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NHTSA Evaluation of the Flex-GTR Legform on US Vehicles

Brian Suntay & Ann MalloryTransportation Research Center Inc.

Jason StammenNHTSA Vehicle Research and Test Center

This is a work of the U.S. Government and is not subject to copyright in the United States; it may be used or reprinted without permission.

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The Pedestrian Global Technical Regulation (GTR No. 9) includes a projectile leg simulating a moving vehicle hitting a stationary pedestrian at 40 km/h

Pedestrian Leg Testing

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Comparison of vehicle performance with TRL versus Flex-GTR legforms

Confirm whether the Flex-GTR legform is sensitive enough to distinguish marginally performing vehicles from poor performing vehicles

Test the Flex-GTR’s durability against aggressive locations on US vehicle bumpers

Goals of the Testing

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TRL

Pedestrian Legforms

Flex-GTR

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TRL Rigid Legform

Impactor

Steel femur and tibia segments◦Frangible steel ligaments

Instrumentation:◦ Tibia accelerometer◦Rotary pot with rigid arm

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Flex-GTR Flexible Legform Impactor◦ Increased biofidelity

Flexible bone core, wire ligaments, knee tension cables

Instrumentation:◦ Tibia and Femur strain

gauges◦ Ligament string

potentiometers (MCL, ACL, PCL, ACL)

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Injury Assessment

Bending Injury MeasuresKnee Bending Angle

MCL Elongation

Shear Injury MeasuresKnee Shear Displacement

ACL/PCL Elongation

Tibia Fracture MeasuresTibia Acceleration

Tibia Bending Moment

TRL Flex-GTR

Volkswagen Passat

Mazda Miata

Honda Civic

Honda Pilot

Chevrolet Silverado

Chevrolet Equinox

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Test Results

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Equinox

Silverado

Pilot

Civic

Miata

Passat

0 5 10 15 20 25 30 35

33.1

26.5

33

33

26.5

31.1

Peak Bending Angle (deg)

TRL Test Results

Equinox

Silverado

Pilot

Civic

Miata

Passat

0 1 2 3 4 5 6 7 8 9 10

7.5

8.3

6.8

8.9

8.9

8.1

Peak Shear Displacement (mm)

Equinox

Silverado

Pilot

Civic

Miata

Passat

0 50 100 150 200 250 300 350 400 450

183

353

401

326

402

307

Peak Tibia Acceleration (g)

Equinox

Silverado

Pilot

Civic

Miata

Passat

0 1 2 3 4 5 6 7 8 9

8.4

5.6

7.1

7.2

6.4

7.9

Peak PCL Elongation (mm)

Equinox

Silverado

Pilot

Civic

Miata

Passat

0 5 10 15 20 25 30 35 40

34.4

22.3

32.1

27.0

24.1

28.2

Peak MCL Elongation (mm)

Equinox

Silverado

Pilot

Civic

Miata

Passat

0 50 100 150 200 250 300 350 400 450 500

378

333

402

475

460

428

Peak Tibia 1 Moment (Nm)

Flex-GTR Test Results

Equinox

Silverado

Pilot

Civic

Miata

Passat

0 2 4 6 8 10 12 14 16 18

11.97.9

15.5

14.8

14.3

13.9

Peak ACL Elongation (mm)

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Comparison of ResultsTRL vs Flex-GTR

Comparison of Results – TRL vs Flex-GTR

Equinox

Silverado

Pilot

Civic

Miata

Passat

0 20 40 60 80 100 120 140 160 180

Fracture Measures

TRL - Tibia AccelerationFlex-GTR - Max Tibia Bend Moment

Injury Measure as % of Limit

Equinox

Silverado

Pilot

Civic

Miata

Passat

0 20 40 60 80 100 120 140 160 180 200

Bending Injury Measures

TRL - Knee Bending Angle Flex-GTR - MCL Elongation

Injury Measure as % of Limit

Equinox

Silverado

Pilot

Civic

Miata

Passat

0 20 40 60 80 100 120 140 160

Shear Injury Measures

TRL - Knee Shear DisplacementFlex-GTR - Max ACL/PCL Elongation

Injury Measure as % of Limit

0 20 40 60 80 100 120 140 1600

20

40

60

80

100

120

140

160

Equinox

Silverado

Miata

PilotPassat

Civic

Shear Injury Measures

TRL % of Injury Limit

Fle

xG

TR

% o

f In

jury

Lim

it0 20 40 60 80 10

012

014

016

018

020

00

20406080

100120140160180200

PilotPassat

Equinox

Silverado

CivicMiata

Bending Injury Measures

TRL % of Injury Limit

Fle

xG

TR

% o

f In

jury

Lim

it

0 20 40 60 80 1001201401601800

20

40

60

80

100

120

140

160

180

Equinox

Silverado

Pilot

CivicMiata

Passat

Fracture Measures

TRL % of Injury Limit

Fle

xG

TR

% o

f In

jury

Lim

it

Comparison of Results – TRL vs Flex-GTR

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The Flex-GTR measures lower values than the TRL legform with respect to their current injury limits◦ In contrast:

Matsui et al., Characteristics of the TRL Pedestrian Legform and the Flexible Pedestrian Legform Impactors in Car-front Impact Tests, Paper Number 09-0206, 21st International Technical Conference on the Enhanced Safety of Vehicles, 2009.

