Freie Univ., Diss.--Berlin, 1999-2000.

Orientador: Celso Pinto Morais Pereira / Banca: José Geraldo Trani Brandão / Banca: Mauro Pedro Peres / Banca: Marcio Tadeu de Almeida / Banca: Carlos Alberto Chaves / Resumo: O presente trabalho visa constatar a alteração nas freqüências de ressonância de rotores, considerando o efeito da flexibilidade dos discos, bem como o momento fletor aplicado ao eixo devido ao efeito giroscópico. A análise por matriz de transferência é utilizada para obter as freqüências naturais do sistema, considerando-o sem amortecimento, e movimento em órbita circular. Realizou-se uma fase experimental, a fim de se verificar a teoria desenvolvida, bem como observar os modos de vibrar do disco, do eixo, e do sistema disco-eixo, e suas respectivas freqüências naturais. / Abstract: The main objective of this work is to investigate the resonant frequencies of rotors, taking into account not only the flexibility of the discs, but also the bending moment (due to the gyroscopic effect) applied to the shaft. The theorical analysis is based in the transfer matrix technique. The system was assumed to be undamped with the shaftdisc in circular orbit motion. An experimental work was carried out in order to obtain the mode shapes and the natural frequencies of the disc, shaft, and of the disc-shaft system. A good correlation was observed between the theorical and experimental results. Keywords: resonant frequencies, flexibility of the discs, disc-shaft system, transfer matrix method. / Doutor

Orientador: Ruís Camargo Tokimatsu / Resumo: Esse trabalho tem a finalidade de projetar, com base em levantamento bibliográfico, uma prótese de disco intervertebral de Ti6Al4V pelo processo DMLS. Os sistemas de imagem de tomografias computadorizadas e ressonâncias magnéticas trabalham de maneira semelhante. Imagens em 3D de dados dos pacientes são construídas através da combinação de fatias 2D tomadas a partir de sistemas de sensores e da interpolação entre eles. A distância entre as fatias desses sistemas de imagens é grosseira comparada com a tecnologia da manufatura aditiva, portanto, esses processos combinam as imagens das fatias dentro de um software para criar um modelo 3D sobrepondo camadas, devido a essa sinergia entre os dois tipos de sistema, pesquisadores de todo o mundo tentam melhorar e inventar próteses para substituir o disco intervertebral através da ciência. Os resultados mostraram que a fabricação de uma prótese de disco com junta esférica pelo processo de manufatura aditiva é viável, porém nos segmentos menores, como na cervical ainda são difíceis de produzir devido à altura do disco intervertebral e ao limite da dimensão das camadas da manufatura aditiva, que atualmente estão por volta dos 20μm, por isso requerem tratamentos superficiais após sua fabricação. Espera-se que este trabalho possa ajudar futuros pesquisadores da área de biomecânica da coluna vertebral. / Abstract: This work has the purpose of designing, based on a bibliographical survey, an intervertebral disc prosthesis of Ti6Al4V by the DMLS process. Computed tomography (CT) imaging systems and MRIs work similarly. 3D images of patients data are constructed by combining 2D slices taken from sensor systems and interpolating between them. The distance between the slices of these imaging systems is rough compared to the additive manufacturing technology, so these processes combine the slice images within a software to create a 3D model overlapping layers because of this synergy between the two system types, researchers around the world try to improve and devise prostheses to replace the intervertebral disc through science. The results showed that the manufacture of a disc prosthesis with spherical joint by the additive manufacturing process is feasible, but in the smaller segments, such as in the cervical still difficult to produce due to the height of the intervertebral disc and to the limit of the size of the layers of the manufacture additives, which are currently around 20μm, so they require surface treatments after their manufacture. It is hoped that this work may help future researchers in the area of spinal biomechanics. / Mestre

