Дисертації: "Integrity of material"

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Masini, Alessia. "The Role of Bi/Material Interface in Integrity of Layered Metal/Ceramic." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-399207.

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The present doctoral thesis summarises results of investigation focused on the characterisation of materials involved in Solid Oxide Cell technology. The main topic of investigation was the ceramic cell, also known as MEA. Particular attention was given to the role that bi-material interfaces, co-sintering effects and residual stresses play in the resulting mechanical response. The first main goal was to investigate the effects of the manufacturing process (i.e. layer by layer deposition) on the mechanical response; to enable this investigation, electrode layers were screen-printed one by one on the electrolyte support and experimental tests were performed after every layer deposition. The experimental activity started with the measurement of the elastic characteristics. Both elastic and shear moduli were measured via three different techniques at room and high temperature. Then, uniaxial and biaxial flexural strengths were determined via two loading configurations. The analysis of the elastic and fracture behaviours of the MEA revealed that the addition of layers to the electrolyte has a detrimental effect on the final mechanical response. Elastic characteristics and flexural strength of the electrolyte on the MEA level are sensibly reduced. The reasons behind the weakening effect can be ascribed to the presence and redistribution of residual stresses, changes in the crack initiation site, porosity of layers and pre-cracks formation in the electrode layers. Finally, the coefficients of thermal expansion were evaluated via dilatometry on bulk materials serving as inputs for finite elements analyses supporting experiments and results interpretation. The second most important goal was to assess the influence of operating conditions on the integrity of the MEA. Here interactions of ceramic–metal interfaces within the repetition unit operating at high temperatures and as well at both oxidative and reductive atmospheres were investigated. The elastic and fracture responses of MEA extracted from SOC stacks after several hours of service were analysed. Layer delamination and loss of mechanical strength were observed with increasing operational time. Moreover, SEM observations helped to detect significant microstructural changes of the electrodes (e.g. demixing, coarsening, elemental migration and depletion), which might be responsible for decreased electrochemical performances. All the materials presented in this work are part of SOC stacks produced and commercialised by Sunfire GmbH, which is one of the world leading companies in the field.

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MEDINA, JORGE ARTURO HINOSTROZA. "PROCEDURE FOR THE ASSESMENT OF STRUCTURAL INTEGRITY OF MATERIAL LIFTING AND HANDLING MACHINERY." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=31772@1.

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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
PROGRAMA DE EXCELENCIA ACADEMICA
BOLSA NOTA 10
Neste trabalho apresenta-se um procedimento para a avaliação da Integridade Estrutural em máquinas de levantamento e movimentação de materiais utilizando a metodologia de Inspeção Baseada em Risco (IBR), com o objetivo de identificar as partes com maior risco de falha. Esta metodologia avalia tanto as Probabilidades de falha como as Consequências de falha para identificar os pontos críticos que serão analisados com prioridade nos programas de inspeção futuros. Um guincho hidráulico de pequeno porte é usado como exemplo da aplicação deste procedimento a equipamentos de grande porte. No desenvolvimento desta metodologia executa-se uma análise detalhada das tensões envolvidas nos principais pontos da máquina, considerando o cálculo analítico, cálculo numérico, medições experimentais e análise de incertezas. Para o cálculo das probabilidades de falha foram considerados os seguintes mecanismos de dano: colapso plástico por carregamento excessivo, fadiga e corrosão. As probabilidades de falha para cada mecanismo são calculadas e classificadas em diferentes níveis, assim como as consequências de falha, o que origina diferentes níveis de risco.
This report presents a procedure for the assesment of Structural Integrity of material lifting and handling machinery, using the methodology of Risk Based Inspection (IBR - Inspeção Baseada em Risco) in order to indentify the parts with high risk of failure. This methodology assesses both probabilities of failure and consequences of failure to identify the critical points; those will be analyzed with priority in future inspection programs. A small hydraulic hoist is used as an example of this procedure applying to big equipments. A detailed strain analysis is carried out for the most important points of the equipment. The strain analysis consider analytic calculations, numeric calculations, experimental measurements and related uncertainly evaluations. In order to calculate the probabilities of failure, the followings damage mechanisms were considered: plastic collapse by excessive loading, fatigue and corrosion. The failure probabilities for each mechanism are calculated and classificated in different levels, as well as failure consequences, that originate different risk levels.

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Nguyen-Dinh, Ngoc. "Experimental study of the trimming of carbon-epoxy composite : machinability and material integrity." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30059.

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Le détourage est la première opération d’usinage après la fabrication et le démoulage des structures composites. Cette opération, qui est généralement effectuée avec un procédé conventionnel d’enlèvement de matière à l’aide d’un outil de coupe, conduit à l'apparition de plusieurs types d’endommagements qui sont suivi par la génération de particules nocives lors d’un usinage sans lubrification. Ces particules, générées lors de l'usinage à sec de composites constituent une menace sanitaire, car elles peuvent rester en suspension dans l'air et s'infiltrer dans le corps de l'opérateur, représentant un risque de danger respiratoire. Malheureusement, la compréhension des phénomènes d’émission de particules lors de l'usinage du composite est actuellement insuffisante. De plus, l’apparition de dommages localisés sur la surface usinée (due à l’interaction entre l’outil et le composite) peut réduire la tenue de la structure en service du fait de la formation de zones de concentration de contraintes. En conséquence, il est nécessaire de mieux comprendre les causes sous-jacentes de la création de dommages, ainsi que la relation entre les dommages induits par l'usinage et le comportement mécanique. Il est important de noter que d’un point de vue industriel le critère de rugosité de surface est largement utilisé pour quantifier la qualité d’usinage de la surface composite ainsi engendrée ; cependant la relation entre ces deux critères reste complexe. Ainsi, afin de répondre à cette problématique, ce travail de thèse s’est concentré sur trois objectifs principaux. Tout d'abord, des études ont été menées sur l'usinabilité d'échantillons de stratifiés composites multidirectionnels à base de résine époxy et de fibres de carbone lors du détourage à l'aide d'outils de coupe en PCD (diamant polycristallin). Plus précisément, l’influence des paramètres de coupe (vitesse d’avance et vitesse de coupe) et de la distance de coupe (usure de l’outil) ont été étudiés afin de voir leur influence sur les efforts de coupe et sur la température d’usinage induite, puis une caractérisation multi-échelle des dommages induits par l’usinage a été menée. Cette caractérisation multi-échelles des dommages induits par l’usinage a consisté à l’observation post-mortem des échantillons usinés à l’aide de différentes techniques telles que la tomographie à rayons X, la microscopie confocale et le MEB. Grâce à cette caractérisation multi-échelles, la qualité d’usinage a été quantifiée à l’aide de nouveaux paramètres tels que le volume de cratères, Cv, basé sur la quantification des défauts de cratères et la profondeur des dommages, D, mesurés à l’aide d’observations tomographiques à rayons X. Le deuxième objectif de cette thèse était centré sur l'influence des paramètres de coupe (vitesse de coupe, vitesse d'avance et profondeur de coupe radiale), la distance de coupe et la géométrie de l'outil sur le nombre de particules nocives générées lors de la coupe. Les résultats de cette étude sur les émissions de poussières pourront être très utiles à la communauté industrielle pour choisir les bonnes conditions d’usinage afin de protéger les opérateurs susceptibles d’inhaler les particules présentes dans l’air dans la zone d’usinage. Les résultats obtenus ont clairement montré que pour réduire les émissions de particules nocives, il était nécessaire d’augmenter la profondeur de coupe radiale ou la vitesse d’avance. Néanmoins cette combinaison de conditions de coupe conduit en général à une mauvaise qualité d'usinage
Trimming is the first operation of machining after the manufacturing and demolding of the composite structures. This operation which is usually conducted with conventional process of material removal (by cutting tool) induces various forms of damage which is accompanied by the generation of harmful particles in case of dry machining. In fact, particles generated during dry machining of composite pose a dangerous threat, as they can get suspended in the air and infiltrate inside body of operators giving rise to risk of respiratory hazard. Unfortunately, the understanding of particulate emission during machining of composite is presently incomplete. In addition, the appearance of damages located on the machined surface (due the interaction tool/plies) can reduce the structural performance in service due to the formation of stress concentration zones. As a result, it is necessary to understand the underlying causes for generation of damage, and also the relationship between machining induced damage and mechanical behavior. It is important to notice that, industrially, surface roughness criterion is widely used to quantify the machined quality of the newly generated composite surface. However, so far this has been ambiguous approach. Hence, to address the problems mentioned, this thesis focuses on three main objectives. Firstly, studies on the machinability of multi-directional specimens made of carbon fiber reinforced plastics laminates (CFRPs) during trimming with PCD (Polycrystalline Diamond) cutting tools. Specifically, the influence of cutting parameters (feed speed and cutting speed), cutting distance (tool wear) on the cutting forces, machining temperature induced as well as the multi-scale characterization of the machining induced damages have been investigated. For the multi-scale characterization of the induced machining postmortem observations of the machined specimens, using different techniques such as X-ray tomography, confocal microscopy and SEM, are used. Thanks to this multi-scale characterization, the machining quality was quantified using newly proposed parameters such as crater volume ‘CV’ based on the quantification of the crater defects and maximum depth of damage (D) based on the X-ray tomography. The second objective of this thesis was focused on influence of cutting parameters (cutting speed, feed speed, and radial depth of cut), cutting distance, and tool geometry on the number of harmful particles generated during trimming. The outcome of this study on the dust emission can be beneficial for the industrial community to select the safe machining condition for protecting the operators who potentially inhale the particles in the air in the machining area. The obtained results clearly highlighted that to reduce the emission of the harmful particles it is necessary to increase the radial depth of cut or the feed rate. However, this combination of cutting conditions, leads to poor machining quality. This inspired to propose a new design of cutting tool geometry in collaboration with ASAHI Company

4

Li, Qian. "SIGNAL INTEGRITY ANALYSIS ON MATERIALS AND VIA STRUCTURES MODELING AND CHARACTERIZATION." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/203472.

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The development of modern digital communication systems has been entered a new era with faster signal transmission and processing capability, called high-speed circuit systems. As their clock frequencies have increased and rise times of signals have decreased, the signal integrity of interconnects in the packaging and printed circuit boards plays a more and more important role. In high-speed circuit systems, the well-designed logic functions most likely will not work well if their interconnects are not taken into account.This dissertation addresses to profoundly understand the signal integrity knowledge, be proficient in calculation, simulation and measurements, and be capable of solving related signal integrity problems. The research mainly emphasizes on three aspects. First of all, the impact of on-wafer calibration methods on the measured results of coplanar waveguide circuits is comprehensively investigated, with their measurement repeatability and accuracy. Furthermore, a method is presented to characterize the physically-consistent broadband material properties for both rigid and flexible dielectric materials. Last but not least, a hybrid method for efficient modeling of three dimensional via structures is developed, in order to simplify the traditional 3D full-length via simulations and dramatically reduce the via build and simulation time and complexity.

5

Zhang, Li Ying Grace. "Fatigue and integrity of hard ceramics and coatings using the soft impressor technique." Thesis, University of Hull, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363272.

