Please read the abstract in the section front of this document. / Dissertation (MSc (Physics))--University of Pretoria, 2006. / Physics / unrestricted

Resin composites have been in the dental field for over forty years. They are now thought to be the most commonly used restorative material due to their aesthetic and mechanical properties. Although resin composites have high success rates as restorations, they do not offer all properties of an ideal restorative material. The aims of this research were to characterise the effects of variation in resin composite formulation on handling, mechanical; and physical properties. In particular the influence of the size and distribution of the inorganic components was investigated through the study of experimental formulations. Packing stress and viscosity were assessed with pentrometer principle at two different temperatures (23 and 37 ºC). It was found that filler size was strongly correlated with both packing stress and viscosity. Additionally, temperature has a dominant effect on packing stress and viscosity. Micro computed tomography [μCT] was used to investigate percentage of voids [% voids] in 3D dimensions. It was found that smaller filler size incorporated less % voids. In contrast filler size and disruption had a little effect on fracture toughness of resin composites. 3D surface topography was used to investigate the surface roughness before and after tooth brush abrasion. It was found filler size had a significant influence in both gloss retention and surface roughness (smaller filler size exhibited higher surface gloss). Finally, the effect of different storage media (distilled water, Coca Cola and red wine) on colour stability and gloss were investigated. It was found that dietary habits effect discolouration of resin composite restorations with the acidic drinks caused more staining.

D.Ing. / The quantification of the surface roughness in order to determine the shear behaviour of rock joints has been performed using many approaches, amongst which the most important are the joint roughness coefficient, statistical methods and the fractal approach. None of these approaches explicitly considers the contribution of grain size to the creation of surface roughness. An investigation has been undertaken to determine whether the grain size may be related to the surface roughness characteristics and also to assess its impact on the shear behaviour of rock joints. The influence of grain size on the shear behaviour of rock joints has been experimentally and numerically studied using a profile measurement approach followed by shear tests in the laboratory. Fresh rock joints in model material made of aggregates of no rite in resin and two natural rock types, namely norite and sandstone, were used for the investigation. A numerical analysis of the study has been performed using the Particle Flow Code PFC20 • Investigation of the model material has resulted in the conceptualisation of grain size parameters. Of the proposed grain size parameters, the average particle size index As has been successfully used to define the particle size distribution of a rock joint for both physical and numerical tests. From the profile measurements, four roughness parameters, n~mely the average inclination angle I, the root mean square of the first derivative Z2, the modified root mean square of the first derivative Z2' and the fractal dimension D, have been computed and a regression analysis conducted. Physical and numerical results have demonstrated that grain size distribution, expressed in terms of average particle size index As shows a good correlation respectively with the root mean square ofthe first derivative Z2, and its modified version Z2'. The root mean square of the first derivative Z2, and the modified root mean square of the first derivative Z2' increase with the average particle size index As. However, no correlation has been found between the grain size parameter and the fractal dimension D or the average inclination angle I. It has also been found that the joint roughness coefficient JRC and the peak friction angle ~P correlate very well with the average particle size index As. The greater the average particle grain size the higher the joint roughness coefficient JRC and the peak friction angle ~p· The type of correlation between JRC and ~P with As depends on the rock type. Exponential shear strength model has been derived where the average particle size index As is related to the peak friction angle via the residual friction angle ~r·

