The brain is a complex organ and its response to the mechanical loads at all strain rates has been nonlinear and inelastic in nature. Split-Hopkinson Pressure Bar (SHPB) high strain rate compressive tests conducted on porcine brain samples showed a strain rate dependent inelastic mechanical behavior. Finite Element (FE) modeling of the SHPB setup in ABAQUS/Explicit, using a specific constitutive model (MSU TP Ver. 1.1) for the brain, showed non-uniform stress state during tissue deformation. Song et al.’s assertion of using annular samples for negating inertial effects was also tested. FE simulation results showed that the use of cylindrical or annular did not mitigate the initial hardening. Further uniaxial stress state was not maintained is either case. Experimental studies on hydration effects of the porcine brain on its mechanical response revealed two different phenomenological trends. The wet brain (~80% water wt. /wt.) showed strain rate dependency along with two unique mechanical behavior patterns at quasi-static and high strain rates. The dry brain’s (~0% water wt. /wt.) response was akin to the response of metals. The dry brain’s response also observed to be strain rate insensitivity in its elastic modulus and yield stress variations. Uncertainty analysis of the wet brain high strain rate data revealed large uncertainty bands for the sample-to-sample random variations. This large uncertainty in the brain material should be taken into in the FE modeling and design stages. FE simulations of blast loads to the human head showed that Pressure played a dominant role in causing blast-related Traumatic Brain Injury (bTBI). Further, the analysis of shock waves exposed the deleterious effect of the 3-Dimensional geometry of the skull in pinning the location of bTBI. The effects of peak negative Pressure at injury sites have been attributed to bTBI pathologies such as Diffuse Axonal Injury (DAI), subdural hemorrhage and cerebral contusion.

No description available.

Mitigation of the blast risk associated with terrorist attacks and accidental explosions threatening critical infrastructure has become a topic of great interest in the civil engineering community, both in Canada and abroad. One method of mitigating blast risk is to retrofit vulnerable structures to resist the impulsive effects of blast loading. A comprehensive re-search program has been undertaken to develop fibre reinforced polymer (FRP) retrofit methodologies for structural and non-structural elements, specifically reinforced concrete slabs and walls, subjected to blast loading. The results of this investigation are equally valid for flexure dominant reinforced concrete beams subject to blast effects. The objective of the research program was to generate a large volume of research data for the development of blast-resistant design guidelines for externally bonded FRP retrofit systems. A combined experimental and analytical investigation was performed to achieve the objectives of the program. The experimental program involved the construction and simulated blast testing of a total of thirteen reinforced concrete wall and slab specimens divided into five companion sets. These specimens were subjected to a total of sixty simulated explosions generated at the University of Ottawa Shock Tube Testing Facility. Companion sets were designed to study one- and two-way bending, as well as the performance of specimens with simply-supported and fully-fixed boundary conditions. The majority of the specimens were retrofitted with externally bonded carbon fibre reinforced polymer (CFRP) sheets to improve overall load-deformation characteristics. Specimens within each companion set were subjected to progressively increasing pressure-impulse combinations to study component behaviour from elastic response up to inelastic component failure. The blast performance of companion as-built and retrofitted specimens was quantified in terms of measured load-deformation characteristics, and observed member behaviour throughout all stages of response. The results show that externally bonded FRP retrofits are an effective retrofit technique to improve the blast resistance of reinforced concrete structures, provided that debonding of the composite from the concrete substrate is prevented. The test results also indicate that FRP retrofitted reinforced concrete structures may survive initial inbound displacements, only to failure by moment reversals during the negative displacement phase. The experimental test data was used to verify analytical techniques to model the behaviour of reinforced concrete walls and slabs subjected to blast loading. The force-deformation characteristics of one-way wall strips were established using inelastic sectional and member analyses. The force-deformation characteristics of two-way slab plates were established using commonly accepted design approximations. The response of all specimens was computed by explicit solution of the single degree of freedom dynamic equation of motion. An equivalent static force procedure was used to analyze the response of CFRP retrofitted specimens which remained elastic after testing. The predicted maximum displacements and time-to-maximum displacements were compared against experimental results. The analysis indicates that the modelling procedures accurately describe the response characteristics of both retrofitted and unretrofitted specimens observed during the experiment.