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Yiğit, Nergiz Seçkin Yavuz. "Industrial product design by using two-dimensional material in the context of origamic structure and integrity/." [s.l.]: [s.n.], 2004. http://library.iyte.edu.tr/tezler/master/endustriurunleritasarimi/T000457.pdf.

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Holmberg, Jonas. "Surface integrity on post processed alloy 718 after nonconventional machining." Licentiate thesis, Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-12191.

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There is a strong industrial driving force to find alternative production technologies in order to make the production of aero engine components of superalloys even more efficient than it is today. Introducing new and nonconventional machining technologies allows taking a giant leap to increase the material removal rate and thereby drastically increase the productivity. However, the end result is to meet the requirements set for today's machined surfaces.The present work has been dedicated to improving the knowledge of how the non-conventional machining methods Abrasive Water Jet Machining, AWJM, Laser Beam Machining, LBM, and Electrical Discharge Machining, EDM, affect the surface integrity. The aim has been to understand how the surface integrity could be altered to an acceptable level. The results of this work have shown that both EDM and AWJM are two possible candidates but EDM is the better alternative; mainly due to the method's ability to machine complex geometries. It has further been shown that both methods require post processing in order to clean the surface and to improve the topography and for the case of EDM ageneration of compressive residual stresses are also needed.Three cold working post processes have been evaluated in order to attain this: shot peening, grit blasting and high pressure water jet cleaning, HPWJC. There sults showed that a combination of two post processes is required in order to reach the specified level of surface integrity in terms of cleaning and generating compressive residual stresses and low surface roughness. The method of high pressure water jet cleaning was the most effective method for removing the EDM wire residuals, and shot peening generated the highest compressive residual stresses as well as improved the surface topography.To summarise: the most promising production flow alternative using nonconventional machining would be EDM followed by post processing using HPWJC and shot peening.

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Lehmensiek, Michel [Verfasser]. "Restoration integrity, but not material or cementation strategy determined secondary caries next to indirect restorations in vitro / Michel Lehmensiek." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2019. http://d-nb.info/1194945376/34.

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Da, Silva Ashley. "Investigation of cretaceous molluscan shell material for isotopic integrity : examples and implications from the baculites compressus/cuneatus biozones (Campanian) of the western interior seaway." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001574.

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da, Silva Ashley. "Investigation of Cretaceous Molluscan Shell Material for Isotopic Integrity: Examples and Implications from the Baculites compressus/cuneatus Biozones (Campanian) of the Western Interior Seaway." Scholar Commons, 2006. http://scholarcommons.usf.edu/etd/3921.

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Whether a global greenhouse interval is a distinct or distant future, it is important to understand the dynamics of a greenhouse system. During such intervals the oceans, in the absence of sizeable polar ice caps, flood the continental shelf. The stratification and circulation of these epicontinental seas are open to debate, because there are no Recent analogs. The carbon and oxygen stable isotope record of fossil molluscan shell from epicontinental seas has the potential to reveal their stratification and seasonal cycles. Whether a global greenhouse interval is a distinct or distant future, it is important to understand the dynamics of a greenhouse system. During such intervals the oceans, in the absence of sizeable polar ice caps, flood the continental shelf. The stratification and circulation of these epicontinental seas are open to debate, because there are no Recent analogs. The carbon and oxygen stable isotope record of fossil molluscan shell from epicontinental seas has the potential to reveal their stratification and seasonal cycles. As a study sample, mollusks from the Baculites compressus and Baculites cuneatus biozones of the Western Interior Seaway of North America were collected from three locations: Kremmling, Colorado; Trask Ranch, South Dakota; Game Ranch, South Dakota. These fossils date to the Campanian (Late Cretaceous). Taxa include ammonites, bivalves, gastropods, and nautiloids. The first part of this investigation, described in Chapter 2, investigates the degree of alteration in these specimens. Elevated concentrations of minor elements such as magnesium and strontium reveal alteration from the original aragonite and/or calcite skeletons. Concentrations of these elements obtained by ICP-OES analysis are compared within several suites of specimens: mode of preservation, shell testing location, shell color, cementation, appearance under light microscope, and appearance under scanning electron microscope. Each of these suites tests a hypothesis about optimal shell preservation. Shell was found to be preserved best in shale rather than concretions, ammonite phragmacone rather than septa, opalescent specimens rather that nonopalescent ones, and uncemented shells rather than cemented shells, especially those with second-order versus first-order cement. Salinity and temperature values were derived for the organisms in the Western Interior Seaway: while bivalves produced unusually low temperatures, the others were reasonable for an inland sea. The second part of this study, described in Chapter 3, examines the isotopic record within exemplary mollusk shells, taken perpendicular to growth lines. The data for this investigation in sclerochronology documents the dominant isotopically enigmatic bottom-water habitat of the Inoceramus, the geochemical signature of the overlying water mass inhabited by Baculites, and short-term migrations between the two water masses in the nautiloid Eutrephoceras.

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Rocha, Gabriel Lopes da. "Aplicação da teoria de representação de funções isotrópicas em sólidos hiperelásticos com duas direções de simetria material." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/82/82131/tde-20082018-152023/.

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Aplicamos a teoria de representação de funções isotrópicas para determinar o número mínimo de invariantes independentes necessários para caracterizar completamente a densidade de energia de deformação de sólido hiperelástico com duas direções de simetria material. Expressamos a densidade de energia em termos de dezoito invariantes e extraímos um conjunto de dez invariantes para analisar dois casos de simetria material. No caso de direções ortogonais, recuperamos o resultado clássico de sete invariantes e oferecemos uma justificativa para a escolha dos invariantes encontrados na literatura. Se as direções não são ortogonais, descobrimos que o número mínimo também é sete e corrigimos um erro em fórmula encontrada na literatura. Uma densidade de energia deste tipo é usada para modelar, na escala macroscópica, materiais de engenharia, tais como compósitos reforçados com fibras, e tecidos biológicos, tais como ossos.
We determine the minimum number of independent invariants that are needed to characterize completely the strain energy density of a hyperelastic solid having two distinct material symmetry directions. We use a theory of representation of isotropic functions to express this energy density in terms of eighteen invariants and extract a set of ten invariants to analyze two cases of material symmetry. In the case of orthogonal directions, we recover the classical result of seven invariants and offer a justification for the choice of invariants found in the literature. If the directions are not orthogonal, we find that the minimum number is also seven and correct a mistake in a formula found in the literature. An energy density of this type is used to model, on the macroscopic scale, engineering materials, such as fiber-reinforced composites, and biological tissues, such as bones.

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Farias, Adalto de. "Análise da tensão residual e integridade superficial no processo de torneamento em material endurecido do aço ABNT 8620 cementado." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3151/tde-01072009-145404/.

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Este trabalho tem a intenção de contribuir com informações sobre a integridade superficial resultante do processo de torneamento em material endurecido de componentes mecânicos fabricados em aço cementado ABNT 8620 (DIN 21 NiCrMo 2). A análise das tensões residuais do corpo de prova foi experimentalmente conduzida pelo Método do Furo Cego Incremental, no qual um pequeno furo é introduzido na superfície do componente e a deformação aliviada é registrada por meio de extensômetros especiais, e também, pelo método da difração de raios-X. A superfície foi analisada através de parâmetros obtidos do mapeamento tridimensional da topografia superficial com instrumento de interferometria laser. Os parâmetros de rugosidade, selecionados para medição, visaram uma caracterização funcional das superfícies obtidas, tais como capacidade de carga, capacidade de retenção de fluidos lubrificantes e resistência ao desgaste. Também foram executados ensaios metalográficos para avaliar a existência de camadas de material alteradas abaixo da superfície. Os resultados indicaram que o torneamento em material endurecido foi capaz de produzir uma superfície resultante com boa área de contato, boa capacidade de carregamento e razoável capacidade de retenção de fluidos uma vez que nem todos os parâmetros se encontraram na faixa funcional ideal. O torneamento em material endurecido induziu tensão de compressão nas camadas das amostras cementadas, cuja condição original era tensão residual de tração. Não foram detectadas alterações expressivas na camada cementada, principalmente na região limítrofe da área transversal com a superfície devido ao aquecimento e rápido resfriamento imposto pelo processo de usinagem.
The aim of the present work is to provide relevant information regarding the obtained surface integrity during hard turning process of mechanical components manufactured from case hardened steel ABNT 8620 (DIN 21 NiCrMo 2). The sample residual stress analysis has been experimentally conducted by the incremental Blind Hole method, in which a small hole is machined on the surface of the component and the relieved deformation is recorded through special strain gages, and by the X-ray diffraction technique. The surface was examined by parameters obtained from the surface topography three-dimensional mapping with a laser interferometer instrument. The selected roughness parameters analysis intends to have a functional characterization such as bearing capacity, fluid and lubricants retention ability and contact wear resistance. In the search for altered material layers beneath the surface, metallographic studies were carried out. The functional bearing area curve analysis parameters indicated that the resulting surface has a good area contact, good bearing capacity and reasonable ability to fluid retention as the reduced valley depth parameter did not produced negative values for all conditions tested. The hard turnig process was able to add compression residual stress condition at the surface, and no significant changes were found at the case hardened layer due to rapid heating and cooling imposed by the hard turning process.

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Blomqvist, Johanna. "Sex i rätten, vad är egentligen straffbart? : Våldtäkt och hämndpornografi, en studie av den sexuella integriteten." Thesis, Uppsala universitet, Juridiska institutionen, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-383313.

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Begrepp som personlig integritet, sexuell självbestämmanderätt samt sexuell integritet är vedertagna begrepp inom juridiken som används av såväl lagstiftare, rättsväsende och doktrin, men trots detta finns det ingen egentlig definition av endera begreppen. Jag har i den här uppsatsen visat att sexuell integritet innebär rätten för den enskilde att själv bestämma när, var, hur och med vem denne vill delta i en sexuell aktivitet. En sexuell aktivitet innebär i sin tur utförande av eller deltagande i en sexuell handling, eller att försätta sig i en sexuell situation. Ett sexualbrott innebär därmed att en person inkräktar på den enskildes rätt till detta val. Våldtäkt har funnits vara urtypen av sexualbrotten. Om en gärning anses utgöra en våldtäkt, utgör den därmed även en kränkning av den utsattes sexuella integritet. Innebörden av den senaste utformningen av våldtäktsbrottet samt vad det innebär att delta frivilligt har diskuterats. Definitionen av frivillighet är av vikt, då detta sedan 1 juli 2018 är den nedersta gränsen för när en gärning utgör en våldtäkt. Vidare illustrerades den osäkerhet som råder inom rättsväsendet gällande straffvärderingen av våldtäkt. Anledningen till denna osäkerhet är frågan om hur stor påverkan det nya rekvisitet om frivillighet bör ha, då det ansetts göra att fler gärningar kan klassificeras som våldtäkt än tidigare. Hämndpornografi har länge behandlats enbart som ett förtalsbrott, det vill säga ett brott mot någons ära och anseende. Numera kan hämndpornografi, det vill säga akten av att sprida sexuellt eller naket material på en annan utan dennes tillåtelse, även behandlas enligt de nya paragraferna om olaga integritetsintrång i 4 kap 6 c, d §§ BrB. Olaga integritetsintrång innefattar även andra typer av gärningar, varför jag valde att hålla mig till termen hämndpornografi för att underlätta för läsaren. Olaga integritetsintrång utgör ett brott mot den enskildes frihet och frid, eller med andra ord dennes personliga integritet. Jag har i den här uppsatsen argumenterat för att hämndpornografi bör urskiljas från resterande punkter i 4 kap 6 c § BrB, då spridande av bild eller annan uppgift om någons sexualliv, samt spridande av bild på någons helt eller delvis nakna kropp har andra skyddsområden jämfört med övriga punkter, nämligen att de båda utgör intrång på den enskildes sexuella integritet. Detta har skett genom problematisering av förarbetena till lagen, analys av relevanta rättsfall samt belysande av utsattas berättelser om hur hämndpornografi påverkat dem. Utöver detta har jag även påvisat att det behövs ytterligare vägledande praxis för att lösa den inkonsekvens och osäkerhet som råder gällande tillämpningen av såväl våldtäkt som olaga integritetsintrång.

