Título :	Assessment of corrosion-fatigue degradation of grade R4 steel sing an electrochemical-mechanical combined approach
Autor :	Canut, Felipe Azevedo
metadata.dc.contributor.email:	felipe.canut@gmail.com
Orientador(es)::	Mamiya, Edgar Nobuo
Coorientador(es)::	Simões, Alda Maria Pereira
Assunto::	Fadiga Corrosão Aço - corrosão Aço grau R4 Potencial de corrosão Espectroscopia de impedância
Fecha de publicación :	5-abr-2023
Data de defesa::	30-ago-2022
Citación :	CANUT, Felipe Azevedo. Influência da adição de zircônia tetragonal estabilizada com céria na resistência à fadiga por flexão em 4 pontos de compósitos Al2O3 – Ce-TZ Assessment of corrosion-fatigue degradation of grade R4 steel sing an electrochemical-mechanical combined approach. 2022. [116] f., il. Tese (Doutorado em Ciências Mecânicas) — Universidade de Brasília, Brasília, 2022.
Abstract:	The study deals with the combined effect of corrosion and mechanical cyclic stresses observed on the grade R4 steel. This material is commonly employed in the production of mooring chains used on Floating Production Storage and Offloading (FPSO). Corrosion-fatigue tests under stress-controlled loading were performed in artificial seawater (3.5 wt.% NaCl) using a corrosion cell developed for this purpose. Fully reversed (R = −1) and tension-tension (R = 0.1) loads were applied. In-air fatigue and no-load immersion tests were also carried out for comparative purposes. The results have shown an acceleration of the failure caused by the corrosive environment when compared to the in-air fatigue. The corrosive environment has a greater detrimental effect towards lower stress amplitudes on the observed corrosion-fatigue life. Periodic corrosion potential measurements were carried out during the experiments and the acquired signals were correlated with the degradation level of the specimen. This technique has proven to be effective in detecting important phenomena, such as pitting formation and crack initiation. Electrochemical Impedance Spectroscopy (EIS) measurements were performed to assess the evolution of the electrochemical system during the corrosion fatigue tests and the results were compared to non-loaded specimens. The specimens were examined in a Scanning Electron Microscope (SEM) and in a Confocal microscope. The corrosion degradation on the surface of the specimens was assessed using the corroded area fraction as an index. The microscopic analysis revealed that the application of mechanical loads together with chemical exposure produces a higher fraction of corroded area when compared to the no-load immersion samples, highlighting the synergistic nature of the corrosion fatigue phenomenon. A higher density of microcracks and pits were observed for the lower fatigue loads while large secondary cracks and few pits were identified for the higher amplitudes. Therefore, the failure of grade R4 steel in the seawater environment could be divided into two regimes: one dominated by electrochemical effects, observed in lower stress amplitudes, and the other dominated by mechanical effects for higher stress amplitudes.
metadata.dc.description.unidade:	Faculdade de Tecnologia (FT) Departamento de Engenharia Mecânica (FT ENM)
Descripción :	Tese (doutorado) — Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2022.
metadata.dc.description.ppg:	Programa de Pós-Graduação em Ciências Mecânicas
Licença::	A concessão da licença deste item refere-se ao termo de autorização impresso assinado pelo autor com as seguintes condições: Na qualidade de titular dos direitos de autor da publicação, autorizo a Universidade de Brasília e o IBICT a disponibilizar por meio dos sites www.bce.unb.br, www.ibict.br, http://hercules.vtls.com/cgi-bin/ndltd/chameleon?lng=pt&skin=ndltd sem ressarcimento dos direitos autorais, de acordo com a Lei nº 9610/98, o texto integral da obra disponibilizada, conforme permissões assinaladas, para fins de leitura, impressão e/ou download, a título de divulgação da produção científica brasileira, a partir desta data.
Agência financiadora:	Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).
Aparece en las colecciones:	Teses, dissertações e produtos pós-doutorado

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