Les traumatismes crâniens demeurent une cause de mortalité importante et entraînent des incapacités graves. La modélisation numérique est un outil moderne pour étudier la biomécanique des chocs crâniens. L’objectif principal de cette thèse a été l’évaluation biomécanique d’un casque de cycliste issu du commerce. Des tests de caractérisation ainsi que des campagnes de chocs normatifs et tangentiels ont permis le développement d’un modèle éléments-finis du casque et sa validation. Afin d’estimer le risque lésionnel encouru lors de chocs réalistes, le modèle de casque a été couplé à un modèle de tête anatomique et différents paramètres intracrâniens ont été calculés. Les valeurs obtenues pour ces paramètres se sont révélées supérieures aux limites de tolérance. Fort de ces constats, une réflexion en profondeur sur la norme EN1078 actuelle a été menée et pour laquelle des modifications ont été proposées afin que le casque protège la tête de façon optimale vis-à-vis de critères biomécaniques. / Traumatic head injuries remain a common cause of death and severe disabilities worldwide. FE modeling of the head is a well accepted tool to study head impact biomechanics. The objective of this PhD thesis was to evaluate the head protection capability offered by a commercial bicycle helmet. Experimental characterization tests, standard and tangential impacts were performed to develop and validate the finite element helmet model. In order to estimate the injury risk sustained in case of realistic head impacts, the helmet model has been coupled to an anatomical head and intracranial parameters were computed. Calculated values were higher than published tolerance limits. An in-deep investigation of the current EN1078 European standard was then carried out and relevant modifications were proposed to assess and optimize bicycle helmets against biomechanical criteria.

By applying the finite element approach to the design and analysis of the impact diffusion helmet, many helmet configurations were able to be analyzed. Initially it was important to determine what design variables had an influence on the impact reducing abilities of the helmet design. The helmet was run through a series of Abaqus simulations that determined that a design with two oval shaped channels running along the length of the helmet was best. Next, these options were optimized to generate the helmet that produced the greatest impact reduction. The optimization simulations determined that a helmet that pushed the channels as far from the impact zone as possible reported the lowest acceleration. This indicated that removing the channels from play was most advantageous from an impact reduction perspective. Finally, a 3-D printed experimental helmet was impact tested and compared to a 3-D printed control helmet. The experimental helmet brought the channels back into the impact zone in order to judge if they had a physical effect on the acceleration. Both the simulations and the subsequent physical testing indicated that the Impact Diffusion Helmet design has a negative influence on the concussion reducing properties of a football helmet.

The diploma thesis is focused on the application of modern technologies in ski helmets development. In the theoretical part is performed the research of the protective gear for skiers including the characteristics of production technologies used for its production. Part of the thesis is also the characteristics of Reverse Engineering and Rapid Prototyping. The practical part deals with the design of the ski helmet using modeling clay with the following conversion to a computer model and editing in available CAx program. Part of the practical part is also production on 3D printer. The thesis is concluded with a technical-economic evaluation of applicated modern technologies used for prototype helmet model production.

Preservation and protection of the head segment is of upmost importance due to the criticality of the functions entailed in this section of the body by the brain and the nervous system. Numerous events in daily life situations such as transportation and sports pose threats of injuries that may end or change a person’s life. In the European Union, statistics report that almost 4.2 million of road users are injured non-fatally, out of which 18% is represented by motorcyclist and 40% by cyclists, being head injuries 34% for bicyclists, and 24% for two-wheeled motor vehicles. Not only vehicles, are a source of injuries for the human head according to the injury report, 6,1 million people are admitted in hospitals for sports related injuries, where sports such as hockey, swimming, cycling presented head injuries up to 28%, 25% and 16% respectively (European Association for Injury Prevention and Safety Promotion, 2013).  According to records the vast majority of head crashes result in an oblique impact (Thibault & Gennarelli, 1985). These types of impacts are characterized for involving a rotation of the head segment which is correlated with serious head injuries. Even though there is plenty of evidence suggesting the involvement of rotational forces current helmet development standards and regulations fail to recognize their importance and account only for translational impact tests. This thesis contains an evaluation for a different developed method for testing oblique impacts. In consequence a new test rig was constructed with basis on a guided free fall of a helmeted dummy head striking an oblique (angled) anvil which will induce rotation. The results obtained are intended to be subjected to a comparison with another oblique test rig that performs experiments utilizing a movable sliding plate which when impacted induces the rotation of a dropped helmeted dummy head. The outcome will solidify the presence of rotational forces at head-anvil impact and offer an alternative testing method. After setting up the new test rig; experiments were conducted utilizing bicycle helmets varying the velocities before impact from 5m/s to 6m/s crashing an angled anvil of 45°. Results showed higher peak resultant values for rotational accelerations and rotational velocities in the new test rig compared to the movable plate impact test, indicating that depending on the impact situation the “Normal Force” has a direct effect on the rotational components. On the other hand a performed finite element analysis predicted that the best correlation between both methods is when the new angled anvil impact test is submitted to crashes with a velocity before impact of 6 m/s at 45° and the movable sliding impact test to a resultant velocity vector of 7,6m/s with an angle of 30° . In conclusion the new test method is meant to provide a comparison between two different test rigs that will undoubtedly have a part in the analysis for helmet and head safety improvements.