Orientador: Rafael Leonardo Xediek Consani / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-22T08:52:37Z (GMT). No. of bitstreams: 1 Silva_MarcosAurelioBomfimda_D.pdf: 3594092 bytes, checksum: deda0a469e83ffee66cb92d7fc6f61b0 (MD5) Previous issue date: 2013 / Resumo: Os objetivos nesta tese, composta por 2 capítulos, foram: (1) avaliar a rugosidade de superfície, microdureza e microinfiltração marginal de uma resina composta nanopartículada quando submetida à degradação em soluções ácidas e (2) avaliar a influência de soluções alcoólicas sobre a rugosidade e dureza de superfície de resinas compostas microparticulada, microhíbrida e nanoparticulada. No capítulo 1, foram preparadas 60 cavidades na face vestibular de incisivos bovinos, restauradas com resina de nanopartículas Filtek Z350 XT (3M/ESPE). Os dentes foram separados em três grupos de tratamento (n = 20): A (controle) - imersão em saliva artificial durante 30 dias; B - Imersão em café por 15 min (3x/dia), durante 30 dias, e C - imersão em Coca-cola® por 15 min (3x/dia), durante 30 dias. Após os períodos de imersão, os espécimes foram analisados quanto à microdureza em microdurômetro com edentador tipo Knoop, rugosidade de superfície em microscópio de força atômica e microinfiltração marginal com penetração de corantes quando submetidos à ciclagem térmica e mecânica. A rugosidade de superfície e microdureza foram submetidas à análise de variância (ANOVA) seguida pelo teste- t com nível de significância de 5% e a microinfiltração marginal ao teste de Mann-Whitney, em nível de significância de 5%. O Grupo A apresentou a menor rugosidade de superfície e a maior média de microdureza quando imerso em saliva artificial. O Grupo C apresentou maiores índices de microinfiltração e redução da microdureza quando imerso em Coca-cola®. Concluiu-se que a imersão em café e Coca-cola® alterou a rugosidade da superfície e aumentou a infiltração nas restaurações. No capítulo 2, foram selecionadas três resinas compostas (Durafill/Kulzer, Z250 (3M/ESPE) e Z350 XT (3M/ESPE). Foram confeccionados 120 espécimes de cada material com 6 mm de diâmetro por 2 mm de espessura. Os espécimes foram analisados quanto à microdureza e rugosidade de superfície semelhante ao descrito no Capítulo 1. Os espécimes foram separados aleatoriamente em quatro grupos (n= 30) de acordo com as soluções ensaiadas: G1- Saliva artificial; G2 - Cerveja/Heineken; G3 - Vodka/Absolut; G4 - Whisky/Johnnie Walker Red Label. As ciclagens de imersão ocorriam por 15 min (3x/dia), durante 30 dias. O teste de rugosidade de superfície e microdureza foram repetidos aos 30 dias de imersão. Os valores obtidos de rugosidade e microdureza foram submetidos ao teste paramétrico de ANOVA complementado pelo teste de Tukey ('alfa'=0,05). Os resultados de rugosidade de superfície revelaram que as resinas compostas apresentaram aumento de rugosidade após 30 dias de imersão em cerveja, vodka e whisky. Houve redução significativa na microdureza das resinas compostas após a imersão nas soluções alcoólicas no período de 30 dias, sendo maior para a resina composta Durafill. Com base nos resultados obtidos pôde-se concluir que as soluções ácidas e alcoólicas exerceram influência negativa sobre a rugosidade e microdureza de superfície das resinas compostas / Abstract: The objectives of this study were to: (1) evaluate the surface roughness, hardness and microleakage of nanoparticle composite resin when subjected to degradation in acidic solutions and (2) evaluate the influence of alcoholic solutions on the roughness and surface hardness of microparticulate, microhybrid and nanoparticulate composite resin. In chapter 1, sixty cavities were prepared on the buccal surface of bovine incisors restored with composite resin Filtek Z350 XT (3M/ESPE). The teeth were divided into three treatment groups (n = 20): A (control) - immersion in artificial saliva for 30 days; B - immersion in coffee for 15 min (3 times daily) for 30 days, and C - immersion in Coca-cola ® for 15 min (3 times daily) for 30 days. After the periods of immersion, the specimens were analyzed for Knoop microhardness, surface roughness by atomic force microscope and microleakage with dye penetration when subjected to thermal and mechanical cycling. The surface roughness and microhardness were subjected to analysis of variance (ANOVA) followed by t-test with a significance level of 5%. The data of microleakage was evaluated by Mann-Whitney test at a significance level of 5%. Group A showed a lower surface roughness and higher average microhardness. Group C had higher rates of reduction of microleakage and microhardness. It was concluded that immersion in coffee and coca-cola ® altered surface roughness and increased infiltration in restorations. In Chapter 2, we selected three composites (Durafill/Kulzer, Z250 (3M/ESPE) Z350 XT (3M/ESPE). 