Analysis of a Frontal Impact of a Formula

SAE Vehicle David RisingJason KaneNick Vernon

Joseph AdkinsDr. Craig Hoff

Dr. Janet Brelin-Fornari

Kettering University

Overview� Introduction

� Formula SAE� Impact Attenuator Rules� Methodology

� Evaluation Criteria� HIC, Neck Loads and Moments, Nij, Femur Loads

� Testing Procedures� Baseline Testing, Pulse Shape Comparison, Critical Speed Test

� Results� Comparison of evaluation criteria� Kinematic Analysis using high speed video

� Conclusions

Introduction - Formula SAE

� Worldwide collegiate competition

� Students conceive, design, and fabricate small formula style cars

� Driver risks have never been tested in a crash environment

Introduction - Formula SAE Impact Attenuator Rules

� 3.3.6.4 Impact Attenuator Data Requirement� The team must submit calculations and/or test data to

show that their Impact Attenuator, when mounted on the front of the vehicle with a total mass of 300 kgs (661 lbs) and run into a solid, non-yielding impact barrier with a velocity of impact of 7.0 m/s (23 ft/s), would give and average deceleration of the vehicle not to exceed 20 g.

� Does not specify deceleration time-history pulse shape

Introduction – Methodology� Evaluate the Impact

Attenuator rule based on ATD Injury Criteria

� Explore the “Safety Envelope” by increasing impact speeds

� Evaluate Pulse Shape� Kinematic Analysis Using

High Speed Video� Evaluate HANS Device

Effectiveness

Typical Test

Test Conditions • 7.0 m/s• 16.5 g avg• 35 ms

Evaluation Criteria - HIC

� Head Injury Criteria (HIC) is used to evaluate the severity of head trauma based on accelerations

� HIC consists of two criterion, HIC36 and HIC15

� HIC36 and HIC15 calculate the highest average acceleration over a 36 ms and 15 ms period respectively

� Values for HIC36 that exceed 1000 and values of HIC15 that exceed 700 represent a 31% chance of skull fracture

Evaluation Criteria - Nij� Nij criteria is based on the resultant neck loads and

moments experienced by the ATD� Nij represents the four major combinations of neck

loading in a frontal crash� Nce: Compression load and Extension moment� Ncf: Compression load and Flexion moment� Nte: Tension load and Extension moment� Ntf: Tensions load and Flexion moment

� Nij values that exceed 1.0 and individual load and moment values that exceed their IARV represent a 22% chance of AIS 3 neck injury

Evaluation Criteria - Femur

� Axial load cell in femur measures compression and tension loads

� Axial loads that exceed 10,000 N represent a 35% chance of a moderate injury to the femur

Procedure� Baseline Test

� Replicate as close as possible the deceleration due to the impact attenuator: 7.0 m/s, 20 g average, 35 ms pulse

� Pulse Shape Comparison� Increased speed to 12.5 m/s, average of 16 g, 80 ms pulse� Three pulse shapes compared: early high-g peak, constant g, and late high-

g peak� Each pulse shape compared both with and without the use of a HANS

device� Critical Speed Test

� Increased impact speed until Injury Assessment Reference Values were exceeded

� Test specifications: 15.6 m/s, 80 ms pulse, 20 g average deceleration� Utilized late high-g pulse shape and was tested with and without HANS

Early High-g Pulse

Constant-g Pulse

Late High-g Pulse

Results – Baseline

� Showed no condition where IARV were exceeded� Test one, two, and three values were negligible

when compared to the IARV� Many values in test four were much closer to the

IARV� May be due to much higher initial velocity (11.2 m/s) and

average deceleration (27.6) than tests one, two, and three

� Femur load cell was not utilized

Results - Baseline

-224394.869.50.66900.9620.293-101.197.47-413.4234611.227.6Baseline Test #4

-43.443.436.20.1580.0290.2960.200-32.4533.1-449.1394.56.916.6Baseline Test #3

-2839.930.60.1710.0570.2660.230-31.4135.14-475.3379.37.116.7Baseline Test #2

----0.1650.0570.2140.240-25.3534.17-413.7381.76.915.7Baseline Test #1

1000070010001111-135310-40004170IARV

Axial Fem

ur Load (N)

HIC

15

HIC

36

Peak R

esultant Head A

ccel(g's)

NtfNcfNteNce

Extension N

eck Mom

ent (N-m

)

Flexion Neck M

oment (N

-m)

Com

pression Neck Load (N

)

Tension Neck Load (N

)

�V (m

/s)

Average A

cceleration (g's)

Test

Results - Baseline

� ATD did not experience maximum acceleration until after 35 milliseconds

� Test Conditions:� Baseline

Test #4

Results - Pulse Shape

� No condition where IARVs were exceeded� On average the constant-g measured values

exceeded that of the early-g and late-g pulses� The average initial velocity of the constant-g pulse

was also 1 m/s higher that the early-g pulse and 2.5 m/s higher that the late-g pulse

