys

(z.B. AlSi1,2Mg0,4, AlSi0,6Mg0,5))

Yield StrengthR p0,2 [MPa]

Introduction Available Metal Grades

ALUMINUM

STEEL

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Acoustics Airborne Noise

Octave Band Filter - Middle Frequency

Insu

lati

on

R

70

50

40

30

20

106 dB / Octave

250125 500 1.000 2.000 4.000 8.000 32.000[Hz]

[dB]

Lead sheet: 2mm; 2

2.7 kg/m2

Steel sheet: 2

mm; 15.6 kg/m

2

Aluminum sheet: 2mm; 5

,7 kg/m2

Polystyrol: 2mm; 1

,0 kg/m2

Inherent Material Insulation Properties

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AcousticsAcoustic Layout

Sound Pressure

Frequency [Hz]

Pre

ssu

redB(A)

Sheet Metal Oscillation

Frequency [Hz]

Rad

iate

d P

ow

er

dB

NOTE: Various value sets represent measurement points at various locations of the vehicle

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AcousticsAcoustic Layout

Load Transmission- Very high local stiffness for a

minimum excitation of the panels

Pulsation of the Floor Panel- Excitation Gearbox Mounting - Homogeneous vibration behavior and

a minimum sound radiation of the floor panel

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Durability TRIP Steel

Body in White incl. Wind Screen, Doors, Hoods, Bonnet, axle carrier, crash beam, and other parts which are relevant for durability behavior

Load cycles104 105 106

Fm

ax5,0kN

1,0

107

3,0

2,0

0,2

0,5

Basic Material data Component Tests

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StiffnessMaterial Comparison

External Diameter

Wei

gh

t p

er u

nit

Len

gth

SteelAluminumMagnesiumCFC 55% II

Base (E x I):Steel Tube 150 x 1

kgm

80 100 120 140 160 mm 200

F

Tubular Sections

0

2

4

6

8

10

12

14

18

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StiffnessDynamic Stiffness

22,9

23,6

28,730,0

22

24

26

28

Hz

32

SOP 1982 1990 1998 2005

1. T

orsi

on

inflated scale

20,8

21,5

26,427,0

20

22

24

Hz

28

1. B

endi

ng

SOP 1982 1990 1998 2005

ideal frequency

1st. natural frequency of the dynamic bending

1st. natural frequency of the dynamic Torsion

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Stiffness Struts and Structural Foams

Structure foam in the side frameBMW 5 series Touring

V-s

trut

TOP VIEW

Thrust Plate

Front TensionStrut

Rear TensionStrut

Cro

ss M

embe

r

BOTTOM VIEW

BMW 6 series Convertible

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Low speed front crash

Side impact crash

High speed rear crash

Low speed rear crash

High speed front crash

Passive Safety (Crash) Impact Zones

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Passive Safety (Crash) Load Path

Front Crash

Side Crash

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Data for rear crash– Car weight: 1978 kg

– Barrier weight: 1365 kg

– Barrier speed: 81,7 km/h

Results:– No impact of fuel tank

– No impact in passenger cabin

– No brittle fracture of trunk lid

Passive Safety (Crash)Results

Rear Crash: BMW 6 Series

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Passive Safety (Crash) Energy Absorption

0

400

800

1200

1800

0 10 20 30 % 50

22MnB5, press hardenedHC500XIP (X-IP Steel)

Elongation

Yie

ld s

tren

gth

Rp0

,2

Nmm²

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Passive Safety (Crash) HCT800C …Dynamic Drop Test

Tested profile

Specimen after crash test

Yield Strength Rp0,2

Tensile Strength Rm

Elong. after Fracture A80

Thickness

Mech. Properties

(as delivered)

692 MPa

901 MPa

11,4

0,99

Mech. Properties

(180°C, 60 min.)

796 MPa

923 MPa

10,8

0,99

± 118 mm

±88

mm

40

80

120

kN

200

Def

orm

atio

n F

orc

e

Deformation Time

157,37 kN (with Bake Hardening Response)

155,84 kN (without Bake Hardening Response)

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Steel

other Steel GradesDC 03/04DX 54DX 56HC160YD, HC180BD, HC180YDHC220BD, HC220YDHC260BD, HC260YD, HC260LADHC300BD, HC300LAD, HC300XDHC340LAD, HC340XDHC380LADHC400TDHC420LADHD680CMS-W1200, Docol1000

Othersplasticother metallic materials

New sports wagon(SOP 2005)

Previous Sports Wagon(SOP 1999)

Passive Safety (Crash) Detailed Material Application

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Others3%

300 to340 MPa6%

260 MPa

9%

200 to220 MPa20%

180 MPa17%

LowStrength

Steel 44%

180 MPa20%

260 MPa6%

300 to340 MPa20%

200 to

220 MPa

13%

LowStrength

Steel 19%

Others3%

Plastics1%

> 900 MPa1%

500 to680 MPa6%

380

to42

0 M

Pa11

%

> 900 MPa1%

New sports wagon(SOP 2005 to present)

Previous sports wagon(1999 to 2005)

Passive Safety (Crash) Detailed Material Application

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Corrosion. Materials and Coatings.

Co

rro

sio

nT

est

Ad

hes

ive

Bo

nd

ing

insufficient coating

sufficient coating

real test on the vehicle

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Costs. Costs for Light Weight Solutions.

Cost tolerance per unit Mass Reduction

Veh

icle

Hei

ght

50% Front

Axle Load DistributionC

ost t

oler

ance

per

unit

Mas

s R

educ

tion

Vehicle Length

50% Rear

Opt G

eom

etry

Optim

um

Profile

s

CR (Dee

p

Draw) HSS

AHSS

Tailor

Roll

ed

Blanks

Tailor

Weld

ed

Blanks

Aluminu

m

Mag

nesiu

m

Carbo

n Fibe

r

Comp.

Cos

t pe

r un

it M

ass

Red

uctio

n

ComparisonBase

Zero Base Line

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Functionality. Summary.

There will be a further Demand on

– Ultra High Strength Steel Grades

– Sheets with a thin Gage

– Corrosion Surface Treatment

Low Strength Steel + High Strenth Steel Grades

Advanced High Strength Steel Grade

Ultra High Strength Steel Grade

Others

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Thank you for your interest