120 specimens were prepared for each material with 6 mm diameter by 2 mm thick. The specimens were analyzed for hardness and surface roughness similar to that described in Chapter 1. The specimens were randomly divided into four groups (n = 30) according to the tested solutions: Artificial Saliva-G1, G2 - Beer / Heineken; G3 - Vodka / Absolut; G4 - Whisky / Johnnie Walker Red Label. The solutions were changed by 3x daily for 30 days. The test of surface roughness and microhardness were repeated at 30 days of immersion. The values of roughness and hardness were tested using parametric ANOVA complemented by Tukey test (5%). The results of surface roughness showed that the composites showed an increase in roughness was statistically significant after 30 days for beer and whiskey. The results showed that the surface microhardness decreased significantly for the composites after immersion in alcoholic solutions within 30 days, being higher for the composite Durafill. Based on the obtained results it can be concluded that the acid solutions and alcoholic exerted negative influence on the roughness and surface microhardness of composite resins / Doutorado / Materiais Dentarios / Doutor em Materiais Dentários

Orientadores: Derval dos Santos Rosa, Armando Moreno Lopes Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-18T11:05:11Z (GMT). No. of bitstreams: 1 Marini_MarcioVinicius_M.pdf: 3583126 bytes, checksum: 5e4af10aedd8586c476507d633cf6c75 (MD5) Previous issue date: 2011 / Resumo: O reforço de estruturas de concreto armado ou protendido têm sido necessário na construção civil devido às falhas causadas por erros em projetos e execuções de obras, corrosões de armaduras, reabilitação após incêndios ou mudanças na utilização das estruturas projetadas. Os métodos convencionais para reforço de estruturas de concreto estão relacionados ao reforço pela adição de barras de aço e de concreto na estrutura ou, ainda, pela instalação de chapas de aço. O uso de fibras de carbono para reforços estruturais é recente, apresentando vantagens em relação aos métodos tradicionais, tais como: fácil manuseio na aplicação, alta aderência entre as fibras de carbono e o concreto e aumento na resistência à corrosão. Sendo assim, o objetivo deste trabalho é avaliar a aderência entre o sistema de reforço com as fibras de carbono e concretos com resistência à compressão de 15 MPa, 40 MPa e 60 MPa. A aderência concreto/fibra foi avaliada por meio de ensaios pull-out em pequenas placas de concreto com fibras de carbono aplicada superficialmente. Do concreto, foram obtidos resultados de sua porosidade e rugosidade; por meio de estereomicroscópia, foram avaliadas características como a textura superficial. Os resultados demonstraram que os concretos com menor relação água/cimento (a/c), ou seja, com maior resistência à compressão apresentaram maior aderência entre si e o sistema de reforço com fibras de carbono e menores valores de porosidade e rugosidade com maior homogeneidade superficial. Em relação aos concretos com maior relação água/cimento (a/c), observou-se o comportamento inverso nas propriedades citadas. De acordo com esses resultados, pôde-se concluir que a resistência à compressão do concreto (substrato) alterou a resistência de aderência com o sistema de reforço com fibras de carbono e também a porosidade; a rugosidade e a característica de superfície não influíram significativamente nestas propriedades / Abstract: Strengthening of conventional or prestressed concrete structures has been used due to failure occurred by design errors, erroneous methods and executives process, corrosion of steel bars of concrete pieces, rehabilitation after damages caused by fire or variations of structure type utilization. Conventional strengthening methods of concrete structure are used adding new steel bars to structure or installing steel plates. However more recent reinforcement methods based on carbon fiber use had been demonstrated advantages, such as: easy and fast application to substrate, high adhesion between carbon fiber and concrete and method to increase corrosion of bars of concrete structures. Thus, this