17. März 2010»Stuttgarter Symposium«

Innovative Vehicle Concept for the Integration of Alternative Power Trains

P. Steinle, M. Kriescher und Prof. H. E. Friedrich,

17. März 2010 »Stuttgarter Symposium«

Stuttgarter Symposium > P. Steinle und M. Kriescher > 17.03.2010, Folie 2

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Institute of Transportation Systems

Institute of Transport Research

Institute of Vehicle Concepts


MotivationLightweight design strategiesGeneral RequirementsTwo different approaches

Rib and Space-FrameHybrid structures

Summary and Conclusion

Table of contents


Resources of water and oil run short

Climate change can not be ignored

Increasing population asks for mobility

Reduction of vehicle’s weight for reduced driving resistanceLess fuel consumption and CO2-emissionsIncreasing efficiencyAlternative energy and storage

MotivationGlobal trends


Shape

Materials ConceptConcept

Requirements

LawCustomer and MarketCO2-Strategy

PackageIntegrationModularisationTechnologies

ShapeGeometry

MaterialsSurfacesProcesses

Step 1

Step 2.1

Step 2.3

Step 2.2

Source: Haldenwanger, Beeh, Friedrich

Lightweight design strategies


LawStVZOEG/EWGECEGlobal (e.g. FMVSS, IIHS)

Customer and MarketImproved modularizationScalable vehicle and propulsion system

CO2-RestrictionsAlternative Propulsion Systems (e.g. BEV, FC)

e-

H2CH4

Rib and Space-FrameRequirements – general


General Requirements

Lightweight Safety

Alternative Propulsion Systems

Cost

Comfort

Customer Acceptance

Rib and Space-FrameRequirements – specific


Vehicle ConceptsTwo Different approachesRib-and Space-Frame Higher specific energy absorption

Top-Down-Method Bottom-up-Method

Detail 1 Detail 2 Detail 3

Detail 1Detail 2

Detail 3

Lightweight and safe body structure


Alternative propulsion system (e.g. Battery) integrated into the vehicle’s floorContinuous side membersContinuous rib structureCrash-Elements between side members and rocker

Fiber Reinforced PlasticsMagnesiumAluminiumSteel

Rib and Space-FrameConcept


Basic idea: rigid B-pillar with flexural joint in the roof pillar and high performance energy absorption below the driver’s seat Minimum deformation in the rib-structure with maximum energy absorption in the crash elements

FCrash

B-Pillar

Side member

Safety-Containment for alternative propulsion systems

Roof Crossbar Joint

Part Requirements: Stiffness, Energy absorption, structural integrity

Rib and Space-Frame Mechanical principle of the rib


Topology Optimization with static substitute loadsBenchmark of different materialsInterpretation and realization of the simulation resultsConversion of the generic design to the real design requirements

Omega profile

Inner Skin

Outer Skin

Reinforcement

SupportCrash-cones

Mass per unit of stiffnessShaft in torsion Fixed: length, section shape Free: section area

200 500 1000 2000

Mass

per

unit

of st

iffne

ssBe

am in

ben

ding

Fixe

d: le

ngth

, wid

th

Free

: thi

ckne

ss

200

500

1000

2000

Rib and Space-FrameDesign of the rib


Crash testSimulation side impact

Simulation and Validation of the B-Rip-Design

New design: ca. 29 kgReference structure: ca. 45 kg

Rib and Space-FrameSimulation und Crash


Rigid structure in the middle of the vehicleEnergy absorption between rocker and side member

Floor Concept: Stiffness, Energy absorption, structural integrity

Rib and Space-FrameMechanical principle of the Crash Compartment


Equivalent masses

Crash compartment

Simplified Model Energy Absorber

+

Performed TestsSide Pole Impact according to:

EuroNCAP FMVSS 214

Variation along x-axis (real life safety)x-axis

Rib and Space-Frame Boundary Conditions of the Crash compartment


Superposition of two different velocities between side member and rocker

Velocity 1: Translation along y-directionVelocity 2: Translation along x-direction