A hydrocode and an explicit finite element code were used to evaluate functionally graded material impacts, meteor impacts, and split Hopkinson pressure bar specimens. Modeling impacts of functionally graded projectiles revealed that density was the primary material characteristic controlling the shock wave profile. A parametric study of material order for functionally graded armor showed that arranging the weaker material in front created the greater stopping power. By modeling an array of meteor impact scenarios, deformation and stress were shown to occur at great depths and possibly cause tectonic movement, like subduction. Three proposed Hopkinson specimens, which were designed to produce either shear or tensile reactions under compressive loading, were evaluated. For two of these specimens, improved stress and strain equations were presented.

No description available.

No description available.

Cette thèse met l'accent sur la recherche scientifique pour développer une classe de procédés à hautesvitesses de déformation des tôles métalliques en alliages d'aluminium et en acier à haute résistance (AHR).Ces technologies emploient une impulsion de pression de courte durée qui propulse la tôle dans une matrice.Ces procédés sont généralement décrits comme procédés de formage par impulsion de pression (PPF). Letravail proposé dans ce mémoire de thèse a permis de surmonter trois obstacles pour l'utilisation desprocédés PPF et la fabrication à moindre coût de structures légères. Le premier obstacle a été le manque decorrélation entre formabilité et vitesses de déformation qui se développent lors d’un procédé PPF. Nous avonsproposé d’analyser la formabilité et la rupture des tôles, et de caractériser les vitesses de déformation et leurl'hétérogénéité pendant le procédé PPF. Le deuxième obstacle a été le manque de lois constitutives validéespour les métaux déformés par le procédé PPF. Nous avons étudié la microstructure et l'évolution despropriétés mécaniques durant le procédé PPF. Le troisième obstacle est le manque de modèles de formabilitéprédictifs validés pour le procédé PPF. Nous avons utilisé la méthode Marciniak-Kuczynski pour la prédictionde la formabilité de l’alliage AA5182 et de l’acier DP600 sous un large éventail de vitesses de déformation etsous différentes directions de ces vitesses. La combinaison de ces résultats de recherche permet une plusgrande capacité prédictive pour concevoir et développer des procédés PPF pour composants d’automobiledésirés à partir d'aluminium et d’acier AHR. / This thesis focuses on scientific investigation to develop and enable a class of high strain ratesheet metal forming of aluminum alloys and advanced high strength steel (AHSS). These technologiesemploy a short duration pressure‐pulse to drive sheet metal into single‐sided dies, and can generally bedescribed as pulse pressure forming (PPF) processes. The work under this thesis has overcome threetechnical barriers to using PPF processing for more cost effective lightweight vehicles. The first technicalbarrier was the lack of understanding of the interrelationship between formability and measured strainrates that develop during PPF processing. The work under this thesis investigated the formability andfracture of sheet metals during PPF, and characterized the strain rate and the strain rate heterogeneity.The second technical barrier was the lack of a validated constitutive model for lightweight materialsduring PPF processing. The work under this thesis investigated the microstructure and mechanicalproperty evolution in metals during PPF. The third technical barrier was the lack of validated andpredictive formability models for PPF processes. The work under this thesis used the Marciniak andKuczynski method of formability prediction to predict the formability of both aluminum alloy AA5182and AHSS alloy DP600 across a wide range of strain rates and strain rate directions. The combination ofthese research results permits a more predictive capacity to design and develop PPF manufacturingprocesses for a desired automotive component made from aluminum alloys and AHSS.

