Дисертації з теми "Head impact biomechanics"
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Young, Tyler James. "Head Impact Biomechanics and Helmet Performance in Youth Football." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/78065.
Повний текст джерелаMaster of Science
Rowson, Steven. "Impact Biomechanics of the Head and Neck in Football." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/42968.
Повний текст джерелаMaster of Science
Keim, Summer Blue. "Head Impact Conditions and Helmet Performance in Snowsports." Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/104049.
Повний текст джерелаMaster of Science
Mild traumatic brain injury in snowsports is a prevalent concern. With as many as 130,000 hospitalized injuries in the U.S. associated with snowsports in 2017, head injury constitutes about 28% and is the main cause of fatality. Studies have found that a combination of rotational and linear velocities is the most mechanistic way to model brain injury, but despite decades of research, the biomechanical mechanisms remain largely unknown. However, evidence suggests a difference in concussion tolerance may exist between athlete populations. To improve the ability to predict and therefore reduce concussions, we need to understand the impact conditions associated with head impacts across various sports. There is limited research on the conditions associated with head impacts in snowsports. These head impacts often occur on an angled slope, creating a normal and tangential linear velocity component. Additionally, the impact surface friction in a snowsport environment is highly variable, but could greatly influence the rotational kinematics of head impact. Currently helmet testing standards don't consider these rotational kinematics, or varying friction conditions that potentially occur in real-world scenarios. The purpose of this study is to investigate the head impact conditions in a snowsport environment to inform laboratory testing and evaluate snow helmet design. We determined head impact conditions through video analysis to determine the impact locations, mechanism of fall, and the kinematics pre-impact. We used these data to develop a test protocol that evaluates snowsport helmets in a realistic manner. Ultimately, the results from this research will provide snowsport participants unbiased impact data to make informed helmet purchases, while concurrently providing a realistic test protocol that allows for design interventions to reduce the risk of injury.
Bland, Megan Lindsay. "Assessing the Efficacy of Bicycle Helmets in Reducing Risk of Head Injury." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/89478.
Повний текст джерелаDoctor of Philosophy
Although cycling offers many health and environmental benefits and is increasing in popularity in the United States, it is not always a perfectly safe activity. The number of cycling-related hospital admissions in the US has been increasing over the past 15 years. Cyclists often sustain head injuries from crashes, which can be particularly debilitating. Fortunately, wearing a helmet can protect against head injuries during a crash. Bicycle helmets are presently designed around safety standards that drop a helmeted dummy head onto a horizontal anvil and require the helmet to limit the force on the head to acceptable levels. However, standards tests overly simplify how cyclists actually hit their head during a crash and are consequently unable to assess how well helmets protect against common brain injuries like concussion. The overarching goal of this research was to evaluate how effectively bicycle helmets protect cyclists from concussion in realistic impact scenarios. Several studies were conducted to achieve this goal. Their individual objectives were to: compare how bicycle helmets reduce impact forces associated with standards tests versus more realistic, angled impact tests; to understand how changing constraints of an angled impact setup influences helmet effectiveness; to develop an unbiased evaluation protocol for bicycle helmets based on realistic cyclist crash scenarios and concussion risk assessment; and finally, to further explore how cyclists impact their head in real-world crashes using advanced techniques for reconstructing bicycle helmet damage from actual accidents. All of these studies lead to improved cyclist safety by stimulating improved helmet evaluation and design, while also providing consumers with information on how protective their helmets are.
Kieffer, Emily Elana. "Sex-Specific Head Impact Exposure in Rugby: Measurement Considerations and Relationships to Clinical Outcomes." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103203.
