Développement d’un outil d’assistance numérique pour la conception des casques de hockey : étude de faisabilité

Abstract

Concussions in sports, especially ice hockey, have been the subject of great public concern in recent years. There has been a real awareness at all levels from professionals to fans and supporters to parents of young players including hockey leagues and equipment manufacturers. Frequent exposure to this type of injury often has serious consequences for neurological health. Based on these findings, some studies have attributed the responsibility for these traumas to the linear and angular accelerations the brain undergoes during a violent shock. CCM Hockey seeks to reduce head accelerations by optimizing the design of their helmets which passes through the choice of geometry and materials. However, it is difficult to establish the relationships between these design choices and the accelerations measured experimentally during impact tests. The poverty of the data provided by the manufacturers of these materials is one of the causes of this difficulty. In addition, the current design process at CCM Hockey, by iteration, does not make up for these shortcomings in addition to being expensive and time consuming. The development of a parameterized finite element model of a head-neck complex equipped with a helmet was therefore considered to replicate the experimental tests conducted at CCM Hockey. The objective of this study is therefore to evaluate the feasibility of using such a tool in the development of new helmets. The specific objectives of this preliminary project are therefore: OS I: Experimental characterization of protective foams; OS II: Modeling and experimental validation of the protective foam; OS III: Validation of the H350 manikin digital model provided by Altair; OS IV: Development of the finite element model of the head-neck-helmet complex; OS V: Experimental validation of the finite element model of the head-neck-helmet complex. In order to meet the first objective, two test benches, a servo-hydraulic machine and a drop tower, were used to obtain the stress-strain curves in pure compression, at different loading speeds for the VN602 foam. Five parameters extracted from these curves were used to compare them and to establish the dependence of the behavior of the VN602 foam in relation to the strain rate. An FEM from these test benches has been used to numerically reproduce the experimental tests. The latter was included in a constitutive law chosen to represent the VN602 foam. This law was completed by adding the experimental curves at different strain rates extracted from the first objective. In the third objective, impact simulations were performed on the FEM of the 50th percentile Hybrid III (H350) manikin reproducing experimental laboratory tests at CCM Hockey. Excessive discrepancies and lack of correlation between experimental and numerical results showed that the model is not validated. The use of an alternative head model, the NOCSAE head, was used for the rest of the project. However, the model must be validated later. In the fourth objective, a head-neckhelmet model has been developed and subjected to impacts. Simulations also reproduced laboratory tests. The numerical results showed that the model adequately represents its physical counterpart in terms of linear accelerations, but the difference is larger in terms of angular accelerations. The adjustment of the behavior law of the foam as well as an investigation on certain physical properties of the NOCSAE head is necessary in a future project. In conclusion, this project allowed, on the one hand, to characterize the behavior of the VN602 foam in respect of the dependence it demonstrates to strain rates and, on the other hand, to demonstrate the possibility of modeling this behavior. The finite element model of H350 cannot be used under the conditions to which it is subjected. However, the development and use of a finite element model of a NOCSAE head- H350 neck-helmet complex has demonstrated the feasibility of using such tool for design and evaluation of new hockey helmets.

Date	13 Jul 2018
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Éric Wagnac (Supervisor) & Yvan Petit (Co-supervisor)