Evaluation of Lower Extremity Injury Mitigation and Investigation of Thoracolumbar Loading of Restrained Occupants During Frontal Crashes By John P. Patalak A Thesis Submitted to the Graduate Faculty of VIRGINIA TECH – WAKE FOREST UNIVERSITY SCHOOL OF BIOMEDICAL ENGINEERING & SCIENCES In Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Biomedical Engineering October 2017 Winston-Salem, North Carolina Approved by: Joel D. Stitzel, PhD, Advisor, Chair Examining Committee: F. Scott Gayzik, PhD Ashley A. Weaver, PhD
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Evaluation of Lower Extremity Injury Mitigation and Investigation of
Thoracolumbar Loading of Restrained Occupants During Frontal Crashes
By
John P. Patalak
A Thesis Submitted to the Graduate Faculty of
VIRGINIA TECH – WAKE FOREST UNIVERSITY
SCHOOL OF BIOMEDICAL ENGINEERING & SCIENCES
In Partial Fulfillment of the Requirements
for the Degree of
MASTER OF SCIENCE
Biomedical Engineering
October 2017
Winston-Salem, North Carolina
Approved by:
Joel D. Stitzel, PhD, Advisor, Chair
Examining Committee:
F. Scott Gayzik, PhD
Ashley A. Weaver, PhD
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ACKNOWLEDGEMENTS
I would like to begin by thanking my wife, Lydia. Only by her continued support,
encouragement and the appropriate balance of sympathy and prodding was I able to
complete this work. Thank you also to my patient children, Duke, Bella, Asher, Saige and
Sarah, who often provided me with needed study breaks.
I also must thank my advisor, Dr. Joel Stitzel. Having been out of academia for
over a decade before starting this degree, your support and advice allowed me to make a
smooth transition back into school and maintain a balance with my work schedule. Thank
you for your backing and wise advice.
Thank you also to my employer, NASCAR, for their flexibility with my time and their
support to pursue this degree. I’d like to thank Tom Gideon, Gene Stefanyshyn and Steve
O’Donnell for their encouragement and patience with my schedule. I’d also like to thank
and recognize Matthew Harper and Curt Cloutier at NASCAR for their willingness to help
and support all our testing. I also want to recognize the late Dr. John Melvin for his passion
of protecting motorsport drivers and his influence on me to pursue this additional
education.
Thank you also to the remaining members of my committee, Dr. Scott Gayzik and
Dr. Ashley Weaver for your advice and aid throughout my classes and with this project. I
would also like to thank my many lab mates who helped me understand and learn the
many processes required to help make these types of projects manageable and
successful. Specifically, I’d like to recognize Dr. Matthew Davis, Derek Jones, James
Gaewsky, Jeff Suhey, Bharath Koya and Logan Miller.
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Lastly, I’d like to thank my parents, Peter and Joan for their efforts and commitment
to loving and raising my brothers and I to create and foster an appreciation for God, family,
country and hard work.
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TABLE OF CONTENTS
Acknowledgements…………………………………………………………………...ii
Table of Contents……………………………………………………........................iv
List of Tables………………………………………………………………….............vi
Chapter II Table 1. Required NASCAR driver safety equipment………………………………………8 Table 2. Average number of incidents per year for full time NASCAR MENCS drivers and lower extremity injuries……………………………………………………………………12 Table 3. Sled test setup……………………………………………………………………….16 Table 4. Tibia peak axial forces for initial gap tests………………………………………..27 Table 5. ATD foot Z-axis acceleration for initial gap tests………………………………...34 Chapter III Table 6. Lumbar injury case summaries…………………………………………………....41 Table 7. THUMS study variables…………………………………………………………….59 Table 8. Seated configuration spine, pelvic and hip angles………………………………64 Table 9. Independent-samples t-test for peak Fz between slouched and upright postures …………………………………………………………………………………………75 Table 10 Independent-samples t-test for peak resultant XY bending moment between slouched and upright postures ………………………………………………..………….…..76 Table 11. One-way ANOVA test for SRA and peak axial compressive force and resultant XY bending moment in upright TIP simulations ……………………….………...78 Table 12. One-way ANOVA test for SRA and peak axial compressive force and resultant XY bending moment in slouched TIP simulations…………………….………….79
LIST OF FIGURES
Chapter II Figure 1. Required NASCAR driver crash safety equipment………………………….…..9 Figure 2. NASCAR driver crash safety equipment………………………………………....9 Figure 3. Quasi-static foam test (post-test)………………………………………………...14 Figure 4. Quasi-static foam test stress strain plots………………………………………..15 Figure 5. Shoulder belt load cells……………………………………………………………17 Figure 6. Sled test acceleration and velocity change...…………………………………...18 Figure 7. Pretest ATD position for test 1 (left) and test 2 (right)………………………….18 Figure 8. Pretest ATD position for test 3 with EA material and Kevlar cover in place…19 Figure 9. Preconditioning of EA foam prior to test 4……………………………………….20 Figure 10. Pretest seat belt restraint assembly…………………………………………….21 Figure 11. Seat belt restraint system anchorage geometry in inches (X-Z plane)……..21 Figure 12. Seat belt restraint system anchorage geometry in inches (X-Y plane)……..22 Figure 13. Test 2 & 4 with 76.2 mm (3.0 in) gap tibia Fz………………………………….23 Figure 14. Test 1 & 3 with 0.0 gap tibia Fz…………………………………………………23 Figure 15. Test 2 & 4 with 76.2 mm (3.0 in) gap tibia MxMy resultant…………………..24 Figure 16. Test 1 & 3 with 0.0 gap tibia MxMy resultant…………………………………..24 Figure 17. Test 2 & 4 with 76.2 mm (3.0 in) gap tibia Mx bending moment…………….25 Figure 18. Test 2 & 4 with 76.2 mm (3.0 in) gap tibia My bending moment…………….25 Figure 19. Test 2 & 4 with 76.2 mm (3.0 in) gap foot Z acceleration……………………..26 Figure 20. Test 1 & 3 with 0.0 gap foot Z acceleration…………………………………….26 Figure 21. Shoulder belt resultant forces of test 2 & 4 with 76.2 mm (3.0 in) gap………28 Figure 22. Lap belt resultant forces of test 2 & 4 with 76.2 mm (3.0 in) gap……………28