<div>Since the discovery of chronic traumatic encephalopathy (CTE) in retired professional football players, the long-term neurological safety of these athletes has been called into</div><div>question. Studies revealed that those who play football are at higher risk for developing neurological deficits such as Parkinson’s and Alzheimer’s diseases. It has also been observed that participation in contact sports can result in neurological changes detectable with magnetic resonance imaging (MRI) that do not present with any easily observable clinical symptoms. Changes in brain chemistry, structure, and blood flow have been observed over the course of a season of contact sports. These changes are thought to be caused by the repetitive head acceleration events (HAEs) sustained by contact sport athletes, with the magnitude and number of HAEs correlating with some changes. This dissertation aims to characterize and reduce the HAEs sustained by contact sport athletes with a specific focus on football players.</div><div><br></div><div>Studies of middle school and high school football players revealed that there are likely offsetting effects that result in similar HAEs between the two groups. As one plays at higher levels of play with typically bigger, stronger, faster athletes that should result in higher magnitude HAEs, there is likely an improvement in tackling technique used at higher levels that make it so there are similar HAEs among different levels of play. Examining middle school football and high school football and girls’ soccer athletes indicate that players that play on two teams (i.e. a player that plays both Varsity and Junior Varsity) may be at an increased risk for neurological changes due to over-exposure. It was revealed when studying post-collegiate football the up stance offensive linemen may help reduce the frequency of HAEs compared to the down stance. However, the skill of the offensive lineman needs to be accounted for to determine if it is beneficial for players to start in this stance.</div><div><br></div><div>Repetitive HAEs (rHAEs), whether due to body or direct head impacts arising from participation in contact sports, are correlated with alterations in white matter health. Fractional anisotropy (FA) and mean diffusivity (MD), two metrics used to assess white matter structural integrity, typically change in opposite directions (one increases while the other decreases) after brain injury. This study investigated the manner in which participation in American football affects the percentage of white matter exhibiting the four possible change combinations: increased FA, increased MD; decreased FA, increased MD; increased FA, decreased MD; decreased FA, decreased MD. Diffusion tensor imaging data of 61 high school football and 15 non-contact athletes were analyzed. After a season of participation, football athletes exhibited a significantly greater percentage of deviant voxels in each of the four categories than were observed from test-retest of non-contact athletes. Even prior to a season of participation, football athletes exhibited significantly more voxels in each of the categories, relative to controls. Of particular concern is that voxels exhibiting jointly decreased FA and MD—a change typically associated with cell death—were observed at a significantly higher rate within football athletes than non-contact athletes. This finding suggests that rHAEs may increase the incidence of cell death, and argues for the greater adoption of methods aimed at reducing mechanical loading on the brain from rHAEs, both through reduction of the number of HAEs, and development of better protective equipment.</div><div><br></div><div>Rugby is a sport that is very similar to football in terms of physicality and overall objective, but there are marked differences in protective equipment and style of play. These differences in protective equipment result in different tackling rules and styles between the two sports that may influence the effect repetitive HAEs can have on neurological health. Therefore, the HAEs experienced over the course of the season by New Zealand collegiate (ages 16+) rugby athletes were characterized. The number of HAEs were compared by position (forward vs. backs) and the peak translation acceleration (PTA) of the HAE was analyzed by position, possession (offense vs. defense), and cause of HAE (tackle vs. ruck). Forwards (although not significantly) tended to sustain more HAEs than backs, but there were no differences in the magnitude of the HAEs by any of the types of comparisons. However, when considering possession and type of HAE simultaneously, it was found that HAEs in a defensive ruck are more severe than those sustained in an offensive ruck. This could be a potential place to work on player technique to reduce the PTA during these situations.</div><div><br></div><div>There are numerous studies that have utilized accelerometers to quantify head motion during a contact event, but a current gap in the field is quantification of the impact force. In order to capture high force events, an instrumented helmet using strain was built to capture this data. Strain gauges were adhered to the inside of a Riddell Speedflex helmet shell and then mounted onto a Hybrid III Headform for testing. The helmet was hit at four different locations (front, right, back, and left) and at different impulse ranges (2-5 Ns, 5-8 Ns, 8-11 Ns, and 11+ Ns). The strain gauges were able to classify the location of the hit with about 95% accuracy and were correlated the impact peak force and impulse. This suggests that it is possible to build an instrumented helmet to be worn by a football player during collision events to capture real impact force and location data.</div>

