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An impact force transducer for anthropomorphic test dummy headforms: Application to study effects of external helmet accessories on biomechanical measures of head injury risk Open Access


Other title
brain injury
skull fracture
Bragg gratings
force transducer
Type of item
Degree grantor
University of Alberta
Author or creator
Butz, Robert C.
Supervisor and department
Dennison, Chris (Mechanical Engineering)
Examining committee member and department
Elias, Anastasia (Chemical and Materials Engineering)
Dennison, Chris (Mechanical Engineering)
Hogan, James (Mechanical Engineering)
Doucette, John (Mechanical Engineering)
Department of Mechanical Engineering

Date accepted
Graduation date
Master of Science
Degree level
The first half of this thesis describes the mechanical design, calibration and validation of an in-fibre Bragg grating based impact transducer. The transducer comprises an in-fibre Bragg grating fixed to an aluminum superstructure (12 mm in diameter, 3 mm thickness) designed to withstand typical impact forces in helmeted impact and to have resonances that exceeds industry standards on mechanical resonance. Calibration experiments were used to determine the transducers sensitivity to force measurements, and calibration results are, on average, within 10% of finite-element modelling predictions of force sensitivity. Validation of force transducers indicated excellent repeatability in both the force and time domain for an impact. The maximum standard deviation of force measurements of 0.4% of the net head force applied to the impacted headform and average error in the time duration of the force transients of only 4%. The latter components of the thesis describe application of the transducers and HybridIII in a biomechanical study of the effects that external helmet accessories (camera mounts) have on measures of skull fracture and brain injury risk in helmeted head impact. The presence of a helmet accessory reduced peak linear acceleration of the head, and forces on the headform skull did not increase. For low velocity impacts, peak angular acceleration and velocity reduced with the presence of a helmet accessory. For high velocity impacts, the peak angular acceleration and velocity of the head increased with the presence of a helmet accessory. Overall, the impacted helmets protected the head from significant skull fracture risk (regardless of the presence of the camera). Average concussion risk increased in high velocity impacts with cameras fixed to helmets.
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. 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.
Citation for previous publication
• Butz, RC and Dennison, CR. (2015) In-Fiber Bragg Grating Impact Force Transducer for Studying Head–Helmet Mechanical Interaction in Head Impact. IEEE/OSA Journal of Lightwave Technology, 33(13), 8pp.• Butz, RC, Knowles, BK, Newman, JA, and Dennison CR. (2015) Effects of external helmet accessories on biomechanical measures of head injury risk: An ATD study using the HybridIII headform. Journal of Biomechanics, submission BM-D-15-00541, under review.

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