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Figure 23. Anti-submarine belt resultant forces of test 2 & 4 with 76.2 mm (3.0 in) gap……………………………………………………………………………………………….29 Figure 24. Chest & head resultant accelerations of test 2 & 4 with 76.2 mm (3.0 in) gap……………………………………………………………………………………………….29 Figure 25. Risk of AIS 2+ tibial plateau or condyle injury as a function of tibia axial force for initial gap tests 2 & 4……………………………………………………………………….30 Figure 26. Risk of AIS 2+ leg shaft fracture as a function of RTI for initial gap tests 2&4……………………………………………………………………………………………….31 Figure 27. Close up view of test 2 & 4 with 76.2 mm (3.0 in) gap foot Z acceleration…32 Figure 28. Risk of AIS 2+ calcaneus, talus, ankle & midfoot fractures as a function of
tests 2 & 4……………………………………………………………………………………….33
Chapter III
Figure 29. Quasi-recumbent driver seating position – Reproduced with permission from SAE 2006-01-3633……………………………………………………………………………..42 Figure 30. Typical NASCAR driver seating position……………………………………….43 Figure 31. 9-point seat belt restraint system……………………………………………….45 Figure 32. 7-point seat belt restraint system……………………………………………….45 Figure 33. BSCI W18 foam quasi-static compression testing…………………………....47 Figure 34. BSCI W18 foam stress strain curve…………………………………………….48 Figure 35. Quasi-static seat belt stress strain curves……………………………………..48 Figure 36. Quasi-static seat belt tensile test setup………………………………………...49 Figure 37. Foam drop test & simulation hemisphere accelerations……………………...49 Figure 38. High speed video frame………………………………………………………….50 Figure 39. Shoulder belt load cells…………………………………………………………..51 Figure 40. Sled test acceleration and velocity change…………………………………….51 Figure 41. Pretest ATD position……………………………………………………………...52 Figure 42. NASCAR driver seat insert & cross-section with seat ramp measurement location…………………………………………………………………………………………..53 Figure 43. Seat ramp angle frequency histogram…………………………………………53 Figure 44. Upright MRI seat insert fitment (Quad Coil in red, MRI patient table in green)…………………………………………………………………………………………….54 Figure 45. MRI driver position and lumbar spine image…………………………………..55 Figure 46. ATD positioning nodes…………………………………………………………...56
Figure 47. Empirical sled test & FE ATD data……………………………………………..57 Figure 48. Empirical sled test & FE seat belt load…………………………………………58 Figure 49. Eight seated configurations………….…………………………………………..60 Figure 50. LHD variable space ……….……………………………………………………..60 Figure 51. Top & side views of PDOF with pulse magnitude depicted by line length (red line indicates 0° frontal with no pulse scaling)……………………………………………….61 Figure 52. FE simulation acceleration pulse………………………………………………..62 Figure 53. Spine, pelvic and hip angles…………………………………………………….63 Figure 54. Seatback angle simulations setup and seat back angle measurement…….65 Figure 55. 30UP lumbar spine axial force (Fz) with inset of peaks.……………………..66 Figure 56. Vertebral body peak compressive force ………………………………………67 Figure 57. Vertebral body peak resultant XY moment ……………………………..…….67 Figure 58. 20UP fringe plot at mean peak maximum strain of cortical bone…………...68 Figure 59. Summary of mean peak maximum principal strains for the eight 0° frontals… ……………………………………………………………………………………………………69
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Figure 60. ASIS XZ motion with respect to time …………………………………………..69 Figure 61. PSIS XZ motion with respect to time …………………………………………..70 Figure 62. Peak averaged shoulder belt forces ……………………………………….…..70 Figure 63. Peak averaged lap belt forces ………………………………………………….71 Figure 64. Peak averaged anti-submarine belt forces …………………………….……...71 Figure 65. Vertebral body peak compressive force for 0° frontals of two different acceleration severities…...…………………………………………………..………………...72 Figure 66. Vertebral body peak resultant XY moment for 0° frontals of two different acceleration severities..……………………………………………………….……………….72 Figure 67. Vertebral body peak compressive force for varying seat back angles ……..73 Figure 68. Vertebral body peak resultant XY moment for varying seat back angles ….73 Figure 69. SRA and mean peak axial force for T12-L1…………………………….……..80 Figure 70. SRA and mean peak XY resultant moment for T12-L1………………………80 Figure 71. ASIS and PSIS traces for the upright posture zero degree frontal simulations………..……………………………………………………………………………..82 Figure 72. ASIS and PSIS traces for the slouched posture zero degree frontal simulations ………………………………………………………………………………..…….82 Figure 73. Peak ASIS and PSIS X-axis displacements …………………………….…….83 Figure 74. Yoganandan thoracic & lumbar spine fracture probability for eight zero degree frontal simulations based on axial force …………………………………...............85
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ABSTRACT
Motor vehicle crashes (MVCs) of passenger vehicles are commonly cited and
reported in published literature as a leading cause of death and injury. Similarly, in
motorsports, on-track crashes are the leading cause of driver injury.
