Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-08-17T18:37:47Z No. of bitstreams: 1 RUDÁ ARANHA – DISSERTAÇÃO (PPGEM) 2017.pdf: 11257254 bytes, checksum: 2d827010d52a9ce6d3f05b9ddf1bf617 (MD5) / Made available in DSpace on 2018-08-17T18:37:47Z (GMT). No. of bitstreams: 1 RUDÁ ARANHA – DISSERTAÇÃO (PPGEM) 2017.pdf: 11257254 bytes, checksum: 2d827010d52a9ce6d3f05b9ddf1bf617 (MD5) Previous issue date: 2017-11-30 / Os materiais compósitos são sinônimos de boas propriedades mecânicas associadas a baixo peso estrutural com vasta aplicação na área da engenharia. A partir dos avanços tecnológicos e da necessidade de desenvolvimento de novos materiais, torná-los multifuncionais surge como interesse imediato. O método mais simples para conferir multifuncionalidade a um compósito é através da introdução de inserts nos compósitos antes de sua fabricação, conferindo-os as mais variadas características, sendo importante entender as consequências geradas a partir do uso dos inserts no processamento das placas. O estudo experimental do escoamento de resina através da pré-forma e os efeitos recorrentes devido à adição dos inserts impermeáveis aos compósitos durante o processo de Moldagem por Transferência de Resina (RTM) são os objetivos deste trabalho. Neste trabalho, foram utilizados reforço de tecido de fi bra de vidro e matriz de resina poliéster na composição de placas de material compósito com dimensões de 250x250x14 mm3 com 1 e 9 inserts impermeáveis de polietileno com dimensões de 50x50x4 mm3, processadas pelos métodos de RTM Light e VARTM para futura aplicação estrutural e/ou balística. Como esperado, a introdução de inserts na pré-forma causou distúrbio no escoamento da resina durante os processamentos, sendo evidenciadas regiões super ciais em algumas das placas, acima dos inserts, onde as bras não foram molhadas. Ao fim dos processamentos foram observadas variações nas espessura das placas, sendo esta uma consequência da compactação das fi bras devido à presença dos inserts. Também foi identi cada a movimentação dos inserts quando os pontos de entrada e saída foram posicionados em planos diferentes no molde. Tal movimentação foi evitada a partir da fixação dos inserts em uma tela antes do processamento. Com o corte das placas, regiões ricas em resina próximas às laterais dos inserts foram observadas, sendo esta uma consequência do mecanismo de afastamento das fibras devido à presença dos inserts. Assim, 4 zonas foram identifi cadas nos compósitos com inserts impermeáveis embebidos. Por fim,nos ensaios de flexão em 3 pontos, falhas de delaminação por cisalhamento tipo II foram identi cadas nos corpos de prova. / Composite materials are synonymous with good mechanical properties associated with low structural weight and have a great variety of applications in the engineering area. Taking into account technological advances and the necessity to develop new materials, make them multifunctional appears as immediate interest. The simplest method to confer multifunctionality to a composite is through the introduction of inserts into the composites, giving them the most varied characteristics. It is important to understand how these inserts will a ect the fabrication process and the structural characterization of the material. The experimental analysis of the ow through the preform and the effects due to the addition of the impermeable inserts to the composite during the process of Resin Transfer Molding (RTM) are the objectives of this work. In this work, reinforcement of glass ber fabric and polyester resin matrix was used in the composition of 250x250x14 mm3 composite materials sheets with 1 and 9 polyethylene impermeable inserts with dimensions of 50x50x4 mm3, processed by the RTM Light and VARTM methods for future structural and/or ballistic application. As expected, introduction of inserts into the preform caused disturbances in resinow during processing, with surface regions in some of the plates above the inserts where the bers were not wetted. At the end of the processing, variations in the thickness of the plates were observed, being this a consequence of the bercompaction due to the presence of the inserts. The movement of the inserts was also identi ed when the resininlet and outlet were positioned on di erent planes in the mold. the inserts movimentation was prevented from attaching the inserts to a mesh before the processing.With the cutting of the plates, resin-rich regions close to the sides of the inserts were observed, which is a consequence of the mechanism of ber spacing due to the presence of the inserts. Thus, 4 zones were identi ed in the composites with embedded impermeable inserts. Finally, in the 3-point bending tests, delamination failures for shear mode II were identi ed in the specimens.

