Concussions are a problem in competitive sports with growing concern over the acute and long-term consequences of repetitive head trauma. Participation in sport increases risk of concussion, particularly contact sports including rugby, hockey and football (Harmon et al., 2013). In rugby league, there are between 8.0-17.5 concussions/1000 player hours, representing roughly 10-15% of all injuries in the sport (Gardner et al., 2015). Shoulder, head, hip and knee are reported to be the most common regions that impact the head and are responsible for the greatest number of concussive injuries in rugby (Cusimano et al., 2013; Fuller et al., 2010; Gardner et al., 2014; Toth, Mcneil, & Feasby, 2005). In each of the common injury events reported in elite men’s rugby, there are unique combinations of impact conditions which include effective mass, compliance, velocity and location of impact. The head-to-head event represents a low mass, low compliance event, whereby the hip and shoulder-to-head collisions represents high mass, high compliance events. Scientists have conducted research in an effort to describe incidence and mechanisms of concussive injury in rugby, however, little is known about the biomechanics of head injury in the sport (Fréchède & Mcintosh, 2009; Fréchède & McIntosh, 2007; McIntosh et al., 2000). The purpose of this thesis is to characterize dynamic response and brain tissue deformation for (1) hip-to-head, (2) shoulder-to-head, (3) knee-to-head, and (4) head-to-head concussion events in men’s rugby. Twenty-nine (29) impact videos of diagnosed concussive injuries associated with the four common injury events were reconstructed in the Neurotrauma Impact Science Lab. Head-to-head impacts were reconstructed in this study using a pendulum system, while hip, shoulder and knee to head impacts were reconstructed using the pneumatic linear impactor. Results of this study demonstrate that the common injury events resulting in concussion in elite men’s rugby have different dynamic response characteristics. Head-to-head events produced significantly greater peak linear and peak rotational acceleration, however no significant differences in maximum principal strain between the injury events. Results of this study can be useful in reducing rates and severity of concussive injury in rugby.

Fossil tracks represent the only direct record of behaviour and locomotion of extinct animals. A computer model using finite element analysis (FEA) has been developed to simulate vertebrate track formation in cohesive substrates. This model has been designed for, and successfully run on, high performance computing (HPC) resources. A number of individual studies were carried out using the computer model to simulate both abstract indenters and virtual dinosaur autopodia. In addition to the simulation studies, two fossil tracks were described, including the first report of bird tracks at the Mammoth Site of Hot Springs, South Dakota (USA) and a re-description of a 'dinosaur tail drag' as the trace of a crocodilian. Using the computer model, it has been shown that in a wet, soft mud the indentation of a non-webbed virtual tridactyl foot created a resultant track with features analogous to 'webbing' between digits. This 'webbing' was a function of sediment deformation and subsequent failure in 3D, specific to rheology. Apparent webbing impressions were clearly developed only within a limited range of sediment conditions and pedal geometry. Indenter (pedal) geometry and morphology affect track depth independently of substrate and loading parameters. More complex morphologies interact with the cohesive substrate creating a lower effective load than that applied. In non-cohesive substrates such as sand, this effect is reversed, and it is the more compact morphologies that indent to a lesser degree. Virtual sauropod tracks were modelled, based on published soft tissue reconstructions of autopodia anatomy, and published mass/centre of mass estimates. It was shown that foot morphology and differential loading between fore- and hind- limbs leads to a range of substrates in which only the manus or pes are able to generate tracks. This offers a new mechanism for the formation of manus-only sauropod trackways, previously interpreted as having been made by swimming dinosaurs. A series of tracks were simulated using input data (loads, pedal morphologies) from four different dinosaurs (Brachiosaurus, Tyrannosaurus, Struthiomimus, and Edmontosaurus). The cohesive substrates used displayed a 'Goldilocks' effect, allowing the formation for tracks only for a very limited range of loads for any given foot. In addition, there was a strong bias toward larger animals, both in homogeneous and theoretically heterogeneous substrates. These findings imply that interpretations from track assemblages must consider that only a small proportion of the total fauna present may be recorded as a track assemblage due to substrate properties. The use of FEA to simulate dinosaur track formation has been shown to be successful, and offers a number of advantages over physical modelling including; consistency between experiments, specific control over input variables, rapid undertaking of repeatable experiments, and the ability to view subsurface deformation non-destructively. It is hoped that this work will lead to an increased interest in modelling tracks, and offer a quantitative method for studying fossil tracks.

