Made available in DSpace on 2014-06-11T19:23:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-01-26Bitstream added on 2014-06-13T18:09:42Z : No. of bitstreams: 1 paula_wcf_me_bau_prot.pdf: 7449514 bytes, checksum: 2e4729f72ced2d131784cfe27d6be1ad (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O cenário mundial tem apresentado um ambiente de alta competição industrial, pressionando cada vez mais as indústrias a tornarem seus processos produtivos mais eficientes. Além da eficiência, a precisão é de extrema importância num ambiente onde as empresas tentam manter padrões e procedimentos que se adaptem às normas internacionais. Um dos processos de acabamento mais utilizados na fabricação de componentes mecânicos de precisão é a retificação, e um dos critérios preponderantes na qualidade final de um produto é a integridade superficial, influenciada principalmente por fatores térmicos e mecânicos. Assim, o objetivo deste trabalho foi investigar as relações intrínsecas entre a qualidade superficial de peças retificadas e o comportamento dos sinais correspondentes de emissão acústica e potência de corte para retificação tangencial plana utilizando-se redes neurais artificiais. A caracterização da qualidade superficial das peças foi analisada por meio de parâmetros de queima superficial, rugosidade e microdureza. Verificou-se que o uso de redes neurais artificiais na caracterização da qualidade de superfícies de peças retificadas obteve bons resultados, apresentando-se como uma proposta interessante para implementação de sistemas inteligentes em ambientes industriais. / The world scenario has presented a high industrial competition, pressuring each time more the industries to change its more efficient productive processes. Besides efficiency, the precision is of extremely in a world where the companies try to maintain patterns and procedures that fit international demands. One of the most used final processes in the manufacturing of mechanical precision components is grinding, and one of the main criteria in the final quality of a product is its surface integrity, mainly influenced by thermal and mechanical factors. Thus, the objective of this work is to investigate the existing relationships between the surface quality of grinding workpieces and the behavior of correspondent signal of acoustic emission and cutting power to the surface grinding machines using artificial neural network. The characterization of the surface quality of the workpieces was analyzed through surface burning parameters, surface roughness and microhardness. It was verified that the use of artificial neural networks in the characterization of quality of surfaces grinding workipieces had positive results, being presented as an interesting proposal to implementation of intelligent systems in the industrial environments.

This thesis investigates the cooling behaviour of polymers during the microinjection moulding process. The work included bespoke experimental mould design and manufacturing, material characterisation, infra-red temperature measurements, cooling analysis and cooling prediction using commercial simulation software. To measure surface temperature of the polymers, compounding of polypropylene and polystyrene with carbon black masterbatch was performed to make materials opaque for the IR camera. The effects of addition of carbon black masterbatch were analysed using differential scanning calorimetry and Fourier transform infrared spectroscopy. Sapphire windows formed part of the mould wall and allowed thermal measurements using an IR camera. They were laser machined on their inside surfaces to generate a range of finishes and structures. Their topographies were analysed using laser confocal microscope. The surface energy of sapphire windows was measured and compared to typical mould steel, employing a contact angle measurement technique and calculated using Owens-Wendt theory. A heating chamber was designed and manufactured to study spreading of polymer melts on sapphire and steel substrates. A design of experiments approach was taken to investigate the influence of surface finish and the main processing parameters on polymer cooling during microinjection moulding. Cooling curves were obtained over an area of 1.92 by 1.92 mm of the sapphire window. These experiments were conducted on the Battenfeld Microsystem 50 microinjection moulding machine. A simulation study of polymer cooling during the microinjection moulding process was performed using Moldflow software. Particular interest was paid to the effect of the values of the interfacial heat transfer coefficient (HTC) on the simulated cooling predictions. Predicted temperature curves were compared to experimentally obtained temperature distributions, to obtain HTC values valid for the material and processing parameters.