Le dimensionnement des inserts pour les structures sandwich se fait usuellement par les méthodes proposées par le « Insert design handbook » de l'ESA, ou le « Military handbook 23A ». Ces méthodes analytiques basées sur la formulation développée par Ericksen en 1953 mènent à des erreurs de la charge admissible à l’arrachement d’environ ±20 % pour certains cas. Dans cette thèse, les principaux modes de rupture d’inserts sont étudiés ; l’endommagement du nid d’abeille Nomex® en cisaillement et la rupture du potting. Une analyse fine du postflambement en cisaillement du nid d’abeille Nomex® est effectuée qui permet de proposer un modèle d'endommagement à 2 paramètres.Puis, les résultats obtenus sont utilisés pour développer un modèle virtuel d’insert qui est validé par comparaison à des essais d'arrachement puis utilisé pour tracer des cartographies des modes de rupture. En utilisant cette méthode, la charge admissible à l’arrachement peut être estimée plus précisément. Cette méthode peut être une alternative face aux modèles analytiques pour le dimensionnement des inserts. Les graphiques obtenus peuvent être fournis aux ingénieurs pour le dimensionnement des inserts comme un outil qui peut réduire le temps de conception-validation. / The insert sizing for sandwich structures is usually made using the methods proposed in the “Insert design handbook” of the ESA and the “Military handbook 23A”. These analytical methods based in the in the research carried by Ericksen in 1953 could lead to errors of the pull-out allowable load prediction in the range of ±20 % for some cases.In this thesis, the principal failure modes of inserts are investigated; the core shear damage of the Nomex honeycomb core, and the potting failure. A detailed analysis of the shear postbuckling of the Nomex honeycomb core is made, allowing to propose a two variables damage model. Then, the obtained results are used to develop an insert virtual model that is validated through comparison with pull-out tests, and then used to draw failure mode maps of inserts. Using this method, the admissible pull-out load of inserts can be estimated more precisely. This method could be an alternative to using the analytical methods for the insert sizing. The resulting charts could be given to engineers as a tool for the insert sizing which could reduce the insert’s design-validation time.

This thesis deals with a summary of different types and characteristics of coatings used for increasing the lifetime of cemented carbide tools. Besides, the thesis includes solving the issue regarding edge chipping during machining interrupted pipe ends at the pipe line, selecting a new type of indexable inserts and indexable inserts holders to increase line productivity and decrease tool costs in the related operation.

Pressing of metallic powders is a manufacturing process widely investigated in the research field and in the industry. This thesis project is focused on optimizing the pressing process of cemented carbide powder utilized for the production of triangular shaped cutting tool inserts. In particular, the filling of powder into the die cavity was investigated with respect to different pressing parameters. The aim of the project was to obtain a uniform density distribution of the powder into the die cavity, and hence to reduce the variation of the height of the insert obtaining more precise dimension of the latter. The tests were carried out at the Sandvik Coromant production department which is the creator of the project. The optimization of the pressing process was performed according to the Design of experiments theory. The dynamic of the sintering process was also investigated. The results showed a significant improvement in the filling of the die cavity and a significant decrease of the variation of the height of the inserts. The new insert obtained has more precise dimensions and is able to meet the more demanding requirements of the customers. The results achieved are directly applicable to a larger number of products, and indicate the direction to follow for further development of the manufacturing process.

The aim of this thesis work was to design and evaluate a wear test method for cemented carbides inserts used in rotary drilling. An appropriate in-house wear test method would provide a better understanding of the wear mechanisms limiting tool life in real drilling. The test method should be easy to use and be able to distinguish between wear of insert materials with different microstructure and properties. The literature study showed few published articles about wear tests and mechanisms concerning rotary drill bit inserts. These methods included two standard wear tests; ASTM G65 and ASTM B611. Furthermore, a modified ASTM G65 test was found as well as an impact-abrasion test. In this work the modified ASTM G65 test, using a rock counter surface, was evaluated in order to understand if the method would mimic the wear of cemented carbides used in rotary drilling. The test method was further developed and showed high repeatability. Measured weight losses showed that the test could distinguish between two common rotary grade materials with a small difference in hardness but with different microstructures. The wear of the tested materials was analyzed with scanning electron microscopy and compared with rotary drill bit inserts collected from the field. The modified test method proved able to produce wear by mechanisms very similar to those found on field worn inserts. Identified wear mechanisms included cracking, fragmentation and spalling of WC grains as well as embedded fragments of WC grains on the surface. In addition, the binder phase was removed and adhered material from the counter surface was detected.

This thesis work sought to find a tribological testing method suitable for cementedcarbide drill bit inserts used when drilling rock. A review of the literature publishedon the matter showed that there are quite a few test methods developed for wearstudies with cemented carbides, but most of them were not designed for the rockdrilling industry. Published studies performed with the found methods and articleswith analyzed field tests have been studied. It is generally agreed upon that the stepsof wear is that the binder disappears first, followed by removal of carbide grains. Themechanisms of binder phase and carbide grain removal is somewhat debated, butalmost every study observes fracture of the carbide grains. The wear test created inthis thesis was shown to give wear linear with time, but not with load. The newmethod was shown to be capable of distinguishing between different cementedcarbides worn in three body abrasion against different rocks. Analysis of the wornsamples shows that there are similarities with bit inserts worn in field testing. Many ofthe observations made during the analysis are also similar to observations inliterature.

