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Efeito da adição de boro na microestrutura e na resistência ao desgaste do aço inoxidável AISI 430 conformado por spray
(Universidade Federal de São Carlos, 2014-08-04) Nascimento, Alexandre Romão Costa; Bolfarini, Claudemiro; https://lattes.cnpq.br/9231627080617037; https://lattes.cnpq.br/7480615370794070
The contact between drill pipes during oil well exploitations induces a severe wear process that might cause well bore pipe wall rupture, fluids leakage, environmental impacts, and possibly fatal accidents. The problem is known by the oil and gas industries since the 1930 s and several solutions have been proposed by researchers and engineers in order to mitigate its deleterious effects. A method that grows popular in the industrial media is the execution of large-scale tests that consists in forcing a cylinder against the inner wall of a pipe. During this test, in order to reproduce operations conditions, the use of drilling mud as a lubricant and a wear resistant coating over the cylinder are both possible. The purpose of this work was to evaluate the effect of boron addition on the microstructure of spray-formed AISI 430 stainless steel as well as in its wear resistance in a condition comparable to the one observed during drill pipes contact. It was then necessary to develop a wear tester capable of reproducing the changes in the contact areathat occurs during the aforementioned contact. The results showed that unlike the conventional API 5L X80 steel, the spray-formed material s wear rates were constant as predicted by Archard s wear law. Despite the different wear rate behaviors, the generated wear debris showed a similar morphology in all tested materials. The tribossystem conditions induced a plastic ratchetting wear mechanism. In the light of Greenwood and Williamson s theoretical model, it was concluded that the observed changes in the wear rate on conventional steels was due to slow changes in the plasticity index which happens much more quickly in the sprayformed steels due to the presence of intermetallic borides. Moreover, considering the established test parameters, the increase in the boron content also increases the AISI 430 steel s wear resistance, since the increase in the area fraction of intermetallics decreases the rate at which metallic asperities contact each other during the test.
Composição de espécies de lianas e sua resposta ao corte em um fragmento de floresta estacional semidecidual, Araras, SP
(Universidade Federal de São Carlos, 2014-08-04) Rocha, Elisangela Xavier da; Penha, Alessandra dos Santos; https://lattes.cnpq.br/9799774247477252; https://lattes.cnpq.br/3486794494112864
Although the knowledge on plant richness of seasonal semideciduous forests has been increased during the last years, we have little information about the composition of lianas species in these phytophysiognomies, especially if one consider the small and degraded ones. In this sense, we sampled the species of lianas, and also their abundances and mechanisms of climbing in a 12.8 ha seasonal semideciduous forest fragment located at Centro de Ciências Agrárias (CCA), University of São Carlos (UFSCar), Araras, São Paulo, southeastern Brazil (22º18 00 S and 47º23 03 W). During one year (from March 2013 to March 2014) we registered the liana species through unsystematic hikes in the area. We found 34 species of lianas (14 families and 23 genera). Sapindaceae and Bignoniaceae were the families with the greatest species richness, eight species each one. We classified Serjania caracasana and S. laruotteana (Sapindaceae) as abundant because they occurred throughout the forest area. On the other hand, we found that Schnella microstachya (Fabaceae), Tynanthus fasciculatus (Bignoniaceae), and S. tristis were considered as rare . Species of lianas with tendrils were the most common in the community (64%), followed by the fickle lianas (24%) and the scandent ones (12%). Although small, degraded and isolated, we argued that these forest communities might present a great part of lianas richness, once they have ecosystem features that favor this life form. These findings may represent the basis for the proposition of management routes of the seasonal semideciduous forests; for example, if one should choose between the selective management of lianas or their unrestricted cutting in such ecosystems.
Programas de diversidade de recursos humanos: uma análise sobre sua adoção no Brasil
(Universidade Federal de São Carlos, 2014-08-04) Reith, Stefanie Landim; Rachid, Alessandra; https://lattes.cnpq.br/6981682198988902; https://lattes.cnpq.br/3311563561943550
The purpose of this master´s degree thesis is to analyze the adoption of diversity programs for inclusion of women and blacks in companies in Brazil. We chose to conduct the survey on companies listed on the ranking "Melhores Empresas para Você Trabalhar" (Best Companies to Work For), in which they participate for human resources management practices evaluated as advanced. Few companies have diversity programs, but more than indicated by the literature review. Most programs are in initial stages. It was also possible to observe the relationship of the adoption of these programs with the size and origin of the capital of the companies surveyed.
Síntese e sinterização de pós-compósitos de aluminaboretos de alta dureza por moagem de alta energia
(Universidade Federal de São Carlos, 2014-08-04) Cerqueira, Valdívio Rodrigues; Morelli, Márcio Raymundo; https://lattes.cnpq.br/0172837599844991; https://lattes.cnpq.br/0169289640534560
This work was aimed to obtain powder composite mixtures of ceramic phases with high hardness through high energy ball milling synthesis and characterization of sintered samples in terms of hardness. In an exploratory phase, many aluminothermic reactions were obtained from basic or precursors oxides such as WO3, TiO2, B2O3, Ti °, B ° and C, whose final products were B4C-TiB2-Al2O3 Al2O3 and (WB or WB2 or W2B5) - TiB2. The resulting powders from the processing of synthesis performed under different conditions were characterized employing the following techniques: X-ray diffraction (XRD), real density, X-ray fluorescence (XRF) and scanning electron microscopy (SEM). Two reactions were selected, where the powders were subjected to variation of milling time of high energy and disintegration procedure change. Samples of the powder were forming under uniaxial pressure of 50 MPa followed by isostatic pressure of 200MPa and sintered at 1600 °C, 1650 °C and 1700 °C under high vacuum aiming to characterize the microstructural evolution and microhardness Vickers. Thus, the results showed that the composite powder represented by Al2O3 - WB - TiB2 sintered at a temperature of 1700 °C allow to obtain apparent densities (% TD) and Vickers hardness, near 99% and 19 GPa respectively. The best results characterized by the density, microstructure and hardness were obtained by enhancing the grinding in ball mill and additional deagglomeration in planetary mill after high energy milling.