L’occurrence en service commercial de fissures macroscopiques dans certains disques de frein TGV a pu être reliée au type de garniture utilisé. L’objectif de cette thèse est de comprendre cette relation, d’identifier les paramètres d’influence et de proposer des voies d’amélioration pour la conception de garnitures à risque de fissuration réduit. Le comportement thermique de quatre couples disque-garnitures est d’abord analysé par le biais d’une campagne expérimentale de freinage originale. Elle met en évidence différents types de localisations thermiques et permet d’identifier des signatures thermiques caractéristiques des garnitures. Le lien entre localisations thermiques et risques de fissuration est ensuite établi à l’aide d’une modélisation thermomécanique. Des indicateurs tenant compte des caractéristiques spatiales et temporelles des localisations thermiques ainsi que des niveaux de température atteints sont proposés. Ils permettent de classer les garnitures testées dans un graphe de « criticité ». Enfin, une étude d’influence des caractéristiques mécaniques et thermiques des garnitures sur les localisations engendrées permet de dégager des préconisations et des voies d’amélioration pour la conception de nouvelles garnitures. La caractérisation expérimentale du comportement de deux nouvelles garnitures, l’une s’approchant le plus des préconisations faites, l’autre s’en éloignant fortement, montre la pertinence de l’approche développée et la validité des préconisations / The occurrence of macroscopic cracks in some TGV brake discs in commercial service has been linked to the pad type used. The objective of this thesis is to understand this relationship, to identify sensitive parameters and to propose guidelines to the design of pads reducing the risk of cracking.The thermal behavior of four disc-pad couples is first analyzed through an original experimental campaign of braking. It highlights various types of thermal localisations and enables to identify thermal signatures characteristic of the various pads. The relationship between thermal localisation and risk of cracking is then determined using thermomechanical modeling. Some indicators taking into account spatial and temporal characteristics of thermal localisations and temperature levels achieved are proposed. They enable to classify the tested pads in a graph of "criticity". Finally, a study of the influence of mechanical and thermal properties of pads on the thermal localisations occurrence enables to propose guidelines and improving ways for the design of new pads. An experimental characterization of the behavior of two new pads, one very close to the given recommendations, the other strongly away from them, shows the relevance of the approach and the validity of the present recommendations

Made available in DSpace on 2014-06-11T19:28:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-01-13Bitstream added on 2014-06-13T19:37:19Z : No. of bitstreams: 1 lemos_ff_me_guara.pdf: 3167749 bytes, checksum: 900a2570260a39cccd178d8a2ecb5b4a (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Para melhor entender os mecanismos degenerativos da coluna vertebral e avaliar o melhor método para seu tratamento é necessário que se conheça o comportamento dos diversos componentes das articulações intervertebrais. Com isso, torna-se essencial o desenvolvimento de dispositivos capazes de simular as condições fisiológicas de movimentos e cargas a fim de realizar testes in vitro que fornecerão dados para posteriormente serem testados in vivo. O objetivo deste trabalho é o desenvolvimento de dispositivos para a realização de testes in vitro com coluna vertebral. Estes dispositivos constam de uma máquina capaz de simular o movimento de flexão-extensão, pré-cargas axiais e a angulação pélvica, e uma lâmina de extensometria para captar as deformações dos tecidos testados. Foram realizados experimentos com discos invertebrais suínos a fim de avaliar a eficiência dos dispositivos. Realizaram-se dois experimentos usando os dispositivos desenvolvidos e um experimento na máquina universal de ensaios. Como resultado obteve-se valores de propriedades mecânicas coerentes com a literatura e o disco intervertebral comportando-se como um material viscoelástico. Outro ponto importante foi a obtenção da pressão intradiscal aproximada relacionando-a com o deslocamento angular da coluna. Conclui-se que os dispositivos apresentaram funcionamento satisfatório, abrindo perspectivas para outros estudos. / The best way to understand the degenerative mechanisms of the vertebral column and to evaluate appropriated methods for its treatment it is necessary to know the behavior of the diverse components of the intervertebral joints. So, it becomes essential to simulate the physiological conditions of movements and loads in order to carry through test in vitro that they will supply datas to be tested in vivo. The objective of this study is the development of devices of low cont for the accomplishment of tests in vitro with spine. These devices consist of a machine capable to simulate the movement of flexion-extension, daily pay-loads and the pelvic inclination, and an extensometry blade to catch the deformations of tested structures. POrcine had been carried through experiments with intervertebral discs in order to evaluate the efficiency od the devices. Two experiments had been become fullfilled using the developed devices and an experiment in the universal test machine. As result we got values of coherent mechanical properties with literature and the intervertebral disc behaving as a viscoelastic material. Another important point was the attainment of the intradiscal pressure approached relating it with the angular displacement of the spine. It is concluded that the devices had presented satisfactory functioning, opening perspective for other studies.