Since the beginning of this century, many improvements have been made to
motorsports driver restraints. These improvements have primarily been focused on
protecting the driver’s head, neck, thorax and pelvis. While research and improvements
in these areas continue, excellent progress over the last decade has allowed resources to
also be focused toward the driver’s extremities and other less frequently occurring injuries.
The first aspect of this research was aimed at expanding and improving frontal
crash protection to the driver’s lower extremities. Evaluation of energy absorbing (EA)
materials was completed using dynamic full-scale sled testing. The second aspect of this
work focused on the influence of variables associated with compression loading of the
thoracolumbar spine during frontal impacts. Finite element (FE) modeling using the Total
Human Model for Safety (THUMS) was utilized to study the effect of initial driver position
and seat ramp design on thoracolumbar compression fracture risk during frontal impacts.
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Chapter I: Introduction and Background
MOTORSPORT RESTRAINT SYSTEMS & CRASHES
Since 2000 improvements have been made to the National Association for Stock
Car Auto Racing, Incorporated (NASCAR®) driver restraint system, resulting in improved
crash protection for motorsports drivers. Advancements in driver restraint safety have
involved seats, head and neck restraints (HNR), seat belt restraint systems and driver
helmets. These enhancements have increased protection for drivers from severe crash
loading. The development and evaluation criteria for many of these systems has been
documented in previous publications (Gramling & Hubbard, 2000) (Melvin et al., 2006) (J.
The Total Human Model for Safety (THUMS) was jointly developed by Toyota
Motor Corporation and Toyota Central R&D Labs., Inc. and is a HBM intended for use in
the automotive crash environment (Toyota Central R&D Labs. Inc., 2015). The first
version of THUMS was completed in 2000. THUMS version 4.01, originally released in
2010, contains over 1.7 million finite elements and includes unique and individual spinal
vertebrae. Each of the nodes, elements and parts can be examined for useful outputs,
such as cross-sectional forces and moments of the thoracolumbar spine vertebrae.
It is important to note the significance of approach validation. Both ATDs and the
THUMS HBM have undergone extensive development and validation studies, however it
is critical to understand and realize the limitations and assumptions associated with each
of these approaches.
The research presented in Chapter III of this thesis used ATD empirical testing and
the THUMS HBM. Supporting tests and studies included quasi-static and dynamic
component testing and magnetic resonance imagining (MRI) of a motorsports driver.
CHAPTER SUMMARIES
CHAPTER II: Evaluation of the Effectiveness of Toe Board Energy Absorbing
Material for Foot, Ankle and Lower Leg Injury Reduction
The objective of this study was to extend protection to the driver’s lower extremities during
frontal impacts through the evaluation of energy absorbing materials on the toe board by
applying established injury criteria.
CHAPTER III: Influence of Driver Position and Seat Design on Thoracolumbar
Loading During Frontal Impacts
The objective of this study was to explore the influence of initial driver position and seat
ramp design on thoracolumbar loading during frontal impacts.
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CHAPTER IV: Summary of Research
A brief summary of the research covered in this thesis.
REFERENCES
Gayzik, F. S., Moreno, D. P., Geer, C. P., Weertzer, S. D., Martin, R. S., & Stitzel, J. D. (2011). Development of a Full Body CAD Dataset for Computational Modeling : A Multi-modality Approach. Annals of Biomedical Engineering, 39(10), 2568–2583. https://doi.org/10.1007/s10439-011-0359-5
Gramling, H., & Hubbard, R. (2000). Sensitivity Analysis of the HANS Head and Neck Support. Society of Automotive Engineers - Technical Paper Series, (724), 1–11. https://doi.org/10.4271/2000-01-3541
Katsuhara, T., Takahira, Y., Hayashi, S., Kitagawa, Y., & Yasuki, T. (2017a). Analysis of Driver Kinematics and Lower Thoracic Spine Injury in World Endurance Championship Race Cars during Frontal Impacts. SAE Int. J. Trans. Safety. https://doi.org/10.4271/2017-01-1432
Melvin, J. W., Begeman, P., Faller, R. K., Sicking, D. L., McClellan, S. B., Maynard, E., … Gideon, T. (2006). Crash Protection of Stock Car Racing Drivers - Application of ... Stapp Car Crash Journal, 50, 415–428.
Patalak, J., & Gideon, T. (2013). Occupant rollover protection in motorsports. SAE International Journal of Transportation Safety, 1(2). https://doi.org/10.4271/2013-01-0800
Patalak, J., & Gideon, T. (2015). Development and Implementation of a Quasi-Static Test for Seat Integrated Seat Belt Restraint System Anchorages. SAE Technical Papers, 2015–April(April). https://doi.org/10.4271/2015-01-0739
Patalak, J., Gideon, T., & Melvin, J. (2013). Examination of a Properly Restrained Motorsport Occupant. SAE International Journal of Transportation Safety. https://doi.org/10.4271/2013-01-0804
Patalak, J., Gideon, T., Melvin, J. W., & Rains, M. (2015). Improved Seat Belt Restraint Geometry for Frontal, Frontal Oblique and Rollover Incidents. SAE International Journal of Transportation Safety, 3(2), 2015-01–0740. https://doi.org/10.4271/2015-01-0740
Patalak, J. P., & Melvin, J. W. (2008). Stock Car Racing Driver Restraint – Development and Implementation of Seat Performance Specification. SAE International Journal of Passenger Cars - Mechanical Systems. https://doi.org/10.4271/2008-01-2974
Ryan, C. (2015). Sonic Wind. Liveright Publishing Corporation.