Повний текст джерелаDoctor of Philosophy
Concussions are injuries that affect many areas of the brain, including those responsible for a person's physical, cognitive, and emotional health. Although concussions were once thought only to present transient symptoms, mounting evidence suggests potential for long-term neurological impairments. The harmful effects of concussion can be from a single, high intensity impact event or the build-up of lower intensity impacts. Clinical changes that can result from concussion include an elevated symptom presentation and changes in gait, or an individual's walking pattern. It is not well understood if similar side effects result after an accumulation of subconcussive impacts. The majority of research on human tolerance to head injury has been based on American football, using helmet-mounted sensors in male athletes. Limited studies have attempted to quantify concussion tolerance in women, despite the differences in men and women's symptoms and recovery time after a concussion. Female's neck strength, hormones, and increased honesty in reporting concussion differ from males, likely contributing to this difference. The research presented in this dissertation was aimed at describing how sex affects the results of subconcussion in a group of male and female athletes to gain a better sense of unhelmeted, sex-specific tolerance to head impacts. On-field data were collected from collegiate rugby players using sensor-embedded mouthguards. Rugby involves high energy, frequent head impacts, does not require protective headgear, and is played the same by both men and women. The females in our study sustained fewer impacts per session than the males, but their impacts were similar in magnitude. The impact energies of the concussive male impacts were higher than those of the concussive female impacts. Both sexes reported concussion-like symptoms in the absence of diagnosed concussion during a season. Females reported more symptoms with a higher severity in-season compared to males after subconcussive and concussive impacts. Female athletes had a slower walking pace and walking speed, a shorter stride length, and spent more time with both feet on the ground post-concussion. The majority of athletes improved in their dual-task gait assessment by the end of the season, suggesting there may not be a negative effect on gait after an accumulation of subconcussive impacts. This work assessed the biomechanics of head impacts and concussions of this population, and evaluated changes in symptom presentation through weekly graded symptom surveys and dual-task gait assessments both after a concussion and as an effect of subconcussive impacts. Understanding the sex-specific clinical effects of head impacts is critical, and can provide insight into concussion diagnostic, management, and prevention tools that are appropriate and effective.
Dawson, Lauren. "Impact Characteristics Describing Concussive Injury in Youth." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34326.
Повний текст джерелаLopik, David van. "A computational model of the human head and cervical spine for dynamic impact simulation." Thesis, Loughborough University, 2004. https://dspace.lboro.ac.uk/2134/7643.
Повний текст джерелаKarton, Clara. "Profiling Brain Trauma in Professional American-style Football and the Implications to Developing Neurological Injury." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39981.
Повний текст джерелаBartsch, Adam Jesse. "Biomechanical Engineering Analyses of Head and Spine Impact Injury Risk via Experimentation and Computational Simulation." Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1291318455.
Повний текст джерелаPearce, Christopher William. "On the dynamic pressure response of the brain during blunt head injury : modelling and analysis of the human injury potential of short duration impact." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/14185.
Повний текст джерелаPeng, Yong. "In-depth accident investigation of pedestrian impact dynamics and development of head injury risk functions." Thesis, Strasbourg, 2012. http://www.theses.fr/2012STRAD024.