Le bilan de masse en surface de l’Antarctique (noté BMS ; résultante de l’équilibre entres les termes d’accumulation et d’ablation) contribue directement aux variations du niveau moyen des mers. Dans le contexte du changement climatique, sa détermination par les modèles atmosphériques est nécessaire pour affiner son estimation présente et future.Les vents violents en périphérie de l’Antarctique de l’Est sont responsables d’un entraînement aérodynamique de la neige en surface qui influence de façon significative le BMS. Le transport de neige par le vent est également à l’origine du développement de formes d’érosion éolienne orientées parallèlement au vent moyen au moment de leur formation et dont la distribution spatiale est un déterminant majeur de la rugosité de surface. Ces éléments de rugosité exercent en retour un effet d’obstacle à l’écoulement qui affecte directement le champ de vent en surface et, par extension, le transport éolien de la neige.Les travaux présentés dans cette thèse portent sur l’observation et la modélisation numérique de l’érosion éolienne de la neige au niveau d’une région côtière de l’Antarctique de l’Est, la Terre Adélie. Dans un premier temps, le modèle atmosphérique régional MAR, qui contient une représentation détaillée des processus de transport éolien, est mis en œuvre à une résolution spatiale de 5 km sur un domaine couvrant la Terre Adélie et comparé sur un mois d’été à des observations météorologiques incluant des mesures continues du vent et du flux éolien massique de neige aérotransportée. Il est montré que les flux éoliens de neige produits par le MAR sont hautement sensibles à la paramétrisation de la rugosité de surface, et qu’une calibration unique de ce paramètre ne permet pas de simuler avec une qualité équivalente le champ de vent en deux points de mesure distants d’à peine 100 km. À partir des observations, les interactions rugosité-érosion sont ensuite étudiées à l’échelle d’évènements individuels d’érosion éolienne. Il est mis en évidence i) que l’effet d’obstacle généré par les formes d’érosion éolienne a un impact inhibiteur sur le flux éolien de neige et ii) que cet effet d’obstacle peut être fortement diminué par l’aptitude des formes d’érosion éolienne à se réorienter parallèlement au vent dominant pendant un événement de transport. L’examen des observations sur une année révèle que ce processus d’ajustement aérodynamique est sujet à des variations temporelles majoritairement reliées à l’historique de la température. Enfin, on montre qu’une reconfiguration du modèle comprenant notamment l’introduction d’une dépendance à la température dans la paramétrisation de la rugosité de surface améliore considérablement la représentation des flux éoliens de neige par le MAR sur l’année considérée. Ces résultats suggèrent qu’une distribution spatiale et temporelle de la rugosité de surface doit être prise en compte dans les modèles atmosphériques pour une simulation réaliste du transport éolien de la neige à l’échelle de l’Antarctique. / The Antarctic ice sheet surface mass balance (SMB; the result of the balance between accumulation and ablation terms) has a direct influence on variations in the global mean sea level. In the context of climate change, atmospheric models are needed to improve its current and future estimation.Intense surface winds over the coastal slopes of East Antarctica are responsible for aerodynamic entrainment of snow at the surface, which has a significant influence on the BMS. Transport of snow by the wind also produces aeolian erosion features aligned parallel to the prevailing winds at the time of their formation. The spatial distribution of these features is a major determinant of surface roughness. On the other hand, surface roughness is an obstacle to flow and directly affects the surface wind field and, by extension, aeolian snow transport.The work presented here is based on observations and numerical modeling of aeolian snow erosion in a coastal stretch of Adélie Land, East Antarctica. First, the regional atmospheric model MAR, which includes a detailed representation of aeolian transport processes, was run at a spatial resolution of 5 km over a zone including Adélie Land and model results were compared with meteorological observations made over one month in summer, including continuous measurements of the wind and the aeolian snow mass flux. Aeolian snow mass fluxes modeled by MAR were highly sensitive to parameterization of surface roughness, and a single calibration of this parameter was not enough to simulate the surface wind field at two measurement points located only 100 km apart with the same accuracy. Consequently, roughness-erosion interactions were analyzed at the scale of individual aeolian erosion events using observations. The results of this analysis underlined that (i) the barrier effect generated by aeolian erosion features had an inhibiting impact on the aeolian snow mass flux and (ii) that the barrier effect can be strongly reduced by the ability of aeolian erosion features to realign with the dominant wind during a transport event. Examination of observations made over a period of one year revealed that this adjustment process is prone to temporal variations mainly linked to past temperatures. Finally, we showed that reconfiguring the model, including introducing temperature dependence in the parameterization of surface roughness considerably improved the representation of aeolian snow mass fluxes by the MAR model for the year concerned. These results suggest that spatial and temporal distribution of surface roughness should be included in atmospheric models for realistic simulations of aeolian snow transport over Antarctica.