This is a master thesis project in Industrial Design Engineering at Luleå University of Technology performed during the spring semester 2019 and with the goal to design a helmet for POC specialized for ski mountaineering.   To cope with new rules in ski mountaineering competitions, to widen the product catalogue of POC and to make ski mountaineering safer and more enjoyable, a double certified helmet was to be designed, meaning certified for both mountaineering and downhill skiing. The end goal with the project was a product concept fully ready to be prototyped and tested for both EN 12492 – mountaineering helmets and EN 1077 – ski helmets standards.   Theories relevant to the project has been researched, they include head injuries, manufacturing methods, anthropometry, and safety certifications. Some takeaways from these were that head injuries in ski mountaineering can be severe or deadly, but can be mitigated by using a helmet, helmets are usually produced by expanding plastic beads into a shock absorbing material, by expanding the beads more, the shock absorbing material gets a lower density, and by expanding them less the material gets a higher density, an easy way to design a helmet that fits well on most people’s heads is to use headforms, and that an easy way to design a helmet that can be EN1077 and EN12492 certified is to use similar dimensions as existing helmets with the same certifications.   Methods used in the project has been: a survey asking users for insight and opinions; analysis of the brand POC; competition research; observations; idea generation - including 6-3-5 and body storming; and creation and evaluation of prototypes.   The project has resulted in information about user’s experiences of SKIMO helmets, users wants and needs, an analysis of POC products, ideas, prototypes for testing functionality, clay models for exploring shape, a concept decision and last but not least, a CAD model and a prototype of the final concept. The survey results together with some observations could be summarized as three problems to solve and six features the helmet should have. 1. Temperature Change. 2. Ventilation holes makes goggle foggy when worn on the on the forehead. 3. The third problem is created as a combination of the EN 1077 standard penetration test for ski helmets and the users need for “extremely good ventilation”.   Requested features were: 1. The users want to be able to where sun glasses in a passive position on top of the helmet. 2. They want head lamp attachment. 3. It should look good. 4. Side straps for goggles are requested. 5. It should be colourful so that it’s easy to detect in the mountain terrain. 6. And of course, it needs to be lightweight.   The result is a SKIMO helmet I chose to call POC Ibex. It’s a helmet with a double layer EPS liner with multiple functions. It allows for ventilation to the forehead without fogging up the goggles and helps withstanding penetration tests while still having big ventilation holes. It has Magnetic removable ear pads, that can be attached without removing the helmet. It’s made from EPS and PC and on the top, it has an extra thick layer of PC for extra protection against rock fall.

Indiana University-Purdue University Indianapolis (IUPUI) / Traumatic Brain Injuries (TBI) are one of the most apprehensive issues today. In recent years a lot of research has been done for reducing the risk of TBI, but no concrete solution exists yet. Helmets are one of the protective devices that are used to prevent human beings from mild TBI. For many years some kind of foam has been used in helmets for energy absorption. But, in recent years non-traditional solutions other than foam are being explored by different groups. Focus of this thesis is to develop a completely new concept of energy absorption for helmet liner by diverting the impact forces in radial directions normal to the direction of impact. This work presents a new design of an advanced layered composite (ALC) for energy dissipation through action of a 3D array of compliant mechanisms. The ALC works by diverting incoming forces in multiple radial directions and also has design provisions for reducing rotational forces. Design of compliant mechanism is optimized using multi-material topology optimization algorithm considering rigid and flexible material phases together with void. The design proposed here needs to be manufactured using the advanced polyjet printing additive manufacturing process. A general and parametric design procedure is explained which can be used to produce variants of the designs for different impact conditions and different applications. Performance of the designed ALC is examined through a benchmark example in which a comparison is made between the ALC and the traditional liner foam. An impact test is carried out in this benchmark example using dynamic Finite Element Analysis in LS DYNA. The comparison parameters under consideration are gradualness of energy absorption and peak linear force transmitted from the ALC to the body in contact with it. The design in this article is done particularly for the use in sports helmets. However, the ALC may find applications in other energy absorbing structures such as vehicle crashworthy components and protective gears. The ultimate goal of this research is to provide a novel design of energy absorbing structure which reduces the risk of head injury when the helmet is worn.