Повний текст джерелаPedestrians are regarded as an extremely vulnerable and high-risk group of road users since they are unprotected in vehicle impacts. More than 1.17 million people throughout the world are killed in road traffic accidents each year. Where, about 65% of deaths involve pedestrians. The head injuries in vehicle-pedestrian collisions accounted for about 30% of all reported injuries on different body regions, which often resulted in a fatal consequence. Such injuries can result in disabilities and long-term sequence, which lead to significant social costs. It is therefore important to study the characteristics of pedestrian accidents and understand the head injury mechanism of the pedestrian so as to improve vehicle design for pedestrian protection. The aim of this study is to investigate pedestrian dynamic response and develop head injury risk functions.In order to investigate the effect of pedestrian gait, vehicle front geometry and impact velocity on the dynamic responses of the head, the multi-body dynamic (MBD) models were used to simulate the head responses in vehicle to pedestrian collisions with different vehicle types in terms of head impact point measured with Wrap Around Distance (WAD), head relative velocity and impact angle. A simulation matrix is established using five vehicle types, and two mathematical models of the pedestrians represented a 50th male adult and a 6 year old child as well as seven pedestrian gaits based on typical postures in pedestrian accidents. In order to simulate a large range of impact conditions, four vehicle velocities (30 km/h, 40 km/h, 50 km/h and 60 km/h) are considered for each pedestrian position and vehicle type.A total of 43 passenger car versus pedestrian accidents were selected from In-depth Investigation of Vehicle Accidents in Changsha, China (IVAC) and German In-Depth Accident Study (GIDAS) database for simulation study. According to real-world accident investigation, accident reconstructions were conducted using multi-body system (MBS) pedestrian and car models under MADYMO simulation environment to calculate head impact conditions, in terms of head impact velocity, head position and head orientation. In order to study kinematics of adult pedestrian, relationship curves: head impact time, throw distance, head impact velocity and vehicle impact velocity, were computed and logistic regression models: head impact velocity, resultant angular velocity, HIC value, head contact force and head injuries, were developed based on the results from accident reconstructions.The automobile windshield, with which pedestrians come into frequent contact, has been identified as one of the main contact sources for pedestrian head injuries. In order to investigate the mechanical behavior of windshield laminated glass in the caseof pedestrian head impact, windshield FE models were set up using different combination for the modeling of glass and PVB, with various connection types and two mesh sizes (5 mm and 10 mm). Each windshield model was impacted with a standard adult headform impactor in an LS-DYNA simulation environment, and the results were compared with the experimental data reported in the literatures.In order to assess head injury risks of adult pedestrians, accident reconstructions were carried out by using Hybrid III head model based on the real-world pedestrian accidents. The impact conditions were obtained from the MBS simulation, including head impact velocity, head position and head orientation. They were used to set the initial conditions in a simulation of a Hybrid III FE head model striking a windshield FE model. Logistic regression models, Skull Fracture Correlate (SFC), head linear acceleration, Head Impact Power (HIP), HIC value, resultant angular acceleration and head injuries, were developed to study brain injury risk.{...]
Murgatroyd, J. "Impact energy absorption of playground surfaces." Thesis, Queensland University of Technology, 1998.
Знайти повний текст джерелаPress, Jaclyn Nicole. "Biomechanics of Head Impacts in Soccer." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/82521.
Повний текст джерелаMaster of Science
Morris, Tyler Pierce. "Evaluating the Head Injury Risk Associated with Baseball and Softball." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/95889.
Повний текст джерелаMS
Fernandes, Fábio António Oliveira. "Biomechanical analysis of helmeted head impacts: novel materials and geometries." Doctoral thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/21227.
Повний текст джерелаA cortiça é um material celular natural capaz de suster quantidades consideráveis de energia. Estas características tornam este material ideal para determinadas aplicações como a proteção de impactos. Considerando equipamentos de segurança passiva pessoal, os materiais sintéticos são hoje em dia os mais utilizados, em particular o poliestireno expandido. Este também é capaz de absorver razoáveis quantidades de energia via deformação permanentemente. Por outro lado, a cortiça além de ser um material natural, é capaz de recuperar grande parte da sua forma após deformada, uma característica desejada em aplicações com multi-impacto. Neste trabalho é efetuada uma avaliação da aplicabilidade da cortiça em equipamentos de segurança pessoal, especificamente capacetes. Vários tipos de cortiça aglomerada foram caracterizados experimentalmente. Impactos foram simulados numericamente para avaliar a validade dos modelos constitutivos e as propriedades utilizadas para simular o comportamento da cortiça. Capacetes foram selecionados como caso de estudo, dado as energias de impacto e repetibilidade de impactos a que estes podem ser sujeitos. Para avaliar os capacetes de um ponto de vista biomecânico, um modelo de cabeça humana em elementos finitos foi desenvolvido. Este foi validado de acordo com testes em cadáveres existentes na literatura. Dois modelos de capacete foram modelados. Um modelo de um capacete rodoviário feito de materiais sintéticos, o qual se encontra disponível no mercado e aprovado pelas principais normas de segurança de capacetes, que serve de referência. Este foi validado de acordo com os impactos da norma. Após validado, este foi avaliado com o modelo de cabeça humana em elementos finitos e uma análise ao risco de existência de lesões foi efetuado. Com este mesmo capacete, foi concluído que para incorporar cortiça aglomerada, a espessura teria de ser reduzida. Então um novo modelo de capacete foi desenvolvido, sendo este uma espécie de modelo genérico com espessuras constantes. Um estudo paramétrico foi realizado, variando a espessura do capacete e submetendo o mesmo a duplos impactos. Os resultados destes impactos e da análise com o modelo de cabeça indicaram uma espessura ótima de 40 mm de cortiça aglomerada, com a qual o capacete tem uma melhor resposta a vários impactos do que se feito de poliestireno expandido.