L’objectif de cette thèse est de contribuer à la détection de défauts dans des pièces réalisées par le procédé de fabrication additive de déposition métallique par laser (DML), en vue d’un contrôle in situ. Le contrôle in situ envisagé porte sur les derniers cordons déposés par le procédé (acier 316L et Inconel 718), pour lesquels des porosités et fissures peuvent apparaître (~ 100 µm). L’inspection est effectuée par méthode ultrasons-laser (UL), c’est-à-dire tout optique et non intrusive (régime thermoélastique). Le procédé DML engendre une microstructure dite à gros grains et des rugosités de surface qui rendent le contrôle ultrasonore plus délicat. En effet, ces caractéristiques microstructurales provoquent la diffusion des ondes élastiques dans le milieu. Ce travail de thèse participe donc à la compréhension de ces phénomènes et de leurs influences pour mieux détecter des défauts subsurfaciques dont les dimensions sont proches des longueurs d’ondes acoustiques. Ainsi, l’inspection en surface a été optimisée par la conception d’un montage optique, permettant de favoriser la génération de l’onde de Rayleigh, par une ligne source laser fine (~200 µm) et présentant des fronts raides. En conséquence, le contenu spectral de l’onde a été augmenté vers les hautes fréquences, c’est-à-dire jusqu’à 10 MHz. La longueur d’onde de Rayleigh (λR) a pu être ainsi diminuée à une valeur proche de celle des défauts recherchés, de l’ordre de 700 µm. Ensuite, les limites de ce dispositif ont été mises en évidence sur des pièces fabriquées par le procédé DML. Ces pièces comportent des défauts usinés, des entailles et des trous génératrice dont les dimensions sont inférieures à λR, leur surfaces est rugueuse (diffraction multiple de l’onde de Rayleigh). Puis, l’inspection de défauts réels subsurfaciques est étudiée. Ces défauts sont créés soit par une variation d’un des paramètres du procédé, le hatch (distance inter-cordon), ou encore par l’utilisation d’une poudre métallique de mauvaise qualité. En dégradant volontairement ces paramètres, les échantillons présentent alors des taux de porosités (Φ) pouvant s’étendre de 0,5% à 10%. Enfin, deux méthodes de corrélations ont été exploitées pour discriminer les taux de porosités : à travers l’étude du degré de ressemblance et l’Analyse en Composantes Principales (ACP). La première méthode, simple et rapide à mettre en œuvre, ne permet cependant pas de distinguer les taux de porosités. En revanche, l’ACP indique qu’il est possible de discriminer tous les défauts. Pour finir, des tests préliminaires ont été effectués afin de montrer qu’il est possible d’effectuer des mesures par méthode UL sur surface rugueuse, tout en conservant un bon rapport signal sur bruit, et ce sans moyenner les signaux, au cours d’un déplacement robotisé. / This thesis contributes to the detection of flaws in laser metal deposition (LMD) additive manufacturing process samples towards an in situ control of the process. The in situ control foreseen concerns the last layers deposited by the process (316L and Inconel 718 steel) for which porosities and cracks may appear (~ 100 µm). The inspection is performed by laser-ultrasonics (LU), an all-optical and non-invasive technic. Experiments are conducted in thermoelastic mode. The LMD process gives rise to coarse grain microstructure and surface roughness, that make the control tricky. Indeed, those characteristics generate scattering elastic waves. Thus, this work contributes to the better comprehension of those phenomena and their effects of the detection on subsurface flaws which dimensions are close to the acoustic wavelength. Surface inspection has been optimized by designing an optical setup, improving the Rayleigh wave generation by using a thin laser line source (~200 µm). Hence, the spectral content has been increased until it reaches 10 MHz, that is to say a wavelength equals to 700 µm (λR). Then, the limits have been brought out through the inspection of LMD samples. Those samples include sided drilled holes and notches which dimensions are less than λR, on rough surface (multiple scattering of Rayleigh wave). Moreover, real subsurface flaws inspections have been studied. The flaws have been created by the instability of one of the process parameter: the hatch (distance between each layer), or by a bad powder quality. By intentionally deteriorating those parameters, the samples, then, have porosity rate (Φ) with ranging from 0.5% to 10%. Finally, two correlation methods have been studied to discriminate porosity rate: through the study of the normalized cross correlation function and by Principal Component Analysis (PCA). The first method, simple and fast to implement, does not allow distinguishing the porosity rates. Nevertheless, the PCA indicates that it is possible to discriminate all the flaws. Finally, preliminary tests have been carried out to show that LU measurements is feasible on rough surfaces, while keeping a good signal-to-noise ratio, without averaging, during an automated displacement.

