Design of an optimally safe football helmet system requires an awareness and evaluation of the factors and variables that can adversely affect the impact attenuating performance of energy absorbing (EA) pad materials needed to minimize transmission of linear and rotational forces applied to the head so that risk of head injury is reduced. For instance, player head sweating can induce high temperatures and moisture within a helmet system (i.e. a Hot-Wet condition) which can result in degradation of helmet EA capacity and cause increased measures of head injury risk levels, which are often used for comparative evaluation of helmet designs. In this study, a “multivariable” experimental method was utilized to demonstrate an efficient means for assessment and comparison of currently representative adult and youth football helmet system designs when subjected to a range of variables that included, among other factors: temperature-moisture effects; impact energy; and, repeat impacts. Both quasi-static (QS) compression testing of commonly used EA materials and dynamic impact testing of full helmet systems were conducted and the results are presented in Tables and graphic form. The EA pad types that were QS tested included: Thermoplastic-Polyurethane (TPU) “waffle shaped” EA pad configurations; load rate sensitive “Gel” foam padding; and, dual and single density elastomeric foam padding. Dynamic helmet repeat impact tests were conducted by using a pendulum impact test device where various helmet designs were mounted to a Hybrid-III head and neck system and impacted against a non-yielding surface at energy levels of 108J and 130J after being subjected to ambient and Hot-Wet conditions. The QS tests showed that a short Hot-Wet soak time of only a few hours’ noticeably diminished EA levels. Also, the dynamic full helmet system testing demonstrated that the “Hot-Wet” condition tended to degrade helmet impact attenuation performance such that, depending on the size and type of EA material provided in the crush zone, head injury risk measures tended to increase. Finally, examples of the use and benefits of a “multivariable” experimental method for helmet injury risk assessment, not reported on previously, are provided.
An energy rate balance is employed to develop the incremental equations of motion for a shock loaded, inelastically constrained rigid-body structural system. Lagrangian multipliers provide the coupling mechanism necessary to reduce the overall system of equations to a set of modified rigid-body equations which include the nonlinear geometric and structural material effects. Kinematic material hardening and a modified yield criteria are used. Examples illustrate the technique and are compared with experimental results.
Since 1996 the NHTSA has warned of the airbag deployment injury risk to front seated children and infants, during frontal impact, and they have recommended that children be placed in the rear seating areas of motor vehicles. However, during most rear impacts the adult occupied front seats will collapse into the rear occupant area and, as such, pose another potentially serious injury risk to the rear seated children and infants who are located on rear seats that are not likely to collapse. Also, in the case of higher speed rear impacts, intrusion of the occupant compartment may cause the child to be shoved forward into the rearward collapsing front seat occupant thereby increasing impact forces to the trapped child. This study summarizes the results of more than a dozen actual accident cases involving over 2-dozen rear-seated children, where 7 children received fatal injuries, and the others received injuries ranging from severely disabling to minor injury. Types of injuries include, among others: crushed skulls and brain damage; ruptured hearts; broken and bruised legs; and death by post-crash fires when the children became entrapped behind collapsed front seat systems. Several rear-impact crash tests, utilizing sled-bucks and vehicle-to-vehicle tests, are used to examine the effects of front seat strength and various types of child restraint systems, such as booster seats and child restraint seats (both forward and rearward facing), in relation to injury potential of rear seated children and infants. The tests utilized sedan and minivan type vehicles that were subjected to speed changes ranging from about 20 to 50 kph (12 to 30 mph), with an average G level per speed change of about 9 to 15. The results indicate that children and infants seated behind a collapsing driver seat, even in low severity rear impacts of less than 25 kph, encounter a high risk of serious or fatal injury, whether or not rear intrusion takes place. Children seated in other rear seat positions away from significant front seat collapse, such as behind the stronger “belt-integrated” types of front seats or rearward but in between occupied collapsing front seat positions, are less likely to be as seriously injured.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.