A capacidade de carga de estacas pode ser determinada experimentalmente através de provas de cargas estáticas ou de ensaios de carregamentos dinâmicos, conforme as prescrições da NBR 6122:2010. Na sua forma tradicional, o ensaio de carregamento dinâmico, fundamentado na teoria da equação da onda unidimensional, consiste em aplicar uma sequência de golpes de energia aproximadamente constante no conjunto de amortecedores colocado sobre a estaca e medir, no seu topo, valores de deformação específica e aceleração em função do tempo. Esse ensaio evoluiu ao longo dos anos com o avanço da tecnologia e com o desenvolvimento de modelos numéricos, que permitem simular a prova de carga estática na estaca ensaiada dinamicamente. Outra evolução, uma verdadeira \"revolução\", foi a introdução do método de energia crescente proposto por Aoki (1989). O presente estudo é uma iniciativa de aprofundamento do método de energia crescente com foco na definição da envoltória máxima de resistência lateral, permitindo recuperar as mobilizações dos atritos no fuste da estaca, perdidas em golpes anteriores ao de máxima energia aplicada, principalmente em camadas próximas ao topo da estaca. Este procedimento foi denominado Método da Envoltória Máxima de Resistência Lateral. É apresentada uma revisão bibliográfica envolvendo provas de cargas estáticas e ensaios de carregamentos dinâmicos para determinar a capacidade de carga em estacas, junto com os métodos analíticos, empíricos e semiempíricos, disponíveis na literatura técnica. São apresentados três estudos de casos de obras no Estado de São Paulo, nos quais foram realizados ensaios estáticos e dinâmicos nas mesmas estacas, sendo 2 pré-moldadas e uma escavada. A aplicação do Método da Envoltória Máxima de Resistência Lateral conduziu a uma definição de maiores capacidades de carga através do CAPWAP, com curvas carga-recalque simuladas aderentes às das provas de cargas estáticas. Além disso, permitiu estimativas mais precisas do efeito de \"setup\" a longo prazo e forneceu maiores detalhes a respeito do comportamento do sistema estaca-solo. / The load capacity of piles can be experimentally determined through static load tests or high strain dynamic load tests, as stated with the requirements of NBR 6122:2010. In its traditional form, the dynamic load test, based on the theory of the one-dimensional wave equation, consists of applying a sequence of constant energy blows upon the pile, and by these blows are measured values of deformation and acceleration as a function of time. The traditional method has evolved through technological advances along the years, with the development of numerical models that simulate the static load test of a pile dynamically tested. Another evolution, a true called \"revolution\", was the introduction of a method of increasing energy test created and proposed by Aoki (1989). The traditional method has evolved through technological advances along the years. The present study is an initiative to deepen the increasing energy method focusing on the definition of the maximum lateral resistance envelope, allowing recovering the mobilized resistance along the shaft, lost in blows prior to the maximum applied energy, especially in layers close to the top of the pile. This procedure was called the Maximum Envelope of Shear Strength. A review is presented involving static load tests and dynamic load tests to determine the load capacity on piles, together with the analytical, empirical and semi empirical methods available in the literature. Three case studies from the State of São Paulo are presented, where static and dynamic tests were performed on the same piles, two driven and one cast-in-place piles. The application of the Maximum Envelope of Shear Strength led to a definition of higher load capacities through the CAPWAP, with simulated load-displacement curves with good correlations in comparison with the static load tests. In addition, it allowed for more accurate estimates of the long-term \"set-up\" effect and provided more detail about the behavior of the pile-soil system.

The strain rate dependent behaviour of fine grained soils is an important aspect of geotechnical engineering. During dynamic or rapid events such as earthquakes and rapid pile testing, a fine grained soil will display significantly different behaviour than may be observed over the long life span of a structure. There is currently little understanding of the factors which influence the behaviour of fine grained soils during dynamic events (extremely high strain rates), making their response difficult to predict. This research investigates the behaviour of fine grained soils subjected to a wide range of constant strain rates in monotonic triaxial compression testing. Each test is conducted under drained conditions to observe the behaviour of soils as they transition from a drained response at lower strain rates, through to an undrained or viscous response at higher strain rate tests. Where the response of soils is drained or partially drained, higher strain rate tests measure a decrease in strength. The point of transition from partially drained to undrained behaviour corresponds to the lowest strain rate dependent strength. Further tests at higher strain rates measure consistently greater strength. The strain rate dependence of three fine grained soils is investigated, enabling a comparison of strain rate effects with soil index properties. The influence of initial state on the strain rate dependence of these Kaolin based model soils is also evaluated. The drained to partially drained response of the soils to strain rate increase is controlled by the coefficient of consolidation. Tests at high strain rates show the undrained or viscous strain rate effect on strength is related to liquidity index. Local strain instrumentation allowed comparison of strain rate effects on small strain stiffness. At higher strain rate the soils display increasingly linear behaviour. At non-linear elastic strains, liquidity index appears to control the magnitude of the strain rate effects on stiffness.