Carbon fibre-reinforced plastics (CFRP) are widely used in aerospace, automobile and other structural applications due to their superior mechanical and physical properties. CFRP outperform conventional metals in high strength-to-weight ratio. Usually, CFRP parts are manufactured near to net-shape;however,machining is unavoidable when it comes to assembly. Drilling the holes are essential to facilitate riveting and bolting of the components. However, conventional drilling (CD) induces different types of damages such as cracking, fibre pull-out, sprintling and delamination due to the abrasive nature, inhomogeneity and anisotropy of CFRP. A novel technique, ultrasonically-assisted drilling (UAD) is hybrid machining technique in which highfrequency (typically above 20 kHz) vibration are superimposed on a standard twist drill bit in axial direction using ultrasonic transducer. UAD has shown several advantages such as thrust force reduction, improving surface quality and lower bur-formation in drilling of conventional metals. UAD has also effectively been used for drilling brittle materials.

Submitted by PEDRO DE OLIVEIRA CONCEIÇÃO JUNIOR null (pedroliveira931@hotmail.com) on 2016-03-23T18:59:49Z No. of bitstreams: 1 dissertação_exemplar_final.pdf: 5761621 bytes, checksum: 84b8fff3fe34ccd2b227c3763843a3c9 (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-03-23T20:05:17Z (GMT) No. of bitstreams: 1 conceicaojunior_po_me_bauru.pdf: 5761621 bytes, checksum: 84b8fff3fe34ccd2b227c3763843a3c9 (MD5) / Made available in DSpace on 2016-03-23T20:05:17Z (GMT). No. of bitstreams: 1 conceicaojunior_po_me_bauru.pdf: 5761621 bytes, checksum: 84b8fff3fe34ccd2b227c3763843a3c9 (MD5) Previous issue date: 2016-02-17 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / As cerâmicas estruturais avançadas, tais como o óxido de alumínio, nitreto de silício, alumina e a zircônia estão sendo cada vez mais utilizadas na engenharia e na medicina. No entanto, muitas destas características que fazem a cerâmica tão atrativa também dificultam a sua fabri-cação por métodos tradicionais de usinagem. Para obter a forma desejada na usinagem de ma-teriais é necessário o uso do processo de retificação. As características da retificação cerâmicas avançadas são muito diferentes das características dos metais. Portanto, é necessário efetuar outros estudos para alcançar uma compreensão mais abrangente e um melhor controle dos parâmetros. Novas alternativas para o monitoramento do processo de retificação de cerâmicas têm sido estudadas. O monitoramento por sinais de vibração é um dos métodos bem-sucedidos utilizados no processo de retificação, pois algumas características que descrevem o comportamento e a influência do processo nas peças retificadas somente são perceptíveis no estudo deste sinal. O presente trabalho tem como objetivo estudar o sinal de vibração, de for-ma a extrair características relacionadas com o acabamento de cerâmicas avançadas no pro-cesso de retificação plana. Foi utilizada uma máquina retificadora tangencial plana com rebolo diamantado e corpos de prova de cerâmica alumina. O sinal de vibração foi medido por um acelerômetro e coletado por um osciloscópio à taxa de amostragem de 2 MHz. Os ensaios foram realizados em diferentes profundidades de corte, adotando