In several cases, current therapies available to treat a large number of musculoskeletal system diseases are unsatisfactory as they provide only temporary or partial restoration of the damaged or degenerated site. In an attempt to maintain a high standard of life quality and minimise the economic losses due to the treatments of these frequently occurring ailments and subsequent lost working days, alternative therapies are being explored. Contrary to the current treatments, tissue engineering aims to regenerate the impaired tissue rather than repair and alleviate the symptoms; thus offering a definitive solution. The annulus fibrosus (AF) of the intervertebral disc (IVD) is a musculoskeletal system component frequently subjected to degeneration and rupture, characterised by predominance of anisotropically arranged collagen fibres. In the present thesis, electrospinning technology is used to fabricate polycaprolactone (PCL) scaffolds intended to replicate the anisotropic structure of the AF.

Two groups of growth regulators were described in Drosophila imaginal disc cell culture Cl.8+. Imaginal disc growth factors (IDGFs) belonging to chitinase-like protein family of carbohydrate binding proteins and Adenosine deaminase-related growth factors (ADGFs), which are active adenosine deaminases influencing homeostasis of key cellular metabolite adenosine. The functions of two of the IDGFs, as well as the effects of extracellular adenosine and its receptor were studied primarily in in vitro cell culture. Our results supported their roles in the regulation of cell survival and energy homeostasis especially in imaginal disc cells. Both the IDGFs and adenosine also play important roles in organismal responses to stress and infection and may interact in vivo.

Dentre os principais e mais efetivos tratamentos superficiais para a melhora das propriedades da superfície dos aços, encontra-se a nitretação e a nitrocarbonetação. Os benefícios da nitretação nos aços são o aumento da dureza, resistência ao desgaste, resistência à fadiga e resistência à corrosão. Por possuírem elementos como cromo, molibdênio e manganês, os aços ferramenta e aços baixa liga de ultra alta resistência são beneficiados pela nitretação. Neste trabalho, estudou-se o efeito da nitretação nos aços SAE 4140 e SAE H13 através de análises metalográficas, espectroscopia de emissão óptica, difração de raios-x, microdureza e ensaio pino-sobre-disco. Para efeito de comparação, amostras de aço SAE 1045 e ferro puro foram nitretadas juntamente com amostras dos dois materiais anteriores. Foram executados três tratamentos diferentes em cada um dos aços, nitretação com baixo potencial de nitrogênio, nitretação com alto potencial de nitrogênio e nitrocarbonetação. Os dois primeiros tratamentos foram realizados em três tempos diferentes de duas, quatro e seis horas e a nitrocarbonetação foi realizada em seis horas. Os resultados mostraram a formação de uma camada nitretada com de camada branca seguida de uma camada de difusão com gradiente de propriedades. Um aumento significativo de dureza superficial é observado com a aplicação dos tratamentos. A nitrocarbonetação junto com alto potencial de nitretação se mostrou não sendo benéfica para a formação da camada em relação à nitretação com mesmo potencial. Nos testes tribológicos realizados, a camada nitretada se mostrou eficiente em aumentar a resistência ao desgaste nos aços SAE 4140 e SAE H13. / Among the main and most effective surface treatments for improving the surface properties of steels are nitriding and nitrocarburizing. The benefits of nitriding in steels are the increase in hardness, wear resistance, fatigue resistance and corrosion resistance. Because they have elements such as chromium, molybdenum and manganese, tool steels and low alloy steels of ultra high strength are benefited by nitriding. In this work, the effect of nitriding on SAE 4140 and SAE H13 steels was studied through metallographic analysis, optical emission spectroscopy, x-ray diffraction, microhardness and pin-on-disc test. For comparison purposes, samples of SAE 1045 steel and pure iron were nitrided together with samples of the two former materials. Three different treatments were performed in each of the steels, nitriding with low nitrogen potential, nitriding with high nitrogen potential and nitrocarburizing. The first two treatments were performed at three different times of two, four and six hours and nitrocarburizing was performed in six hours. The results showed the formation of a nitrided layer with a white layer followed by a gradient layer of properties. A significant increase in surface hardness is observed with the application of the treatments. Nitrocarburizing together with high nitriding potential proved to be of no benefit to the formation of the layer in relation to nitriding with the same potential. In the tribological tests carried out, the nitrided layer proved efficient in increasing wear resistance in SAE 4140 and SAE H13 steels.