Smith, R. D., Hayashi, S., Kitagawa, Y., & Yasuki, T. (2011). A Study of Driver Injury Mechanism in High Speed Lateral Impacts of Stock Car Auto Racing Using a Human Body FE Model. SAE International. https://doi.org/10.4271/2011-01-1104
Toyota Central R&D Labs. Inc. Documentation Total Human Model for Safety ( THUMS ) AM50 Pedestrian / Occupant Model Academic Version 4.02_20150527 (2015).
6
Chapter II: Evaluation of the effectiveness of toe board energy absorbing material for foot, ankle and lower leg injury reduction
John P. Patalak1,2,3 & Joel D. Stitzel1,2
1Wake Forest University School of Medicine, Winston-Salem, North Carolina
2Virginia Tech, Wake Forest University School of Biomedical Engineering and Sciences, Winston-Salem, North Carolina
3National Association for Stock Car Auto Racing, Incorporated
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1. ABSTRACT
Since 2000 numerous improvements have been made to the National Association
for Stock Car Auto Racing, Incorporated (NASCAR®) driver restraint system, resulting
in improved crash protection for motorsports drivers. Advancements have included
seats, head and neck restraints (HNR), seat belt restraint systems, driver helmets and
others. These enhancements have increased protection for drivers from severe crash
loading. Extending protection to the driver’s extremities remains challenging. While
the drivers’ legs are well contained for lateral and vertical crashes, they remain largely
unrestrained in frontal and frontal oblique crashes.
Sled testing was conducted for the evaluation of an energy absorbing (EA) toe board
material to be used as a countermeasure for leg and foot injuries. Testing included
baseline rigid toe boards, tests with EA material covered toe boards and pretest
positioning of the 50th percentile male frontal Hybrid III Anthropomorphic Test Device
(ATD) lower extremities. ATD leg and foot instrumentation included foot acceleration
and tibia forces and moments.
The sled test data were evaluated using established injury criteria for tibial plateau
fractures, leg shaft fractures and calcaneus, talus, ankle & midfoot fractures.
A polyurethane energy absorbing (EA) foam was found to be effective in limiting axial
tibia force and foot accelerations when subjected to frontal impacts using the NASCAR
motorsport restraint system.
2. INTRODUCTION
For the 2017 NASCAR racing season all national series drivers are required to comply
with the crash restraint and protection equipment listed in Table 1 and shown in Figures 1
and 2. The development and evaluation criteria for many of these systems has been
documented in previous publications (J. P. Patalak & Melvin, 2008), (J. Patalak, Gideon,
Accelerator, brake and clutch pedal placement and design vary greatly according to driver
preference, driver stature, track configuration and vehicle setup. For this sled test series,
the variability of the pedal assemblies was removed from the experiment, thereby creating
uniform and symmetrical toe board interaction for both the left and right lower extremities.
While careful ATD setup was conducted and detailed pretest measurements taken, very
small variances in contact parameters (friction, angle, surface area, speed) between the
right and left shoe and toe board during empirical testing were found. This is evident in
small (< 2 ms) differences in acceleration or force initiation times. For the injury probability
curves, right and left tibia axial forces and moments were averaged.
The seat belt restraint system adjustment, installation and tightening sequence are also
critical for test repeatability. Seat belt restraint system forces and ATD resultant head and
chest accelerations are shown in Figures 21-24. The pelvis x-axis accelerometer channel
was lost during test four.
28
Figure 21. Shoulder belt resultant forces of test 2 & 4 with 76.2 mm (3.0 in) gap
Figure 22. Lap belt resultant forces of test 2 & 4 with 76.2 mm (3.0 in) gap
29
Figure 23. Anti-submarine belt resultant forces of test 2 & 4 with 76.2 mm (3.0 in) gap
Figure 24. Chest & head resultant accelerations of test 2 & 4 with 76.2 mm (3.0 in) gap
The use of the EA foam reduced the averaged left and right peak axial tibia force by 40.6%
when compared to the rigid toe board. Previous research utilizing EA materials ranging
from 172 kPa (25 psi) through 931 kPa (135 psi) also produced similar ranges of peak
force percentage reductions (Rudd et al., 2005). Tibia axial force and driver mass has
been identified as a good predictor of tibial plateau fractures (Kuppa, Wang, Haffner, &
30
Eppinger, 2001). The associated AIS 2+ injury risks were calculated for tests 2 and 4 and
are shown in Figure 25.
Figure 25. Risk of AIS 2+ tibial plateau or condyle injury as a function of tibia axial force for initial gap tests 2 & 4.
The Revised Tibia Index (RTI) as summarized by Kuppa, et al uses both the tibia axial
force and the tibia resultant of the medial-lateral and the anterior-posterior moments.
Using an axial critical force of 12 kN and a critical resultant bending moment of 240 Nm,
the RTI was calculated for initial gap Tests 2 & 4, with the results shown in Figure 26.
31
Figure 26. Risk of AIS 2+ leg shaft fracture as a function of RTI for initial gap tests 2&4.
While RTI is calculated with the medial-lateral (Mx) and anterior-posterior (My) tibia
bending moment resultant, Figures 17 and 18 demonstrate that the primary contributor to
RTI in this test series is the anterior-posterior (My) bending moment. Video analysis of
test two (76.2 mm (3.0 in) gap, rigid) indicates the right foot contacts the toe board
approximately two milliseconds before the left foot. This staggered foot contact is also
confirmed by the foot accelerations in Figure 27. A delayed contact could increase the
impact speed of the foot and toe board, depending on the engagement of the restraint
system at the specific time.