duas velocidades da peça (vw), obtendo condições de usinagem brandas às mais severas. Medições de microscopia con-focal foram realizadas após a retificação das peças com objetivo de caracterizá-las. A rugosi-dade Ra das peças usinadas foi medida em quatro pontos ao longo das mesmas, por meio de um rogosímetro portátil. O processamento digital do sinal de vibração foi realizado, aplicando ferramentas computacionais e estatísticas de análise em cada passada de usinagem, compa-rando com os valores da rugosidade medidos. A faixa de frequência entre 800 Hz e 2 kHz foi a mais interessante para o estudo, e que melhor se relacionou com a condição da cerâmica após a retificação. Foi encontrada uma correlação entre a vibração e a integridade da peça cerâmica, pois o aumento da vibração é diretamente proporcional à rugosidade em cada profundidade de corte utilizada. Infere-se que a vibração pode ser utilizada para monitorar a retificação de cerâmica, devido à sua relação com a condição das peças. / Advanced structural ceramics such as aluminum oxide, silicon, nitride, alumina and zirconia are increasingly being used in engineering and medicine. However, many of these features that make ceramics so attractive also make them difficult to manufacture by traditional machining methods. To obtain the desired shape in the machining of these materials is necessary to use grinding process. The characteristics of the grinding of advanced ceramics are very different from those of metals. Therefore, it is necessary to perform other studies to gain a broader understanding and better control of the parameters. New alternatives for monitoring of ceramic grinding process have been studied. Monitoring vibration signals is one of the successful methods used in the grinding process, as some characteristics that describe the behavior and influence the process in parts ground only are noticeable in the study of this signal. This research aims to study the vibration signal, searching for the extraction of features that best relate to the characterization of machined parts. A surface grinding machine with diamond grinding wheel and alumina ceramic workpieces was used. The vibration signal was measured by an accelerometer and collected by the oscilloscope, using 2 MHz of sample rate. Tests were conducted at different depths of cut, adopting two different feed speeds (vw), which ranged from low to severe grinding conditions. Confocal microscopy was performed after the grinded of the workpieces in order to characterized them. The surface roughness Ra of each finished workpiece was measured at four areas along its surface, using a portable roughness measurer. The vibration digital signal processing was performed by applying computational tools on each pass machining. The frequency range between 800 Hz and 2 kHz was the most interesting for the study, and which better was related to the condition of the ceramic after the grinding process. A correlation between the vibration and the integrity of the ceramic workpiece was found, because the increased vibration is directly proportional to the surface roughness at each depth of cut used. It is inferred that the vibration can be used to monitor the grinding process of ceramic because of its relationship with the condition of the workipiece.