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Hu, Ching Wen. "Fabric integrity evaluation of structural materials using infrared thermography." Thesis, University of South Wales, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395349.

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Shekaran, Asha. "Beta 1 integrins in bone formation during development and engineering integrin-specific hydrogels for enhanced bone healing." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/51720.

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Healing large bone defects remains a clinical challenge. While autografts are the gold standard treatment for large bone defects, they are limited by availability and donor site pain. Growth factor treatments such as BMP therapy provide a promising alternative but are expensive and present clinical safety concerns, primarily due to delivery of BMPs at supraphysiological doses. Integrins are ECM receptors which mediate crucial cell functions such as adhesion and differentiation. Therefore, understanding the role of integrins in bone formation and directing desired interactions may enable modulation of host cell functions for therapeutic applications. In this work, beta 1 integrins were deleted in osteolineage cells of transgenic mice at three different stages of differentiation to elucidate their role in bone development. We also engineered bioartificial PEG-based matrices which target the pro-osteogenic alpha 2 beta 1 integrin to promote bone healing. Conditional deletion of beta 1 integrins in osteochondroprogenitor cells under the Twist 2 promoter resulted in severe pre-natal skeletal mineralization defects and embryonic lethality. Targeted deletion of beta 1 integrins in osterix-expressing osteoprogenitors resulted in growth abnormalities, reduced calvarial mineralization, impaired femur development, and tooth defects. However, mice lacking beta 1 integrins in osteocalcin-expressing osteoblasts and osteocytes displayed only a mild skeletal phenotype, indicating that beta 1 integrins play an important role in early skeletal development, but are not required for mature osteoblast function. PEG hydrogels functionalized with the integrin-specific GFOGER ligand enhanced bone regeneration, induced defect bridging in combination with low doses of rhBMP-2 and stimulated improved bone healing compared collagen sponges, which are the clinical standard delivery vector for BMP-2 therapy. These results suggest that treatment with bioartificial integrin-specific PEG hydrogels may be a promising clinical strategy for bone regeneration in large bone defects.

16

Oyekoya, Oyedele O. "Structural integrity of engineering components made of functionally graded materials." Thesis, Cranfield University, 2008. http://hdl.handle.net/1826/3802.

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Functionally graded materials (FGM) are composite materials with microstructure gradation optimized for the functioning of engineering components. For the case of fibrous composites, the fibre density is varied spatially, leading to variable material properties tailored to specific optimization requirements. There is an increasing demand for the use of such intelligent materials in space and aircraft industries. The current preferred methods to study engineering components made of FGM are mainly modelling particularly those that are finite element (FE) based as experimental methods have not yet sufficiently matured. Hence this thesis reports the development of a new Mindlin-type element and new Reissner-type element for the FE modelling of functionally graded composite (FGC) structures subjected to various loadings such as tensile loading, in-plane bending and out-of-plane bending, buckling and free vibration. The Mindlin-type element formulation is based on averaging of transverse shear distribution over plate thickness using Lagrangian interpolation. Two types of Mindlintype element were developed in this report. The properties of the first Mindlin-type element (i.e. Average Mindlin-type element) are computed by using an average fibre distribution technique which averages the macro-mechanical properties over each element. The properties of the second Mindlin-type element (i.e. Smooth Mindlin-type element) are computed by using a smooth fibre distribution technique, which directly uses the macro-mechanical properties at Gaussian quadrature points of each element. The Reissner-type element formulation is based on parabolic transverse shear distribution over plate thickness using Lagrangian and Hermitian interpolation. Two types of Reissner-type element were developed in this report, which include the Average and Smooth Reissner-type elements. There were two types of non-linearity considered in the modelling of the composite structures, which include finite strain and material degradation. The composite structures considered in this paper are functionally graded in a single direction only, but the FE code developed is capable of analysing composite structures with multidirectional functional gradation. This study was able to show that the structural integrity enhancement and strength maximisation of composite structures are achievable through functional gradation of material properties over the composite structures.

17

Chen, Shouhua. "Forming and structural integrity of lightweight materials for transport applications." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/33242.

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The research described in this PhD dissertation covers two aspects of lightweight materials for transport applications. One aspect is manufacturing process for lightweight metallic alloys and the other is structural integrity assessment for composite materials. In both cases, there was industrial interest in the research from aerospace, marine and automotive manufacturers. The first study relates to forming of lightweight metallic alloys. A new forming technique was developed to form lightweight turbine blade preforms. The second study relates to structural integrity of composite sandwich structures. The resistance of sandwich composite structures to high rate loading conditions from an air blast was investigated. In the first study, a novel electrical upsetting process, Gleeble Electrical Upsetting (GEU), was developed and conducted in a Gleeble 3800 Thermomechanical Simulator. By means of a resistance heating system in the Gleeble, a sharp decreasing temperature gradient and localized high upsetting ratio of an Aluminium Alloy (AA2011) round bar could be achieved. The forming results showed that three key forming parameters played important roles in the electrical upsetting process. The three parameters were heating rate, forming temperature and forming speed. A processing window was assessed to determine the optimum forming process for the GEU technique. In the second study, the air blast resistance of full scale GFRP and CFRP-skinned sandwich composite panels has been researched. Explosive charges of 38 - 100 kg TNT equivalent were employed in these studies to achieve high rate air blast loading. High-speed photography and DIC system were employed during the air-blast loading to monitor the deformation of these structures under shock loading. Failure mechanisms have been revealed using DIC and confirmed in post-test sectioning. Full-scale experimental results presented in this thesis were compared with FEA simulations. The two research studies performed in this PhD thesis emphasise the importance of manufacture process control and structural integrity assessment. In both cases, the materials studied are to be employed in transport applications. The Lee Family PhD Scholarship along with provision of testing materials from aerospace, marine and automotive manufacturers has provided for an interesting PhD study.

18

Oyekoya, Oyedele. "Structural integrity of engineering components made of functionally graded materials." Thesis, Cranfield University, 2008. http://dspace.lib.cranfield.ac.uk/handle/1826/3802.

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Functionally graded materials (FGM) are composite materials with microstructure gradation optimized for the functioning of engineering components. For the case of fibrous composites, the fibre density is varied spatially, leading to variable material properties tailored to specific optimization requirements. There is an increasing demand for the use of such intelligent materials in space and aircraft industries. The current preferred methods to study engineering components made of FGM are mainly modelling particularly those that are finite element (FE) based as experimental methods have not yet sufficiently matured. Hence this thesis reports the development of a new Mindlin-type element and new Reissner-type element for the FE modelling of functionally graded composite (FGC) structures subjected to various loadings such as tensile loading, in-plane bending and out-of-plane bending, buckling and free vibration. The Mindlin-type element formulation is based on averaging of transverse shear distribution over plate thickness using Lagrangian interpolation. Two types of Mindlintype element were developed in this report. The properties of the first Mindlin-type element (i.e. Average Mindlin-type element) are computed by using an average fibre distribution technique which averages the macro-mechanical properties over each element. The properties of the second Mindlin-type element (i.e. Smooth Mindlin-type element) are computed by using a smooth fibre distribution technique, which directly uses the macro-mechanical properties at Gaussian quadrature points of each element. The Reissner-type element formulation is based on parabolic transverse shear distribution over plate thickness using Lagrangian and Hermitian interpolation. Two types of Reissner-type element were developed in this report, which include the Average and Smooth Reissner-type elements. There were two types of non-linearity considered in the modelling of the composite structures, which include finite strain and material degradation. The composite structures considered in this paper are functionally graded in a single direction only, but the FE code developed is capable of analysing composite structures with multidirectional functional gradation. This study was able to show that the structural integrity enhancement and strength maximisation of composite structures are achievable through functional gradation of material properties over the composite structures.

19

Gopalakrishnamurthy, Sharath H. "Structural integrity inspection using dynamic responses /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p1418023.

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20

James, Susan Patricia. "Improving the mechanical integrity of the bone cement mantle." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12477.

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21

Lewis, David Kent. "Characterization of flaws and structural integrity by ultrasonic spectroscopy /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487268021747317.

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22

Kulish, Aleksandr. "Etude paramétrique d’un procédé d’impression 3D (LMD) en vue d’optimiser l’intégrité matière : Application à l’alliage maraging 1.2709." Thesis, Lyon, 2022. http://www.theses.fr/2022LYSEE001.

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La thèse de doctorat présentée dans ce travail est consacrée à une méthode innovante de production de moules d'injection plastique. Cette méthode combine la technologie additive laser, notamment le rechargement par injection coaxiale de poudre (LMD) et la technique de traitement laser visant à réduire les contraintes résiduelles. Par conséquent, l'objectif principal du présent travail est d'optimiser et d'analyser la méthode de fabrication proposée en ce qui concerne les propriétés finales des pièces déposées. L'étude paramétrique de LMD des "simples cordons", des structures de type "mur" et des "cubes" a été réalisée. La LMD d'échantillons cubiques a été analysée en fonction de la densité, des contraintes résiduelles et de la microstructure afin d’obtenir les paramètres optimaux de LMD. Les paramètres optimaux de LMD ont été vérifiés lors du dépôt à long terme d'échantillons cubiques et cylindriques en une seule et plusieurs fois. La tenue en fatigue ainsi que la densité, la microdureté et la microstructure ont ensuite été évaluées. La simulation numérique a également été réalisée pour prédire les champs thermiques générés pendant le procédé LMD. Enfin, cette thèse comprend l'étude numérique et expérimentale du processus de traitement laser (de détentionnement) visant à réduire les contraintes résiduelles et à éviter les post-traitements durables tels que le vieillissement
The PhD thesis presented in this work is dedicated to the innovative method of plastic injection mould production. This method combines laser additive technology, namely, the Laser Metal Deposition (LMD) and technique of laser treatment aiming to reduce the residual stresses. Therefore, the main objective of the present work is to optimize and analyze the proposed fabrication method regarding the final properties of deposited parts. The parametrical study of “single-bead”, multi-bead “wall” and multi-bead “cube” LMD has been carried out. The LMD of cubic specimens has been analyzed with respect to the density, residual stresses and microstructure in order to find the optimal deposition parameters. The optimal LMD parameters have been verified during the longtime deposition of cubic and cylindrical specimens in a single operating session and after multiple pauses. The fatigue resistance as well as the density, microhardness and microstructure were then evaluated. The numerical simulation has been also performed to predict the thermal fields generated during LMD. Finally, this thesis includes the numerical and experimental study of laser treatment process aiming to reduce the residual stresses and avoid the possible long-lasting post-treatment such as aging

23

Conradie, Johannes Hendrik. "Characterising failure of structural materials using digital images." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96755.

