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Refino de grão na transformação austenítica em aço rolamento previamente conformado a frio
(Universidade Federal de São Carlos, 2012-08-07) Martins, Ivan Augusto; Balancin, Oscar; https://lattes.cnpq.br/8379205949387493; https://lattes.cnpq.br/6003731305973377
In this work is presented the characteristics of the steel C80U Modified, usually applied for bearing components produced through cold forming, as evaluated the influence of prior cold work on the microstructure after heat treatment by quenching and tempering. Starting from spheroidized carbides annealed structure, samples of strip steel were previously cold-rolled to different deformation degrees. The thickness reduction was based on the equivalent strain, calculated by numerical simulation in reference of a real cold formed part. These samples were quenched and tempered, and then the austenitic grain size for each different conditions of prior cold work was evaluated. By X-ray diffraction techniques the fractions of retained austenite for each degree of prior cold work were measured. Mechanical and metallurgical analysis were also carried out in rerolled strips as annealed in delivery condition, in order to characterize the fundamental properties related to drawing process.
Avaliação da durabilidade de argamassas e pastas de cimentos do tipo Portland preparados com um clínquer contendo resíduo de bauxita como matéria-prima
(Universidade Federal de São Carlos, 2012-08-07) Balbino, Thiago Gabriel Ferreira; Rodrigues, José de Anchieta; https://lattes.cnpq.br/4000441989868775; https://lattes.cnpq.br/9432872503151132
The structures of Portland cement are frequently exposed to aggressive environments, which can lead to their degradation. Thus, the study of durability is very important to avoid damages caused by early failures as well as spending on repairs. In this work, the durability of mortars and pastes prepared with a Portland cement containing bauxite residue (BR) as raw material was evaluated and Brazilian commercial cements CPV-ARI and CPII-Z 32 were used as references. Tests were also performed with addition of silica fume to the synthesized cement. The strength and the hydration products after 28 days of cure were evaluated, as well as the chemical, strength and microstructural changes of mortars and pastes subjected to Na2SO4 attack. Acidic attacks using HCl and H2SO4 and leaching tests using distillated water were also carried out. The results showed that the synthesized cement presented a NaC3A phase, which was more resistant to Na2SO4 attack. The uniaxial compressive strength of the mortar prepared with the synthesized cement after curing for 28 days was 39 MPa, and increased to 54 MPa with the addition of silica fume. However, there were some weaknesses in the hydrated structure, such as a large amount of portlandite and high porosity of mortars. The addition of silica fume could overcome these problems and also improved the mortars resistance to acidic and sulfate attacks. The leaching tests showed that sodium was the most leached element from the synthesized cement mortars. The addition of silica fume was also positive in this case, since it strongly reduced the sodium reactivity. Among the elements that could be detected, there were no excess of toxic ones leached from the synthesized cement mortars, which suggests that the BR incorporation would not damage the environment or public health safety.
Solução numérica das equações de Maxwell para cavidades dielétricas bidimensionais
(Universidade Federal de São Carlos, 2012-08-07) Melzi, André Luis Rossi; Novaes, Marcel; https://lattes.cnpq.br/6150586582241018; https://lattes.cnpq.br/4996732021238082
The objective of this work is to find numerical solutions for Maxwell's equations in two-dimensional dielectric cavities. Such structures can trap light by means of total internal reflections and can be used for constructing lasers in the micron scale, known as microlasers. The shape of the cavity affects the dynamics of rays inside it, so that it can be regular or chaotic, and completely determines the emission pattern of the radiation. During the development of our computational algorithms, we have considered the problem of the circle, whose dynamics is integrable, and the stadium, which has chaotic dynamics. We partially reproduced results in the literature. In addition, we also considered a new geometry, which probably can provide unidirectional emission, a goal that is being sought by the scientific community.