L'objectif scientifique de la thèse est de contribuer à améliorer la compréhension des mécanismes lésionnels découlant de l’impact non pénétrant d’un projectile en région thoracique latérale. Concrètement, l’application concerne l’amélioration de l’évaluation du potentiel lésionnel et l’optimisation de projectiles dits « à létalité réduite ». Cette étude a été menée dans le cadre du projet PARCHOC, associant la Délégation Générale pour l’Armement-Techniques Terrestres, le laboratoire PRISME de l’université d’Orléans, les sociétés Nexter munitions, ITC élastomère et ATCOM télémétrie. Il s’agit notamment de mettre en évidence les paramètres des projectiles qui doivent être maîtrisés pour limiter le risque lésionnel. Nous avons d’abord réalisé une étude pour caractériser des projectiles d'essais constitués d'un culot rigide et d'une ogive en mousse d'élastomère. Les propriétés dynamiques des élastomères ont été caractérisées par le système des barres de Hopkinson. Ce travail a permis la mise au point d'un modèle numérique de comportement des élastomères. Des essais ainsi que des simulations d’impacts sur cibles rigides ont ensuite été réalisés afin d'étudier l'influence du couple masse-vitesse et des caractéristiques mécaniques des élastomères sur le chargement généré. Dans la seconde partie de l'étude, des essais sur cibles biologiques instrumentées ont été menés à l’aide des projectiles d'études précédemment caractérisés. Les résultats expérimentaux et numériques montrent que la dangerosité des projectiles est liée à l’action qu’ils exercent sur la structure osseuse thoracique après sa fragilisation et que le mécanisme lésionnel est fortement dépendant de l’impulsion transmise par le projectile lors de l’impact. / The scientific objective of the thesis was to make a contribution in the understanding of the injury mechanisms following the blunt impact of a projectile on the lateral thoracic region. Practically, the application concerns safety certification and optimization of less-lethal projectile. This research was supported by the project PARCHOC partners: the Délégation Générale pour l’Armement-techniques terrestres, the PRISME laboratory (Orléans university),the companies Nexter munitions, ITC élastomère and ATCOM télémétrie. In particular, we have sought the principal projectile parameters which must be controlled to limit injury risk. Firstly, we have performed a study based on specialized test projectiles, made with a rear rigid part and soft foam (elastomeric) nose. The foams’ chemical formulations were made so that the dynamical properties (measured with the Hopkinson bar apparatus) were those expected. Experiments and simulations of the impacts on rigid wall target have been made to investigate how the mass-velocity couple and the foam material properties influence the impact force. Secondly, an experimental campaign was made using pig anatomical parts and the projectiles previously studied. Experimental and numerical results obtained during the thesis demonstrate that the dangerous nature of the projectiles used is essentially linked to the action on the thoracic bone structure after it has been weakened by the impact. Furthermore, injuries are strongly dependent upon the impulse transmitted during the impact.

A finite element model was developed for a range of human head-sUAS impacts to provide multiple case scenarios of impact severity at two response regions of interest: global and local. The hypothesis was that for certain impact scenarios, local response injuries of the brain (frontal, parietal, occipital, temporal lobes, and cerebellum) have a higher severity level compared to global response injury, the response at the Center of Gravity (CG) of the head. This study is the first one to predict and quantify the influence of impact parameters such as impact velocity, location, offset, and angle of impact to severity of injury. The findings show that an sUAS has the potential of causing minimal harm under certain impact scenarios, while other scenarios cause fatal injuries. Additionally, results indicate that the human head’s global response as a less viable response region of interest when measuring injury severity for clinical diagnosis. It is hoped that the results from this research can be useful to assist decision making for treatments and may offer different perspectives in sUAS designs or operation environments.

Military personnel often experience mild traumatic brain injury (mTBI) from exposure to improvised explosive devices (IEDs). Soldiers typically endure blast trauma from the IED pressure wave as well as blunt trauma from ensuing head impacts. Researchers have not reached a consensus on whether the biomechanical response from blunt or blast trauma plays a more dominant role in mTBI because the specific biomechanical sources of injury are often undetermined. Consequently, the goal of this dissertation was to conduct three separate studies in order to characterize the mechanical behavior of the brain after exposure to mTBI conditions. For Study 1, mild blunt and blast trauma were induced in Sprague-Dawley rats using a custom-built device. In-house diffusion tensor imaging (DTI) software was used to make 3-D reconstructions of white matter fiber tracts before and after injury (1, 4, and 7 days). Axonal integrity was characterized by examining the fiber count, fiber length, and fractional anisotropy (FA). In-house image analysis software also quantified the microstructural variations in Hematoxylin and Eosin (H&E) stained brain sections, where significant differences in parameters such as the area fraction (AF) and nearest neighbor distance (NND) correlated to voids that formed after water diffused extracellularly from axons. Study 2 employed a computational approach involving the development of a finite element (FE) model for the rat head followed by the simulation of blunt and blast trauma, respectively. FE parameters such as von Mises stress, pressure, and maximum principal strain were analyzed at various locations including the skull, cerebral cortex, corpus callosum, and hypothalamus to compare injury cases. Study 3 involved interruption mechanical testing of porcine brain, a suitable animal surrogate of human brain. Compression, tension, and shear experiments were performed at a strain rate of 0.1 s-1 to examine the differential mechanical response. Microstructural changes in H&E stained brain sections were analyzed with in-house image analysis software to quantify differences among stress states at strains of 0.15, 0.30, and 0.40. Studies 1 and 2 confirmed that the brain behaves differently in response to blunt and blast trauma, respectively, while Study 3 further demonstrated the stress state dependent behavior of brain tissue.

