Optimization Side Crash Performance Using a Hot-Stamped B-Pillar

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Optimization Side Crash Performance Using a Hot-Stamped B-Pillar

Bryan MacekBenteler Automotive

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Program Manager’s Slide

Highlights– Met all impact performance targets– 46% weight reduction versus baseline– No change to final assembly process– Cost effective solution

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Development Cycle

PerformanceTargets

Design of Record

Theory and Analysis

Design and Execution

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Test Criteria

• FMVSS 214 Dynamic Side Impact• FMVSS 214 Static Crush• IIHS Dynamic Side Impact

– Measures clearance between Centerline of steering wheel and B-Pillar inner

– Heavily dependent on B-Pillar performance– Most difficult to meet

IIHS side impact, courtesy http://www.iihs.org

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Dual Phase 5901.8 mm min. thk13.0 lbs.

Dual Phase 5902.3 mm min. thk.3.0 lbs

Design Solution (Baseline)

• Geometry– B-Pillar Reinforcement Assembly (16.0 lbs total)

• Main Stamping• Bulkhead at upper hinge / beltline• Hinge reinforcement at lower hinge

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• Clip Model– Created a component-level model of the b-pillar

assembly– Ran multiple iterations to optimize thickness

distribution

• Full Vehicle– Submitted best component designs to customer for

full vehicle FEA

Iteration Process

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Design Solution (baseline)

Passenger zone remains straight, protecting the occupant

Deformation zone absorbs energy safely away from occupant

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Design Methodology

• Energy Management– Structural Deformation

• High deformation load to limit intrusion• Controlled deformed shape to limit

intrusion– Reaction Movement

• Absorbs energy by moving vehicle• Even deformation load to limit deflection• High deformation load to increase

reaction movement

IIHS side impact, courtesy http://www.iihs.org

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Crash Energy Management

NewStylePillar

Old Style Pillar

Deflection

Force

The area under the Force Deflection curve is the amount of energy absorbed

ReducedIntrusion

Pushing the car away from the crash absorbs energy

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Hot Stamped DB2001.4 mm min. thk10.1 lbs

Dual Phase 5902.3 mm min. thk.3.0 lbs

Design Solution (Improved)

• Geometry– B-Pillar Reinforcement Assembly (13.1 lbs total)

• Main Stamping• Bulkhead at upper hinge / beltline• Hinge reinforcement at lower hinge

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Design Solution (Improved)

Passenger zone remains straight, protecting the occupant

Deformation zone absorbs energy safely away from occupant

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Possibilities for strategic strengthened hot formed parts

1-piece-designs

√

Advanced Design Options

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Design Solution (final)

• Materials– Hot Stamped DB200 Stamping)

• Yield = 950 MPa (+171%)• Tensile = 1300 MPa (+117%)• Elongation = 6% (-74%)

– HSLA 050 (Lower Stamping)• Yield = 345 MPa (-1.4%)• Tensile = 420 MPa (-30%)• Elongation = 22% (-4.5%)• Galvaneal for corrosion

resistance

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Design Solution (final)

• Materials– Thickness

• Upper Stamping = 1.3-1.6-1.9-1.0 mm(Tailor Rolled)

• Lower Stamping = 1.4 mm• 8.7 lbs total (-46%)

• Upper Stamping = 1.3-1.6-1.9-1.0 mm

1.3

1.6

1.9

1.0

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Advanced High Strength Steel

Overview of Steel Grades

0

2 0 0

4 0 0

6 0 0

8 0 0

1 0 0 0

1 2 0 0

1 4 0 0

1 6 0 0

1 8 0 0

0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0 4 5 5 0

E lo nga t io n , %

UTS,

MPa

.

DDQ, UDDQ

P, BH, IFHSHSLA

FB

DPTRIP

CPPM

HS

SU

HS

S

Mul

tipha

sest

eels

Mar

-te

ns.

CP = complex phasePM = partial martensiticDP = dual phaseFB = ferritic bainiticTRIP = transformation induced plasicityHSLA = high strength low alloyedP = rephosphorizedBH = bake hardeningIFHS = interstitial free high strengthDDQ = deep drawing qualityUDDQ = ultra deep drawing qualityBTR 165 = European Benteler gradeDB 200 = US Benteler grade

Tens

ile S

treng

th BTR 165 hot formed

BTR 165 as rolled

PH

SMaterials Overview Steel gradesMaterials Overview Steel grades

DB200Hot Stamped

DB200As Rolled

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• highest material strength with high ductility

• high potential of weight reduction

• best form accuracy

• no spring-back-effect

• complex geometries feasible

• excellent intrusion control in crash events

Benefit of Hot StampingBenefit of Hot Stamping

Hot Stamping Benefits

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Tailor Rolling Benefits

• Allows complete tuning of deformed shape• Allows weight reduction by removing low-stress

material• No stress risers from welded joints• Unlimited number of thickness changes

1,0 mm

1,0 mm

1,75 mm

1,3 mm

1,75 mm

1,6 mm

1,75 2,51,75

6,6 kg

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Processes

Hot Stamping Process

coil blank furnace handlingpresscooling

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 100 200 300 400 500 600 700

Meßweg in mm

Ban

dd

icke

in m

m

gewalztes Bandprofil

Sollprofil

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

1,8

0 200 400 600 800 1000Meßweg in mm

Ban

dd

icke

in m

m

gewalzte BandkonturSollprofil

Tailor Rolling Process

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But can I weld it?

• Design for Manufacturability– Stamped design

• Requires no changes to mating parts• Requires no changes to assembly process

– Weldable• Requires no special weld capital• Requires no special weld testing

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Design Solution (final)

• Processes– Spot Welding

• No special equipment needed• Sufficient joint strength for crash

– Projection Welding• Ultra High Strength Steel allowed hinge tapping

plates to be replaced by simple weld nuts

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Design Solution (final)

Passenger zone remains straight, protecting the occupant

Deformation zone absorbs energy safely away from occupant

Deformation allowed in hot stamped material to increase energy absorption

base final

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You’ve seen this slide before

Highlights– Met all impact performance targets– 46% weight reduction versus baseline– No change to final assembly process– Cost effective solution

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Roof Rail-reinforcement

Doorbeam

A-Pillar-reinforcement

B-Pillar-reinforcement

Side member-reinforcement

Rear Bumper

Front BumperFront Bumper

BeltlineReinforcement

reinforcement

BeltlineReinforcementReinforcementReinforcement

Rocker Panel-reinforcementRocker Panel-reinforcement

Tunnel

Product Samples for Hot Stamping

MountingplateFront wall

CarrierUnderstructure

Other Applications

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• Questions & Answers

Questions and Answers