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Thesis (MEng)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: The fracture of ductile materials is currently regarded as a complex and challenging phenomenon to characterise and predict. Recently, a bond-based, non-local theory was formulated called the peridynamic theory, which is able to directly solve solid mechanics problems that include fracture. The failure criterion is governed by a critical stretch relation between bonds. It was found in literature that the critical stretch relates to the popular fracture mechanics parameter called the critical energy release rate for predicting brittle linear-elastic failure. It was also proposed that the non-linear critical energy release rate or J-integral can be used to model ductile failure using peridynamics. The aim of this thesis was to investigate the validity of using the J-integral to determine the critical stretch for predicting ductile failure. Standard ASTM fracture mechanics tests on Compact Tension specimens of Polymethyl methacrylate, stainless steel 304L and aluminium 1200H4 were performed to determine the critical energy release rates and non-linear Resistance-curves. Furthermore, a novel peridynamic-based algorithm was developed that implements a critical energy release rate based failure criterion and Digital Image Correlation (DIC) measured full surface displacement fields of cracked materials. The algorithm is capable of estimating and mapping both the peridynamic damage caused by brittle cracking and damage caused by plastic deformation. This approach was used to validate the use of an energy release rate based failure criterion for predicting linear-elastic brittle failure using peridynamics. Also, it showed a good correlation among the test results for detecting plastic damage in the alloys when incorporating the respective J-integral derived critical stretch values. Additionally, Modified Arcan tests were performed to obtain Mode I, Mode II and mixed Mode fracture load results of brittle materials. Mode I peridynamic models compared closely to test results when using the Mode I critical energy release rate, derived critical stretch and served as validation for the approach. Moreover, it was argued that Mode I failure criteria cannot in principle be used to model shear failure. Therefore, it was proposed to rather use the appropriate Mode II and mixed Mode critical energy release rates to predict the respective failures in peridynamics. Also, for predicting ductile failure loads it was found that using a threshold energy release rate derived from the R-curve yielded considerably more accurate failure load results compared to the usage of the critical energy release rate, i.e. J-integral. In this thesis it was shown that there exists great potential for detecting and characterising cracking and failure by using a peridynamic-based approach through coupling DIC full displacement field measurements and the critical energy release rate of a particular structural material.
AFRIKAANSE OPSOMMING: Duktiele breeking van materiale word tans beskou as 'n kompleks- en uitdagende fenomeen om te voorspel en te karakteriseer. 'n Binding-gebaseerde, nie-lokale teorie is onlangs geformuleer, genaamd die peridinamika teorie. Die laasgenoemde stel ons in staat om soliede meganiese probleme met krake direk op te los. Die falings kriterium word bemagtig deur die kritiese strekfaktor tussen verbindings. Daar was bewys dat die kritiese strekfaktor in verband staan met die popul^ere breek meganika parameter, genaamd die kritiese vrylatings-energie-koers vir die voorspelling van bros line^ere-elastiese faling. 'n Onlangse verklaring meen dat die kritiese strekfaktor vir duktiele falingsgedrag, bereken kan word met die nie-line^ere kritiese vrylatings-energie-koers, beter bekend as die J- integraal. Die doel van hierdie tesis was om te meet hoe geldig die gebruik van die J-integraal is om die kritiese strekfaktor te bereken, om sodoende duktiele breking te ondersoek. Standaard ASTM breukmeganika toetse op Polimetilmetakrilat, vlekvrye staal 304L en aluminium 1200H4 is uitgevoer om die kritiese vrylatings-energie-koers en Weerstandskurwes te bepaal. Verder was 'n nuwe peridinamies-gebaseerde algoritme ontwikkel. Die laasgenoemde implementeer die berekening van 'n kritiese strekfaktor, gebaseer op die kritiese vrylatings-energie-koers, sowel as Digitale Beeld Korrelasie (BDK) vol oppervlaks-verplasings veld metings van gebreekte materiale. Dit is in staat om die peridinamiese skade te bereken, tesame met die beeld wat veroorsaak was van bros krake en plastiese vervorming in duktiele materiale. Hierdie benadering is aangewend om die gebruik van 'n vrylatings-energie-koers gebaseerde falings kriterium vir bros line^ere-elastiese falings in peridinamika te bekragtig. 'n Goeie korrelasie tussen toets resultate is ook gevind vir die opsporing van skade wat veroorsaak is deur plastiese deformasie in die legerings waar die onderskeilike J-integrale gebruik was as falings kriteria. Daarbenewens, was Verandere Arcan toetse uitgevoer om die Modes I, Modes II en gemenge Modes falingsresultate te verkry. Die Modes I peridinamiese model het goed vergelyk met die toetsresultate en het gedien as bekragtiging vir die falingsbenaderings. Verder was dit aangevoer dat Modes I falings kriterium in beginsel nie gebruik kan word om skuiffaling te modelleer nie. Dus was dit voorgestel om eerder die toepaslike Modes II en gemengde Modes kritieke vrylatings-energie-koerse te gebruik om onderskeie falings te voorspel in peridinamiese modelle. Dit was ook gevind dat vir die voorspelling van duktiele falingslaste die drumpel vrylatings-energie-koers, wat verkrygbaar is vanaf die Weerstands-kurwe, aansienlik meer akkurate resultate gee, in vergelyking met die gebruik van die kritiese vrylatings-energie-koers, m.a.w. die J-integraal. In hierdie tesis was dit gewys dat daar groot potensiaal bestaan vir die opsporing en karakterisering van krake en falings met 'n peridinamies-gebaseerde benadering, deur dit te skakel met BDK vol verplasings veld metings en die kritiese vrylatings-energie-koers van 'n bepaalde strukturele materiaal.

24

Black, Sean C. E. "The effect of abrasive properties on the surface integrity of ground ferrous materials." Thesis, Liverpool John Moores University, 1996. http://researchonline.ljmu.ac.uk/5100/.

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The effect of the thermal properties of alumina and CBN abrasives on workpiece temperatures in grinding was investigated. A review of the literature revealed a lack of knowledge of the thermal properties of CBN limiting the accuracy of theoretical predictions of the heat conduction in CBN grinding. A grain contact analysis was developed to predict the energy partitioning between the workpiece and wheel. The analysis takes into account two dimensional transient heat transfer in the grain and maintains temperature compatibility at the grain wear flatworkpiece interface. The proportion of the total grinding energy entering the workpiece, termed the partition ratio, was estimated by correlating measured temperature distributions with theoretical distributions. The partition ratios when grinding with CBN were substantially lower than grinding with alumina wheels for a range of ferrous materials. The lower partition ratios with CBN grinding were attributed to the higher thermal conductivity of the CBN abrasive. The effective thermal conductivity of alumina and CBN grains were quantified by correlating the theoretical partitioning model with the measured results. The effective thermal conductivity of CBN was found to be considerably lower than the reported theoretical value albeit much higher than the effective thermal conductivity of alumina. A model to predict the background temperature in grinding was proposed based on the experimental findings. The thermal model takes into account a triangular heat flux distribution in the grinding zone, the real length of contact and experimentally validated grain thermal properties. The input parameters to the thermal model were specified. To avoid temper colours on the workpiece surface the maximum background temperature must not exceed 450 to 500deg. C. for commonly used ferrous materials.

25

Jarrosson, Bruno P. "Closure integrity testing of heat sealed aseptic packaging using scanning acoustic microscopy." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-07212009-040225/.

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26

Kishawy, Hossam Eldeen A. "Chip formation and surface integrity in high speed machining of hardened steel /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0003/NQ42858.pdf.

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27

Galéa, Vincent. "Surface integrity and tool performance in the turning of hardened steel." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17030.

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28

Beranek, Maggi Marie. "The influence of surface integrin binding patterns on specific biomaterial-cell interations [i.e., interactions] a dissertation /." San Antonio : UTHSC, 2008. http://proquest.umi.com.libproxy.uthscsa.edu/pqdweb?did=1588776891&sid=1&Fmt=2&clientId=70986&RQT=309&VName=PQD.

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29

Smith, Stephen R. "An investigation into the effects of hard turning surface integrity on component service life." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/17526.

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30

Yang, Jing 1988. "Grinding effects on surface integrity, flexural strength and contact damage resistance of coated hardmetals." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/396135.