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Figure 27. Close up view of test 2 & 4 with 76.2 mm (3.0 in) gap foot Z acceleration
Injury criteria for the calcaneus, talus, ankle and midfoot fractures has been correlated to
lower tibia axial force (Yoganandan et al., 1996), (Kuppa et al., 2001). While the ATD in
this sled test series was only equipped with upper tibia axial load cells, the assumption
that the axial force is continuous throughout the tibia is used to evaluate this additional
injury criterion.
The probability of an AIS 2+ calcaneus, talus, ankle and midfoot fractures as a function of
axial lower tibia force was calculated for the averaged left and right peak forces for the
initial gap tests 2 and 4 and is shown in Figure 28.
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Figure 28. Risk of AIS 2+ calcaneus, talus, ankle & midfoot fractures as a function of
tests 2 & 4.
The Z-axis ATD foot acceleration data was recorded and is shown in Figure 19 for tests 2
and 4 and in Figure 20 for the no gap tests. As expected, for tests 1 and 3 the ATD foot
acceleration is very similar to the sled acceleration peak and duration. In tests 2 and 4,
the ATD foot accelerations are significantly larger due to the velocity debt caused by the
initial gap between the foot and the toe board. Figure 27 shows a 25 millisecond window
of this acceleration data.
Video analysis of both tests indicates initial positive accelerations occurring around 33 to
34 milliseconds due to foot plantar flexion as the heel of the racing shoe contacts the toe
board just slightly before the rest of the foot. The ATD foot acceleration peaks are
tabulated in Table 5.
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Table 5. ATD foot Z-axis acceleration for initial gap tests
ATD Foot Z-axis Acceleration (G)
Test Left Peak (time of) Right Peak (time of) Average
2 -663.2 (36.1 ms) -577.5 (35.5 ms) 620
4 -439.5 (36.5 ms) -385.3 (37.2 ms) 412
The beneficial contribution of the EA Foam in test 4 is demonstrated by the smaller peak
acceleration values, the longer duration of negative acceleration and a lack of a post
negative peak acceleration polarity change. While foot injury criteria utilizing only the ATD
foot acceleration data is not widely recognized as a suitable injury predictor, the addition
of the EA Foam follows the occupant protection principle of reducing peak acceleration by
extending the time duration via non-injurious displacement.
Assuming 34 milliseconds as a first point of contact between the foot and the toe board,
the sled/toe board velocity was 34.6 kph (21.5 mph) when contact was made with the
relatively static ATD feet. The EA foam permitted the velocity debt of the ATD feet to be
compensated over a longer duration, thereby limiting the peak acceleration required.
It is important to note the NASCAR driver restraint system does not utilize knee bolsters,
which are often used in passenger vehicles as significant pelvic restraint devices during
frontal impacts. Motorsport pelvic restraint is accomplished via the anti-submarine and
lap belts, along with the seat pan ramp comprised of SFI 45.2 foam.
As noted in Figure 18 the anterior-posterior (My) tibia bending moment is the primary
contributor to the bending moment portion of the RTI calculation. In actual application, the
EA foam will be covered with a Kevlar cover, intended to maintain its position and help
protect the material. Therefore, the tests were conducted with the Kevlar covered EA
foam and with a bare aluminum rigid toe board. While the Kevlar material and thereby
coefficient of friction was maintained under the heel of the shoe, it was not on the toe
board surface itself. While this difference is representative of the actual implementation
35
of the countermeasure, it also could affect the toe board surface coefficient of friction
between tests. However, the mechanism of the EA foam itself, that is compression under
load, also inherently limits the ability of the foot to translate parallel to the toe board
surface.
6. SUMMARY
For the initial foot gap condition tests, a polyurethane EA foam was found to effectively
reduce averaged axial tibia forces by 28.9 percent and averaged foot accelerations 33.5
percent when subjected to severe frontal impacts using a motorsport restraint system.
The risk of AIS 2+ tibial plateau or condyle injury was reduced by 35%, the risk of AIS 2+
leg shaft fracture was reduced by 6% and the risk of AIS 2+ calcaneus, talus, ankle &
midfoot fractures was reduced by 32%.
7. FUTURE WORK
Tests 1 and 3 with the ATD foot in contact with the toe board pretest (no gap) exhibited
similar tibia axial loads and foot accelerations for both the rigid and EA Foam toe boards.
Additional research could determine the possibility of tuning the EA foam to provide some
benefit at the no gap condition (with and without toe board intrusion), while attempting to
retain the demonstrated benefits during the initial gap condition. While the motorsport
restraint system is different than passenger vehicles, further study may show that the
lower extremity responses are similar, thereby allowing a study for application of this
preventive measure into passenger vehicles. Additional analysis could also include
quantifying the temperature sensitivity of the EA foam regarding its influence on injury risk
reduction. Other EA materials, such as aluminum honeycomb may be investigated for
suitability, given its increased operating temperature and reduced temperature sensitivity
when compared to the polyurethane EA Foam. Lastly, using this empirical testing as
36
validation, future FE modeling could allow for further study of foot positioning, intrusion
effects, pedal interactions and driver bracing/active muscle influences.
8. ACKNOWLEDGMENTS
The presented testing was funded by NASCAR. The authors would like to thank Matthew
Harper and Curt Cloutier of NASCAR, Matt Ray of BSCI and Ed Kuligowski of Takata for
their help and contributions to this testing.
