- 201 views
- 437 downloads
Development and Characterization of a Mechanical Surrogate Neck Prototype for Use in Helmet Certification Applications
-
- Author / Creator
- Ogle, Megan K.
-
Sport activities account for over half of all injuries in youths and young adults, with head injuries consistently ranked in the top five most common injury types. Despite mandated helmet use, contact sports, such as hockey and football, expose the players to a greater risk of suffering head and brain injuries compared to the general public due to high speed collisions between athletes. Nearly all current helmets are certified against linear acceleration, which has been found to be a contributor to focal traumatic brain injury (TBI) such as cerebral contusions and intracerebral hemorrhages. Biomechanical research on TBI, specifically mild traumatic brain injury, suggests a predictor variable for brain tissue damage is angular motion of the head. This has opened a debate in standard organizations about the validity of current helmet certification methods. Central to this debate is the development of a standardized surrogate neck model that offers lifelike biomechanical data in direct head impact testing.
The objective of this study is to develop and characterize a Phase 1 mechanical surrogate neck prototype for intended use in helmet certification experimental methods. The neck model is to exhibit realistic response, relative to the human cadaver, in both quasi-static bending and direct head impact to fill the gaps between currently available surrogate neck models and available cadaver data.
The Phase 1 neck model approximately matched the overall dimensions of a 50th percentile human male. The neck prototype was characterized in flexion and extension sagittal bending as well as direct head impact, and was compared to previous cadaveric literature to ascertain whether the Phase 1 neck can offer head kinematics and upper neck kinetics comparable to cadaveric models. Bending moments ranging up to 2 Nm and head impacts up to 5 m/s were simulated. When subjected to sagittal bending, the summation of all vertebral rotations was 80% less than the rotations presented in previous cadaver literature. In head impact, the Phase 1 neck yielded head kinematics within 35% and upper neck kinetics within 45% of those reported in the selected cadaveric literature. Although the peak results of the Phase 1 neck exceeded the 20% target to peak cadaver data, this Phase 1 attempt to characterize a novel mechanical surrogate neck prototype offered valuable insight to optimize the design in future iterations. Additionally, further testing of cadaveric necks to yield a broader dataset to which can be compared to the Phase 1 neck, and further testing of the prototype neck to understand whether it yields head kinematics comparable to what has been measured for athletes, is suggested.
The impact response of the Hybrid III neck and the Phase 1 neck were also compared. At 1.5 m/s impacts to the Hybrid III headform, it was found that differences in the Hybrid III headform COG kinematics exceeded 40% and the differences in upper neck kinetics exceeded 80% between the two neck models. These are important findings because it can be concluded that neck compliancy does in fact make a difference on the obtained biomechanical data, which contradicts the current assumption in helmet certification protocol.
The maximum inter-test variance of the Phase 1 neck was 44% in flexion rotations and 71% in extension rotations, respectively. In impact, the maximum inter-test variance of peak biomechanical measures was 38%. Although these values exceed the 20% inter-test variance target to achieve repeatability, these results show the variance of the Phase 1 neck is comparable to cadaver literature, which can be up to 40% in quasi-static bending and up to 140% in dynamic experiments.
Simple linear regression models of impact data showed biomechanical measures scale approximately linearly with impact speed, as evidenced by R2 values of 0.90 or greater. Additionally, the Phase 1 neck sustained approximately 80 experiments without failure.
This thesis documents that the Phase 1 neck model is a durable component with inter-test variance comparable to cadaver literature. These results could be interpreted to convey that the Phase 1 neck is a first step towards a reusable neck model to be used in a controlled laboratory setting that could mimic cadaveric response. A neck model that exhibits realistic impact response, relative to the human, could increase the biofidelity of helmet certification and assessment experimental protocol. -
- Graduation date
- Fall 2018
-
- Type of Item
- Thesis
-
- Degree
- Master of Science
-
- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.