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This thesis assesses the influence of substrate surface integrity on different mechanical (flexural strength and contact damage resistance under spherical indentation) and tribological (scratch resistance as well as cracking and delamination response under Brale indentation) properties for a TiN-coated fine-grained hardmetal grade (WC-13 wt.%Co). In doing so, three different surface finish conditions are studied: as-sintered (AS), ground (G), mirror-like polished (P) and ground plus thermal annealed (GTT). Moreover, a relevant part of the work is devoted to nude hardmetal substrates. The result indicates that grinding induces significant alterations in the surface integrity. It yielded in high roughness and emergence of a topographic texture; anisotropic distribution of microcracks within a thin subsurface layer; severe deformation, microstructure refinement and phase transformation of binder regions; and large compressive residual stresses. Subsequent ion etching and coating deposition resulted in a significant residual stresses decrease while damage induced by grinding was not completely removed in the substrate surface. On the other hand, high temperature annealing (GTT condition) completely relieved the referred residual stresses, but without inducing any additional change in terms of existing damage. This was not the case for the metallic binder phase where such treatment induced an unexpected microporosity, development of a recrystallized subgrain structure and reversion of grinding-induced phase transformation. Strength of hardmetals was significantly enhanced by grinding, as compared to AS and P conditions. Such beneficial effect is partly lost during the subsequent ion etching and coating deposition stages. On the other hand, strength of coated GTT condition increases compared to that of the corresponding uncoated one. Systematic residual stress analysis combined with extensive fractographic inspection reveal that strength variations measured after individual manufacturing chain or heat treatment steps (grinding, ion-etching, coating and/or thermal annealing) may be rationalized on the basis of effective residual stress state and location, either at the surface or at the subsurface, of strength-controlling flaws. Independent of substrate surface finish, coated AS, G and P samples exhibit similar critical load for initial substrate exposure as well as same predominant failure mode as they get scratched. However, clear differences in the failure scenario were evidenced. Scratch track for G samples exhibited discrete and localized substrate exposure, compared to the more pronounced and continuous exposure for AS and P ones. On the other hand, GTT samples showed lower critical load and changes in the mechanisms for the scratch-related failure; the latter depending on the relative orientation between scratch and grinding directions. Coated hardmetals exhibit more brittleness and lower adhesion strength, under Brale indentation testing conditions, with decreasing binder content. Grinding is discerned to promote delamination, compared to the polished condition, but also to strongly inhibit radial cracking. Such a response is analyzed on the basis of the interaction between elastic-plastic deformation imposed during indentation and several grinding-induced effects: remnant compressive stress field, pronounced surface texture and microcracking within a thin microcracked subsurface layer. Contact damage resistance of coated hardmetals, subjected to spherical indentation, is enhanced by grinding of the substrate previous to coating stage. Such beneficial effects are discerned regarding both crack nucleation at the coating surface and subsequent propagation into the hardmetal substrate. The grinding-induced compressive residual stresses are pointed out as the main reason for the improved response against contact loading. Such statement is sustained by the lower damage resistance evidenced in coated GTT specimens.
En este trabajo se estudia la influencia de la integridad superficial del sustrato sobre diferentes propiedades mecánicas (resistencia tanto a la rotura en flexión como al daño inducido por contacto) y tribológicas (resistencia al rayado así como el comportamiento bajo solicitaciones de indentación Brale) de una calidad fina de metal duro (WC-13% peso Co) recubierta con una capa de TiN. La investigación incluye la consideración de cuatro acabados superficiales: en condiciones de sinterizado (AS), rectificado (G), pulido (P), y rectificado más un tratamiento térmico de recocido (GTT). Los resultados indican que el rectificado induce alteraciones importantes en la integridad superficial: se incrementa la rugosidad y emerge una textura superficial; se evidencia la existencia de microfisuras, anisotrópicamente distribuidas a nivel subsuperficial; se introduce una deformación muy severa, lo cual da lugar a un refinamiento de la microestructura y transformación de fase en el ligante metálico; y finalmente, se inducen tensiones residuales compresivas elevadas. Estas tensiones se ven reducidas durante las etapas subsecuentes de pulverización por bombardeo iónico y deposición de la capa cerámica. Por su parte, las tensiones residuales referidas si son completamente eliminadas en las muestras GTT, aunque sin que el tratamiento posterior al rectificado induzca cambio alguno respecto al daño existente. Éste no es el caso para la fase metálica, donde el tratamiento de recocido conlleva la aparición de una inesperada microporosidad, recristalización microestructural a nivel subsuperficial y la reversión de la transformación de fase inducida durante el rectificado. La operación de rectificado resultó en un incremento significativo de la resistencia a flexión del metal duro. Este efecto positivo se perdió parcialmente al recubrir el material. Por el contrario, la deposición de la capa de TiN promovió un aumento de la resistencia mecánica para la condición GTT. Las variaciones en resistencia a rotura determinadas se explican considerando las tensiones residuales efectivas existentes en cada caso y la ubicación, en la superficie o por debajo de ella, de los defectos críticos responsables de la rotura del material. La carga crítica para la exposición del sustrato en el ensayo de rayado resultó ser Independiente del acabado superficial, para las muestras AS, G y P. Sn embargo, el daño irreversible inducido por el indentador bajo condiciones de contacto y deslizamiento simultáneo fue discreto y localizado para las muestras G, a diferencia de la exposición continua y más pronunciada del sustrato que se evidenció en las condiciones AS y P. Por su parte, las muestras GTT mostraron una carga crítica inferior y cambios relevantes en el mecanismo de fallo correspondiente. El ensayo de indentación Brale de metales duros recubiertos indicó una mayor fragilidad y una menor resistencia a la adhesión para la calidad con menor contenido de ligante metálico. En este marco experimental, y en comparación con el acabado de pulido, se evidenció que el rectificado del sustrato favorece la delaminación, pero también inhibe la aparición de fisuras radiales en metales duros recubiertos. La respuesta observada se analiza y explica sobre las bases de la interacción entre la deformación elasto-plástica impuesta durante la indentación y las alteraciones en integridad superficial resultantes del rectificado. El rectificado del sustrato, previo a la deposición de una capa cerámica, incrementa la resistencia al daño inducido bajo solicitaciones de contacto esférico. Esta influencia positiva se evidencia en términos no solo de la nucleación de fisuras sino también de la subsecuente propagación de ellas dentro del sustrato de metal duro. La principal razón de ello son las elevadas tensiones residuales de compresión introducidas en el proceso de rectificado. Esta afirmación se sustenta por la menor resistencia al daño por contacto que se determinó en las muestras GTT recubierta

31

Arai, S. "Surface integrity control of piezoelectric materials in ultra precision grinding on the basis of machine design assessment." Thesis, Cranfield University, 2004. http://dspace.lib.cranfield.ac.uk/handle/1826/10441.

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The target of this research work was to establish a surface integrity control methodology in ultra precision grinding for piezoelectric materials, taking into account the interaction between the material removal manner and the machine design contributions. Whilst there are many respective research works concerning the microscopic material removal behavior on brittle materials and the design characterization of individual machine components, it was necessary to identify the design characteristics in order to ensure a consistent and fine surface integrity ( i.e. surface roughness, surface atness, textural damage ) in contact machining. For example, in a thermal analysis of a machine structure, the considerable inuences of internal and external heat sources were observed, which resulted in heat ows in aerostatic and hydrostatic components. After identifying several thermal error modes, a substantial improvement of thermal stability was applied successfully onto the machine structure. However, the major contributions arising from this research work are considered to be the following. ( i ) Suggestion of a method to achieve optimized grinding conditions for piezoelectric materials ( ii ) Identification of a link between material removal behavior and the machine design contribution (iii)Development of a novel tooling component Following a static and dynamic assessment of three grinding machine structures, it was conciuded that an enhanced damping performance at the loop distance, between the grinding wheel and work tooling, is beneficial to obtain a fine surface finish together with a at surface, whereas past researchers have claimed that static stiffness and high resonant frequencies should be the prime aim.

32

Chlup, Martin. "Hodnocení průběhu silového zatížení při vystružování za použití moderních vystružovacích hlavic MT3 v závislosti na integritě povrchu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229943.

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The diploma work deals with the evaluation of force load procedure problems when using reaming head MT3 depending on selected criteria of surface integrity of machined hole. It is possible to eliminate some unwanted elements when reaming by force load procedure analysis. These negative elements can influence both the tool e.g. its previous wear and the defect of a newly made hole.

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Huang, Bo. "Cryogenic Processing of Al 7050-T7451 Alloy for Improved Surface Integrity." UKnowledge, 2016. http://uknowledge.uky.edu/me_etds/78.

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Al 7050-T7451 alloy with good combinations of strength, stress corrosion cracking resistance and toughness, is used broadly in the aerospace/aviation industry for fatigue-critical airframe structural components. However, it is also considered as a highly anisotropic alloy as the crack growth behavior along the short transverse direction is very different from the one in the long transverse direction, due to the inhomogeneous microstructure with the elongated grains distributed in the work material used in the sheet/plate applications. Further processes on these materials are needed to improve its mechanical and material properties and broaden its applications. The material with ultra-fine or nano grains exhibits improved wear and corrosion resistance, higher hardness and better fatigue life, compared to the one with coarse grains. In recent times, the development of novel processing technologies has gained great attention in the research community to enhance the properties of the materials employed in the aerospace, biomedical, precision instrument, automotive, nuclear/power industries. These novel processing technologies modify the microstructure of this alloy and improve the properties. The aim of this dissertation is to investigate the effects of cryogenic processes, including friction stir processing (FSP), machining and burnishing, on Al 7050-T7451 alloy to solve the inhomogeneity issue and improve its surface integrity. FSP is applied to modify the microstructure of Al 7050-T7451 alloy for achieving more homogeneous structure with near ultra-fine grains (UFG) which were less than 2 µm, particularly in cryogenic FSP with liquid nitrogen as the coolant. Approximately 10% increase could be observed from the hardness measurement from the samples processed by cryogenic FSP, in contrast to dry FSP. Also, the texture change from Al (200) to Al (111) could be achieved in all the samples processed by dry and cryogenic FSP. Cryogenic machining and burnishing processes were also applied to enhance the surface integrity of the manufactured components with near-UFG structure. The highest cutting temperature was reduced by up to 44.7% due to the rapid cooling effect of liquid nitrogen in cryogenic machining, compared with dry machining. Nano grains were produced in the refined layers induced by cryogenic burnishing. And, up to 35.4% hardness increase was obtained within the layer depth of 200 µm in the cryogenically-burnished surface. A numerical finite element method (FEM) model was developed for predicting the process performance in burnishing. Less than 10% difference between the experimental and predicted burnishing forces was achieved in the simulation of cryogenic burnishing, and reasonable predictions were also achieved for temperatures, severe plastic deformation (SPD) layers.

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Coudert, Jean-Baptiste. "Impact de l'usinage de superfinition sur la zone affectée par le procédé : application à un matériau multiphasé." Thesis, Dijon, 2014. http://www.theses.fr/2014DIJOS074.