work aims to evaluate adhesion process between strengthening concrete system employing carbon. In the experimental study was used concrete specimens with compressive strength of 15 MPa, 40 MPa and 60 MPa. The interface adherence of concrete/fiber was evaluated through pull-out test type on concrete slabs, where carbon fiber was superficially applied. Results of concrete porosity and roughness were obtained through a stereo microscope that assesses characteristics as the superficial texture. The obtained results showed that concretes with lower water/cement ratio (w/c) had higher values of adhesion between carbon fiber and concrete, lower porosity values and higher superficial homogeneity. Opposite behavior was observed in concretes with higher water/cement ratio (w/c). According to the obtained results was possible to note that the compressive strength concrete (substrate) modified the adherence resistance between concrete and carbon fiber, where higher compression strength increased adherence between concrete and carbon fiber. Also the results indicated that both the concrete surface characteristics and the roughness were not influenced significantly / Mestrado / Estruturas / Mestre em Engenharia Civil

Avaliar a microdureza e rugosidade de superfície do esmalte bovino antes e após clareamento com agentes de baixa e alta concentração, ambos com ou sem adição de cálcio. Método: Foram utilizados sessenta fragmentos dentais bovinos, aleatoriamente divididos em cinco grupos (n=12), de acordo com o agente clareador utilizado. As amostras foram clareadas utilizando-se peróxido de carbamida 20% (PC 20%) ou peróxido de hidrogênio 40% (PH 40%), ambos com ou sem adição de cálcio (2000ppm) na sua formulação, e o tempo de aplicação foi de acordo com as instruções do fabricante. Em seguida, as amostras foram lavadas e armazenadas em saliva artificial até a próxima sessão de clareamento. Os tratamentos foram realizados por 14 dias (quatorze dias). A análise da superfície do esmalte foi realizada com os testes de Rugosidade superficial (`cutoff 0,25mm) e Microdureza Knoop (50g/15s), antes e após os tratamentos. Foi realizada uma análise exploratória dos dados e os grupos foram submetidos à análise de variância (ANOVA) e teste de Tukey (significância de 5%). Resultados: Após o clareamento o grupo clareado com PH 40% apresentou valores mais baixos de microdureza mas sem diferença significativa para o PC 20% e PH 40% com cálcio. Houve diferença estatística significativa entre as leituras iniciais e finais. Para rugosidade superficial não foram observadas diferenças entre os materiais testados; porém houve aumento da rugosidade para todos os grupos após o clareamento, exceto para o grupo controle. Conclusão: Concluiu-se que houve diminuição da microdureza para todos os agentes clareadores testados. Houve um aumento da rugosidade superficial logo após o clareamento dental. / Objective: To evaluate the effects of bleaching with hydrogen peroxide 40% (HP 40%) and carbamide peroxide 20% (CP 20%), with and without the addition of calcium (2000ppm), in enamel through the Knoop microhardness and roughness tests. Method: bovine enamel blocks (3mm2) were prepared and included and randomly divided into five experimental groups (n=12) and subjected to different treatments. The Group 1 and 2 were bleached carbamide peroxide with or without calcium, and G3 e G4 were bleached HP 40% with or without calcium. The group 5 were immersed in saliva artificial (control group). The samples were washed and stored in artificial saliva to the next bleaching session. The treatments were carried out for 14 days. The analysis of the enamel surface was performed with test surface roughness and Microhardness, before and after treatment. An exploratory analysis of the data and the groups were subjected to analysis of variance was performed (ANOVA) and Tukey test (5% significance). Results: All specimens were subjected to testing Knoop microhardness before the treatment (initial reading), after the bleaching treatment. The bleached group with 40% PH had the lowest values of microhardness. There was a statistically significant difference between the initial and final readings. For surface roughness were no differences between the tested materials; but there was an increase of roughness for all groups after bleaching. Conclusion: It was concluded that there was decrease of microhardness for all tested bleaching agents. There was an increase in surface roughness after tooth whitening.