� The addition of the HANS device reduced the tension neck load in every test

Results – Pulse Shape

4394373452670.3310.0940.40.387-52.7842.29-509.5159012.514.5Late High-g HANS #2

1485354437660.2820.0930.4090.433-54.9647.49-516.8137012.517.7Late High-g HANS #1

353149240540.42500.1730.195-22.8122.86-461.3264111.212.9Late High-g #2

484273449550.53400.3240.245-31.7415.58-505.2329712.116.6Late High-g #1

3581321423620.250.1520.3150.695-65.2648.18-870.6137012.517.5Constant-g HANS#2

4614364587630.39800.3280.608-57.5238.29-1184206612.518.2Constant-g HANS#1

4877306557550.61400.5040.691-73.3825.16-1011363112.516.8Constant-g #2

3866281450520.53500.4260.651-71.1219.88-950.3324012.517.7Constant-g #1

4043312507680.5050.1170.477NA-41.6771.23-270.9187612.117.6Early High-g HANS #2

2342258400750.43300.3280.469-55.6464.29-710.4186211.215.8Early High-g HANS #1

1821249420740.58200.4810.344-45.9441.42-814.6311511.615.6Early High-g #2

2256251421780.53500.4260.651-44.7729.91-927.8313111.616.9Early High-g #1

1000070010001111-135310-40004170IARV

Axial Fem

ur Load (N)

HIC

15

HIC

36

Peak R

esultant Head

Accel(g's)

NtfNcfNteNce

Extension N

eck M

oment (N

-m)

Flexion Neck M

oment

(N-m

)

Com

pression Neck

Load (N)

Tension Neck Load

(N)

�V

(m/s)

Average A

cceleration (g's)

Test

Results – Pulse Shape

�V

(m/s)

Average

Acceleration (g's)

Axial Fem

ur Load (N

)

HIC

15

HIC

36

Peak R

esultant H

ead Accel(g's)NtfNcfNteNce

Extension N

eck M

oment (N

-m)

Flexion Neck

Mom

ent (N-m

)

Com

pression N

eck Load (N)

Tension Neck

Load (N)

Test

602%72%29%22%-36%-63%86%98%134%6%-50%8%9.2%Late High-g

-6%17%0%17%-44%--31%-3%-15%92%5%-50%0%3.5%Constant-g

57%14%8%-6%-16%--11%-6%7%90%-44%-40%0%2.8%Early High-g

Comparison with and w/o HANS

2940363444670.3070.0940.4050.41-53.944.9-513148012.516.1Late High-g Hans Avg

4098342505630.3240.0760.3220.652-61.443.2-1027171812.517.9Constant-g Hans Avg

3193285453710.4690.0590.4030.469-48.767.8-491186911.616.7Early High-g Hans Avg

Average Values w/ HANS

419211344540.4800.2490.22-27.319.2-483296911.614.8Late High-g Avg

4372294504540.57500.4650.671-72.322.5-981343612.517.3Constant-g Avg

2039250420760.55900.4540.498-45.435.7-871312311.616.3Early High-g Avg

Average Values w/o HANS

Results – Critical Speed� During the critical late high-g test the tension neck load,

HIC15, HIC36, and femur load IARV were exceeded� The use of the HANS device reduced the tension neck load

below the IARV� The use of the HANS did not affect the HIC15, HIC36, and

femur load values

Axial Fem

ur Load (N)

HIC

15

HIC

36

Peak R

esultant Head

Accel(g's)

NtfNcfNteNce

Extension N

eck M

oment (N

-m)

Flexion Neck M

oment

(N-m

)

Com

pression Neck

Load (N)

Tension Neck Load

(N)

�V

(m/s)

Average A

cceleration (g's)

Test

1349010421412960.4180.1030.3510.491-45.4240.4-1421230515.620.0Critical Late High-g HANS

13550114315491010.8130.0750.7020.589-58.6957.92-1150481715.620.0Critical Late High-g

Results – Critical Speed Kite Graph (no HANS)

Test Conditions •15.6 m/s• 20 g avg• 80 ms

Results – Critical Speed Kite Graph (w/ HANS)

Test Conditions •15.6 m/s• 20 g avg• 80 ms

Conclusions

� The baseline tests that approximated the Formula SAE rules (7.0 m/s, 20-g average deceleration) resulted in measured injury values that were negligible compared to the IARV

� The tests comparing pulse shape all resulted in values which were less than the IARV

� The statistically highest values comparing pulse shape were seen during the constant-g test however, the average acceleration was slightly higher for these tests

Conclusions Cont.

� The addition of a HANS device reduced the tension neck load in every test and brought the test value below the IARV for the critical speed test

� An impact from 15.6 m/s with a 20-g average deceleration rate was found to pose a serious risk of injury to the driver, with and without the HANS device.

� To reduce the risk of injury to the driver, horizontally mounted tubes should be placed a

Acknowledgements

� Janet Brelin-Fornari, John Young and the Kettering University Crash Safety Center for the use of their facility.

� Denton Safety Systems for the use of their equipment

� Jamie Jones and Red Horse Racing for the donation of a HANS device for testing.

� Lynn St. James and HANS for the donation of two new HANS devices.

References� Gideon, T., Melvin, J., Streetz, L., and Willhite, S. “ATD Neck Tension

Comparisons for Various Sled Pulses”, Society of Automotive Engineers, 2002, SAE 2002-01-3324.

� Society of Automotive Engineers. 2006 Formula SAE Rules. http://students.sae.org/competitions/formulaseries/

� Eppinger R., Sun E., Bandak F., Haffner M., Khaewpong N., Maltese M., Kuppa S., Nguyen T., Takhounts E., Tannous R., Zhang A., Saul R. Development of Improved Injury Criteria for the Assessment of Advanced Automotive Restraint Systems – II. November, 1999, The National Highway Traffic Safety Administration.

� FMVSS 208. May 27, 1998 The National Highway Traffic Safety Administration, DOT.

� Trauma.org. Abbreviated Injury Scale. Accessed on August 22, 2006. http://www.trauma.org/scores/ais.html.

Thank You For Your Time

Any Questions?