9. REFERENCES
Crandall, J. R., Martin, P. G., Sieveka, E. M., Pilkey, W. D., Dischinger, P. C., Burgess, A. R., … Schmidhauser, C. B. (1998). Lower limb response and injury in frontal crashes. Accident Analysis and Prevention, 30(5), 667–677. https://doi.org/http://dx.doi.org/10.1016/S0001-4575(98)00006-2
Funk, J. R., Tourret, L. J., & Crandall, J. R. (2000). Experimentally produced tibial plateau fractures. Proceedings of the 2000 International Ircobi Conference on the Biomechanics of Impact, September 20-22, 2000, Montpellier, France, (September), 171–182.
Gramling, H., & Hubbard, R. (2000). Sensitivity Analysis of the HANS Head and Neck Support. Society of Automotive Engineers - Technical Paper Series, (724), 1–11. https://doi.org/10.4271/2000-01-3541
Kuppa, S., Wang, J., Haffner, M., & Eppinger, R. (2001). Lower extremity injuries and associated injury criteria. 17th ESV Conference, 4, 1–15. Retrieved from https://24.199.232.26/security/library/LowerExtremityInjuries.pdf
Melvin, J. W., Begeman, P., Faller, R. K., Sicking, D. L., McClellan, S. B., Maynard, E., … Gideon, T. (2006). Crash Protection of Stock Car Racing Drivers - Application of ... Stapp Car Crash Journal, 50, 415–428.
National Highway Traffic Safety Administration - NCSA. (2016). General Accident Statistics - Quick Facts 2015. Retrieved from https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/812348
Patalak, J., Gideon, T., Beckage, M., & White, R. (2011). Testing, Development & amp; Implementation of an Incident Data Recorder System for Stock Car Racing. Society of Automotive Engineers, Inc. https://doi.org/10.4271/2011-01-1103
Patalak, J., Gideon, T., & Melvin, J. (2013). Examination of a Properly Restrained Motorsport Occupant. SAE International Journal of Transportation Safety. https://doi.org/10.4271/2013-01-0804
Patalak, J., Gideon, T., Melvin, J. W., & Rains, M. (2015). Improved Seat Belt Restraint Geometry for Frontal, Frontal Oblique and Rollover Incidents. SAE International Journal of Transportation Safety, 3(2), 2015-01–0740. https://doi.org/10.4271/2015-01-0740
37
Patalak, J. P., & Melvin, J. W. (2008). Stock Car Racing Driver Restraint – Development and Implementation of Seat Performance Specification. SAE International Journal of Passenger Cars - Mechanical Systems. https://doi.org/10.4271/2008-01-2974
Rudd, R. W., Kitagawa, Y., Crandall, J. R., & Poteau, F. C. (2005). Evaluation of energy-absorbing materials as a means to reduce foot/ankle axial load injury risk. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 218, 279–293. https://doi.org/10.1243/095440704322955803
SAE. SAE J211-1 Instrumentation for Impact Test - Part 1 - Electronic Instrumentation (2014).
SFI. SFI Foundation, Inc. Specification 45.2 Impact Padding, Pub. L. No. 45.2 (2013). SFI Foundation Inc. Retrieved from http://www.sfifoundation.com/wp-content/pdfs/specs/Spec_45.2_032713.pdf
SFI. SFI Foundation, Inc. Specification 16.6 Advanced Motorsport Restraint Assemblies, Pub. L. No. 16.6 (2014). USA: SFI Foundation Inc. Retrieved from http://www.sfifoundation.com/wp-content/pdfs/specs/Spec_16.6_122914.pdf
SFI. SFI Foundation, Inc. Specification 38.1 Head and Neck Restraint Systems, Pub. L. No. 38.1 (2015). SFI Foundation Inc. Retrieved from http://www.sfifoundation.com/wp-content/pdfs/specs/Spec_38.1_031615.pdf
Smith, R. D., Hayashi, S., Kitagawa, Y., & Yasuki, T. (2011). A Study of Driver Injury Mechanism in High Speed Lateral Impacts of Stock Car Auto Racing Using a Human Body FE Model. SAE International. https://doi.org/10.4271/2011-01-1104
Somers, J. T., Granderson, B., Melvin, J. W., Tabiei, A., Lawrence, C., Feiveson, A., … Patalak, J. (2011). Development of head injury assessment reference values based on NASA injury modeling. Stapp Car Crash Journal, 55(November), 49–74. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/22869304
Yoganandan, N., Pintar, F., Boynton, M., Begeman, P., Priya, P., Kuppa, S., … Eppinger, R. (1996). Dynamic Axial Tolerance of the Human Foot-Ankle Complex. Society of Automotive Engineers, Inc., 962426.
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Chapter III: Influence of driver position and seat design on thoracolumbar loading during frontal impacts
John P. Patalak1,2,3, Matthew L. Davis4, James P. Gaewsy1,2, Joel D. Stitzel1,2 & Matthew Harper3
1Wake Forest University School of Medicine, Winston-Salem, North Carolina
2Virginia Tech, Wake Forest University School of Biomedical Engineering and Sciences, Winston-Salem, North Carolina
3National Association for Stock Car Auto Racing, Incorporated, Concord, NC
4Elemance, LLC, Winston-Salem, NC
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1. ABSTRACT
Previous research has detailed contributing factors to thoracolumbar compression fracture
injury risk during frontal impacts in motorsport drivers utilizing a nearly recumbent driving
position (Katsuhara, Takahira, Hayashi, Kitagawa, & Yasuki, 2017b; Trammell, Weaver,
& Bock, 2006; Troxel, Melvin, Begeman, & Grimm, 2006). This type of injury is very rare
for upright seated motorsport drivers. While numerous improvements have been made to
the driver restraint system used in the National Association for Stock Car Auto Racing,
Incorporated (NASCAR®) since 2000, two instances of lumbar compression fractures
have occurred during frontal impacts. Using computation modeling, this study explores
the influence of initial driver position and seat ramp design on thoracolumbar loading
during frontal impacts.
