Shashi Kuppa - 2002 SAE Govt/Industry Mtg


SLIDE 1:
PERFORMANCE OF HEAD RESTRAINTS AS A FUNCTION OF SEAT BACK STRENGTH IN REAR IMPACT SLED TESTS

Shashi Kuppa, James Saunders - NHTSA R&D
Lou Molino - NHTSA NPS


SLIDE 2:
BACKGROUND
- NHTSA recently proposed an upgrade to the dynamic test option in FMVSS 202
- The head rotation with respect to torso should not exceed 12 degrees for a 50th percentil male HIII dummy and 20 degrees for a 95th percentile male HIII dummy in a 17.5 km/h rear impact sled test.


SLIDE 3:
FMVSS 202 SLED TESTS
- to examine the performance of current seats with respect to the upgraded dynamic test:
- DeltaV=17.5km/h sled tests with OEM seats

[table]
50% HIII DUMMY
 - Head Restraint Height(mm) 	750
 - OEM Seats			Taurus

50% HIII DUMMY
 - Head Restraint Height(mm) 	800
 - OEM Seats			Taurus, Volvo, Camry, Easi
 
95% HIII DUMMY
 - Head Restraint Height(mm) 	800
 - OEM Seats			Saab, Deville


SLIDE 4:
TYPICAL SLED PULSE
[graph chart]


SLIDE 5:
TEST WITH 50TH PERCENTILE HIII MALE DUMMY IN TAURUS SEAT WITH 750mm HEAD RESTRAINT HEIGHT
[photo still from video] - interior of passenger dummy, left passenger side door perspective.

 - seat rotation = 18 deg.
 - head rotation = 42 deg.
 - Nij(upper) = 0.2
 - HIC15 = 23


SLIDE 6:
TEST WITH 50TH PERCENTILE HIII MALE DUMMY IN TAURUS SEAT WITH 800mm HEAD RESTRAINT HEIGHT
[photo still from video] 

 - seat rotation = 8.4 deg
 - head rotation = 22 deg.
 - Nij(upper) = 0.1
 - HIC 15 = 35


SLIDE 7:
SUMMARY OF 202 TESTS	
[bar chart, no absolute figures]


SLIDE 8:
RELATIONSHIP BETWEEN SEAT ROATATION AND HEAD ROTATION IN OPTIONAL 202 DYANMIC TESTS
[graph]


SLIDE 9:
SEAT AND HEAD ROTATION IN 202 SLED TESTS WITH 50th PERCENTILE MALE
Taurus 99 vs. Volvo 2000 {graph of pulses]
indicates head rotation with respect to torso / seat rotation
peak Nij occurs approximately at time of peak head rotation


SLIDE 10:
SUMMARY OF RESULTS
- relative head rotation with respect to torso depends on the seat roattion as well as the head restraint height.
- Nij and other neck measures increase with the increase in relative head rotation.
- seat cushion, head restraint flexibility, upholstery and other characteristics of the seat may also influence dummy head and torso kinematics


SLIDE 11:
SEAT BACK STIFFNESS AND HEAD ROTATION
Additional sled tests conducted with the FMVSS 202 pulse (17.5 km/h) using the 95th percentile male HIII dummy
- head restraint height = 800 mm
- backseat = 50 mm
- seat strength = varied
	* baseline: 35Nm/deg
	* 200%: 70Nm/deg
	* 500%: 175Nm/deg
	* rigid


SLIDE 12:
Tests conducted at JHU - APL
[PHOTO:	 dummy in seat- side view]
pointers - head contact switch, string potentiometer, load bolts, adjustable shock absorbers


SLIDE 13:
INITIAL POSITION (95M vs. 50M)
(800 mm head restraint height, backset=50mm)
[still photos] side-by-side comparison of the two positions


SLIDE 14:
HEAD CG LEVEL AT MAX TORSO HEIGHT
(95M vs> 50M)
[still photos] side-by-side comparison of the two positions



SLIDE 15:
INITIAL HEAD CONTACT (95M vs 50M)
[still photos] side-by-side comparison of the two positions


SLIDE 16:
MAX HEAD ROTATION (95M vs 50M)
[still photos] side-by-side comparison of the two positions



SLIDE 17:
EFFECTS OF SEATBACK STIFFNESS ON DUMMY KINEMATICS
HEAD CONTACT (95M vs 50M)
[still photos] baseline stiffness vs. 500% stiffness side-by-side comparison of the two positions


SLIDE 18:
EFFECT OF SEATBACK STIFFNESS ON REARWARD SEAT ROATATION
[bar chart]

SEATBACK RTATIONAL STIFFNESS: peak rotation
 100%:	28
 200%:	20
 500%:	11	
 Rigid:  0


SLIDE 19:
[bar chart]
EFFECT OF SEATBACK SIFFNESS ON HEAD AND CHEST ROTATION


SLIDE 20:
[bar chart]
EFFECT OF SEATBACK STIFFNESS ON HEAD ROTATION AND CONTACT TIME


SLIDE 21:
[bar chart]
EFFECT OF SEATBACK STIFFNESS ON UPPER NECK RESPONSE


SLIDE 22:
[bar chart]
EFFECT OF SEATBACK STIFFNESS ON Nij NECK INJURY CRITERIA


SLIDE 23:
CONCLUSIONS
- tests conducted at APL did not show conclusive trends between seatback stiffness and relative head to torso rotation for the 95th male HIII dummy

- the flexibility of head restraint influenced head kinematics after head contact

- Future Testing: similar sled tests at 17.5 km/h DeltaV with 50th percentile male HIII dummy