This master´s thesis deals with the measurement of surface roughness on a roundness instrument Talyrond TR595S. The aim was to expand possibilities of measuring on this roundness instrument. The main benefit of this thesis is creation of the proposal for the roughness measurement components in a horizontal and vertical plane. Thesis also includes the procedure for measuring of the roughness of the circular components including calculation of measurement uncertainty.

Modern nuclear reactors still use Zirconium-4 Alloy (Zircaloy®) as the cladding material for fuel elements. A substantial amount of research has been done to investigate the boiling heat transfer behind the cooling mechanism of the reactor. Boiling heat transfer is notoriously difficult to quantify in an acceptable manner and many empirical correlations have been derived in order to achieve some semblance of a mathematical model. It is well known that the surface conditions on the heat transfer surface plays a role in the formulation of the heat transfer coefficient but on the other hand it also has an effect on the pressure drop alongside the surface. It is therefore necessary to see whether there might be an optimum surface roughness that maximises heat transfer and still provides acceptably low pressure drop. The purpose of this study was to experimentally measure pressure drop and heat transfer associated with vertical heated tubes surrounded by flowing water in order to produce flow boiling heat transfer. The boiling heat transfer data was used to ascertain what surface roughness range would be best for everyday functioning of nuclear reactors. An experimental set-up was designed and built, which included a removable panel that could be used to secure a variety of rods with different surface roughnesses. The pressure drop, surface temperature, flow rate and heat input measurements were taken and captured in order to analyse the heat transfer and friction factors. Four rods were manufactured with different roughnesses along with a fifth rod, which remained standard. These rods were tested in the flow loop with water in the upward flow direction. Three different system mass flow rates were used: 0kg/s, 3.2kg/s and 6.4kg/s. Six repetitions were done on each rod for the tests; the first repetition was not used in the results since it served the purpose to deaerate the water in the flow loop. The full range of the power input was used for each repetition in the tests. For the heat transfer coefficient at a system mass flow rate of 3.2kg/s, satisfactory comparisons were made between the test results and those found in literature with an average deviation of 14.53%. At 6.4kg/s system mass flow rate the comparisons deviated on average 55.45%. The velocity of the fluid in the test section was calculated from the pressure drop and was validated using separate tests. The plain rod, with no added roughness, was found to be the optimal surface roughness which is what is used in industry today. The flow loop was in need of a couple of redesigns in order to produce more accurate results. Future work suggestions include adding more rods in the test section in order to investigate the nature of heat transfer in a rod bundle array as well as implementing all the suggested changes listed in the conclusion. / Dissertation (MEng)--University of Pretoria, 2017. / Mechanical and Aeronautical Engineering / MEng / Unrestricted

Objetivo: Comparar in vitro la rugosidad superficial de una resina compuesta tipo BulkFill: Aura® BulkFill (SDI) con la resina Tetric N-Ceram® BulkFill (Ivoclar Vivadent) al ser inmersas a dos bebidas rehidratantes: Sporade® y Gatorade®. Materiales y métodos: Se utilizaron 88 especímenes de resina divididos en cuatro grupos, confeccionados con una matriz metálica (10mm x 4mm). Se insertó las resinas con una espátula de resina, y se fotoactivó con la lámpara Elipar LedTM, con una intensidad de 1200 mW/cm2. Se sumergieron los especímenes en agua destilada. A las 24 horas, se midió la rugosidad con el rugosímetro Mitutoyo SJ-210P. Luego, se realizó la inmersión en bebidas rehidratantes