FlexPLI vs. EEVC LFI Correlation - UNECE

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FlexPLI vs. EEVC LFI Correlation

5th IG GTR9-PH2 Meeting 6-7/December/2012

Japan Automobile Standards Internationalization Center (JASIC)

Action List Item 1. j) Evaluate and decide on performance / injury criteria and threshold values

GTR9-5-13

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IWG Questions from NHTSA

Reference : National Highway Traffic Safety Administration (NHTSA), Overview of NHTSA Pedestrian Activities, 4th IG GTR9-PH2 Meeting Document, GTR9-4-19 (2012)

GTR9-5-13

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Leg Fracture Evaluation

64 mm

Knee center

Upper Tibia Acceleration

No instrumentation

Injury Criterion

EEVC LFI FlexPLI

374 mm

137 mm

217 mm

297 mm

134 mm

214 mm

294 mm

Upper end of tibia

Femur-3 BM

Femur-2 BM

Femur-1 BM

Tibia-1 BM

Tibia-2 BM

Tibia-3 BM

Tibia-4 BM

BM: Bending Moment

Injury Criteria

� EEVC LFI measures upper tibia acceleration at one location � FlexPLI measures tibia bending moment at four locations

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Predominant factor for EEVC LFI upper tibia acceleration �� Applied force magnitude

Mizuno et al. (2012) EEVC LFI Upper Tibia Acceleration

TFFxm �� sb22 ��

2

sb2A m

FFxa ��

Equation of Motion of tibia

2202

20A

6)06.0(

066.0

�

��

��

��

��

LLx

xa

Tibia acceleration Bumper force Spoiler force

Fb

Fs L0

0.066 m

�2

x0

x2

aA

T

Reference : Mizuno, K. et al., Comparison of Reponses of the Flex-PLI and TRL Legform Impactors in Pedestrian Tests, SAE World Congress, SAE Paper #2012-01-0270 (2012)

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Predominant factor for FlexPLI tibia bending moment �� Applied force magnitude AND point of force application

Mizuno et al. (2012)


FlexPLI Tibia Bending Moment

s0

s0sb0bs

)()()( zL

zLFzLFzM ��

� �b00

ssbbb )( zL

LzFzFzM �

��

)}(),(max{ bsmax zMzMM �

Max. tibia bending moment

Bending moment Bumper and spoiler force

Point of force application

Fb

Fs L0

zb

zs

R1

R2

M

M(zb)

M(zs)

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Leg Fracture Evaluation Mizuno et al. (2012)


FE Validation of Predominant Factors for EEVC LFI Upper Tibia Acceleration

Tibia acc. Bumper force Spoiler force

Presumed from Rigid body model

Fb

Fs

0 5 10 15 20 0

50

100

150

200

250

Tibi

a ac

cele

ratio

n (G

)

Fb+ Fs (kN)

TRL legform FE Model

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Leg Fracture Evaluation Mizuno et al. (2012)


FE Validation of Predominant Factors for FlexPLI Tibia Bending Moment

Bend moment Bumper and spoiler force

Point of force application

Presumed from Rigid body model

Fb

Fs

R1

R2 Bending moment

diagram

M(zb)

M(zs)

Flex-PLI FE model

max{M(zs), M(zb)} (kNm)

Tibi

a be

nd m

omen

t (kN

m)

0.0

0.1

0.2

0.3

0.4

0.6 0.8 1.0 1.2

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Leg Fracture Evaluation Takahashi et al. (2012)

Reference : Takahashi, Y. et al., Validation of Pedestrian Lower Limb Injury Assessment using Subsystem Impactors, IRCOBI Conference (2012)

Baseline Model

250 mm

450 mm

650 mm

275 mm

30 mm SP

BP

BLE

SP Location

30 mm -20 mm 0 mm

BP/SP Stiffness

0

5

10

15

0 40 80 120

Forc

e (k

N)

Deflection (mm)

BP

Base Stiff

0

5

10

15

0 40 80 120

Forc

e (k

N)

Deflection (mm)

SP

BaseStiff

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Reference : Takahashi, Y. et al., Validation of Pedestrian Lower Limb Injury Assessment using Subsystem Impactors, IRCOBI Conference (2012)

