optimization of an o-eea-energy absorber for a pedestrian protection loadcase of a vehicle front...

Optimization of an O-EEA-energy absorber for a

pedestrian protection loadcase of a vehicle front

structure with HyperStudy and LS-Dyna

Ihf:

M.Eng. Alexander Froloff,

Prof. Dr.-Ing. Armin Huß,

Dipl.-Ing. Heiko Beck

Novelis Deutschland GmbH:

Dipl.-Ing. Christian Müller

Novelis Deutschland GmbH

Am Eisenwerk 30

58840 - Plettenberg

Ingenieurbüro Huß & Feickert GbR mbH

Im Kohlruß 1-3

65835 Liederbach

5th European HyperWorks Technology Conference

09-11-2011

© 2011 Ingenieurbüro Huß und Feickert GbR mbH

Agenda

• Introduction into the pedestrian safety

• FE-Model

• Definition of Design Variables

• Optimization results

• Summary

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Introduction

• EU-Directive 2003/102/EG

- 2 steps phasing-in of safety standards for the protection of vulnerable road

users

• relaxed by EU-Directive 78/2009 und 631/2009

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Introduction

• crash tests for pedestrian safety prescribed by EU-Directive

Upper leg

Child`s head Adult`s head

Lower leg

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Introduction

• bio-mechanical limit values according to EU-Directive 78/2009

* limit values according to EU directive 2003/102/EG

Velocity Acceleration Bending angle Shear displacement

40 km/h 170g (150g*) 19° (15°*) 6 mm

Lower leg

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FEM - Model

• Ford Taurus from George Washington University

- reduction to the supporting front structure

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FEM - Model

• Ford Taurus from George Washington University

- reduction to the supporting front structure

- modifying of the bumper structure

• fitting of the cross beam to absorber-geometry

• lower fascia moved forward and stiffened (with shell elements)

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Legform impactor

• Livermore Software Technology Corporation (LSTC)

- detailed simulation model of the real impactor

• different material description (stiff femur- and tibia-cylinder)

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Energy absorber

• OHLER(R) -Extruded Energy Absorber (O-EEA)

- developed by Novelis Deutschland GmbH and OTSUKA LTD (Japan)

• Material: Polypropylen, 100% recyclable

• Adaptable to fascia or cross-beam

• Manufacturing:

- extrusion of the square tube

- imprinting of the grooves

Width Height Peak Valley specific weight

50 mm 70 mm 0,9 mm 1,3 mm 0,3 kg/m

Standard parameter of the OHLER(R) OEEA

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Energy absorber

• FEM-Model

- Absorber divided into cross stripes

• different wall thickness is assigned to the stripes

- (simulation of the thinning of the wall-thickness)

- fully integrated shell elements

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Design Variables

Height

Width

Groove depth

Groove distance Wall thickness

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Absorber – Geometry

• reduction of the absorber width changes the distance to the fascia

- side member divided in two pieces

- distance between the side members is parameterized and related to the

variation of absorber width

- load transmission via rigid elements

Side member

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wall thickness of the absorber

manufacturing-related exponential thinning of material from

valley to peak

• thinning out depends on

- imprinting distance

• distance between peak and valley

- nominal thickness

• thickness before deep-drawing (groove imprinting)

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Wall-thickness of the absorber

five absorber segments

with different wall thickness

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• assumption, because of groove-depth variable

12,10

0001,0ln

3,1

3

12,1

v

j evt

02,9

0008,0ln

3,2

3

12,1

v

j evt

15,5

0395,0ln

3,3

3

12,1

v

j evt

65,3

35,0ln

3,4

3

12,1

v

j evt

99,2

176,0ln

3,5

3

12,1

v

j evt

9,59,2 3 v

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Overview of the Design Variables

Thickness

[mm]

v3

[-]

Width

[mm]

Height

[mm]

Groove-

Distance

[mm]

Groove-

Depth

[mm]

Nominal Value 0,9* 2,9 40 70* 15,0 4,0

Lower Bound 0,9 2,9 40 70 15,0 4,0

Upper Bound 2,0 5,9 50* 50 16,5* 7,0*

Variable

t1(v3)

v3 B H RA RT

t2(v3)

t3(v3)

t4(v3)

t5(v3)

* nominal value of the absorber before optimization

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Optimization

• HyperStudy 10.0

• Constraints • Acceleration

• Bending angle

• Shear displacement

• Objectives • Acceleration

• Bending angle

• Optimization method

- Adaptive Response Surface Method

• solved with LS-Dyna on a 4-node Linux cluster

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Optimization results

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Before

Optimization Design 1 Design 2

Width 50 mm 50 mm 50 mm

Height 70 mm 50 mm 50 mm

Groove-

Depth 7,0 mm 4,8 mm 5,05 mm

Groove-

Distance 16,5 mm 15,6 mm 15,15 mm

Wall –

Thickness 0,9 mm 0,7 mm 0,7 mm

Acceleration 170 g 132,5 g 132,3 g

Bending angle 22° 15,8° 15,9°

Shear displacement 1.8 mm 1,54 mm 1,58 mm

Acceleration

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- 23%

Bending angle

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- 28%

Internal Energy

+ 65%

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Design comparison – plastic strain

Absorber before

optimization

Design 2

Design 1

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specific weight

150,0

200,0

250,0

300,0

350,0

before optimizationDesign 1

Design 2

334

164 170

sp

ec

ific

we

igh

t [g

r./m

]

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Summary

• Optimization results

- reducing of the biomechanical limit values

- higher rate of the plastic strain

- smaller dimensions

- less weight

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© 2011 Ingenieurbüro Huß und Feickert GbR mbH ingenieurbüro huß & feickert

Thank you for your attention!

../Fußgänger Leg/ihf_Projekte_Crash_Fußgänger_Insassen_leg.ppt

09-11-2011