This dissertation forms part of a research project assigned to the University of Pretoria by Eskom (the primary electricity utility in South Africa). The project aims to address, amongst others, the limitations imposed by shaft runout on the usable frequency range of diagnostic data measured by eddy current proximity probes on turbogenerator shafts. This research includes an experimental investigation into the effects of artificially induced faults on a laboratory-scale rotor system, the development and analysis of a mathematical (numerical) model of this rotor system and the development of data processing techniques (including artificial intelligence) to determine the rotor’s condition, faults and diagnostic signal parameters from both the experimental and numerical results. Furthermore, a methodology is to be developed to perform runout compensation in an unsupervised manner. These techniques are then to be implemented for proximity probe vibration data measured on turbogenerators. As part of the research project, this dissertation specifically focuses on the development and rotor dynamic analysis of numerical (finite element) models of the experimental (laboratory-scale) rotor system (using finite element software MSC.Nastran), including gyroscopic effects, a nonlinear force model for the hydrodynamic journal bearing of the rotor system (capable of capturing oil whirl and oil whip instabilities) as well as simulated faults (such as unbalance and rotor-stator rubbing). Since MSC.Nastran does not have a built-in nonlinear hydrodynamic journal bearing model, a custom model of such a bearing was developed and incorporated into the finite element solver, further expanding its already powerful rotor dynamic modelling capabilities. Rotor dynamic analyses performed include the calculation of critical speeds (synchronous complex modes analysis), Campbell diagrams (asynchronous complex modes analysis), steady state frequency response due to unbalance (synchronous frequency response analysis) and nonlinear transient response during rotor run-up. Amongst others, this dissertation explores the seemingly largely unexplored/undocumented capability of finite element software MSC.Nastran to perform rotor dynamic analyses using rotor models constructed with three-dimensional elements. Software (MATLAB code) was also developed to perform post-processing of the simulation results as well as signal processing for investigating the spectral content of transient results. The support structure of the laboratory-scale rotor system was experimentally characterised and an experimental modal analysis was performed on the rotor (excluding its support structure) and its results used to update the finite element rotor models. The transient dynamic response of the experimental rotor system during run-up due to unbalance and rubbing was also analysed in order to validate the developed numerical rotor system models. The numerical results are found to be in good agreement with the experimental results. / Dissertation (MEng)--University of Pretoria, 2015. / Mechanical and Aeronautical Engineering / Unrestricted

