Introduction: Wearing a helmet is necessary in sports-related events to prevent the head injury because the occurrence of head injuries was reduced from 4.25 per 100,000 to 0.68 per 100,000 when helmet was regulated by National Operating Committee on Standards for Athletic Equipment (NOCSAE) \[1\]. Facemask, as one helmet component, plays a major role in protecting the face. Although current helmet evaluation standard excluded the facemask, the effect of facemask on head kinematic response varied by different impact settings. Moreover, brain strain, which quantified the change ratio of brain tissue deformation due to the impact to the head, was demonstrated as the main cause leading to traumatic brain injury. However, the effect of facemask on brain response was not fully known despite literature on quantifying facemask effect on helmet performance \[2\]. The objective of this study is to evaluate the effect of facemask on brain response under different locations.

Method:  The Global Human Body Model Consortium (GHBMC) head & neck finite element (FE) model and Riddell Speed Classic football helmet FE model were combined for the simulation. An impactor with the velocity of 6 m/s was used to hit the frontal, lateral, frontal boss, rear, rear boss and frontal facemask site of combined head & neck-helmet model with and without facemask.  The cumulative strain damage measure (CSDM) with 15% of brain strain level, which means the proportion of brain volume exceeding the peak strain of 15% to the whole brain volume, was used to quantify brain strain distribution. To evaluate the effect of facemask on brain strain distribution, CSDM15 results of the same impact from head & neck-helmet model with and without facemask were compared.

Results: Under the frontal impact, CSDM15 of head & neck-helmet model with facemask was 0.26. When facemask was removed, CSDM15 increased to 0.28. Under the lateral impact, CSDM15 of head & neck-helmet model with facemask was 0.20. When facemask was removed, the CSDM15 increased to 0.23. Under frontal boss impact, CSDM15 of head & neck-helmet model with facemask was 0.42, and the removal of facemask induced slightly increased CSDM15 of 0.43. Under the rear impact, CSDM15 of head & neck-helmet model with facemask was 0.16. When facemask was removed, CSDM15 increased to 0.22. Under the rear boss impact, CSDM15 of head & neck-helmet model with facemask was 0.26, while the removal of facemask decreased the CSDM15 to 0.24. Under the frontal facemask impact, CSDM15 of head & neck-helmet model with facemask was 0.46, while the removal of facemask decreased CSDM15 to 0.17.

Discussion & Conclusion: This study demonstrated that the effect of facemask on brain strain distribution was different, depending on different impact locations. The inclusion of facemask reduced brain strain distribution response under frontal, lateral, frontal boss, and rear impact. However, facemask increased brain strain distribution response under rear boss and frontal facemask impact, especially for frontal facemask impact for which a 170% increase was observed. In the future, the facemask impact to different positions of the face needs to be further investigated. Meanwhile, facemask should also be included when evaluating helmet performance.

Reference:

\[1\] Levy, Michael L., et al. "Birth and evolution of the football helmet." Neurosurgery 55.3 (2004): 656-662.

\[2\] Rowson et al. "Quantifying the effect of the facemask on helmet performance." Proceedings of the Institution of Mechanical Engineers, Part P: Journal of sports engineering and technology 232.2 (2018): 94-101.


Facemask Generally Helps Reduce Brain Strain but Increases Strain in Frontal Facemask Impact and Rear Boss Impact

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

IMECE2020 - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.