Cork is a natural cellular material capable of withstanding considerable amounts of energy. These features make it an ideal material for some applications, such as impact protection. Regarding personal safety gear, synthetic materials, particularly expanded polystyrene, are typically used. These are also able to absorb reasonable amounts of energy by deforming permanently. On the other hand, in addition to cork being a natural material, it recovers almost entirely after deformation, which is a desired characteristic in multi-impact applications. In this work, the applicability of agglomerated cork in personal safety gear, specifically helmets, is analysed. Different types of agglomerated cork were experimentally characterized. These experiments were simulated in order to assess the validity of the constitutive models used to replicate cork's mechanical behaviour. In order to assess the helmets from a biomechanical point of view, a finite element human head model was developed. This head model was validated by simulating the experiments performed on cadavers available in the literature. Two helmet models were developed. One of a motorcycle helmet made of synthetic materials, which is available on the market and certified by the main motorcycle helmets safety standards, being used as reference. This helmet model was validated against the impacts performed by the European standard. After validated, this helmet model was analysed with the human head model, by assessing its head injury risk. With this helmet, it was concluded that a thinner helmet made of agglomerated cork might perform better. Thus, a new helmet model with a generic geometry and a constant thickness was developed. Several versions of it were created by varying the thickness and subjecting them to double impacts. The results from these impacts and the analyses carried out with the finite element head model indicated an optimal thickness of 40 mm, with which the agglomerated cork helmet performed better than the one made of expanded polystyrene.
Campolettano, Eamon Thomas. "On-Field Measurement of Head Impacts in Youth Football: Characterizing High Magnitude Impacts and Assessing Balance Outcomes." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/77657.
Повний текст джерелаMaster of Science
Daniel, Ray. "Head Acceleration Measurements in Helmet-Helmet Impacts and the Youth Population." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/32063.
Повний текст джерелаMaster of Science
Nadarasa, Jeyendran. "Modélisation par éléments-finis des traumatismes crâniens du nourrisson." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAD003.
Повний текст джерелаImpact biomechanics aim at studying injuries, establishing tolerance limit and propose efficient protective systems. The finite-element method permits to study precisely injury mechanisms by avoiding questions linked to experimentation and ethics. For the human adult head biomechanics, this methodology was taken earlier and several stable and validated models exist worldwide, among which one can find the Strasbourg University Finite Element Head Model (SUFEHM). This thesis aims at widening the human head biomechanics by studying infant head trauma. The research work has been conducted in two steps. In the first one, an infant eye numerical model was developed in order to study retinal hemorrhages. The second one consisted in improving the infant head model by integrating medical images data such as axonal fiber density and orientations into the infant brain and by validating the mechanical formulation of the infant skull in order to predict skull fractures
MacAlister, Anna Margaret. "Head Impacts in Hockey and Youth Football: Biomechanical Response and Helmet Padding Characteristics." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/76964.