Indiana University-Purdue University Indianapolis (IUPUI) / Lattice structures have seen increasing use in several industries including automotive, aerospace, and construction. Lattice structures are lightweight and can achieve a wide range of mechanical behaviors through their inherent cellular design. Moreover, the unit cells of lattice structures can easily be meshed and conformed to a wide variety of volumes. Compliant mechanism make suitable micro-structures for units cells in lattice structures that are designed for impact energy absorption. The flexibility of compliant mechanisms allows for energy dissipation via straining of the members and also mitigates the effects of impact direction uncertainties. Density-based topology optimization methods can be used to synthesize compliant mechanisms. To aid with this task, a proposed optimization tool, coded in MATLAB, is created. The program is built on a modular structure and allows for the easy addition of new algorithms and objective functions beyond what is developed in this study. An adjacent investigation is also performed to determine the dependencies and trends of mechanical and geometric advantages of compliant mechanisms. The implications of such are discussed. The result of this study is a compliant mechanism lattice structure for impact energy absorption. The performance of this structure is analyzed through the application of it in a football helmet. Two types of unit cell compliant mechanisms are synthesized and assembled into three liner configurations. Helmet liners are further developed through a series of ballistic impact analysis simulations to determine the best lattice structure configuration and mechanism rubber hardness. The final liner is compared with a traditional expanded polypropylene foam liner to appraise the protection capabilities of the proposed lattice structure.

Ice hockey, one of the most popular sports in the world, is a contact sport that is always associated with huge risks of traumatic brain injuries (TBIs) resulting from high-velocity impacts. Although technology in player protection equipment has advanced over the years, mild traumatic brain injuries (mTBIs) like concussion remain prevalent. Finite Element (FE) analysis presents a methodology to recreate accidents in an effort to study the effects of protective helmets and predict brain injuries. This study aimed at improving the response of an existing ice hockey helmet FE model during different impact conditions and reconstructing an ice hockey collision using FE simulations. First, the shear response of the Expanded Polypropylene (EPP) material for the helmet liner was improved by means of a single element simulation to replicate the experiments. Simulations of helmet drop tests were then performed to validate the helmet FE model. Two different designs of the helmet model were implemented, one with normal properties of the foam and the other with a softer foam. Actual cases of ice hockey accidents were then reconstructed using positioning and impact velocities as input from video analysis. As player to player collisions had not been reconstructed for ice hockey using two player models, it was decided to use two full body Human Body Models (HBMs) for the reconstruction. The biomechanical injury parameters for the accident reconstruction were plotted and compared with injury thresholds for concussion. The kinematic results achieved from the drop test simulations showed a considerable decrease in peak values for resultant accelerations, resultant rotational accelerations, and resultant rotational velocities. These results also exhibited better CORrelation and Analysis (CORA) scores than previously achieved. The biomechanical analysis of the accident reconstruction showed the strains in the brain for the concussed player to be more than the threshold for concussion, which confirms the validity of the reconstruction approach. The results of this study show an improved response of the helmet FE model under different impact conditions. They also present a methodology for ice hockey accident reconstruction using two full body HBMs.

Urban cycling is gaining popularity worldwide. Inadequate local and international guidelines on street cycling have contributed to a significant increase in road traffic, including increased accidents involving cyclists. In parallel, worldwide, safety data indicates that low-income countries have a high average rate of traflic fatalities (27,5 deaths per 100,000 population), more than three times higher compared to high-income countries (8,3 deaths per 1000.000 population) [1]. Another study found that safety and security factors have not been sufficiently addressed in previous studies regarding bicycle mobility. These factors seem to be more relevant in developing countries than developed ones, and more research is needed [2]. ... [From: Introduction]