Intimate partner violence (IPV) is a global human rights issue that affects approximately 25% of women and 10% of men and is the leading cause of homicides of women worldwide. Multiple studies have been conducted by medical and dental practitioners to screen for indicators of IPV so that victims can be directed toward resources for help. However, despite its prevalence, injury patterns indicative of intimate partner homicide (IPH) have not previously been studied. Given that blunt force injuries are the primary type of trauma associated with IPV and the second leading trauma associated with IPH (after gunshot trauma), craniofacial fracture patterns from blunt force trauma associated with IPH served as the focus of this study. Using computed tomography (CT) scans obtained from the New Mexico Office of the Medical Investigator of identified victims of IPH, the fracture location and quantity of fractures were compared a compilation of results from previously published studies on IPV. In addition, data on fracture type were collected on the IPH sample, as this can provide information about the fracture-causing blow. This study aimed to determine whether there are differences in fracture patterns associated with IPH versus incidence of IPV that were survived. It was found that some trends present in IPV cases were maintained in IPH cases--such as a concentration of fractures to the mid-face-- fractures in IPH cases were more distributed over the skull and presented with an more frequently on the upper face and cranial vault, as well as fractures to the right side of the body.

North American bison (Bovidae: Bison bison) incur blunt impacts to the interparietal and frontal bones when they engage in head-to-head fights. To investigate the impact mitigation of these bones, a finite element analysis of the skull under loading conditions was performed. Based on anatomical and histological studies, the interparietal and frontal bones are both comprised of a combination of haversian and plexiform bone, and are both underlain by bony septa. Additionally, the interparietal bone is thicker than the frontal. Data regarding the mechanical properties of bison bone are scarce, but the results of a phylogenetic analysis infer that the material properties of the closely-related domestic cow bone are a suitable proxy for use in the FEA. Results of the FEA suggest that the thickness of the interparietal in conjunction with the bony septa may prevent focal stresses by helping to absorb and disperse the blunt impact energy about the skull.

Les impacts non transfixiants sur les gilets pare-balles sont responsables de lésions non pénétrantes potentiellement létales, regroupées sous le terme d’effets arrière (Behind Armor Blunt Trauma : BABT). De telles lésions fermées se retrouvent également lors d’impacts thoraciques de projectiles d’Armes à Létalité Réduite cinétiques (ALRc). Afin d’améliorer le pouvoir protecteur des protections balistiques et de mieux maitriser le pouvoir vulnérant des ALRc, il est nécessaire de définir un critère lésionnel permettant de prédire l’importance des lésions en cas de traumatisme thoracique fermé de type balistique. Ce critère se doit d’être bien corrélé à la gravité du traumatisme, et de pouvoir être facilement transposable à l’ensemble des systèmes d’évaluation des protections balistiques et des ALRc. La gravité du traumatisme a été définie ici par le volume de la contusion pulmonaire. L’utilisation de cette valeur nécessitait le recours au modèle animal. Or, nous avons démontré que le thorax du modèle porcin n’offrait pas le même comportement biomécanique lors de l’impact que le thorax de l’adulte jeune. Nous avons donc développé un critère, l’impulsion de pression intrathoracique maximale (PImax), basé sur la mesure de la pression intrathoracique lors de l’impact, et donc indépendant du comportement biomécanique de la paroi thoracique vis-à-vis de ses effets sur le poumon. Ce critère très bien corrélé avec le volume de la contusion pulmonaire, quelque soit le type d’impact thoracique balistique (ALRc ou BABT), a l’avantage de pouvoir être transposable aux autres moyens d’évaluations balistiques tels que les modèles numériques ou mécaniques de thorax, afin de s’affranchir de l’expérimentation animale / When non-penetrating, impacts on bulletproof jackets can lead to potentially lethal blunt injuries known as behind armor blunt trauma (BABT). Impacts of less lethal kinetic weapons (LLKW) can also lead to such injuries. To both improve the protection capabilities of the BPJ and better comprehend the ounding potential of the LLKW, we need to design a wounding criterion to predict the injury severity of ballistic blunt thoracic trauma. In one hand, this criterion has to be well correlated with the severity of the injuries, and in the other hand, it has to be easily used with all the LLKW and BPJ assessment systems in use. First, we defined the pulmonary contusion volume as the severity of the injuries. Studying the pulmonary contusion involves the use of animal experiments. But we demonstrated that the biomechanics of the chest wall are different in animals and young adults. Then, we developed the maximum pressure impulse criterion (PImax). As it is based on the intrathoracic pressure measure during the blunt impact, it is independent from the chest wall behavior. This criterion can be used with the other assessment tools as the numerical simulation mechanical chest surrogates. This can help to reduce the use of animal experiments, which is more and more expensive, heavy and questionable on the ethical aspect