A capacidade de carga de estacas pode ser determinada experimentalmente através de provas de cargas estáticas ou de ensaios de carregamentos dinâmicos, conforme as prescrições da NBR 6122:2010. Na sua forma tradicional, o ensaio de carregamento dinâmico, fundamentado na teoria da equação da onda unidimensional, consiste em aplicar uma sequência de golpes de energia aproximadamente constante no conjunto de amortecedores colocado sobre a estaca e medir, no seu topo, valores de deformação específica e aceleração em função do tempo. Esse ensaio evoluiu ao longo dos anos com o avanço da tecnologia e com o desenvolvimento de modelos numéricos, que permitem simular a prova de carga estática na estaca ensaiada dinamicamente. Outra evolução, uma verdadeira \"revolução\", foi a introdução do método de energia crescente proposto por Aoki (1989). O presente estudo é uma iniciativa de aprofundamento do método de energia crescente com foco na definição da envoltória máxima de resistência lateral, permitindo recuperar as mobilizações dos atritos no fuste da estaca, perdidas em golpes anteriores ao de máxima energia aplicada, principalmente em camadas próximas ao topo da estaca. Este procedimento foi denominado Método da Envoltória Máxima de Resistência Lateral. É apresentada uma revisão bibliográfica envolvendo provas de cargas estáticas e ensaios de carregamentos dinâmicos para determinar a capacidade de carga em estacas, junto com os métodos analíticos, empíricos e semiempíricos, disponíveis na literatura técnica. São apresentados três estudos de casos de obras no Estado de São Paulo, nos quais foram realizados ensaios estáticos e dinâmicos nas mesmas estacas, sendo 2 pré-moldadas e uma escavada. A aplicação do Método da Envoltória Máxima de Resistência Lateral conduziu a uma definição de maiores capacidades de carga através do CAPWAP, com curvas carga-recalque simuladas aderentes às das provas de cargas estáticas. Além disso, permitiu estimativas mais precisas do efeito de \"setup\" a longo prazo e forneceu maiores detalhes a respeito do comportamento do sistema estaca-solo. / The load capacity of piles can be experimentally determined through static load tests or high strain dynamic load tests, as stated with the requirements of NBR 6122:2010. In its traditional form, the dynamic load test, based on the theory of the one-dimensional wave equation, consists of applying a sequence of constant energy blows upon the pile, and by these blows are measured values of deformation and acceleration as a function of time. The traditional method has evolved through technological advances along the years, with the development of numerical models that simulate the static load test of a pile dynamically tested. Another evolution, a true called \"revolution\", was the introduction of a method of increasing energy test created and proposed by Aoki (1989). The traditional method has evolved through technological advances along the years. The present study is an initiative to deepen the increasing energy method focusing on the definition of the maximum lateral resistance envelope, allowing recovering the mobilized resistance along the shaft, lost in blows prior to the maximum applied energy, especially in layers close to the top of the pile. This procedure was called the Maximum Envelope of Shear Strength. A review is presented involving static load tests and dynamic load tests to determine the load capacity on piles, together with the analytical, empirical and semi empirical methods available in the literature. Three case studies from the State of São Paulo are presented, where static and dynamic tests were performed on the same piles, two driven and one cast-in-place piles. The application of the Maximum Envelope of Shear Strength led to a definition of higher load capacities through the CAPWAP, with simulated load-displacement curves with good correlations in comparison with the static load tests. In addition, it allowed for more accurate estimates of the long-term \"set-up\" effect and provided more detail about the behavior of the pile-soil system.