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Lors de l’usinage, les conditions de pression et de température à la surface usinée sont trèsélevées. La microstructure et l’état mécanique du matériau sont impactés, ce qui a desconséquences sur la réactivité chimique de la surface usinée. Dans cette thèse, ons’intéresse au tournage de superfinition de l’acier inoxydable martensitique X4CrNiMo16-5-1traité thermiquement (dénommé APX4 optimisé). Il présente la particularité d’êtremultiphasé à la température ambiante (martensite, ferrite et austénite). L’objectif est dequantifier les relations entre les conditions de coupe, les propriétés d’usage et ladégradation par corrosion des surfaces usinées. Des essais d’usinage en coupe orthogonale(type QST) ont été réalisés afin de comparer directement les résultats expérimentaux auxprédictions numériques 2D des surfaces usinées.Les changements de phase du matériau ont été étudiés par des essais de calorimétriejusqu’à 1200°C. Les cycles thermiques réalisés ont mis en évidence différentestransformations métallurgiques. L’étude bibliographique complémentaire permet deconclure quant aux possibilités de transformation de phase en usinage, qui sont quasiinexistantes du fait des cinétiques de chauffage extrêmement élevées en tournage.Les échantillons usinés ont été caractérisés avec une étude microstructurale parmicrographie optique et par MEB-EBSD. Ces deux techniques mettent en évidence lesdéformations importantes en extrême surface indiquées par l’étirement des îlots de ferriteparallèlement à la surface usinée. Ces résultats microstructuraux ont été mis en relationavec les résultats de microdureté Vickers. Une relation de la dureté superficielle a étéexprimée en fonction des conditions de coupe. La technique EBSD a permis de montrer pourles échantillons usinés dans les conditions les plus sévères la déformation de la ferrite avecapparition de sous-joints de grain, un affinement microstructural de la martensite et uneaccentuation de l’affinement de la matrice martensitique à proximité de la ferrite déformée.Une simulation numérique de prédiction des déformations à l’échelle macroscopiquea été réalisée. Ces résultats numériques ont été comparés aux résultats de déformation etde microdureté issus d’une campagne d’essais. Des essais numériques complémentairesappliqués à l’échelle de la microstructure (matériau considéré biphasé) permettent ded’appréhender la déformation de la phase ferritique et son influence locale sur ladéformation de la matrice martensitique. Ces résultats sont cohérents avec les résultatsexpérimentaux.Les phénomènes de corrosion par piqûres ont été étudiés par le biais d’essais depolarisation à l’aide de la microcellule électrochimique et d’essais spécifiques pulsés. Cesderniers essais ont permis l’analyse des piqûres générées (en diamètre et en densité). Larésistance à la corrosion localisée des surfaces d’acier inoxydable martensitique reste bonneaprès usinage, même améliorée (densité de piqûres plusieurs fois plus faible que l’état deréférence). Ce comportement est corroboré à l’état de compression de la surface.La microdureté de surface, qui est contrôlée majoritairement par l’avance, conditionne lepotentiel de piqûre. L’augmentation du diamètre de piqûre a été reliée à l’affinementmicrostructural (observé à partir d’un certain seuil de microdureté superficielle)
During machining, pressure and temperature conditions at the machined surface are veryintensive. Machined material microstructure and mechanical state are changed, whichimpacts the chemical reactivity of the machined surface. In this PhD study, we focus onsuperfinish turning of heat treated martensitic stainless steel X4CrNiMo16-5-1 (namedoptimized APX4). It has to be mentioned that this material has a multiphased microstructureat ambient temperature (martensite, ferrite and austenite). The aim is then to quantifyrelationships between cutting conditions, properties and the deterioration (corrosion) ofmachined surfaces. Machining trials in orthogonal cutting configuration (QST) have beenrealized in order to compare experimental results directly to 2D numerical forecast ofmachined surfaces.Material phase transformations have been studied by calorimetry tests until 1200°C. Testshave evidenced different metallurgical transformations. The complementary bibliographystudy allows to conclude that phase transformation possibilities during machining are veryquasi nonexistent due to extremely high heating kinetics in turning.Machined samples have been characterized by a microstructural study by opticalmicrography and SEM-EBSD. Both techniques highlight high strains in extreme machinedsurface as indicated by the stretching of ferrite islands in parallel to the machined surface.Microstructural results have been linked to the Vickers microhardness results. Surfacehardness has been expressed as a function of the cutting conditions.EBSD measurements have shown for machined samples in the most severe conditionsstraining of the ferrite with low angle grain boundaries, microstructural refining ofmartensite and heightening of martensitic matrix close to the strained ferrite.A numerical simulation predicting strains at the macroscopic scale has been carried out.These numerical results have been compared to strain and microhardness results arise fromone trials campaign. Further numerical simulations applied at the microstructure level(considered as biphased material) allow understanding of ferritic phase strain and its localinfluence on martensitic matrix strain. These results are consistent with experimentalresults.Pitting corrosion phenomenon has been studied by polarization testing using theelectrochemical microcell and specific pulsed testing. Last used method has been conductedto analyze the generated pits (diameter and density). Localized corrosion resistance ofmachined martensitic stainless steel surfaces remains good, even improved (few times lowerpitting density than the reference state). This behaviour is corroborated to the compressivestate of the surface.Surface microhardness, which is mainly controlled by the feed rate, conditions the criticalpitting potential. Increased pitting diameter has been linked to microstructural refining(observed above a surface microhardness level)

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Rodrigo, Navarro Aleixandre. "Functional living biointerfaces to direct cell-material interaction." Doctoral thesis, Universitat Politècnica de València, 2015. http://hdl.handle.net/10251/51461.

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[EN] This thesis deals with the development of a living biointerface between synthetic substrates and living cells to engineer cell-material interactions for tissue engineering purposes. This living biointerface is made of Lactococcus lactis, a non-pathogenic lactic bacteria widely used as starter in the dairy industry and, recently, in the expression of heterologous proteins in applications such as oral vaccine delivery or membrane-bound expression of proteins. L. lactis has been engineered to display the III 7-10 fragment of the fibronectin fused to GFP as reporter protein. Fibronectin is a ubiquitous protein present in the extracellular matrix, a complex mesh of structural and adhesive proteins which serve as mechanical support and development niche for cells of a wide variety of tissues. This fragment contains two important sequences, RGD and PHSRN. RGD is an adhesive sequence that interacts with a wide range of integrins, membrane-bound receptors that play a role in cellular processes such as adhesion, migration, proliferation and differentiation. On the other hand, PHSRN binds synergistically with RGD to some integrins such as alpha-5-beta-1 and others, increasing the specificity of this interaction. Genetically engineered L. lactis has been thoroughly characterized to test its capabilities as a living interface. This strain was found to express the FNIII 7-10-GFP fragment covalently linked to the cell wall and biological activity and expression levels of this fragment was assessed with techniques such as Western blot, ELISA and immunofluorescence. Moreover, this strain still holds the ability to develop biofilms, communities of sessile, attached bacteria to abiotic surfaces which helps greatly in the generation of a stable monolayer of bacteria between synthetic substrates and mammalian cells. Mammalian cell behaviour in response to the expressed fibronectin fragment on L. lactis membrane was also assessed. Several cell lines were tested, such as Fn-/Fn- and NIH3T3 fibroblasts, C2C12 myoblasts and human bone-marrow derived mesenchymal cells. This living biointerface was found to trigger cell adhesion and FAK phosphorylation, a marker for intracellular integrin-mediated signalling in all of the tested cell lines. It also triggered myoblast-to-myotube differentiation on C2C12 cells. In hMSCs, the cell-wall exposed fibronectin fragment was found to enhance the phosphorylation of ERK1/2, a kinase involved in the MAPK pathway, which is deeply involved in a multitude of cellular processes related to differentiation, proliferation and migration. Nevertheless, this thesis is a proof of concept that this novel system can be further exploited to express almost any desired protein or small molecule to help in the development of new tissues from progenitor cells. These molecules can be either secreted in the medium or displayed in the membrane, and can also be constitutively expressed or in-demand, due to the great flexibility of L. lactis and the wide variety of expression systems available. This interface based on living bacteria establishes a new paradigm in surface functionalization for biomedical engineering applications.
[ES] Esta tesis aborda el desarrollo de una biointerfase viviente entre materiales sintéticos y células vivas con el objetivo de dirigir la interacción célula-material en aplicaciones de ingeniería tisular. Esta biointerfase está compuesta de Lactococcus lactis, una bacteria láctica no patógena, ampliamente usada en la industria láctea como inóculo, y, recientemente, en la expresión heteróloga de proteínas para su uso como vacunas de administración oral o su expresión en membrana. L. lactis ha sido genéticamente modificado para expresar el fragmento III 7-10 de la fibronectina, unida a GFP como reporter. La fibronectina es una proteína presente de forma ubicua en la matriz extracelular, una compleja red de proteínas adhesivas y estructurales cuyo propósito es servir como soporte estructural y como nicho de desarrollo para diversos tejidos. Este fragmento contiene dos secuencias importantes, RGD y PHSRN. RGD es una secuencia adhesiva de unión que interacciona con una amplia variedad de integrinas, receptores de membrana que juegan muchos e importantes papeles en diferentes procesos celulares, como adhesión, proliferación, migración o diferenciación. Por otra parte, PHSRN se une a las integrinas de forma sinérgica con RGD facilitando aún más estos procesos y aumentando la especificidad de esta interacción. Esta cepa de L. lactis modificada ha sido ampliamente caracterizada para estudiar su idoneidad como interfaz funcional viviente. Se ha demostrado que L. lactis es capaz de expresar el fragmento FNIII7-10-GFP covalentemente anclado a la pared celular bacteriana, habiéndose caracterizado también su actividad biológica con técnicas como Western blot, ELISA e inmunofluorescencia. Esta cepa mantiene la capacidad de desarrollo de biofilms presente en la gran mayoría de microorganismos. Los biofilms son comunidades de bacterias sésiles adheridas a un sustrato que pueden ser usadas como interfase física entre células de mamífero y sustratos abióticos. También se ha estudiado la respuesta celular a la fibronectina expuesta en la membrana de L. lactis. Se estudiaron varias líneas celulares, como fibroblastos Fn-/Fn- y NIH3T3, mioblastos C2C12 y células mesenquimales humanas derivadas de médula ósea. Esta interfase viviente fue capaz de provocar respuesta celular en forma de adhesión en todas las líneas estudiadas, además de inducir diferenciación de mioblastos a miotubos en C2C12 y de provocar la fosforilación de FAK, un marcador de señalización celular mediada por integrinas. En células mesenquimales humanas se demostró la capacidad del fragmento de fibronectina expuesto para fosforilar ERK1/2, una kinasa perteneciente a la ruta de señalización MAPK, ruta que forma parte de muchos procesos celulares importantes como diferenciación, proliferación y migración. Pese a todo, esta tesis es sólo una prueba de concepto de un sistema que puede ser utilizado para expresar casi cualquier proteína o molécula pequeña deseada, que puede ser muy útil en el desarrollo de nuevos tejidos a partir de sus células progenitoras. Estas moléculas pueden ser secretadas en el medio o ancladas en la pared celular, de forma constitutiva o bajo demanda, debido a la flexibilidad y amplia variedad de sistemas de expresión disponibles para L. lactis. Esta biointerfase basada en bacterias vivas establece un nuevo paradigma en el campo de la funcionalización de superficies para aplicaciones de ingeniería biomédica.
[CAT] Aquesta tesi aborda el desenvolupament d'una interfase viva entre materials sintètics i cèl·lules vives amb l'objectiu de dirigir la interacció cèl·lula-material, per al seu ús en aplicacions d'enginyeria tissular. Aquesta interfase està composta de Lactococcus lactis, un bacteri làctic, no patogènic i àmpliament utilitzat en l'industria làctica com a inòcul, i, recentment, en l'expressió heteròloga de proteïnes per al seu ús com vacunes d'administració oral o per a la seva expressió en membrana. L. lactis ha sigut genèticament modificada per a expressar el fragment III7-10 de la fibronectina, unida a GFP com a reporter. La fibronectina és una proteïna present de forma ubiqua en la matriu extracel·lular, una complexa xarxa de proteïnes adhesives i estructurals que s'utilitzen com a suport estructural i com a nínxol de desenvolupament per a diversos teixits. Aquest fragment conté dos seqüències importants, RGD i PHSRN. RGD és una seqüència adhesiva d'unió a integrines, receptors de membrana que juguen molts i molt importants papers en diferents processos cel·lulars, com poden ser adhesió, proliferació, migració o diferenciació. Per altra banda, PHSRN s'uneix a les integrines de forma sinèrgica amb RGD facilitant encara més aquests processos i augmentant l'especificitat d'aquesta interacció. Aquesta modificació genètica de L. lactis ha estat àmpliament caracteritzada per provar les seves característiques com a interfase funcional vivent. S'ha demostrat que L. lactis és capaç d'expressar el fragment FNIII 7-10-GFP covalentment ancorat a la paret cel·lular bacteriana, havent-se caracteritzat també la seva activitat biològica amb tècniques com Western blot, ELISA i immunofluorescència. A més, aquest cep manté la capacitat de desenvolupament de biofilms, comunitats de bacteris sèssils adherits a un substrat que poden ser utilitzades com a interfase física entre cèl·lules de mamífer i substrats abiòtics. També s'ha estudiat la resposta cel·lular a la fibronectina expressada en la paret cel·lular de L. lactis. El estudi es va fer utilitzant diverses línies cel·lulars, com fibroblasts Fn-/Fn- i NIH3T3, mioblasts C2C12 i cèl·lules mesenquimals humanes derivades de medul·la òssia. Aquesta interfase vivent va ser capaç de provocar resposta cel·lular en forma d'adhesió a totes les línies estudiades, a més d'induir diferenciació de mioblasts a miotubs en C2C12 i de provocar la fosforilació de FAK, un marcador de senyalització cel·lular mediat per integrines, en les línies assajades. En cèl·lules mesenquimals humanes es va demostrar la capacitat del fragment de fibronectina exposat per fosforilar ERK1/2, una kinasa pertanyent a la ruta de senyalització MAPK, ruta que forma part de molts processos cel·lulars importants com diferenciació, proliferació i migració. Malgrat tot, aquesta tesi mostra només una prova de concepte d'un sistema que pot ser utilitzat per expressar gairebé qualsevol proteïna o molècula petita desitjada, que pot ser molt útil en el desenvolupament de nous teixits a partir de les seves cèl·lules progenitores. Aquestes molècules poden ser secretades en el medi o ancorades a la paret cel·lular, de manera constitutiva o sota demanda, a causa de la flexibilitat i àmplia varietat de sistemes d'expressió disponibles per L. lactis Aquesta biointerfase basada en bacteris vius estableix un nou paradigma en el camp de la funcionalització de superfícies per a aplicacions d'enginyería biomèdica.
Rodrigo Navarro, A. (2015). Functional living biointerfaces to direct cell-material interaction [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/51461
TESIS

36

Holmes, John Duncan. "Building worship facilities which integrate AV technology in their design." Theological Research Exchange Network (TREN), 1988. http://www.tren.com.