Quasi-static component testing, dynamic component testing, an instrumented driver fit
check, a seat ramp angle survey, and sled testing were conducted to provide
computational finite element (FE) model inputs and serve as validation tests. Upright
magnetic resonance imaging (MRI) was conducted with a driver to visualize vertebral body
locations with respect to the driver seat. FE modeling was conducted with the 50th
percentile male Hybrid III FE model (Humanetics, Plymouth, MI) to validate a motorsport
restraint system model. Sprague and Geers analysis was used to quantify and identify
the optimally tuned FE model parameters. A 3-factor latin hypercube (LHD) sample space
was created for acceleration magnitude and the principal direction of force (PDOF) about
the Z-axis and about the Y-axis across 20 simulations. The Toyota Total Human Model
for Safety (THUMS) was then used in four unique seat ramp angles in two unique
postures, for a total of eight THUMS seated configurations. All eight configurations were
subjected to the 20 variable values of the LHD sample space for a total of 160 simulations.
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A FE motorsport restraint system model was developed and validated against empirical
component and sled test data. The THUMS was used in the validated motorsport restraint
system. As seat ramp angles (SRA) increased, peak axial compressive force of T12, L1
and L2 decreased. For each SRA, the slouched THUMS initial position (TIP) produced
lower peak axial compressive forces. The peak XY resultant bending moment of T12 and
L1 also decreased as SRA increased.
2. INTRODUCTION
The focus of this paper is thoracolumbar induced loading of motorsports drivers during
frontal impacts. Two NASCAR drivers are known to have experienced compression
fractures of vertebral bodies during frontal or frontal oblique impacts. Table 6 shows the
specifics of these two cases.
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Table 6. Lumbar injury case summaries
Case 1 Case 2
Driver 32 YO male, 180.3 cm (71 in), 74.8 kg (165 lbs)
21 YO male, 175.3 cm (69 in), 76.2 kg (168 lbs)
Crash Pulse 41 G XY Resultant Peak, 61.2 kph (38 mph) XY ΔV, 17° XY PDOF right of front, 20° XZ
Sprague, M. A., & Geers, T. L. (2004). A spectral-element method for modelling
cavitation in transient fluid-structure interaction. International Journal for Numerical
Methods in Engineering, 60(15), 2467–2499. https://doi.org/10.1002/nme.1054
Stocki, R. (2005). A method to improve design reliability using optimal Latin hypercube
sampling. Computer Assisted Mechanics and Engineering Sciences, (January).
Retrieved from http://www.ippt.pan.pl/~rstocki/cames_olh_impr_draft.pdf
Troxel, T. B., Melvin, J. W., Begeman, P. C., & Grimm, M. J. (2006). Biomechanical
Investigation of Thoracolumbar Spine Fractures in Indianapolis-type Racing Car
Drivers during Frontal Impacts. Engineering, (724), 776–0790.
https://doi.org/10.4271/2006-01-3633
Yoganandan, N., Arun, M., W., J., Stemper, B., D., Pintar, F., A., & Maiman, D., J.
(2013). Biomechanics of Human Thoracolumbar Spinal Column Trauma From
Vertical Impact Loading. Annals of Advances in Automotive Medicine, 57, 155–166.
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Chapter IV: Summary of Research
The research included in this thesis summarizes important advancements and
additions to the knowledge base of protecting motorsport drivers during severe frontal
impacts. The use of a combination of biomechanical approaches and tools including
ATDs, FE HBMs, live volunteer fit checks, MRI scans and other tests, culminated in the
identification of methods to significantly reduce lower extremity injury risk and contribute
to a better understanding of thoracolumbar loading.
While research must continue to better understand thoracolumbar loading and the
associated fracture risk, the research presented in Chapter II resulted in NASCAR driver
safety rule changes and the mandatory implementation of the EA foam in the race cars.
The methods of this research and the findings themselves may be applicable to
occupants in other similarly configured restraint systems, such as military vehicles, child
restraints and space travel.
The research presented in Chapter II of this thesis has been published in Traffic Injury
Prevention. The Chapter III research has been submitted to the Society of Automotive
Engineers for publication.
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CURRICULUM VITAE
JOHN P. PATALAK Graduate Student Senior Director, Safety Engineering Virginia Tech-Wake Forest University NASCAR R&D Center Center for Injury Biomechanics 7010 West Winds Blvd 575 N. Patterson Ave, Suite 120, Concord, NC 28027 Winston-Salem, NC 27101 Email: [email protected] Email: [email protected]
Professional Specialization Sixteen years of experience in occupant safety research and development to identify systems and principles promoting the reduction of occupant injury during high severity vehicular accidents. Occupant safety is investigated through a combination of investigating accidents, laboratory quasi-static and dynamic testing and computer modeling. Specific areas of focus include identifying occupant injury risks, developing and verifying solutions and implementing improvements.