This study investigated the effect on microleakage of different bonding agents and glass and polyethylene fibers inserted at gingival margins of class V composite restorations. Sixty premolars were sterilized. Class V cavities were prepared, 1 mm below the cementoenamel junction. Prepared tooth were randomly divided into 12 groups (n=10). In experimental groups fiber inserts were inserted at the gingival seat. The control groups had no inserts. Restorations were incrementally placed and polymerized. Specimens were then stored in water and thermocycled for 500 cycles, then immersed in 2% procion dye and sectioned buccolingually, then dye penetration was assessed. Data were analyzed with the Kruskal-Wallis test and analysis of variance of ranks. No significant differences were found among the types of fiber or the two types of composites. Significant differences were found between the bonding agents. SE and LS show significantly lower microleakage than NT in class V composite restorations in dentin.

This study investigated the effect on microleakage of different bonding agents and glass and polyethylene fibers inserted at gingival margins of class V composite restorations. Sixty premolars were sterilized. Class V cavities were prepared, 1 mm below the cementoenamel junction. Prepared tooth were randomly divided into 12 groups (n=10). In experimental groups fiber inserts were inserted at the gingival seat. The control groups had no inserts. Restorations were incrementally placed and polymerized. Specimens were then stored in water and thermocycled for 500 cycles, then immersed in 2% procion dye and sectioned buccolingually, then dye penetration was assessed. Data were analyzed with the Kruskal-Wallis test and analysis of variance of ranks. No significant differences were found among the types of fiber or the two types of composites. Significant differences were found between the bonding agents. SE and LS show significantly lower microleakage than NT in class V composite restorations in dentin.

Malaria is considered the most prevailing human parasitic disease. Despite various chemotherapeutic interventions being available, the parasite responsible for the most lethal form of malaria, Plasmodium falciparum, is continuously developing resistance towards drugs targeted against it. This, therefore, necessitates the need for validation of new antimalarial development. Polyamine biosynthetic enzymes, particularly S-adenosylmethionine-L-decarboxylase (PfAdoMetDC), has been identified as a suitable drug target for protozoan parasitic diseases due to its essential role in cell proliferation. Furthermore, in Plasmodium polyamine biosynthesis, PfAdoMetDC is organised into a unique bifunctional complex with ornithine decarboxylase (PfAdoMetDC/ODC) covalently linked by a hinge region, distinguishing this enzyme as unique a drug target. However, inhibitors targeting this pathway have not been successful in clinical assessment, creating the need for further research in identifying novel inhibitors. This study focused on the structural and functional characterisation of protein-specific properties of the AdoMetDC domain in P. falciparum parasites, as well as identifying novel inhibitors targeting this enzyme as a potential antimalarial therapeutic intervention. In order to develop novel inhibitors specifically targeting PfAdoMetDC through a structure-based drug discovery approach, the three-dimensional structure is required. However, due to a lack of structural and functional characterisation, determination of the crystal structure has been challenging. Heterologous expression of monofunctional PfAdoMetDC was achieved from a wild-type construct of the PfAdoMetDC domain including the covalently linked hinge region. In chapter 2, deletion of a large non-homologous, low-complexity parasite-specific insert (A3) in monofunctional PfAdoMetDC resulted in an increased yield, purity and sample homogeneity, whilst maintaining protein functionality and structural integrity. However, truncation of the proposed non-essential hinge region resulted in low-level expression of insoluble protein aggregates and a complete loss of protein activity, indicating that the hinge region is essential for monofunctional PfAdoMetDC. However, in the absence of the three-dimensional PfAdoMetDC crystal structure, novel derivatives of a well-known AdoMetDC inhibitor, MDL73811, were tested for their activity against heterologous PfAdoMetDC, as well as their potency against P. falciparum parasites, in chapter 3. The compound Genz-644131 was identified as a lead inhibitor of PfAdoMetDC, however, the poor membrane permeability of the compound resulted in low in vitro activity. Drug permeability of Genz-644131 into P. falciparum infected erythrocytes and its potency was significantly improved by its encapsulation into a novel immunoliposome based drug delivery system. The results presented here provide essential information for development of a unique strategy in obtaining suffiecient levels of fully active recombinant PfAdoMetDC of sufficient purity for crystallisation studies and subsequent structure-based drug design efforts. The combination of Genz-644131 with the novel drug delivery system, which markedly improved its potency against PfAdoMetDC may proof to be a viable antimalarial chemotherapeutic strategy for future investigations. / Thesis (PhD)--University of Pretoria, 2014. / tm2015 / Biochemistry / PhD / Unrestricted

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