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Pu, Zhengwen. "CRYOGENIC MACHINING AND BURNISHING OF AZ31B MAGNESIUM ALLOY FOR ENHANCED SURFACE INTEGRITY AND FUNCTIONAL PERFORMANCE." UKnowledge, 2012. http://uknowledge.uky.edu/me_etds/5.

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Surface integrity of manufactured components has a critical impact on their functional performance. Magnesium alloys are lightweight materials used in the transportation industry and are also emerging as a potential material for biodegradable medical implants. However, the unsatisfactory corrosion performance of Mg alloys limits their application to a great extent. Surface integrity factors, such as grain size, crystallographic orientation and residual stress, have been proved to remarkably influence the functional performance of magnesium alloys, including corrosion resistance, wear resistance and fatigue life. In this dissertation, the influence of machining conditions, including dry and cryogenic cooling (liquid nitrogen was sprayed to the machined surface during machining), cutting edge radius, cutting speed and feed rate, on the surface integrity of AZ31B Mg alloy was investigated. Cryogenic machining led to the formation of a "featureless layer" on the machined surface where significant grain refinement from 12 μm to 31 nm occurred due to dynamic recrystallization (DRX), as well as increased intensity of basal plane on the surface and more compressive residual stresses. Dry and cryogenic burnishing experiments of the same material were conducted using a fixed roller setup. The thickness of the processed-influenced layer, where remarkable microstructural changes occurred, was dramatically increased from the maximum value of 20 μm during machining to 3.4 mm during burnishing. The burnishing process also produced a stronger basal texture on the surface than the machining process. Preliminary corrosion tests were conducted to evaluate the corrosion performance of selected machined and burnished AZ31B Mg samples in 5% NaCl solution and simulated body fluid (SBF). Cryogenic cooling and large edge radius tools were found to significantly improve the corrosion performance of machined samples in both solutions. The largest improvement in the material's corrosion performance was achieved by burnishing. A finite element study was conducted for machining of AZ31B Mg alloy and calibrated using the experimental data. A user subroutine was developed and incorporated to predict the grain size changes induced by machining. Good agreements between the predicted and measured grain size as well as thickness of featureless layers were achieved. Numerical studies were extended to include the influence of rake angle, feed rate and cutting speed on the featureless layer formation.

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Burgos, Diego Felipe Sarzosa. "Avaliação da vida à fadiga em materiais homogêneos e juntas soldadas incluindo efeitos de fechamento de trinca." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/3/3135/tde-04062013-153636/.

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Esta tese investiga o efeito do fechamento de trinca sobre as previsões da vida à fadiga em materiais homogêneos e juntas soldadas. É apresentada uma metodologia para a simulação numérica do fenômeno de fechamento de trinca induzido por plasticidade utilizando o método dos elementos finitos. Ensaios laboratoriais de propagação de trinca por fadiga do aço ASTM A516 Gr. 70 à temperatura ambiente foram realizados usando corpos de prova típicos da mecânica da fratura nas condições soldada e homogênea. Estes resultados foram usados para validar a metodologia numérica do cálculo da carga de abertura de trinca. Comparações entre a vida de propagação experimental e as estimativas obtidas por meio da integração da lei de propagação, incluindo o efeito do fechamento de trinca, foram feitas usando vários critérios para o cálculo da carga de abertura. As análises numéricas permitem estimar a carga de abertura de trinca analisando a evolução do campo de tensões, deformações e deslocamentos na região próxima à trinca, que está influenciada pelo contato das faces da trinca. Menores níveis de proteção da trinca devido ao fechamento foram obtidos para o corpo com heterogeneidade mecânica quando comparado ao corpo homogêneo na modelagem numérica. Durante o ensaio de propagação o corpo homogêneo apresentou taxas de propagação de trinca relativamente menores quando comparadas ao espécime soldado. A não inclusão do efeito do fechamento de trinca resulta em previsões da vida à fadiga conservadoras em aproximadamente 20% para todos os casos estudados neste trabalho. Análises tridimensionais do fenômeno de fechamento de trinca revelam que o crescimento da trinca por fadiga no estagio II parece estar controlado pelo retardo que acontece na superfície do corpo de prova. Incluído o efeito do fechamento de trinca nas previsões, as estimativas da vida à fadiga foram bastante próximas das obtidas experimentalmente, com diferenças conservadoras entre 1% e 15% dependendo do método de cálculo da carga de abertura. Os resultados apresentados mostram que vidas à fadiga mais acuradas e, ainda, conservadoras são feitas incluindo o efeito do fechamento de trinca na metodologia de cálculo da vida remanescente de componentes estruturais.
This thesis investigates the effect of crack closure on fatigue life predictions in homogeneous material and welded joints. It presents a methodology for numerical simulation of the phenomenon of plasticity-induced crack closure by using the finite element method. Experimental tests of fatigue crack propagation on ASTM A516 Gr 70 steel at room temperature were performed using typical specimens of fracture mechanics in two conditions: welded and homogeneous; these results were used to validate the numerical methodology for calculating the crack opening load. Comparisons between experimental propagation life and estimations obtained by numerical integration of propagation law, including the effect of crack closure, have been made using various criteria to calculate the opening load .The numerical analyses allow to predict the opening load by analyzing the evolution of stresses, deformations and displacements fields in the region near the crack which is growing and is influenced by the contact of the crack flanks. Lower levels of protection due to crack closure were obtained for the specimen with mechanical heterogeneity when compared to the homogeneous specimen in the numerical analyses. During the test of fatigue crack propagation the homogeneous specimen had smaller crack growth rates when compared to the welded specimen. Fatigue life predictions without including the effect of crack closure result in conservative estimations around 20% for all studied cases. Three-dimensional analysis of the phenomenon of crack closure shows that the fatigue crack growth in stage II appears to be controlled by the delay that occurs on the specimen surface. Including the effect of crack closure in life predictions, the estimates of fatigue life were quite close to those obtained experimentally, with conservative differences between 1% and 15% depending on the method of opening load calculation. The results show that the fatigue life predictions can be made more accurate and yet remain conservative when the effect of crack closure is included on the methodology for calculating the remaining life of structural components.

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Hughes, Trenton Whiting. "An evaluation of membrane materials for the treatment of highly concentrated suspended salt solutions in reverse osmosis and nanofiltration processes for desalination." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1083.

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Collie, Angela M. B. "The macrophage response to biomaterial topography : gene expression, integrin signaling, and surface adhesions /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/8115.

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41

Fraioli, Roberta. "Functionalization of titanium with integrin-selective ligands for orthopedic and dental applications." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/404303.

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Despite being biocompatible and with adequate mechanical properties for application as a bone replacement material, titanium lacks osteoinductive capacity, i.e. it supports new bone growth on its surface but does not foster its formation. This may lead to failure of the implant due to poor osseointegration. Together with infection, this is in fact the main cause of failure of orthopedic and dental implants. Therefore, this thesis explores the possibility to convert titanium surface into a bioactive substrate, which is actively capable of influencing cell fate in vitro and enhance implant osteointegration in vivo. To install such bioactivity, surface chemical functionalization was chosen, since it allows for the modification of the external layer of the material, which is responsible for the interactions with the surrounding tissues, while leaving the bulk properties unaffected. Two families of extracellular matrix (ECM)-inspired integrin-binding biomolecules were tested. Integrins are the major cell surface receptor, whose main role is to mediate cell-surface interactions; thus, addressing these receptors could be beneficial to tune cell response to the surface. One type of biomolecule tested is a double-branched peptidic ligand that allows for the simultaneous presentation of the cell-adhesive RGD (Arg-Gly-Asp) motif and the synergic PHSRN (Pro-His- Ser-Arg-Asn) motif, which synergizes the RGD-mediated binding to integrin a5ß1. Alternatively, non peptidic integrin-selective ligands were tested as surface coating molecules. These highly stable ligands were designed by the group of Prof. Kessler at the Technische Universität München (TUM, Munich, Germany) to be selective for either integrins a5ß1 or avß3 and are introduced in a review paper included in the thesis. The role of both of these receptor subtypes in several bone biology events is currently matter of discussion in literature. Grafting of the ligands on titanium was either carried out via physisorption or chemical anchoring. Silanization was used to create a covalent bond between the synthetic molecules and the metallic oxide. Two cell types were used for the in vitro testing of the functionalization system: human osteoblast-like cells (SaOS-2) and mesenchymal stem cells. The testing of different combinations of biomolecule, grafting technique and cell type is the subject of the four full-papers reported in the thesis. Two of these papers also include the in vivo study of the effect of the chemical functionalization in an animal model. The thesis also includes a work focused on the merging of two surface modification techniques, namely chemical functionalization and topographical modification, to create a multifunctional titanium substrate that simultaneously addresses the problem of infection and poor osseointegration: the nanostructure of the topography acts as the bactericidal element, while the surface-grafted biomolecules give eukaryotic cell-instructive properties to the material. This work was carried out during a stay at the Centre for Cell Engineering at the University of Glasgow (Prof. Dalby, UoG, Glasgow, UK). Overall, the collection of works presented in the thesis delineates a comprehensive scenario of how chemical functionalization with ECM-inspired ligands can act as a powerful tool to tune cell behavior and, ultimately, guide the biological response at the peri-implant site.
El objetivo principal de este proyecto de tesis es la instalación de bioactividad en la superficie de titanio para implantes ortopédicos y dentales a través de un proceso de funcionalización superficial. A pesar de ser biocompatible y con buenas propiedades mecánicas para substituir el tejido óseo dañado o ausente, el titanio carece de capacidades osteoinductivas, es decir, soporta pero no favorece los procesos de formación de hueso. Esto puede llevar a la fallida del implante debido a una falta de osteointegración. Las modificaciones superficiales permiten transformar la superficie bioinerte del titanio en una superficie bioactiva que estimula la producción de hueso, sin afectar las propiedades mecánicas del material. Para lograr dicha bioactividad, en este trabajo de tesis se inmovilizaron dos familias de moléculas peptidicas inspiradas en la matriz extracelular de las células que interactúan con las integrinas, los receptores celulares más importantes que transmiten la información entre las células y su matriz. El primer tipo de biomolécula testada es una molécula ramificada, cuyas dos extremidades llevan dos motivos peptídicos distintos: el motivo de adhesión celular RGD (Arg-Gly-Asp) y el motive de sinergia PHSRN (Pro-His-Ser-Arg-Asn), que incrementa la afinidad para la integrina a5ß1, muy relevante en procesos de crecimiento óseo. La segunda familia de biomoléculas abarca dos peptidomiméticos selectivos para la integrina a5ß1 o la integrina avß3, cuyo rol en la formación de hueso es también objeto de discusión en la literatura, y que fueron sintetizados por el grupo del Prof. H. Kessler de la Technische Universität München. Para la inmovilización de las moléculas en el titanio se utilizaron dos técnicas distintas: la fisisorción, que sólo está basada en la formación de enlaces débiles electrostáticos, puentes hidrogeno, etc., y la unión covalente, más estable, mediante la silanización de la superficie metálica. Las superficies de titanio modificadas se testaron con dos tipos celulares relevantes en el contexto de la substitución de material óseo: células de osteosarcoma (SaOS-2) y células mesenquimales (hMSCs), ambas de procedencia humana. La combinación de esos factores originó cuatro estudios, tres de los cuales son reportados como trabajos publicados. Dos de esos estudios incluyen también un análisis in vivo en un modelo animal, que permitió comprobar el efecto de la funcionalización en un escenario clínico real. Finalmente, se llevó a cabo un estudio en colaboración con el Prof. M. Dalby del Centre for Cell Engineering de la University of Glasgow para combinar la funcionalización química y la nanotopografia, obteniendo así una superficie de titanio multifuncional: las nanoestructuras superficiales son bactericidas, pero carecen de propiedades adhesivas, que pueden ser proporcionadas a través de la inmovilización de motivos peptídicos. En conjunto, los resultados de esta tesis demuestran que la funcionalización química es una herramienta poderosa para optimizar la respuesta celular en la superficie del biomaterial e inducir la respuesta biológica deseada.