EEVC Legform Model

Case StiffnessSteel Material parameters of steelBone Flexural rigidity = 555.6 Nm2

Stiffness of Tibia

CaseStiffness SP

Location (L2 in mm)

CaseStiffness SP

Location(L2 in mm)BP SP Tibia BP SP Tibia

^ Base Base Bone 30 V1-S Base Base Steel 30

V2-B Stiff Base Bone 30 V2-S Stiff Base Steel 30

V3-B Base Stiff Bone 30 V3-S Base Stiff Steel 30

V4-B Base Stiff Bone 0 V4-S Base Stiff Steel 0

V5-B Base Stiff Bone -20 V5-S Base Stiff Steel -20

Simulation Matrix

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0.0

0.5

1.0

1.5

2.0

2.5

V1 V2 V30.0

0.5

1.0

1.5

2.0

2.5

V1 V2 V3

Nor

mal

ized

Mea

sure

Nor

mal

ized

Mea

sure

Effect of BP/SP Stiffness Tibia Bending Moment

@ BP Height Tibia Acceleration

@ BP Height

Baseline Stiff BP Stiff SP Baseline Stiff BP Stiff SP

Bone Steel

0.0

0.5

1.0

1.5

2.0

2.5

V3 V4 V50.0

0.5

1.0

1.5

2.0

2.5

V3 V4 V5

Nor

mal

ized

Mea

sure

Nor

mal

ized

Mea

sure

Effect of SP Location Tibia Bending Moment

@ BP Height Tibia Acceleration

@ BP Height

SP Forward SP Forward

Bone Steel

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y = 0.0482x + 1310R = 0.014

0

300

600

900

1200

1500

1800

0 100 200 300 400 500

TRL Legform Flex-PLI

Human Model Tibia Bending Moment (Nm)

TRL

Legf

orm

Mod

el

Upp

er T

ibia

Acc

el. (

m/s

2 )

Human Model Tibia Bending Moment (Nm)

Flex

-PLI

Mod

el

Tibi

a Be

ndin

g M

omen

t (N

m)

y = 1.259x - 72.798R = 0.90

0

100

200

300

400

500

0 100 200 300 400 500

�No correlation between TRL legform upper tibia acceleration and human tibia bending moment

�Good correlation between Flex-PLI and human tibia bending moment

CAE Correlation Study Correlation of Tibia Injury Measures TEG-096

(Flex-PLI)

Konosu et al. (2009)

GTR9-1-05r1

Reference : Japan Automobile Standards Internationalization Center (JASIC), Technical Discussion - Biofidelity, 1st IG GTR9-PH2 Meeting Document, GTR9-1-05r1 (2011)

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Leg Fracture Evaluation � EEVC LFI upper tibia acceleration is solely determined by the

magnitude of applied forces

� FlexPLI tibia bending moment depends on both the magnitude of applied forces and loading locations

� Excessive stiffness of the tibia of EEVC LFI results in much higher sensitivity to the change in the applied force magnitude compared to human bone stiffness

� EEVC LFI upper tibia acceleration shows no correlation with human tibia bending moment due to the use of acceleration as a measure and an excessive stiffness of the tibia

� Direct correlation of EEVC LFI upper tibia acceleration and FlexPLI tibia bending moment makes no sense

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Knee Injury Evaluation

� EEVC LFI individually evaluates bending and shear � FlexPLI measures elongation of ligaments sensitive to both

bending and shear

Shear Disp.

Bending Angle

Individual Measurement

EEVC LFI FlexPLI Injury Criteria

Knee-PCL EL

Knee-MCL EL

Knee-ACL EL

Femur-3 BM

Femur-2 BM

Femur-1 BM

Tibia-1 BM

Tibia-2 BM

Tibia-3 BM

Tibia-4 BM

EL: Elongation Combination

Shearing force Bending force +

MCL LCL

ACL PCL

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Knee Injury Evaluation

� ACL/PCL elongations are sensitive to both bending and shear � MCL elongation is not sensitive to shear due to its length and

distance from center of knee rotation in valgus bending

PCL

ACL

Lateral Impact

MCL LCL

Shear

Valgus Bending

(Posterior View)

MCL: Medial Collateral Ligament ACL: Anterior Cruciate Ligament PCL: Posterior Cruciate Ligament LCL: Lateral Collateral Ligament