Submitted by DANILO MARCUS SANTOS RIBEIRO null (danpayne16@msn.com) on 2017-07-11T18:22:50Z No. of bitstreams: 1 dissertação_danilo_marcus_v9_final.pdf: 3798083 bytes, checksum: 8969b64b8101340dd46391b7669f950a (MD5) / Approved for entry into archive by LUIZA DE MENEZES ROMANETTO (luizamenezes@reitoria.unesp.br) on 2017-07-14T16:55:13Z (GMT) No. of bitstreams: 1 ribeiro_dms_me_bauru.pdf: 3798083 bytes, checksum: 8969b64b8101340dd46391b7669f950a (MD5) / Made available in DSpace on 2017-07-14T16:55:13Z (GMT). No. of bitstreams: 1 ribeiro_dms_me_bauru.pdf: 3798083 bytes, checksum: 8969b64b8101340dd46391b7669f950a (MD5) Previous issue date: 2017-05-25 / Pesquisadores tem avaliado um grande número de técnicas de monitoramento para controlar a condição superficial de peças. O diafragma piezelétrico de titanato zirconato de chumbo (PZT) é utilizado em muitos campos de pesquisa, mas estes sensores não são comuns no mo-nitoramento dos processos de usinagem. Este trabalho propõe um método para monitorar a condição superficial da peça (usinagem normal e queima) usando um diafragma piezelétrico e técnicas de extração de características. Uma comparação é feita com o sensor convencional de emissão acústica (EA), que é um sensor amplamente utilizado no monitoramento dos proces-sos de usinagem. Os ensaios de usinagem foram realizados em uma máquina de retificação de superfícies utilizando aço ABNT 1045 e rebolo CBN, onde os sinais foram coletados a 2 MHz. As peças foram cuidadosamente analisadas por meio de inspeção visual, rugosidade superficial, medidas de dureza e análises metalográficas. Estudo do conteúdo de freqüência de ambos os sinais foi realizado com o objetivo de selecionar bandas estreitamente relacionadas com a condição da superfície da peça. Filtros digitais foram aplicados aos sinais puros e as características foram extraídas e analisadas. Os valores RMS (Root Mean Square) filtrados nas faixas selecionadas para ambos os sensores apresentaram um ajuste melhor à regressão linear, o que é altamente desejável para estabelecer um limiar para detecção da queima e im-plementação em um sistema de monitoramento. Além disso, os resultados do índice RMSD (Root Mean Square Deviation) mostraram um excelente comportamento para o monitoramen-to da queima decorrente do processo de retificação para ambos os sensores. O método foi va-lidado usando um rebolo diferente, o que mostra claramente sua eficácia e demonstra o uso potencial do diafragma piezelétrico de baixo custo para o monitoramento da queima no pro-cesso de retificação. / Researchers have evaluated a great number of monitoring techniques in order to control the surface condition of ground parts. Piezoelectric diaphragm of lead zirconate titanate (PZT) are used in many fields, but these sensors are not common in the monitoring of machining pro-cesses. This paper proposes a method for monitoring the workpiece surface condition (normal grinding and burn) by using a piezoelectric PZT diaphragm transducer and feature extraction techniques. A comparison is made with conventional acoustic emission sensor, which is a traditional sensor in the monitoring of machining processes. Grinding tests were performed in a surface-grinding machine with SAE 1045 steel and CBN grinding wheel, where the signals were collected at 2 MHz. The workpieces were thoroughly analysed through visual inspec-tion, surface roughness and hardness measurements, and metallographic analyses. Study on the frequency content of both signals was carried out in order to select bands closely related to the workpiece surface condition. Digital filters were applied to the raw signals and features were extracted and analyzed. The RMS values filtered in the selected bands for both sensors presented a better fitting to the linear regression, which is highly desirable for setting a threshold to detect burn and implementing into a monitoring system. Also, the RMSD index results show an excellent behavior for grinding burn monitoring for both sensors. The method was validated by using a different grinding wheel, which clearly shows its effectiveness and demonstrates the potential use of the low-cost piezoelectric diaphragm for grinding burn mon-itoring.