Повний текст джерелаMaster of Science
Wu, Lyndia C., Calvin Kuo, Jesus Loza, Mehmet Kurt, Kaveh Laksari, Livia Z. Yanez, Daniel Senif, et al. "Detection of American Football Head Impacts Using Biomechanical Features and Support Vector Machine Classification." NATURE PUBLISHING GROUP, 2017. http://hdl.handle.net/10150/627166.
Повний текст джерелаCanaple, Bertrand. "Contribution au développement d'un outil de simulation prédictif des lésions cranio-encéphaliques par reconstruction d'accidents de la circulation." Valenciennes, 2001. https://ged.uphf.fr/nuxeo/site/esupversions/2da57bb0-4297-47b6-afd3-65f19f98f2b1.
Повний текст джерелаIn traffic accidents, head injuries are considered to be frequent and serious. Because of the various kind of injuries (bone, vascular and neurology) and limitations of the biomechanical representation of the head, old and simple protection criteria (such as the HIC or the peak linear acceleration of the head ) are still used in standard tests. Contrary to the others body segments, it’s not possible to use a direct approach (consisting in impacting biological human body models) to determine the tolerance and the threshold. In order to better represent the physical phenomena, an original research methodology that is based on traffic accidents reconstruction is developed. The first batch of works deals with the definition of a new finite element model of the head. The features concern the cerebro-spinal fluid described by an hyperelastic material defined by a sliding without separation interface with the brain in order to represent its relative movement with respect to the skull. The confrontations with experimental tests made on cadaver’s head confirm the model prediction. An accident reconstruction methodology has been developed. It is based on kinematics reconstruction, experimental reconstruction of the vehicle’s collision, multibody simulation of the second collision and study of the internal head response with the head model. This reconstruction approach is then validated on a real automotive accident. Furthermore, the development of a generic model applied to motorcycle accidents is also analysed. From the results of the automotive accident reconstruction, the intercerebral contusion observed has been bridged to a particular time duration of a certain level of von Mises stresses
Khatib, Ali. "A Comparison of Brain Trauma Characteristics from Head Impacts for Lightweight and Heavyweight Fighters in Professional Mixed Martial Arts." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39712.
Повний текст джерелаBeeman, Stephanie Marie. "Biomechanical Response of Human Volunteers and Surrogates in a Variety of Loading Regimes." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/78305.
Повний текст джерелаPh. D.
Kang, Yun Seok. "Evaluation of Biofidelity of Anthropomorphic Test Devices and Investigation of Cervical Spine Injury in Rear Impacts: Head-Neck Kinematics and Kinetics of Post Mortem Human Subjects." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313554843.
Повний текст джерелаDelille, Rémi. "Contribution à la compréhension du comportement mécanique de l'os du crâne humain sous différents moyens de conservation et de sollicitation." Phd thesis, Université de Valenciennes et du Hainaut-Cambresis, 2007. http://tel.archives-ouvertes.fr/tel-00270740.
Повний текст джерелаDes essais ont été réalisés sur 20 SHPM (Sujet Humain Post Mortem) « frais ». Un protocole spécifique a été développé afin de prélever 19 éprouvettes par crâne. Au total, 380 échantillons ont été testés en flexion trois points. Les courbes effort/déplacement ont servi de référence pour l'identification du comportement élastique. De nombreuses relations par zones et orientations osseuses ont été obtenues.
Des essais de cyclage dans la zone élastique ont été réalisés sur 105 échantillons prélevés sur 7 SHPM congelés. L'effet de la vitesse de sollicitation a été étudié. Cette seconde campagne permet de comparer les éprouvettes en fonction de leur mode de conservation. Une corrélation a été mise en évidence et a permis d'extrapoler le module d'élasticité à l'état « frais » d'un SHPM testé congelé.
Ces deux campagnes d'essais ont permis d'aboutir à une corrélation entre le module d'élasticité équivalent et les propriétés géométriques (épaisseur et densité) d'un SHPM « frais ».