Orientador: Paulo Henrique Ferreira Caria / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-26T23:57:45Z (GMT). No. of bitstreams: 1 Croci_CarlaScanavini_D.pdf: 2191804 bytes, checksum: 241804b941eb07ee59e376a484582b5f (MD5) Previous issue date: 2015 / Resumo: O tratamento da má oclusão de Classe II deve incluir distalização dos molares superiores e restrição ao deslocamento anterior da maxila, quando causada por protrusão maxilar. Quando comprometida por características dentoalveolares, apenas a distalização de molares superiores é necessária. Pouco se sabe sobre o modo como as forças aplicadas aos molares superiores são dissipadas ao osso e alvéolo do primeiro molar superior. Utilizando os melhores benefícios do Método dos Elementos Finitos, este estudo tem como objetivo elucidar os aspectos biomecânicos envolvendo a distalização dos molares superiores, após a aplicação de forças externas de direção distal aos primeiros molares superiores com diferentes magnitudes e vetores de força. Foi desenvolvido um modelo analítico a partir de imagens tomográficas com espessura de corte de 3mm. As imagens foram visualizadas no programa Mimics Materialize 10.01 e segmentadas para a obtenção da maxila e dos dentes superiores. Cada dente foi modelado isoladamente e introduzido no modelo da maxila, de tal modo que o modelo final incluiu a maxila com todos os dentes superiores, com seus pontos de contato. A partir daí foi construído um modelo CAD tridimensional, pelo processo reverso (Rhinoceros 3D 4.0 software). O modelo final pode ser exportado para o programa de Elementos Finitos (Ansys 14.0) para a geração da malha final. Uma força concentrada de 450 g foi aplicada aos molares superiores considerando 3 angulos de tração: alta (+30°), horizontal (0°) e baixa (-30º). A força aplicada gerou estresse de Von Mises dissipado para a parte posterior da maxila na tração alta, e para a parte anterior da maxila para as trações horizontal e baixa. Foram visualizadas áreas de estresse de tração nos molars superiores, em seus alvéolos e na parte anterior da maxila para as trações baixa e horizontal e estresse de compressão na crista zigomaticoalveolar para a tração alta. No alvéolo, como pode ser visualizado nos resultados para a tração baixa foi encontrado estresse de compressão na face palatina do alvéolo do primeiro molar superior e no palato, enquanto a tração alta gerou estresse de compressão na face distovestibular do alvéolo do primeiro molar superior / Abstract: The treatment of Class II malocclusion must include upper molar distalization and restriction of the anterior displacement of the maxilla, when its caused by maxillary protrusion. When compromised with dentoalveolar characteristics, only upper molars distalization is needed. Little is known how forces applied to upper molars are dissipated to its alveolus and to the bone. Using at best the benefits of Finite Element Analisys, this study aimed to elucidate the biomechanical aspects involving upper molars distalization, after applying extra-oral forces on the upper molars in distal direction with different magnitudes and vectors. It was developed an analytical model from CT images with both slice thickness and a scan increment of 3 mm. The CT scans were read into visualization software (Software Mimics Materialize 10.01), where the images were segmented by thresholding to obtain maxilla and upper teeth. Each tooth was modeled separately and introduced in maxilla's model, such way that final model included all maxillary teeth engaged in its base with contact points between them, and built a three-dimensional CAD model, by reverse process (Rhinoceros 3D 4.0 software). These models could then be read into a FE Program (Ansys 14.0) for mesh generation. A concentrated force of 450g was applied on the upper molars considering three angles of pull: high (+30°), horizontal (0°) and low (-30º). The force applied caused Von Mises stresses dissipated to posterior part of maxilla in high traction, and anterior part of maxilla to low and horizontal traction. Tensile stress areas were seen on teeth, upper molars alveolus and anterior part of maxilla to low and horizontal traction and posterior part of maxilla to high traction with compressive stress on zygomatic alveolar crest. In the alveolus, as can be seen on the results, low and horizontal traction generate a compression stress on the upper molars alveolus distolingual surface and in the palate; high traction generate a compression stress on the upper molars alveolus distobuccal surface / Doutorado / Anatomia / Doutora em Biologia Buco-Dental