O clareamento dental é o meio disponível mais simples, comum e conservador para o cirurgião-dentista proporcionar aos pacientes o padrão de cor de seus dentes mais desejado. Em alguns casos, os dentes que vão ser clareados podem apresentar restaurações realizadas com compósitos dentais, que são mais suscetíveis a alterações químicas, quando comparados a outros materiais restauradores. Alguns estudos mostraram que diferentes concentrações de agentes clareadores levaram a um aumento significativo da rugosidade superficial e das porosidades em compósitos dentais. Este estudo avaliou o efeito de dois agentes clareadores (Whiteness HP Blue 20%, Whiteness HP Max) sobre a rugosidade superficial de dois compósitos dentais, um micro-híbrido (Esthet X, Denstply) e outro nanoparticulado (Z 350, 3M ESPE). Um total de oito corpos de prova (9 x 2 mm) foram confeccionados com auxílio de uma matriz de teflon, sendo divididos em 4 grupos (Esthet X + Whiteness HP Blue 20%; Esthet X + Whiteness HP Max; Z 350 + Whiteness HP Blue 20%; Z 350 + Whiteness HP Max), sendo n=2. Os corpos de prova foram armazenados em saliva artificial neutra e, após 24 horas, foram polidos com discos de óxido de Alumínio (Sof-lex, 3M ESPE). Após sete dias de imersão salivar, cada corpo de prova foi levado a um microscópio de força atômica para obtenção do valor inicial de rugosidade superficial (Ra em nm). Em seguida, sem remover o corpo de prova do microscópio, o agente clareador foi aplicado sobre a superfície do corpo de prova, segundo as instruções do fabricante, de modo que permitisse uma posterior observação da mesma área do corpo de prova observada inicialmente, para obtenção do valor final de rugosidade superficial. Imagens em duas e três dimensões foram obtidas de cada corpo de prova para observação de alterações da topografia. Os resultados foram tratados estatisticamente por ANOVA e pelo teste de contraste Student-Newman-Keuls (p < 0,05). Não houve alteração significativa na rugosidade superficial (Ra) dos corpos da prova de compósitos micro-híbrido e nanoparticulado, submetidos aos agentes clareadores Whiteness HP Blue 20% e Whiteness HP Maxx. No entanto, independente do agente clareador utilizado, foram observadas maiores alterações topográficas nas imagens de microscopia de força atômica da superfície do compósito micro-híbrido do que nas imagens do nanoparticulado. / Dental bleaching is the simplest, the most common and conservative available way for dentists to offer their patients the standard color of teeth more desired. In some cases, the teeth that will be bleached may include restorations made of resin composites, which are more prone to chemical alteration compared with other restoration materials. Some studies have showed that different concentrations of bleaching gels might lead to a significant increase in surface roughness and amount of porosities in composite resins. This study evaluated the effect of two bleaching gels (Whiteness HP Blue 20%, Whiteness HP Max) on surface roughness of two resin composites, micro-hybrid (Esthet X, Denstply) and nanoparticled (Z350, 3M ESPE). A total of eight specimens (9 x 2 mm) were produced with a Teflon mold help, and were divided into four groups (Esthet X + Whiteness HP Blue 20%; Esthet X + Whiteness HP Max; Z 350 + Whiteness HP Blue 20%; Z 350 + Whiteness HP Max), with n=2. They were stored in neutral artificial saliva and, after 24 hours, were polished with aluminium oxide discs (Sof-lex, 3M ESPE). After seven days of salivary immersion, each specimen was taken to an atomic force microscope for recording initial value of surface roughness (Ra in nm). After that procedure, without removing the specimen from microscope, the bleaching gel was applied on the surface of the specimen, following manufacturers instructions, in order to allow posterior observation of the same area of the specimen initially observed, for recording the final value of surface roughness. Two-dimensional and 3D images were taken from each specimen group for observation of surface alterations. The results were statistically analyzed by ANOVA and the SNK test (p< 0.05). There were no statistically significant differences in the surface roughness (Ra) for specimens of micro-hybrid and nanoparticled composites, submitted to the bleaching agents Whiteness HP Blue 20% and Whiteness HP Maxx. However, there were noticed larger surface alterations in atomic force microscope images on the surface of micro-hybrid composites than on the nanoparticled, independently of the bleaching agent used.

Esse trabalho apresenta o método de correlação angular de speckle. Esse método foi melhorado para ser aplicado na medição de rugosidade na faixa de 30 m a 0,1 m. Um programa de computador foi desenvolvido para processar imagens e calcular a correlação angular, e novas fórmulas matemáticas foram deduzidas. / This work presents the speckle pattem angular correlation method. This method was improving to be applicable in the roughness measuring in the range of 0,1 m to 30 m. A software was developed to process image and to calculate the angular correlation, and new mathematical equations were formulating.