Research has included creating novel ways of testing unique safety systems at component and full scale levels to make engineering recommendations regarding safety devices and systems. Along with industry standards testing, unique quasi-static and dynamic tests have been created, conducted and validated. Computer modeling has been utilized to shorten design iteration cycles and study both occupant kinematics and vehicle structures. Education Penn State University, Bachelor of Science, Mechanical Engineering 1997-2001 Virginia Tech – Wake Forest University, Master of Science, Biomedical Engineering 2015-Present Thesis: Evaluation of Lower Extremity Injury Mitigation and Investigation of Thoracolumbar Loading of Restrained Occupants During Frontal Crashes Research Lab: Virginia Tech – Wake Forest University Center for Injury Biomechanics Advisor: Dr. Joel Stitzel Licensure Professional Engineer (P.E.), North Carolina – License 033826 Professional Background Senior Director, Safety Engineering NASCAR (National Association for Stock Car Auto Racing) – Concord, NC 2005 – Present
• Research, develop and approve driver and vehicle safety specifications and systems
• Investigate, analyze and determine injury mechanisms for crashes
• Evaluate and make engineering recommendations regarding submitted safety devices
• Design, develop and conduct component and full scale quasi-static and dynamic tests
• Perform failure analysis studies, draft test reports and deliver presentations
• Design and fabricate test fixtures, part prototypes, inspection equipment and instrumentation accessories
• Supervise and develop computer safety modeling efforts
• Develop and manage incident database for internal and external research projects
• Direct involvement and responsibility for end user satisfaction for released systems and specifications
• Coordination, communication and implementation of safety improvements to industry manufacturers
• Mentor and manage director reports and interns
• Responsible for advocating, designing and conducting safety research efforts
• Reviews scientific content and quality of test specifications, safety equipment and data Mechanical Engineer ARCCA, Incorporated – Penns Park, PA 2001 – 2005
• Participated in the design, fabrication, setup and execution of frontal, rear and side impact vehicle crash tests and sled tests including data acquisition requirements
• Investigated motor vehicle accidents with regard to vehicle crashworthiness, occupant protection, restraint systems performance and accident reconstruction
• Designed and fabricated test fixtures for seat strength analysis, restraint system performance, head form impacting and human surrogate inversion testing
• Authored quasi-static and dynamic test protocols, reports and presentations
• Performed laboratory and on-site forensic inspections and analysis
• Studied human tolerance historical data and performed human subject quasi-static testing
Professional Affiliations Biomedical Engineering Society Society of Automotive Engineers
• Motorsports Engineering Committee Member (2010 – Present)
• Co-chair for Motorsports Safety
• Reviewer, SAE Congress – Motorsports safety Global Institute for Motor Sport Safety Frontal Head Restraint Review Panel Member Publications Patalak, J. Stitzel, J. “Evaluation of the Effectiveness of Toe Board Energy Absorbing Material for Foot, Ankle and Lower Leg Injury Reduction”. Traffic Injury Prevention Journal 2017. doi: 10.1080/15389588.2017.1354128 Patalak, J., Gideon, T., Melvin, J., and Rains, M., "Improved Seat Belt Restraint Geometry for Frontal, Frontal Oblique and Rollover Incidents," SAE Int. J. Trans. Safety 3(2):93-109, 2015, doi:10.4271/2015-01-0740. Patalak, J. and Gideon, T., "Development and Implementation of a Quasi-Static Test for Seat Integrated Seat Belt Restraint System Anchorages," SAE Technical Paper 2015-01-0739, 2015, doi:10.4271/2015-01-0739. Patalak, J., Gideon, T., and Krueger, D., "Design, Development and Testing of an Improved Stock Car Driver's Window Net Mounting System," SAE Int. J. Trans. Safety 2(1):165-181, 2014, doi:10.4271/2014-01-0508. Patalak, J., Gideon, T., and Melvin, J., "Examination of a Properly Restrained Motorsport Occupant," SAE Int. J. Trans. Safety 1(2):261-277, 2013, doi:10.4271/2013-01-0804. Patalak, J. and Gideon, T., "Ballistic Testing of Motorsport Windshields," SAE Int. J. Trans. Safety 1(1):127-133, 2013, doi:10.4271/2013-01-0801. Patalak, J. and Gideon, T., "Occupant Rollover Protection in Motorsports," SAE Int. J. Trans. Safety 1(2):386-398, 2013, doi:10.4271/2013-01-0800.
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Somers, J.T., Melvin, J.W., Tabiei, A., Lawrence, C. Feiveson, A., Ploutz-Snyder, R., Patalak, J. “Development of Head Injury Assessment Reference Values Based on NASA Injury Modeling,” Stapp Car Crash Journal, Volume 55, November 2011, SAE Paper 2011-22-0003, Patalak, J. and Gideon, T., "Quasi-Static Testing of Tubular Roll Cage and Stock Car Chassis Joints," SAE Technical Paper 2011-01-1105, 2011, doi:10.4271/2011-01-1105. Patalak, J., Gideon, T., Beckage, M., and White, R., "Testing, Development & Implementation of an Incident Data Recorder System for Stock Car Racing," SAE Technical Paper 2011-01-1103, 2011, doi:10.4271/2011-01-1103. Patalak, J. and Melvin, J., "Stock Car Racing Driver Restraint – Development and Implementation of Seat Performance Specification," SAE Int. J. Passeng. Cars - Mech. Syst. 1(1):1349-1355, 2009, doi:10.4271/2008-01-2974. Patents Retaining System (Incident Data Recorder Mounting Shoe), US Patent 666,134, Issued 2012 Retaining Coupler (Incident Data Recorder Mounting Shoe), US Patent 656,883, Issued 2012 Strain Gage Load Cell Anchor (Seat Belt Load Cell), US Patent 9580042, Issued 2017 Deformable Seat Bracket, US Patent Application US20160176321A1, Filed 12/18/2014
Awards
• Society of Automotive Engineers - Excellence in Oral Presentation Award – August 2013
• Society of Automotive Engineers – Ralph H. Isbrandt Automotive Safety Engineering Award - 2016
• Virginia Tech - Wake Forest University School of Biomedical Engineering & Sciences Student Research Symposium – 1st Place Masters Presentation – May 2017