Orientador: Lourenço Correr Sobrinho / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-28T02:03:49Z (GMT). No. of bitstreams: 1 LyraeSilva_JoaoPaulo_D.pdf: 5649364 bytes, checksum: 4a23d0622075770d464eab54068e0f3f (MD5) Previous issue date: 2015 / Resumo: Os objetivos neste estudo foram (1) investigar a influência de diferentes métodos de ensaio de resistência à flexão de cerâmicas odontológicas de acordo com a norma ISO 6872; (2) avaliar o efeito do proporcionamento do teste de resistência à flexão biaxial para cerâmicas odontológicas por Análise de Elementos Finitos. Estudo 1 - dez discos em cera (Ø 12 mm x espessura de 1.2 mm) e barras em resina acrílica (25 mm de comprimento x 5 mm de espessura e 2 mm de altura) foram usinadas usando o sistema CAD/CAM. Em seguida, os padrões em cera e resina usinados foram incluídos em revestimento para técnica de cera perdida e pastilhas de cerâmica à base de disilicato de lítio foram injetadas. Para a análise de elementos finitos, três modelos tridimensionais foram gerados usando elementos hexaédricos e a análise foi realizada de acordo com os testes. Estudo 2 - três modelos tridimensionais de elementos finitos para teste de resistência à flexão biaxial foram gerados usando elementos hexaédricos simulando as condições da ISO 6872 e em proporções dimensionais de 75% e 50%. Todas as pontas aplicadoras foram consideradas superfícies de contato e uma carga de 120 N foi aplicada. Os materiais foram considerados como homogêneos, lineares, elásticos e isotrópicos. Os discos cerâmicos assumiram as propriedades mecânicas do dissilicato de lítio (96 GPa e 0,23 coeficiente de Poisson). Fricção entre os sistemas de carga e os cilindros foi desconsiderada. Restrições foram aplicadas nas extremidades do disco cerâmico, para evitar o deslocamento do espécime. Análise estática estrutural de contato foi considerada linear (MSC Marc 2010, MSC Software Corporation) e os resultados foram analisados usando von Mises (VM) e Máximo Principal (MPS). No estudo 1, diferenças significantes foram observadas para os valores de resistência à flexão obtidos com diferentes métodos, com maiores valores para resistência à flexão biaxial que para a flexão de três pontos. Maiores concentrações de tensão foram encontradas nas amostras nas áreas correspondentes ao contato da ponta aplicadora e suportes para ambos os métodos. Os resultados no estudo 2 mostram que maior concentração de tensão foi observado no ponto de carregamento e nas áreas de apoio, para todos os modelos do teste. O mesmo padrão de distribuição de tensão foi produzido para as diferentes proporções de piston on three ball. Já no estudo 1, pode-se concluir que: (I) para os valores de resistência à flexão, diferenças estatísticas foram verificadas para o mesmo material, quando foram utilizados diferentes métodos de ensaio (resistência à flexão uniaxial e biaxial). Para o estudo 2, de acordo com as análises de Von Mises e Resistência Máxima Principal, reduzindo a proporção da ISO 6872 houve aumento de concentração de tensão, no entanto, a distribuição de tensões nos discos de teste foi influenciada pelos diferentes design do teste / Abstract: The aims of these studies were: (1) to assess the influence of different test methods for assessing the flexural strength of dental ceramics according to the ISO 6872 standard; (2) to evaluate effect of proportioning biaxial flexural strength test on ceramic dental by Finite Element Analysis. Study 1 - ten waxed discs (12 mm in diameter and 1.2 mm thickness) and acrylic resin beams (25 mm length x 5 mm thickness and 2 mm height) were milled using CAD/CAM system. Then, the patterns were invested and lithium disilicate-based ceramic ingots were pressed. For FEA, three-dimensional (3D) models were generated and meshed using eight-node hexahedral elements and analysis was performed according to the tests. Study 2 - three models of 3D finite element of the biaxial flexure tests were generated and meshed using eight-node hexahedral elements simulating conditions of ISO 6872 parameters and its proportion of 75% and 50%. All loading systems were considered contacting surfaces and a 10 N load was applied. The materials were assumed as homogeneous, linear-elastic and isotropic. Ceramic disc assumed the mechanical property of lithium disilicate (96 GPa and 0.23 Poisson¿s ratio). Friction between the loading systems and the cylinder was considered negligible. Constraints were applied at the edges of the ceramic disc, to avoid the dislodgement of the specimen. Static structural analysis considering non-linear contact was performed (MSC Marc 2010, MSC Software Corporation) and the results were analyzed using von Mises (VM), and Maximum Principal (MPS). In study 1, significant differences were observed for the flexural strength values obtained with the different testing methods, with higher values for the biaxial flexural test than for the three point bending. Higher stress concentration was found in the specimens at the contact areas corresponding to the loading point and supports for the both test methods. The results of study 2 showed that more stress concentration was revealed at load point and support areas for all test designs. The same pattern of stress concentration was produced for the different proportions of piston on three ball test. For study 1 it was possible to conclude that: (I) for flexural strength values, statistical differences were verified for the same material when different testing methods (uniaxial and biaxial flexural strength) were performed. For study 2, according to the von Misses and Maximum principal stress analysis reducing the proportion of ISO 6872 the stress concentration increases, however, the stress concentration at the testing discs was influenced by the different test design / Doutorado / Materiais Dentarios / Doutor em Materiais Dentários