abstract: Introduction. Intervertebral disc degeneration (DD) is one of the most common diagnoses in patients with neck pain and contributes to worldwide disability. Despite the advances in diagnostic imaging today, little is known about functional status of cervical DD. The purpose of this research was to 1) develop and validate an ovine model of cervical spine DD, 2) to quantify and compare the effect of disc lesions on dynamic spinal stiffness, and 3) study the effect of disc lesions on spinal accelerations and displacements during two types of spinal manipulative therapy (SMT). Methods. Fifteen sheep received surgically induced disc injury to the mid-cervical spine via scalpel wound a minimum of five months earlier and 15 sheep served as controls. All animals were biomechanically assessed at the level of the lesion using swept-sine mechanical loads from 0-20 Hz under load control to quantify dynamic dorsoventral (DV) spine stiffness (load/deformation, N/mm). The effect of disc lesion on stiffness was assessed using a one-factor repeated measures ANOVA comparing 32 mechanical excitation frequencies. Tri-axial accelerometers rigidly attached to adjacent vertebrae across the target level further evaluated the effect of disc lesion on spinal motion response during two types of SMTs. A 2x6x2 repeated measures ANOVA examined the effect of disc lesion and SMT force-time profile on spine motion response. Postmortem histological analysis graded specimens at the target site and comparison was made with descriptive statistics. Results. Annular disc tears were only observed in the disc lesion group and the mild degeneration identified was localized to the injured annular tissue that did not progress to affect other areas of the disc. No difference in overall DD grading was found among the groups. DV stiffness was significantly increased in the disc lesion group by approximately 34% at 31 of 32 frequencies examined (p<.05). SMTs resulted in decreased displacements in the disc lesion group (p<.05), and SMT type significantly influenced spinal accelerations for both the DV and axial planes. Conclusion. Disc lesions in the ovine cervical spine produce localized annular degenerative changes that increase the cervical spine dynamic stiffness and reduce its spinal motion response during manual examination and treatment that is further augmented by the force-time profile administered by the clinician. / Dissertation/Thesis / Doctoral Dissertation Kinesiology 2015

