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TECHNICAL PAPERS

The Influence of Surface Padding Properties on Head and Neck Injury Risk

[+] Author and Article Information
Daniel L. A. Camacho, Roger W. Nightingale, Barry S. Myers

Department of Biomedical Engineering and Division of Orthopaedic Surgery, Duke University, Durham, NC 27708-0281

J Biomech Eng 123(5), 432-439 (Apr 17, 2001) (8 pages) doi:10.1115/1.1389086 History: Received April 13, 1999; Revised April 17, 2001
Copyright © 2001 by ASME
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References

Figures

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Computational model of the human head and cervical spine. The rigid face was coupled to the rigid maxillofacial region of the skull and assigned mass properties such that the mass, moment of inertia, and centroid of the entire head matched the data of Walker et al. 23. Contact interactions were defined between the impact surface and the finite element skull model. No contact interactions existed between the impact surface and the rigid face.
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Parametric variation of the stress–strain loading curve of expanded polystyrene (EPS) foam, showing the range of padding stiffness tested. The EPS curve was produced from experimental compression tests. The data points of this curve and the scaled versions of this curve were directly used as input to the urethane foam material model of LS-DYNA3D.
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Parametric variation of the Hysteresis Unloading Factor of the foam model. As the factor is decreased from 1.0 to 0.0, more energy is dissipated by the pad.
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Impact surface orientations
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Effects of variations of pad stiffness on peak resultant neck force (a), peak occiput-C1 moment (b), peak resultant head acceleration (c), and Head Injury Criterion values (d). Peak resultant neck forces were minimized for stiffness scale factors from 0.5–1.0. Peak resultant head accelerations and HIC values were minimized for a stiffness scale factor equal to 0.5.
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Effects of variations of pad thickness on peak resultant neck force (a), peak occiput-C1 moment (b), peak resultant head acceleration (c), and Head Injury Criterion values (d). Peak resultant head accelerations and HIC values markedly decreased as pad thickness increased. Pad thickness had no systematic effects on neck force and only modest effects on neck moment.
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Effects of surface friction on peak resultant neck force (a), peak occiput-C1 moment (b), peak resultant head acceleration (c), and Head Injury Criterion values (d). Increases in friction substantially increased neck forces and moments, with most of the changes occurring for COFs below 0.2.
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Effects of variations of the Hysteresis Unloading Factor on peak resultant neck force (a), peak occiput-C1 moment (b), peak resultant head acceleration (c), and Head Injury Criterion values (d). Increased energy return from the pad (higher Hysteresis Unloading Factor) resulted in increases in all the measures.
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Comparison of impact surface performance. For all impact angles, the effective pad produced lower peak resultant neck forces, peak resultant head accelerations, peak neck occiput-C1 moments, and HIC values than the other impact surfaces. The ineffective pad produced higher peak resultant neck forces and peak moments (with the exception of the 0 deg impact) than the rigid surface. The rigid surface produced much higher peak head accelerations and HIC values than any of the padded surfaces.

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