y se midió la rugosidad final a los 7 días. Resultados: La rugosidad inicial y final de las resinas Aura® BulkFill (SDI) y Tetric N-Ceram® BulkFill (Ivoclar Vivadent) presentaron diferencias significativas después de la inmersión en bebidas rehidratantes. Para los especímenes de Aura® BulkFill (SDI) al someterla a Sporade® se encontró una media inicial de 1.20 y una media final de 1.76 y los valores para Gatorade® fueron 0.77 y 1.73. Mientras que la rugosidad superficial de Tetric N-Ceram® BulkFill (Ivoclar Vivadent) al sumergirla en Sporade® fue 0.82 y 1.55, y en Gatorade® 0.77 y 1.73. Al comparar la diferencia de la rugosidad superficial final e inicial (deltas), la resina Aura® BulkFill presentó diferencias significativas mientras que, Tetric N-Ceram® BulkFill no tuvo diferencias al sumergirlas en ambas bebidas rehidratantes. Conclusiones: Las resinas estudiadas incrementaron su rugosidad luego de ser inmersas a las bebidas mencionadas. / Objective: To compare in vitro the surface roughness of a BulkFill composite resin: Aura® BulkFill (SDI) with Tetric N-Ceram® BulkFill resin (Ivoclar Vivadent) when immersed in two rehydration drinks: Sporade® and Gatorade®. Materials and methods: 88 resin specimens divided into four groups were used, with a metal matrix (10 mm x 4 mm). The resins were inserted with a resin spatula, and photo-activated with the Elipar LedTM lamp, with an intensity of 1200 mW/cm2. The specimens were immersed in distilled water. After 24 hours, the roughness was measured with the Mitutoyo SJ-210P rugosimeter. Then, the immersion in rehydration drinks was performed and the final roughness was measured after 7 days. Results: The initial and final roughness of the resins Aura® BulkFill (SDI) and Tetric N-Ceram® BulkFill (Ivoclar Vivadent) showed significant differences after immersion in rehydration drinks. For specimens of Aura® BulkFill (SDI) when subjected to Sporade® an initial mean of 1.20 and a final average of 1.76 was found and the values for Gatorade® were 0.77 and 1.73. While the surface roughness of Tetric N-Ceram® BulkFill (Ivoclar Vivadent) when immersed in Sporade® was 0.82 and 1.55, and in Gatorade® 0.77 and 1.73. When comparing the difference of the final and initial surface roughness (deltas), the Aura® BulkFill resin showed significant differences while, Tetric N-Ceram® BulkFill did not have differences when immersing them in both rehydration drinks. Conclusions: The resins studied increased their roughness after being immersed in the aforementioned beverages. / Tesis

OBJECTIVES: To evaluate the effects of different machining modes on the flexural strength CAD-CAM restorative materials. MATERIALS AND METHODS: Four different CAD-CAM materials were used: VITA MARKII, VITA Enamic (VITA Zahnfabrik), Empress CAD, and e.max CAD (Ivoclar Vivadent). Rectangular bars for each material (except e.max CAD) were made by three procedures: saw cut, normal mill and fast mill. Each subgroup had a sample size of 5. Saw cut bars were cut by a BUHLER diamond blade saw. Milled bars were made using SIRONA CEREC MCXL milling unit. The 3-point flexural strength test was performed using a universal testing machine. Surface roughness was measured using a profilomer. Student t-test and Tukey-Kramer statistical analysis were performed to check significant differences. RESULTS: e.max CAD saw cut group was significantly stronger than the milled group. There was no difference in the strength of the Empress CAD groups. Enamic saw cut group was significantly stronger than the normal milled but not the fast milled one. There was no significant difference between the Enamic milled groups. Vita MKII saw cut was significantly stronger than both milled groups. There was no difference in the strength between the milled MKII groups. The surface roughness of the saw cut groups in all materials were significantly less than their milled counterparts in both longitudinal and transverse measurements. CONCLUSION: Machining had a significant effect on the surface roughness of materials. Damage from machining can cause the material to have lower flexural strength.