Rib and Space-FrameGlobal Vehicle Behavior of the Crash compartment

x

y


Discrete Energy absorberCollapse according to shear forces

Continuous energy absorberBetter acceptance of shear forcesLarge-scale support of the rockerRobust against different impact scenarios

Rib and Space-FrameResults of the Crash compartment

Discrete structure Continuous structure

Lower intrusions with the same weight


Real life crash represents the worst caseImproved load carrying capacityReduced accelerations (compared to the discrete structure)

Rib and Space-FrameResults and further proceedings of the Crash compartment

Further ProceedingDifferent types of energy absorbers (Geometry, Material)Integration of the floor into the energy absorption


Table of contents

MotivationLightweight design strategiesGeneral RequirementsTwo different approaches

Rib and Space-FrameHybrid structures

Summary and Conclusion


Motivation

collapse of the rocker‘s and side piece‘s cross-section during pole-crash -> energy must be absorbed by various other componentsa stabilisation of the cross-section during bending should lead to a much higher weight specific energy-absorption of the rocker -> higher freedom of design and choice of materials for the surrounding structures, like the floor panels -> possibility of an overall weight reductionthe storage of critical components like Li-Ion batteries in the underbody requires a low intrusiondemand for a simple, lightweight concept made of relatively cheap materials, adaptable to different kinds of vehicle concepts

floor structure developed by DLR during SLC-project


Basic principle

Absorption of crash energy through elongation of material

Stabilisation of cross section

stabilisation of the beam by a core structurethe core must stay intact, throughout the entire bending process, in order to increase weight specific energy absorptionsimplified LS-Dyna-calculations showed an increase in weight specific energy absorption by a factor of about 2,5


Testing performed in cooperation with DOWForce-displacement curve

0

5

10

15

20

25

30

35

0 50 100 150 200 250 300 350 400 450 500Displacement [mm]

Forc

e [k

N]

Steel section (hollow)

Steel section (foam-filled)

hollow beam foam filled beam

DC 04 - beam filled with foam bythe DOW chemical company

weight specific energy absorption [J/kg]

0,00

100,00

200,00

300,00

400,00

500,00

600,00

steel section (hollow) steel section (foam- filled)


Geometric variations

Force-displacement curve

0

5

10

15

20

25

30

35

40

45

0 50 100 150 200 250 300 350 400 450 500

Displacement [mm]

Forc

e [k

N]

Steel section (hollow)

Steel section (foam-filled)

Steel section (sideways, foam-filled)

deformation mode stays the same for different cross sectionstest with a crosssection rotated by 90 ° leads to higher peak force but earlier failure of the material -> steel with a higher max. strain would lead to even better results


Integration into the underbody structure, basic principle

conventional rectangular topology:

difficulty in designing an appropriate support structure

a ring-like shaped, filled structure should lead to comparatively low strain values, distributed over a large portion of the structure


LS-Dyna-Simulation results with a simplified body structure

modified pole crash:

the modified pole crash was performed to avoid the addition of virtual weights

car body is fixedweight of pole= 1380 kgspeed of pole = 29 km/hintrusion is slightly more severe compared to a regular pole crash


Modified pole crash results with a simplified body structure

results of the new structure:reduction of intrusion by a factor of 2,7, compared to a full vehicle with interior, even without floor panel, seat structure etc.proof of the basic principle: the underbody structure is deformed as one „ring“, without any collapse of particular parts


Deformation behaviour


Summary and conclusions

Two different approaches for lightweight and safe vehicle structures for small/medium and large scale productionDLR Rib and Space-Frame with high intrusion resistance of the B-Rip and Crash compartment An underbody structure composed of a ring-like filled structure results in a very high intrusion resistance during pole crash. A large portion of the underbody could therefore be used for the storage of critical components like Li-Ion batteriesA more detailed car body structure is needed to make accurate weight predictionsOptimization of the structure by decreasing intrusion resistance in favor of reduced weight seems reasonable

For further questions and to see a model of the car body please visit our exhibition stand

Thank you for your attention

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17. März 2010»Stuttgarter Symposium«