National Highway Traffic Safety Administration

49th GRSP Session May 2011

Nha Nguyen

Update on Pedestrian Leg Testing

1

Informal document GRSP-49-23(49th GRSP, 16-20 May 2011,agenda items 4(a))

GTR9-1-12

Pedestrian Leg Testing

Projectile leg simulates a moving vehicle hitting a

stationary pedestrian

2

Pedestrian Legforms

TRL

Flex-GT

Flex-GTR3

Background

The Flex-GTR had not been tested against aggressive

vehicles in the US fleet and there was concern about its

durability

There was also concern about topping out the Flex-

GTR’s measurement limits (Mallory, 2010)

Fracture Bend Shear4

Goals of the Testing

This series of impacts was done to test the Flex-GTR against

aggressive US vehicles to see if it would survive

Confirm whether the Flex-GTR legform can distinguish

marginally performing vehicles from poor performing vehicles

5

Test Sequence

Due to durability concerns, the TRL legform was tested on each

vehicle first to rank the vehicles in order of increasing

aggressiveness

The Flex-GT was then tested on each vehicle to rank them for

the Flex-GTR tests

This allows us to get in as many tests as possible before possibly

damaging the legform

6

Volkswagen Passat

Mazda Miata

Honda Civic

7

Honda Pilot

Chevrolet Silverado

Chevrolet Equinox

8

Test Results

9

7,5

8,3

6,8

8,9

8,9

8,1

0 2 4 6 8 10

Equinox

Silverado

Pilot

Civic

Miata

Passat

Peak Shear Displacement (mm)

TRL Test Results

33,1

26,5

33

33

26,5

31,1

0 5 10 15 20 25 30 35

Equinox

Silverado

Pilot

Civic

Miata

Passat

Peak Bending Angle (deg)

183

353

401

326

402

307

0 50 100 150 200 250 300 350 400 450

Equinox

Silverado

Pilot

Civic

Miata

Passat

Peak Tibia Acceleration (g)

*Performed under GTR conditions with legform 25 mm above ground reference level10

9,0

14,4

8,8

10,2

9,4

8,5

0 5 10 15 20

Equinox

Silverado

Pilot

Civic

Miata

Passat

Peak PCL Elongation (mm)

12,3

8,4

11,9

14,4

22,8

12,7

0 5 10 15 20 25

Equinox

Silverado

Pilot

Civic

Miata

Passat

Peak ACL Elongation (mm)

35,7

23,5

35,5

36,6

31,6

42,5

0 10 20 30 40 50

Equinox

Silverado

Pilot

Civic

Miata

Passat

Peak MCL Elongation (mm)

382,6

332,9

417,6

383,1

395,2

329,6

0 100 200 300 400 500

Equinox

Silverado

Pilot

Civic

Miata

Passat

Peak Tibia 1 Moment (Nm)

Flex-GT Test Results

*Performed under GTR conditions with legform 25 mm above ground reference level

11

8,36

5,61

7,05

7,15

6,36

7,91

0 2 4 6 8 10

Equinox

Silverado

Pilot

Civic

Miata

Passat

Peak PCL Elongation (mm)

34,37

22,28

32,05

26,99

24,14

28,23

0 10 20 30 40

Equinox

Silverado

Pilot

Civic

Miata

Passat

Peak MCL Elongation (mm)

377,5

332,61

402,04

474,6

460,48

428,36

0 100 200 300 400 500

Equinox

Silverado

Pilot

Civic

Miata

Passat

Peak Tibia 1 Moment (Nm)

Flex-GTR Test Results

*Performed under GTR conditions with legform 75 mm above ground reference level

11,93

7,87

15,5

14,8

14,3

13,88

0 5 10 15 20

Equinox

Silverado

Pilot

Civic

Miata

Passat

Peak ACL Elongation (mm)

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Comparison of Results

TRL vs GTR

13

Comparison of Results –TRL vs Flex-GTR

0 20 40 60 80 100 120 140 160 180

Equinox

Silverado

Pilot

Civic

Miata

Passat

Injury Measure as % of Limit

Fracture Measures

TRL - Tibia Acceleration Flex-GTR - Max Tibia Bend Moment

0 50 100 150 200

Equinox

Silverado

Pilot

Civic

Miata

Passat

Injury Measure as % of Limit

Bending Injury Measures

TRL - Knee Bending Angle Flex-GTR - MCL Elongation

0 20 40 60 80 100 120 140 160

Equinox

Silverado

Pilot

Civic

Miata

Passat

Injury Measure as % of Limit

Shear Injury Measures

TRL - Knee Shear Displacement Flex-GTR - Max ACL/PCL Elongation

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Comparison of Results –TRL vs Flex-GTR