PCL

MCL ACL

LCL

(Anterior-oblique view)

Otte et al. (2005)

Knee Anatomy

Center of Rotation

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Human Model MCL Elongation (mm) Fl

ex-P

LI M

odel

M

CL E

long

atio

n (m

m)


Human Model MCL Elongation (mm)

TRL

Legf

orm

Mod

el

Knee

Ben

ding

Ang

le (d

eg) y = 0.9821x - 1.0628

R = 0.75

0

10

20

30

40

0 10 20 30 40

y = 0.5584x + 10.335R = 0.55

0

10

20

30

40

0 10 20 30 40

Both TRL legform knee bending angle and Flex-PLI MCL elongation show good correlation with human MCL elongation

TEG-096 (Flex-PLI)

GTR9-1-05r1

Correlation of MCL Injury Measures


Knee Injury Evaluation GTR9-5-13

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Human Model ACL Elongation (mm)


Human Model ACL Elongation (mm)

TRL

Legf

orm

Mod

el

Knee

She

ar D

ispla

cem

ent (

mm

)

y = -0.2699x + 3.8541R = 0.13

0

2

4

6

8

10

12

0 2 4 6

y = 1.3654x + 3.1228R = 0.68

0

2

4

6

8

10

12

0 2 4 6

�No correlation between TRL legform knee shear displacement and human ACL elongation

�Good correlation between Flex-PLI and human ACL elongation

Flex

-PLI

Mod

el

ACL

Elon

gatio

n (m

m)

GTR9-1-05r1

Correlation of ACL Injury Measures


Knee Injury Evaluation GTR9-5-13

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Knee Injury Evaluation � EEVC LFI individually evaluates knee bending and shear

� FlexPLI directly evaluates elongations of knee ligaments

� Human MCL elongation is insensitive to knee shear due to its length and the distance from the center of knee rotation

� Both EEVC LFI and FlexPLI correlate with human MCL elongation

� EEVC LFI knee shear does not correlate with human ACL elongation due to sensitivity of human ACL elongation to knee bending angle

� Correlation analysis between EEVC LFI knee shear displacement and FlexPLI ACL elongation does not make sense, while correlation analysis between EEVC LFI knee bending angle and FlexPLI MCL elongation is valid

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GTR9-4-18

BASt Study

Reference : BASt, FlexPLI vs. EEVC WG 17 PLI Benefit Estimation, 4th IG GTR9-PH2 Meeting Document, GTR9-4-18 (2012)

Correlation Study - MCL GTR9-5-13

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JAMA Study – Correlation of Knee Bending Measures Correlation Study - MCL

0

5

10

15

20

25

30

35

0 5 10 15 20 25 30 35

18 Simp. ModelCom-ACom-BCom-C (CAE)Com-CCom-ECom-E (CAE)Com-FCom-F (CAE)Com-GCom-HCom-H (CAE)Linear Regression

FlexPLI MCL Elongation (mm)

TRL-

LFI K

nee

Bend

ing

Angl

e (d

eg)

Flex-GTR Test Flex-GTR CAE

R=0.675

Threshold 19 deg

Threshold 22 mm

FlexPLI tends to provide more conservative results than EEVC LFI

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References �National Highway Traffic Safety Administration (NHTSA), Overview of NHTSA Pedestrian

Activities, 4th IG GTR9-PH2 Meeting Document, GTR9-4-19 (2012)

�Mizuno, K. et al., Comparison of Reponses of the Flex-PLI and TRL Legform Impactors in Pedestrian Tests, SAE World Congress, SAE Paper #2012-01-0270 (2012)

�Takahashi, Y. et al., Validation of Pedestrian Lower Limb Injury Assessment using Subsystem Impactors, IRCOBI Conference (2012)

�Japan Automobile Standards Internationalization Center (JASIC), Technical Discussion - Biofidelity, 1st IG GTR9-PH2 Meeting Document, GTR9-1-05r1 (2011)

�BASt, FlexPLI vs. EEVC WG 17 PLI Benefit Estimation, 4th IG GTR9-PH2 Meeting Document, GTR9-4-18 (2012)

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Thank you for your attention

GTR9-5-13

FlexPLI vs. EEVC LFI Correlation - UNECE

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