Les derniers travaux ont porté sur le développement d'un nouveau prototype de tête. Pour cela, 7 calottes, provenant de SHPM congelés, ont été testées en compression. Les propriétés élastiques du prototype sont issues des campagnes expérimentales précédentes et présentent une distinction entre chaque zone. Ce prototype a été validé par des essais statiques et dynamiques en compression dans différentes zones osseuses.
Strickland, John Scott. "Experimental Analysis of Protective Headgear Used in Defensive Softball Play." UNF Digital Commons, 2019. https://digitalcommons.unf.edu/etd/880.
Повний текст джерелаAmewoui, Ekoue-Adjoka Foli Noël. "Impact de l’opération de perçage sur l’intégrité des tissus osseux : modélisation et expérimentation." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0095.
Повний текст джерелаBone drilling is commonly practised in various surgical operations for orthosynthesis screws insertion or placement of dental and cochlear implants. During bone drilling procedure, the thermomechanical constraints resulting from the tool-bone interaction can damage the bone tissues in the vicinity of the drilling area. Thus, a significant increase in temperature can cause thermal osteonecrosis. It is therefore important to optimize the operating conditions (spindle speed and feed rate, geometry of the drill, drilling operation strategy ...) in order to reduce the risk of damage to bone tissues. To do this, it is necessary to analyse and understand the effects of cutting conditions on the mechanisms controlling the drill-bone interaction. The present work aims to contribute to the understanding of these mechanisms by combining an experimental approach with numerical and analytical modelling. The experimental study investigates the effect of the cutting speed, feed rate of the drill and the microstructure of the drilled area on the resulting cutting forces (thrust force and axial torque) and temperature rise during the drilling of porcine bone specimens and biomechanical test materials (Sawbones). These materials have the advantage of a uniform microstructure per given sample unlike bone. Numerical models of orthogonal cutting and bone drilling are implemented using the Finite Element code ABAQUS / Explicit. The purpose of this development is to analyse the influence of bone constitutive and damage laws on the model predictions (cutting mechanism, temperature and cutting forces). In order to propose a simplified approach, an analytical modelling based on moving heat source theory is developed for predicting bone thermal response. The relevance and limits of the approach proposed is shown through experimental validation
Anderson, Robert William Gerard. "A study on the biomechanics of axonal injury." 2000. http://hdl.handle.net/2440/37911.
Повний текст джерелаThesis (Ph.D.)--Mechanical Engineering, 2000.
Anderson, Robert William Gerard. "A study on the biomechanics of axonal injury." Thesis, 2000. http://hdl.handle.net/2440/37911.
Повний текст джерелаThesis (Ph.D.)--Mechanical Engineering, 2000.
Palomar, Toledano Marta. "Assessment of head injury risk caused by impact using finite element models." Doctoral thesis, 2020. http://hdl.handle.net/10251/135254.