Soft robots allow for almost arbitrary continuous deformation by leveraging the nonlinear, large deformation of soft materials. However, this flexibility of possible motions comes often at the price of restricting a robot for a particular application. Efforts to create modular robots have emerged in recent years, but gaps remain. Here we design four different kinds of modular soft actuators, for bending, linear expansion, bilinear expansion, torsion, such that they all occupy the same 3×3×3in3volume and can be connected to each other to form arbitrary 3D assemblies by coupling to each other mechanically, pneumatically, and electronically. The actuators can be mechanically connected through magnets. Rather than connecting each actuator independently to a pneumatic line, coupling between adjacent actuators allows for a single pressure and vacuum line to run through an assembly, each actuator has its own controller and can be actuated independently by operating two valves which connect the internal chamber of each actuator to the central pressure and vacuum lines. All actuators are connected to the same central controller analogously to the pneumatic coupling. To optimize the designs and assemblies, finite element simulations were used to iterate designs before any fabrication took place. We showcase the modularity of our actuators in three applications: a walking robot, a claw actuator, and a balance plate.<div><br></div><div>Buckling is typically associated with something that occurs in hard materials and is thought of as undesirable, but with soft robotics, buckling can be leveraged to accomplish useful tasks. Buckling experiments involving 1D and 2D buckling as well as applications for the buckling of linear actuators are shown. Buckling patterns in 1D are modified by changing the number of actuators as well as the angles of the boundary condition. By changing the length of the actuator assembly, different buckling modes are observed. By modifying the angle of the fixed ends, different buckling patterns are forced as well. With this knowledge, several applications are demonstrated. A parallel robot is demonstrated that can cause rotation in either direction by modifying the angle at an end to force it to buckle in a certain way. Another application that is demonstrated is the ability to change the overall shape of an assembly by simply modifying the order in which actuation occurs. This demonstrates how something that is typically associated with mechanical failure, buckling, can be used advantageously with soft robotics. Additionally, buckling is demonstrated that is analogous to biological systems.<br></div>

This diploma thesis is concerned with the design of lift table with hydraulic actuator system. Lift table is supposed to perform vertical motion and tilting the upper desk in horizontal axis. In background research are explored various suitable movement mechanisms and types of actuating systems. After choosing the right mechanism type for lifting and tilting, actuating system and various design components the force and strength calculations are performed analytically and by finite element analysis. The hydraulic schema, 3D model of assembly and drawings are made.

First, an in vitro growth experiment was performed to test the hypothesis that applying dynamic unconfined compression during culture produces het- erogeneous remodeling in newborn bovine articular cartilage explants. Het- erogeneous measures of cartilage microstructure were obtained by biochemical assays and quantified polarized light microscopy. Significant differences were measured between the GAG content in the inner and outer portions of the sam- ples stimulated with dynamic unconfined compression. The COL fiber network was found to be more highly aligned in the inner portion of the sample than in the peripheral region. Next, a poroelastic finite element model with a remodeling subroutine was developed to test the hypothesis that the magnitude of relative interstitial fluid velocity and maximum principle strain stimulate GAG and COL fiber network remodeling, respectively, in articular cartilage during culture with dynamic unconfined compression. The GAG remodeling law was successful in predicting the heterogeneous changes in GAG content. The collagen remodeling law was not successful in predicting the changes in the COL network microstructural orientation, suggesting another mechanical cue is responsible for stimulating the remodeling of the COL fiber network.

<p>The U.S. Army needs a Heavy Dry Support Bridge (HDSB) that can support the Military Load Class (MLC) 96 Heavy Equipment Transporter (HET) tractor trailer carrying an M-I Tank. An existing Axial Folding Bridge (AFB), which was originally designed for MLC 70 loading, has been proposed for load upgrade to demonstrate the feasibility of achieving MLC 96 capacity. This report reviews the upgrade, a finite element model of the bridge, and the actual testing of the bridge to verify the model.</p> <p> The bridge was modeled using the Structural Analysis and Design/Integrated Structural Design System (STAAD-III/ISDS) finite element analysis software. The analysis demonstrated that the existing bridge could be upgraded by simply bolting flat, thin plate elen1ents to the bottom chord of the structure using existing pin plate connector bolt holes and longer bolts. These plates effectively stiffen the bridge structure and maintain a stress level for all elements of the bridge that is no higher for the MLC 96 loading than was experienced for the unrein forced MLC 70 base structure. The modification added 208.7 kg per center section, or an increase in weight of 4.6%, for an increase in load capacity of 37%.</p> <p> A working load static test was conducted on a modified bridge. Four hydraulic actuators applied incremental loading on the bridge. Strain gauge and deflection data were recorded and compared to the analytical model. The model proved to be more flexible than the bridge, but the data showed good correlation in terms of stress ratios between various members. Stress levels were acceptable for the given loading, demonstrating that MLC 96 had successfully been achieved on the bridge.</p> / Master of Science

Please read the abstract in the section 00front of this document / Thesis (PhD (Applied Mathematics))--University of Pretoria, 2000. / Mathematics and Applied Mathematics / unrestricted