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Quitadamo, Annalisa. "Logistica integrata nel Supply Chain Management: analisi, valutazione, ottimizzazione del flusso dei materiali e gestione dei trasporti in Effer Spa." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3404/.

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Caudill, James R. "ENHANCED SURFACE INTEGRITY WITH THERMALLY STABLE RESIDUAL STRESS FIELDS AND NANOSTRUCTURES IN CRYOGENIC PROCESSING OF TITANIUM ALLOY TI-6AL-4V." UKnowledge, 2019. https://uknowledge.uky.edu/me_etds/134.

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Burnishing is a chipless finishing process used to improve surface integrity by severe plastic deformation (SPD) of surface asperities. As surface integrity in large measure defines the functional performance and fatigue life of aerospace alloys, burnishing is thus a means of increasing the fatigue life of critical components, such as turbine and compressor blades in gas turbine engines. Therefore, the primary objective of this dissertation is to characterize the burnishing-induced surface integrity of Ti-6Al-4V alloy in terms of the implemented processing parameters. As the impact of cooling mechanisms on surface integrity from SPD processing is largely unexplored, a particular emphasis was placed upon evaluating the influence of cryogenic cooling with liquid nitrogen in comparison to more conventional methodologies. Analysis of numerical and experimental results reveals that burnishing facilitates grain refinement via continuous dynamic recrystallization. Application of LN2 during SPD processing of Ti-6Al-4V alloy suppresses the growth of new grains, leading to the formation of near-surface nanostructures which exhibit increased microhardness and compressive residual stress fields. This is particularly true in cryogenic multipass burnishing, where successive tool passes utilizing lower working pressures generate thermally stable work hardened surface layers, uniform nano-level surface finishes, and significantly deeper layers of compressive residual stresses.

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ALENCAR, DONIZETE A. de. "Avaliacao de integridade de revestimentos de combustiveis de reatores de pesquisa e teste de materiais utilizando o ensaio de correntes parasitas." reponame:Repositório Institucional do IPEN, 2004. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11236.

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Made available in DSpace on 2014-10-09T12:49:48Z (GMT). No. of bitstreams: 0
Made available in DSpace on 2014-10-09T14:03:09Z (GMT). No. of bitstreams: 1 09810.pdf: 7314670 bytes, checksum: 5232e1c4a6554def247601f9a049ba1f (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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Ritchie, Porter. "The Susceptibility of Electric Resistance Welded Line Pipe to Selective Seam Weld Corrosion." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1586336007742949.

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Reyes, Catherine Diane. "Collagen- and Fibronectin-Mimetic Integrin-Specific Surfaces That Promote Osseointegration." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11599.

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Cell adhesion to the extracellular matrix through cell-surface integrin receptors is essential to development, wound healing, and tissue remodeling and therefore represents a central theme in the design of bioactive surfaces that successfully interface with the body. This is especially significant in the areas of integrative implant coatings since adhesion triggers signals that regulate cell cycle progression and differentiation in multiple cellular systems. The interactions of osteoblasts with their surrounding extracellular matrix are essential for skeletal development and homeostasis and the maintenance of the mature osteoblastic phenotype. Our objective was to engineer integrin-specific bioactive surfaces that support osteoblastic differentiation and promote osseointegration by mimicking these interactions. We target two specific integrins essential to osteoblast differentiation the type I collagen receptor alpha2beta1 and the fibronectin receptor alpha5beta1. The central hypothesis of this project was that the controlled presentation of type I collagen and fibronectin binding domains onto well-defined substrates would result in integrin-specific bioadhesive surfaces that support osteoblastic differentiation, matrix mineralization, and osseointegration. We have demonstrated that these biomimetic peptides enhance bone formation and mechanical osseointegration on titanium implants in a rat tibia cortical bone model. We have also shown that the presentation of multiple integrin-binding ligands synergize to enhance intracellular signaling and proliferation. Finally, we demonstrate the advantage of the short biomimetic peptides over the native ECM proteins. This research is significant because it addresses current orthopaedic implant limitations by specifically targeting cellular responses that are critical to osteoblastic differentiation and bone formation. This biomolecular approach provides a versatile and robust strategy for developing bioactive surfaces that enhance bone repair and osseointegration of orthopaedic implants.

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Torres, Gómez Glòria. "Materials híbrids funcionals de tipus molecular. Hexacianoferrat integrat en polímers conductors com a electrodes en bateries recarregables de liti." Doctoral thesis, Universitat Autònoma de Barcelona, 2001. http://hdl.handle.net/10803/3121.

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Tot i continuant la línia d'investigació de materials híbrids moleculars, aquest treball té com a objectiu principal la síntesi, caracterització i estudi de les propietats electroquímiques de nous híbrids basats en l'anió ferricianur (hexacianoferrat,[Fe(CN)6]3-) com a espècie inorgànica electroactiva en materials amb polipirrol (PPi) opolianilina (PAni) com a matriu polimèrica conductora.

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Kingsriter, Marilyn G. "The effects of instructional methods and materials which integrate music and literacy on reading attitudes and interests of second graders /." free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9901252.

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Fratta, Giusy. "Analisi e razionalizzazione dei flussi di materiale in ingresso e dei trasporti in un'ottica di logistica integrata: il caso Denso Manufacturing Italia S.p.A." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amslaurea.unibo.it/1318/.

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Negli ultimi anni è emerso chiaramente come la logistica rivesta un’importanza fondamentale per le aziende e costituisca un ottimo strumento per assicurarsi e mantenere un solido vantaggio competitivo. Inoltre, osservando l’ambiente attuale si evince come il sistema logistico sia caratterizzato da un progressivo aumento di complessità, sia in seguito alle maggiori esigenze dei mercati e sia come conseguenza della globalizzazione. In questo quadro evolutivo è mutato profondamente il ruolo ricoperto dalla logistica all’interno delle organizzazioni. Rispetto alla concezione tradizionale, che considerava la logistica come una funzione esclusivamente interna all’azienda, si è assistito al progressivo coinvolgimento dei fornitori e dei clienti ed è emersa la necessità di coordinare gli sforzi dell’intera supply chain, con l’obiettivo di migliorare il livello di servizio globalmente offerto e di ridurre i costi logistici totali. Tali considerazioni sono state il filo conduttore dell’analisi presentata di seguito, basata su uno studio svolto presso la DENSO Manufacturing Italia S.p.A., finalizzato all’analisi dei flussi in ingresso ed in particolar modo alla razionalizzazione degli imballi e dei trasporti, in un’ottica di integrazione con i fornitori. In particolare, la prima parte della trattazione introduce gli argomenti dal punto di vista teorico. Infatti, nel primo capitolo verrà illustrato il tema della logistica integrata e della sua evoluzione nel tempo, in relazione all’ambiente competitivo attuale ed alle nuove richieste dei mercati, approfondendo il tema della logistica in ingresso e del trasporto merci. Quindi, nel secondo capitolo verrà trattato il tema degli imballi, analizzandone le ripercussioni sull’intera catena logistica ed offrendo una panoramica dei metodi che permettono l’integrazione tra gli imballaggi ed i sistemi di trasporto, movimentazione e stoccaggio. Invece, la seconda parte dello studio sarà dedicata alla presentazione dell’azienda in cui è stato realizzato il progetto di tesi. Nel terzo capitolo verranno introdotte sia la multinazionale giapponese DENSO Corporation che la sua consociata DENSO Manufacturing Italia S.p.A., specializzata nella produzione di componenti per il mercato automotive, presso cui si è svolto lo studio. Nel quarto capitolo verrà descritto il layout dell’impianto, per poi presentare la logistica in ingresso allo stabilimento, ponendo maggiore attenzione ai flussi provenienti dal nord Italia – ed in particolare dal Piemonte – su cui si incentra il lavoro di tesi. Quindi, nella terza ed ultima parte verrà presentata in dettaglio l’analisi condotta durante lo studio aziendale. In particolare, il quinto capitolo tratta dei flussi di materiale provenienti dall’area piemontese, con l’analisi degli imballi utilizzati dai fornitori, delle consegne e delle modalità di trasporto. Infine, nel sesto capitolo saranno proposte delle soluzioni migliorative relativamente a tutte le criticità emerse in fase di analisi, valutandone gli impatti sia in termini economici che in relazione all’efficienza del flusso logistico.

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Sterr, Julia Maria Claudia [Verfasser], Horst-Christian [Akademischer Betreuer] Langowski, Horst-Christian [Gutachter] Langowski, and Jens-Peter [Gutachter] Majschak. "Influence of gases on the integrity of packaging materials upon high pressure treatment / Julia Maria Claudia Sterr ; Gutachter: Horst-Christian Langowski, Jens-Peter Majschak ; Betreuer: Horst-Christian Langowski." München : Universitätsbibliothek der TU München, 2017. http://d-nb.info/1149252308/34.

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