Seat belts save lives; however, unintentional injuries are still the leading cause of death for those between 1 and 44 years in the United States. Seat belts also cause injuries during motor vehicle crashes (MVCs) and obesity changes how seat belts fit. The purpose of this retrospective causal inference quantitative study was to reduce the knowledge gap in scholarly research on seat belt fit in relation to blunt cerebrovascular injuries (BCVI) during MVCs and seat belt compliance. The theoretical framework used was based on H.W. Heinrich's domino theory. The research questions focused on the following dependent variables: BCVI, compliance, and seat belt fit; and independent variables: the size of the individual and seat belt fit. Secondary and primary data were used and analyzed using Spearman's Rank-Order Correlation. The results yielded no relationship between seat belt fit and BCVI in the secondary data (n = 97). In the primary data (n = 138), there was significance found between seatbelt fit and a) seat belt use, and b) BMI. The study contributed to positive social change by enhancing the awareness of the knowledge deficit regarding seat belt fit, and BCVIs sustained during MVCs, and that comfort was influenced by seat belt fit and had a role in compliance. Seat belts were not used by 5.3% and 9.5% or used incorrectly by 3.2% and 2.9% of the people in the primary data and secondary data sets. This knowledge may contribute to a) future seat belt testing to ensure it is done in such a manner that seat belts fit everyone; b) new seat belt laws to ensure that they are consistent across all states, and c) medical care focusing on seat belt fit as a mechanism of injury (blunt) to ensure screenings are done with the appropriate diagnostic tools.

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No description available.

The emerging and competitive environment in the space technology requires the improvements in the capability of aerodynamic vehicles. This leads to the analysis in drag reduction of the vehicle along with the minimized heat transfer rate. Using forward facing solid aerospike is the simplest way among the existing drag reduction methodologies for hypersonic blunt cone bodies. But the flow oscillations associated with this aerospike makes it difficult to implement. When analyzing this flow, it can be understood that this oscillating flow can be compared to conical cavity flow. Therefore in the spiked flows, it is decided to implement the technique used in reducing the flow oscillation of the cavities. Based on this method the shallow conical cavity flow generated by the aerospike fixed ahead of a 120o blunt cone body is fissured as multiple cavities by so many disks formed from 10o cone. Now the deep conical cavities had the length to mean depth ratio of unity; this suppresses the unnecessary oscillations of the shallow cavity. The total length of the telescopic aerospike is fixed as 100mm. And one another conical tip plain aerospike of same length is designed for comparing the telescopic spike’s performance at hypersonic flow Mach numbers of 5.75 and 7.9. A three component force balance system capable of measuring drag, lift and pitching moment is designed and mounted internally into the skirt of the model. Drag measurement is done for without spike, conical tip plain spiked and telescopic spiked blunt cone body. The three configurations are tested at different angles of attack from 0 to 10 degree with a step of 2. A discrete iterative deconvolution methodology is implemented in this research work for obtaining the clean drag history from the noisy drag accelerometer signal. The drag results showed the drag reduction when compared to the without spike blunt cone body. When comparing to the plain spiked, the telescopic spiked blunt cone body has lesser drag at higher angles of attack. Heat transfer measurements are done over the blunt cone surface using the Platinum thin film gauges formed over the Macor substrate. These results and the flow visualization give better understanding of the flow and the heat flux rate caused by the flow. The enhancement in the heat flux rate over the blunt cone surface is due to the shock interaction. And in recirculation region the heat flux rate is very much lesser when compared to without spike blunt cone body. It is observed that the shock interaction in the windward side is coming closer towards the nose of the blunt cone as the angle of attack increases and the oscillation of the oblique shock also decreases. Schlieren visualization showed that there is dispersion in the oblique shock, particularly in the leeward side. In the telescopic spike there are multiple shocks generated from each and every disk which coalesces together to form a single oblique shock. And the effect of the shock generated by the telescopic spike is stronger than the effect of the shock generated by the conical tip plain spike.