Повний текст джерела[CAT] Les càrregues d'impacte son la font primària de lesions al cap i poden resultar en un rang de severitat des de lleu a greu. Degut als múltiples entorns en que poden desencadenar-se lesions per impacte (accidents automobilístics, esports, caigudes accidentals, violència), aquestes poden afectar potencialment a tota la població independentment del seu estat de salut. Malgrat el creixent esforç en investigació per comprendre la biomecànica de les lesions per traumatisme al cap, encara no és del tot possible realitzar prediccions precises ni prevenir aquestos esdeveniments. En aquesta Tesi, s'han estudiat alguns aspectes del comportament a impacte dels diferents teixits biològics involucrats mitjançant el desenvolupament d'un model numèric de cap humà a partir d'imatges de tomografia computeritzada (TAC). S'han realitzat simulacions en elements finits (EF) d'assajos experimentals de la literatura amb la finalitat de validar el model numèric desenvolupat, establint unes propietats mecàniques adequades per a cadascun dels seus constituents. D'aquesta manera es pot aconseguir una predicció del risc de sofrir danys traumàtics. Part d'aquesta Tesi es centra en l'entorn balístic, específicament en cascs de combat antibales, els quals són susceptibles de causar traumatisme degut a l'elevada deformació que sofrixen durant l'impacte. Previament a l'estudi d'aquests fenòmens d'alta velocitat, s'han realitzat assajos experimentals i numèrics per a caracteritzar la resposta mecànica d'alguns materials compostos en condicions d'impacte a baixa velocitat. Al començament d'aquesta Tesi s'ha realitzat una revisió de l'estat de l'art sobre els criteris existents per quantificar el trauma cranioencefàlic. Aquest és un aspecte clau per a les simulacions numèriques, ja que l'utilitat d'alguns d'aquestos criteris per a la predicció de lesions cerebrals és encara un debat obert. Mitjançant EF s'han realitzat simulacions numèriques d'impactes balístics en un cap protegit amb un casc de combat. Gràcies a la posterior aplicació de diferents criteris de dany sobre els resultats obtinguts s'ha evaluat el nivell de protecció que asseguren els protocols d'acceptació de cascs de combat, així com les estratègies per a determinar les seues talles. S'ha demostrat que les normatives existents són capaces de mitigar alguns mecanismes de trauma però no aconseguixen prevenir altres com els gradients de pressions intracranials. A més, s'ha demostrat que algunes estratègies per determinar les talles més comunament adoptades pels fabricants (com produir només un tamany de calota i adaptar el gruix de les escumes interiors a les diferents dimensions dels subjectes) haurien de ser reconsiderades ja que existeix un major risc de traumatisme quan la distància entre el cap i la calota del casc no és suficient. Seguint la línia de proteccions personals, alguns dels materials compostos comunament utilitzats en la indústria de l'armament s'han combinat per a crear distintes possibles configuracions de calota amb la finalitat d'optimitzar la relació entre pes i protecció. Materials lleugers com l'UHMWPE han resultat en un comportament menys eficient que el d'apilats de teixit d'aramida a l'hora de limitar la BFD (deformació màxima a la calota del casc a la zona d'impacte). Cap al final de la Tesi es presenta un model numèric detallat de cap humà, que inclou trenta-tres de les estructures anatòmiques principals. Aquest model s'ha desenvolupat per a la simulació d'un accident eqüestre en el qual apareixen múltiples lesions cranioencefàliques. Principalment, es pretén establir un criteri mecànic per a la predicció de l'hematoma subdural (HS) basat en la ruptura dels vasos sanguinis intracranials. S'ha proposat un valor umbral de ruptura en tensions de 3.5 MPa, pero tant aquest límit com la ubicació del vas danyat són altament dependents de l'anatomia específica de cada subjecte.
[EN] Impact loading is the primary source of head injuries and can result in a range of trauma from mild to severe. Because of the multiple environments in which impact-related injuries can take place (automotive accidents, sports, accidental falls, violence), they can potentially affect the entire population regardless of their health conditions. Despite the increasing research effort on the understanding of head impact biomechanics, accurate prediction and prevention of traumatic injuries has not been completely achieved. In this Thesis, some aspects of the impact behaviour of the different biological tissues involved have been analysed through the development of a numerical human head model from Computed Tomography (CT) images. FE simulations of experimental tests from the literature have been performed and enhanced the validation of the head model through the establishment of proper material laws for its constituents, which enable adequate prediction of injury risks. Part of this Thesis focuses on the ballistic environment, especifically in bulletproof composite helmets, which are susceptible to cause blunt injuries to the head because of their large deformation during impact. Prior to the study of these high-speed impacts, experimental tests and finite element (FE) models have been performed to characterise