Made available in DSpace on 2016-12-08T17:19:32Z (GMT). No. of bitstreams: 1 Parte 1_CAPA.pdf: 112741 bytes, checksum: 77f664f41fd325d0dc88d0a1e1c7d4fe (MD5) Previous issue date: 2007-12-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The present work deals with the design, fabrication and operation of a cavitation erosion equipment and with the preliminary results obtained by its testing. A new cavitation erosion testing machine was designed, fabricated and tested, using a rotating disc with holes for generating cavitation. The developed equipment has as main advantages, in relation to the existing ones, low fabrication cost due to its smaller size and reduced number of components, the specimen quantity of up eight per test and a lower power needed to carry out the testing. It is small size equipment, capable of generating the necessary bubbles for causing the erosion by cavitation on the specimen surfaces at the speed of 4400 rpm and maximum power of 30 kW. Two types of rotating discs were investigated: with cavitation inducers holes and with pins. The rotating disc with inducer holes was more efficient as its power consumption was only 14 kW and the disc with inducer pins was 23 kW for practically the same erosion rate obtained by bronze and aluminium, both at the rotation speed of 4400 rpm. The cavitation erosion is responsible for surface damage caused exposure to this phenomenon. The equipment is capable of testing simultaneously 8 specimens of different materials, what shows the variety of possible materials which can be performed simultaneously in short period of time. The specimen erosion was confirmed by its loss of mass, using an analytical balance with accuracy of 0,2 mg and by the analyses of the eroded surface through the photograph analyses from the scanning electron microscope, MEV. The occurrence of cavitation due to micro-jets impact was confirmed by the microphotographs of circular craters in the aluminium specimens. The tested and discussed materials in this work presented different behavior when exposed to cavitation erosion. Bronze and brass showed a practically constant and linear erosion rate as seen in the lost mass versus testing time graphs. But, aluminium presented much lower wear, except for 10 to 15 hours of testing. After this period of time, a substantial reduction in the wear rate was occurred due to the formation of a fine layer of alumina which provided an increase in the aluminium wear resistance. According to the results obtained by the nodular cast iron specimens, it was observed that the cemented layer increased the erosion resistance to cavitation and decreased the specimen surface oxidation, however, the occurrence of surface oxidation prejudiced a more accurate analyses. / O presente trabalho consiste no projeto, construção e operação de uma máquina de ensaio de erosão por cavitação e dos primeiros resultados obtidos por meio deste equipamento. Um novo conceito de máquina de ensaio de erosão por cavitação foi projetado, construído e ensaiado, usando um disco rotativo com furos e pinos indutores de cavitação. O equipamento projetado possui como principais vantagens, em relação aos equipamentos já existentes, o baixo custo de fabricação devido ao menor tamanho do equipamento, número reduzido de componentes, a quantidade de até oito amostras por ensaio e a menor potência necessária para realização dos ensaios. Trata-se de uma máquina de pequeno porte, capaz de gerar as bolhas necessárias para o surgimento da erosão por cavitação nas superfícies dos corpos de prova na rotação de até 4400 rpm e potência máxima de 30 kW. Foram investigados dois tipos de discos rotativos: com furos indutores e com pinos indutores de cavitação. O disco rotativo com furos indutores foi mais eficiente, pois consumiu a potência de 14 kW e com pinos indutores a potência consumida foi de 23 kW, para a mesma rotação de 4400 rpm, e apresentaram praticamente a mesma taxa de erosão verificada no bronze e alumínio. A erosão por cavitação é responsável por danos causados nas superfícies expostas a este fenômeno. O equipamento é capaz de ensaiar simultaneamente 8 corpos de prova de diferentes materiais, o que demonstra a variedade possível de materiais de estudos que podem ser feito em conjunto, em reduzidos períodos de tempo. A erosão nos corpos de prova foi verificada pela perda de massa, usando uma balança analítica de precisão 0,2 mg, e pela análise da superfície erodida através da análise das fotografias obtidas no microscópio eletrônico de varredura, MEV. A ocorrência da cavitação por impacto de micro-jatos foi comprovada com as micro-fotografias de crateras circulares nas amostras de alumínio. Os materiais ensaiados e discutidos neste trabalho apresentaram comportamentos diferentes quando exposto à erosão por cavitação. O bronze e o latão tiveram uma taxa de erosão praticamente constante e linear demonstrada nos gráficos de perda de massa em relação ao tempo de ensaio. Já o alumínio apresentou um desgaste muito inferior, mas acentuado entre 10 e 15 horas de ensaio. Após este período ocorreu. uma redução significativa na taxa de desgaste, devido a formação de uma fina camada superficial de alumina que conferiu um aumento na resistência ao desgaste do alumínio. De acordo com os resultados obtidos com os corpos de prova em ferro fundido nodular, constata-se que a camada de cementação aumentou a resistência à erosão por cavitação e visivelmente diminuiu a oxidação superficial dos corpos de prova, porém a oxidação superficial ocorrida nestas amostras comprometeram uma análise mais apurada.