Neste trabalho, foi investigado o comportamento tribológico dos pares cerâmicos aluminanitreto de silício no deslizamento em água e em uma suspensão de sílica coloidal em água (hidrosol). O objetivo foi verificar a possibilidade de atingir um coeficiente de atrito da ordem de unidades de milésimos, aqui chamado de ultra-baixo coeficiente de atrito (UBCA), verificar se a mudança do meio, de água para hidrosol, diminui o running-in do coeficiente de atrito, e verificar o efeito da variação da rugosidade inicial da alumina no comportamento do atrito. Os ensaios foram realizados na configuração de teste esferasobre- disco, no qual a esfera foi de nitreto de silício e o disco de alumina, sob carga normal de 54 N e velocidade de 1 m/s. A água utilizada nos ensaios foi destilada e deionizada, e a sílica coloidal amorfa, hidrofílica, sem porosidade e de tamanho médio de partícula de 12 nm foi a Aerosil® 200, e o hidrosol foi preparado com pH 8,5 num eletrólito de NaCl de 1 mM. A esfera de nitreto de silício, adquirida comercialmente, e a alumina, sinterizada em laboratório, foram caracterizadas quanto a densidade, as fases foram determinadas por difração de raios X, microscopia eletrônica de varedura (MEV) observada em amostras ceramográficas atacadas. Algumas propriedades mecânicas como dureza, módulo de elasticidade e tenacidade à fratura foram determinadas. Duas condições de rugosidade dos discos de alumina foram utilizadas nos ensaios tribológicos, 350 nm e 10 nm RMS. Em todos os ensaios, em água, em hidrosol e independentemente da rugosidade inicial do disco o coeficiente de atrito no regime permanente apresentou pequena dispersão de valores de 0,002 a 0,006, e não foi possível estabelecer diferença entre elas. A menor rugosidade do disco de alumina acarretou menor desgaste e menor período de running-in de coeficiente de atrito, tanto em água quanto em hidrosol. Os ensaios em meio de hidrosol acarretaram menor desgaste das cerâmicas e apresentaram menor running-in de coeficiente de atrito, comparados aos ensaios com água. O disco de alumina apresentou menor desgaste do que a esfera de nitreto de silício, em todas as condições estudadas. Com a análise das perdas volumétricas, da rugosidade final das superfícies desgastadas, das curvas de coeficiente de atrito e das espessuras mínimas de filme lubrificante, calculadas com uso de modelo da literatura, foi possível relacionar a diminuição do desgaste e do running-in de coeficiente de atrito em meio de hidrosol, com a presença da sílica na superfície ou próxima dela. / In this work, the tribological behavior of the alumina-silicon nitride couple was investigated under water and hydrosol (colloidal silica suspensions in water) lubricated sliding. The purposes were to study how an ultra-low friction coefficient can be achieved and to analyze the effects of the environment, lubricant and alumina roughness changes on the friction behavior. Ball-on-disk tests with a normal load of 54 N and a sliding speed of 1 m/s were carried out, using a silicon nitride ball and an alumina disk. The water used as lubricant was distilled and deionized. The silica was amorphous colloidal and hydrophilic, without porous and with a 12 nm medium particle diameter, commercially named Aerosil ® 200. The hydrosol was obtained with a pH value of 8,5 and a 1mM NaCl electrolyte. To estimate the minimum film thickness, formed during the lubricated sliding tests, a theory model was used. The commercial silicon nitride balls and the alumina disks, which were conformed and sintered in laboratory, were characterized by density, X-ray diffraction and scanning electron microscopy measurements. The mechanical properties such as hardness, Young modulus and fracture toughness were determined. The friction coefficient values obtained in the steady state regime showed low standard deviations (0,002 to 0,006) under all conditions. A shorter period of running-in was observed with the lower disk roughness, both in water and hydrosol lubrication. The hydrosol lubricated sliding produced a lower wear and friction running-in comparing with the tests under water lubrication. The alumina disk always showed lower wear than the silicon nitride ball. The volume loss, friction coefficients, worn surfaces roughness and minimum film thickness results suggest that the wear and friction coefficient running-in decrease was caused by the presence of silica on the sliding surfaces or on the near surface regions.