0

20

40

60

80

100

120

140

160

180

0 20 40 60 80 100 120 140 160 180

Fle

x-G

TR

% o

f In

jury

Lim

it

TRL % of Injury Limit

Fracture Measures

0

20

40

60

80

100

120

140

160

180

200

0 20 40 60 80 100 120 140 160 180 200

Fle

x-G

TR

% o

f In

jury

Lim

it

TRL % of Injury Limit

Bending Injury Measures

0

20

40

60

80

100

120

140

160

0 20 40 60 80 100 120 140 160

Fle

x-G

TR

% o

f In

jury

Lim

it

TRL % of Injury Limit

Shear Injury Measures

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Summary of Findings

• The Flex-GTR measures lower values than the TRL legform

• The current Flex-GTR seems to be able to distinguish

differences in relatively aggressive vehicle bumper designs

better than the previous version

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Sensitivity

• Testing with a previous version of the Flex-GTR legform showed an inability of the legform to

distinguish among vehicles that performed poorly

•Measurements reached a limit (Mallory, 2010)

• Improvement in the current series of tests may be due to changes in Flex-GTR legform

•Cable stop gap increase

•Femur: 8 mm 9.1 mm

•Tibia: 9 mm 10.3 mm

• Three additional tests performed on the centers of the three passenger cars

Fracture Bend Shear

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Volkswagen Passat

Mazda Miata

Honda Civic

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

0 20 40 60 80 100 120 140

Civic

Miata

Passat

Fracture Measures

Flex-GTR (New) - Max Tibia Bend Moment

Flex-GTR (Old) - Max Tibia Bend Moment

0 20 40 60 80 100 120 140

Civic

Miata

Passat

Bending Injury Measures

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

0 20 40 60 80 100 120

Civic

Miata

Passat

Shear Injury Measures

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

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

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Summary of Findings

The Flex-GTR measures lower values than the TRL legform

The current Flex-GTR seems to be able to distinguish differences in relatively aggressive vehicle bumper designs better than the previous version

Topping out is not a concern with the current Flex-GTR

Flex-GTR repeatability was not directly evaluated, but

Silverado Flex-GTR tests 1001 and 1002 showed similar numbers at the same impact location, which is promising

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Injury Measurement

Injury Reference

Value (FlexTEG)

Chevrolet Silverado

Impact Location Center

GTR (1001) GTR (1002)

Femur Moment

(Nm)

Femur 3 (Upper)

--*

73.67 77.28

Femur 2 (Middle) 139.48 138.52

Femur 1 (Lower) 252.05 245.58

Tibia Moment

(Nm)

Tibia 1 (Upper)

340 Nm (380 Nm)

332.73 332.61

Tibia 2 (Mid Upper) 311.07 319.53

Tibia 3 (Mid Lower) 233.53 237.41

Tibia 4 (Lower) 110.52 107.91

MCL Elongagtion (mm) 22 mm -- 22.28

ACL Elongation (mm) 13 mm 8 7.87

PCL Elongation (mm) 13 mm 5.41 5.61

LCL Elongation (mm) --* -4.16 -3.76

Tibia Acceleration (g) --* -59.21 -59.39

Velocity (m/s) --* 11.055 11.137

Flex-GTR Repeatability – Chevy

Silverado

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Summary of Findings

• The Flex-GTR measures lower values than the TRL legform

• The current Flex-GTR seems to be able to distinguish differences in relatively aggressive vehicle bumper designs better than the previous version• Topping out is not a concern with the current Flex-GTR

• Flex-GTR repeatability was not directly evaluated, but• Silverado Flex-GTR tests 1001 and 1002 showed similar numbers at the

same impact location, which is promising

• The Flex-GTR was observed to be durable• Survived US vehicles• A majority of the issues that were observed were minor and repairable

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Observations and Durability Assessment (Flex-GT)

Pinching of wires between blue tab

and metal knee condyle

Wear and tear of plastic sheath around

knee tension cables

Pushed Surface of the Legform

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Observations and Durability Assessment (Flex-GT)

Tibia and Femur knee blocks are rotated/not flush with each other

Pushed Surface of the Legform

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Observations and Durability Assessment (Flex-GTR)

Misalignment of the knee after Passat and

Miata impacts

Tear in the neoprene skin and scratches

on the femur knee block25

Issues with Flex-GTR

• Needed to modify the legform in order for its flight to be within GTR tolerances for forward pitch (specific to the VRTC launch system)• Removed black protective end caps

• Konosu-san (JARI) informed us that they cut out notches at the top and bottom of the launch plate to accommodate for the end caps

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

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Summary of Findings

• Durability:

• The Flex-GTR seems to be able to distinguish differences in

relatively aggressive vehicle bumper designs better than the

previous version

• Flex-GTR repeatability was not directly evaluated, but

• Silverado Flex-GTR tests 1001 and 1002 showed similar numbers at the

same impact location, which is promising

• The Flex-GTR was observed to be durable

• Survived US vehicles

• A majority of the issues that were observed were minor and repairable

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Summary of Findings

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Injury criteria:

The Flex-GTR measures lower values than the TRL legform

Injury results were not consistent with previous testing:

Previous study has shown that it’s rare to injure the ACL or PCL without

injuring MCL. However, in the VW and Honda Civic tests, we observed

ACL elongation that exceeded the injury criteria before the MCL

exceeding injury criterion.

The findings raise concerns on whether the Flex GTR is

properly modeling the impact or that the injury criteria are

appropriate

Conclusion

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Flex-GTR legform is found to be durable

Additional research and testing needed to address the injury

criteria concerns

Currently, more world fleet data is needed

Different evaluation criteria may result in different counter-

measures (design and cost benefit)

Thank you

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