the mechanical response of composite materials subjected to low velocity impact. The implementation of a continuum damage mechanics approach coupled to a Hashin failure criterion and surface-to-surface cohesive relations to the numerical model provided a good matching with the impact behaviour obtained experimentally, capturing the principal damage mechanisms. A review of the head injury criteria currently available in the literature has been performed at the beginning of this Thesis. This is a key issue for the numerical simulations, as the suitability of some criteria to predict head injuries is still an open question. Numerical simulation of ballistic impacts on a human head protected with a combat helmet has been conducted employing explicit FE analysis. The level of protection ensured by helmet acceptance protocols as well as their sizing strategies have been studied and discussed by means of the application of different mechanical-based head injury criteria. It has been demonstrated that current helmet testing standards do mitigate some specific forms of head trauma but fail to prevent other injury mechanisms such as the intracranial pressure gradients within the skull. Furthermore, it has been demonstrated that some well-established helmet sizing policies like manufacturing one single composite shell and adapting the thickness of the interior pads to the different head dimensions should be reconsidered, as there is a great risk of head injury when the distance between the head and the helmet shell (stand-off distance) is not sufficient. Following the line of personal protections, some composite materials commonly employed in the soft body armour industry have been combined into different helmet shells configurations to optimise the ratio of weight-to-head protection. Light materials like UHMWPE appear to be less efficient than integral woven-aramid lay-ups in the limitation of the backface deformation (BFD), the maximum deformation sustained by the helmet at the impact site. A detailed head numerical model including thirty-three of its main anatomical structures has been developed for the simulation of an equestrian accident that resulted in many head injuries. Above all, the establishment of a mechanical criterion for the prediction of subdural hematona (SDH) based on the rupture of the head blood vessels is intended. A stress threshold for vein rupture has been set on 3.5 MPa, but both this limit and the location of vessel failure are highly dependent on the specific anatomy of the subject's vascularity.
Palomar Toledano, M. (2019). Assessment of head injury risk caused by impact using finite element models [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/135254
TESIS
Wright, Alexander David. "Novel Compliant Flooring Systems from Head to Toes: Influences on Early Compensatory Balance Reactions in Retirement-Home Dwelling Adults and on Impact Dynamics during Simulated Head Impacts." Thesis, 2011. http://hdl.handle.net/10012/6015.
Повний текст джерелаChiu, Shi-Hung, and 邱士紘. "The Biomechanical Analysis of the Head and Neck during Rear-end Impact by using Lifemod." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/45369920050460330930.
Повний текст джерела國立中興大學
生物產業機電工程學系
93
Among all the car accidents, the rear-end impact commonly happens and the whiplash injuries to head or neck tends to be the most frequent cases. However, there is still much clinical controversy over such whiplash injuries caused by whiplash effect. In this study, the software ADAMS and LifeMOD are used to establish the model of human head, neck and up-torso. By using this model, it was to simulate rear-end impact and observed the biomechanics analysis in the whiplash effect to cervical spine and the soft tissues of human neck. The result showed that in the initial stage, the flexion occurred in the upper cervical spine and extension in the lower cervical spine. Meanwhile, the cervical spine first formed an S-shaped curve and then bended back totally to forms a C-shaped curve. The maximum horizontal acceleration of head was 1.5 times of the impacted one and arose later during the whiplash effect. Besides, the results in analysis of facet joint showed that when the impact acceleration reached over 7g, the cervical spine might hurt itself because the rotation angle surpassed the physiological value. In the intervertebral disk research, the human head activities which caused cervical spine transformation have contributed to main factor of neck injuries. Apparently, all these testified the accuracy of the established human models by comparing to relative experiments. Upcoming, it will present the whiplash effect more clearly through the establishment of muscles on the model and benefit a lot to clinical diagnosis and injury prevention.
(6622721), Roy J. Lycke. "Investigating and Modeling the Mechanical Contributions to Traumatic Brain Injury in Contact Sports and Chronic Neural Implant Performance." Thesis, 2019.
Знайти повний текст джерела(6237179), Yukai Zou. "Developing Population-Specific Brain Atlases and Monitoring Repetitive Head Impacts for Early-to-Middle Adolescent Collision-Sport Athletes." Thesis, 2020.
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