Yoon et al., Evaluation of Usefulness and Repeatability for Pedestrian Protection Flex-PLI, Paper Number 11-0425, 22nd International Technical Conference on the Enhanced Safety of Vehicles, 2011.

Aggressive vehicle bumper impact locations chosen

Summary of Findings

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Flex-GTR Vehicle Sensitivity

Testing with a previous version of the Flex-GTR legform suggested an inability of the legform to distinguish among vehicles that performed poorly (Mallory, 2010)

Results from current series of tests

Three additional tests performed on the center of the three passenger cars

Sensitivity

Fracture Bend Shear

Equinox

Silverado

Pilot

Civic

Miata

Passat

0 20 40 60 80 100

120

140

160

180

Fracture Measures

Injury Measure as % of Limit

Equinox

Silverado

Pilot

Civic

Miata

Passat

0 20 40 60 80 100

120

140

160

180

200

Bending Injury Measures

Injury Measure as % of Limit

Equinox

Silverado

Pilot

Civic

Miata

Passat

0 20 40 60 80 100 120 140 160

Shear Injury Measures

Injury Measure as % of Limit

Volkswagen Passat

Mazda Miata

Honda Civic

Comparison of Old and New Flex-GTR Data – Center Impacts

Civic

Miata

Passat

0 20 40 60 80 100 120 140

Fracture Measures

Flex-GTR (New) - Max Tibia Bend MomentFlex-GTR (Old) - Max Tibia Bend Moment

Civic

Miata

Passat

0 20 40 60 80 100 120 140

Bending Injury Measures

Flex-GTR (New) - MCL ElongationFlex-GTR (Old) - MCL Elongation

Civic

Miata

Passat

0 20 40 60 80 100 120

Shear Injury Measures

Flex-GTR (New) - Max ACL/PCL ElongationFlex-GTR (Old) - Max ACL/PCL Elongation

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The Flex-GTR measures lower values than the TRL legform with respect to their current injury limits

The Flex-GTR seems to be able to distinguish differences in relatively aggressive vehicle bumper designs

Summary of Findings

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Flex-GTR Durability

Observations and Durability Assessment (Flex-GTR)

Misalignment of the knee after impacts

Tear in the neoprene skin and scratches on the femur knee

block

Femur strain gauge #2 (middle gauge)◦Broken gauge/wire◦Still being investigated

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The Flex-GTR measures lower values than the TRL legform with respect to their current injury limits

The Flex-GTR seems to be able to distinguish differences in relatively aggressive vehicle bumper designs

The Flex-GTR was observed to be durable◦ Survived US vehicle bumper impacts that exceeded

injury limits◦ A majority of the issues that were observed were minor

and repairable

Summary of Findings

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Flex-GTR Repeatability(Additional Observation)

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Flex-GTR RepeatabilityInjury Measurement

Injury Reference

Value (FlexTEG)

Chevrolet Silverado

Impact Location Center

GTR (1001) GTR (1002) %Difference

Femur Moment (Nm)

Femur 3 (Upper)--*

73.7 77.3 5%

Femur 2 (Middle) 139.5 138.5 1%

Femur 1 (Lower) 252.1 245.6 3%

Tibia Moment (Nm)

Tibia 1 (Upper)

340 Nm (380 Nm)

332.7 332.6 0%

Tibia 2 (Mid Upper)311.1 319.5 3%

Tibia 3 (Mid Lower)233.5 237.4 2%

Tibia 4 (Lower) 110.5 107.9 2%

MCL Elongation (mm) 22 mm -- 22.3 NA

ACL Elongation (mm) 13 mm 8 7.9 1%

PCL Elongation (mm) 13 mm 5.4 5.6 4%

LCL Elongation (mm) --* -4.2 -3.8 10%

Tibia Acceleration (g) --* -59.2 -59.5 1%

Velocity (m/s) --* 11.1 11.1 0% Average: 3%

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The Flex-GTR measures lower values than the TRL legform with respect to their current injury limits

The Flex-GTR seems to be able to distinguish differences in relatively aggressive vehicle bumper designs

The Flex-GTR was observed to be durable◦ Survived US vehicle bumper impacts that exceeded injury limits◦ A majority of the issues that were observed were minor and

repairable

Flex-GTR repeatability was not directly evaluated, but◦ Silverado Flex-GTR tests 1001 and 1002 showed similar values at

the same impact location, which is promising

Summary of Findings

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NHTSA Evaluation of the Flex-GTR Legform on US Vehicles

Brian Suntay & Ann MalloryTransportation Research Center Inc.

Jason StammenNHTSA Vehicle Research and Test Center

This is a work of the U.S. Government and is not subject to copyright in the United States; it may be used or reprinted without permission.