https://ri.ufs.br/jspui/handle/riufs/19609 2026-05-03T17:40:55Z 2026-05-03T17:40:55Z Santos, Luiara Lima https://ri.ufs.br/jspui/handle/riufs/19668 2024-07-23T12:00:58Z 2024-04-29T00:00:00Z

Título: Corrosão sob tensão em aço ASTM A516 com revestimento Cr3C2-25NiCr por HVOF Autor(es): Santos, Luiara Lima Abstract: Thermal spray deposited coatings (HVOF) are widely used on the surface of steel substrates to protect against corrosion and wear, in order to increase the durability of the material. The Cr3C2-25NiCr composite coating plays a protective role, with the NiCr matrix providing corrosion resistance and the chromium carbide providing durability and high resistance to abrasive wear. In this study, the protective behavior of the Cr3C2- 25NiCr coating was analyzed under conditions conducive to stress corrosion. For this purpose, three ASTM A516 steel specimens were used as the metallic substrate, in addition to which they were subjected to different levels of plastic deformation by threepoint bending (1%, 5% and 15%). To simulate the corrosive environment, the samples were placed in an autoclave at a temperature of 60 °C and a CO2 pressure of 20 bar, and the test lasted three months. To obtain the results, metallography, pitting depth analysis, crack quantification and SEM images were carried out. The coating did not show corrosion, but many cracks were identified and pitting was found just below them. However, the severity of the damage intensified as the percentage of deformation increased.

2024-04-29T00:00:00Z Carvalho, Lucas Silva https://ri.ufs.br/jspui/handle/riufs/19601 2024-07-23T11:55:07Z 2024-04-11T00:00:00Z

Título: Influência de aditivo na produção de compósitos de matriz gesso com fibra de coco verde Autor(es): Carvalho, Lucas Silva Abstract: The development of composite materials with natural fibers has been growing along with man's need to find renewable and low-cost resources for the production of new materials, such as gypsum-green coconut fiber matrix composites. The problem with this study is that green coconut waste generates numerous environmental problems. In this study, composites made of gypsum matrix with recycled green coconut fiber were produced in percentages of 5%, 10% and 20% fiber. The effect of the Bianco additive on the processing of the gypsum matrix and the composites was evaluated. It can be concluded that the additive increased the workability of the matrix and the composites, since it increased the setting time of the gypsum and facilitated the manual processing of the specimens. The additive used reduced the compressive strength of the gypsum matrix. Incorporating the fibers into the gypsum matrix reduced the density of the composites, which is explained by the low density of the green coconut fibers. The maximum compressive strength (MPa) of the composites with 5% and 10% fiber was lower than the pure and additive gypsum matrices, concluding that the coconut fiber did not reinforce the matrix. The composites of pure gypsum matrix and gypsum added with 20% fiber showed an increase in mechanical strength compared to the composites with 10% fiber, which led to the need to repeat the production of the composites with 20% fiber, which had a high content of fiber incorporated into the matrix, making it difficult to distribute and disperse the coconut fibers.

2024-04-11T00:00:00Z Santos, José Antônio Prado Viana https://ri.ufs.br/jspui/handle/riufs/19334 2024-07-24T15:11:42Z 2023-12-22T00:00:00Z

Título: Desenvolvimento de dispositivo para testes de fricção fadiga de arames Autor(es): Santos, José Antônio Prado Viana Abstract: The phenomenon of fatigue friction is present in various engineering equipment, since it is common to have components that are in contact under pressure between surfaces and that suffer small cyclic slips. The process, for example, affects the tension armature wires of submarine umbilicals. The present study aims to develop a device capable of promoting fatigue friction in test specimens of submarine umbilical armor wires. The wire used to make the device was the same as that used as a test specimen, with a diameter of 6 mm, medium carbon content, cold deformed and with a zinc layer deposited on the surface. To create the device, its stress mode was observed and the bending stress corresponding to the effort was calculated, which cannot be greater than the yield stress of the material to avoid accumulating plastic deformations in the device. By comparing the constructed SN curves, it was found that the device was not effective in influencing the fatigue resistance of the material, except at the lowest applied voltage level. Then, through microscopic images, it was found that the damage caused by the device to the test specimens was not enough to overcome the zinc layer of the material. The results indicated that the device caused slight damage that was not enough to promote a decrease in the material's fatigue resistance at most cyclic stress levels.

2023-12-22T00:00:00Z Araújo, Paula Larissa Lima https://ri.ufs.br/jspui/handle/riufs/18561 2024-07-24T15:12:49Z 2023-05-12T00:00:00Z

Título: Estudo do extrato de Anacardium Occidentale como inibidor verde de corrosão Autor(es): Araújo, Paula Larissa Lima Abstract: The extract of Anacardium Occidentale was evaluated as a possible green corrosion inhibitor for steel low carbon in NaCl 3,5% solution. For this, potentiodynamic polarization, electrochemical, impedance spectroscopy (EIS), contact angle measurements, scanning electron microscopy (SEM) were performed. The polarization curves show that the presence of the extract causes a significant change in the Ecorr, which varies from -498 to -687 mV, classifying the cashew leaf extract as a cathode inhibitor. The electrochemical impedance, in turn, showed a small increase in Rp and a reduction in the capacitance of the electric double layer, indicating that the molecules present in the extract absorb and form a complex with the iron ions on the metal surface. The contact angle measurements revealed the formation of a hydrophobic protective film who was defined by immersion in NaCl 3,5% solution in absence and presence of inhibitor showed angles of 24 º and 64 º respectively. The SEM indicates that the film formed after three days of immersion was more homogeneous and compact, this ensure a better protection for the material. The gravimetric analysis revealed that the efficiency of the extract as a corrosion inhibitor is greater after 3 days immersed, reaching values higher than 40%.

2023-05-12T00:00:00Z