Estudo da corrosão e corrosão-fadiga em ligas de Al e Al - Li de alta resistência para aplicação aeronáutica

Moreto, Jéferson Aparecido

doi:10.11606/t.88.2012.tde-22102012-112635

Cited by 7 publications

(13 citation statements)

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“…Comparing both alloys when tested in a saline fog environment, it is observed that the AA2128-T851 presented a slight improved corrosion fatigue resistance. This fact may be linked to the corrosion results obtained by Moreto 24 . This author has concluded that the AA2128-T851 exhibited a better corrosion resistance than AA2524-T3, therefore it is more resistance to oxidation in the presence of the saline fog during the corrosion fatigue tests, that the testing time was much shorter than the 15 days of the salt spray tests.…”

Section: Resultssupporting

confidence: 53%

Effect of salt-water fog on fatigue crack nucleation of Al and Al-Li alloys

et al. 2013

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Fatigue and corrosion-fatigue tests were performed to quantify the fatigue properties of AA2524-T3 and AA2198-T851 Al alloys. High cycle axial fatigue tests were carried out under air and salt-water fog conditions. In air, the specimens were fatigue tested at a frequency of 50 Hz, using specimens with and without preconditioning in a salt spray chamber, and for the corrosion fatigue condition, the tests took place at a frequency of 30 Hz in a salt-water fog condition. In all cases it was used a sinusoidal waveform and a stress ratio (R) of 0.1. The results indicate that the saline environment had a deleterious effect on the fatigue life of the two aluminum alloys. AA2524-T3 exhibited a better fatigue strength than AA2198-T851 when fatigue tested in air. However, considering the corrosion fatigue test in a saline fog environment an inverse behavior was observed with the AA2198-T851 exhibiting higher fatigue strength.

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Section: Resultssupporting

confidence: 53%

Effect of salt-water fog on fatigue crack nucleation of Al and Al-Li alloys

et al. 2013

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“…This kind of knowledge is only developed by research and for that reason request a series of tests and provides the necessary material for the laboratory of mechanical tests of EESC-USP. This was how were developed works as the Moreto (2012) or Pascoal (2014) and the present research continued going deeper in the same direction in order to supply new tools for designers. The aspects of fatigue structure design touched in the present work are highlighted, in Figure 1.…”

Section: Statement Of the Problemmentioning

confidence: 84%

“…The A1 test was done by others researchers (Pascoal, 2014) and (Moreto, 2012) and the tests A2, A3, A4, and C1 were done by the present author in addition of some of the mentioned researchers in order to add results to validate them.…”

Section: Tests Designmentioning

confidence: 99%

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Fatigue crack propagation in AA 7050-T7451 alloy considering environment, stress ratio, rolling direction and waveform effects

Barbosa¹,

Fernando²

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AcknowledgmentI'm so graceful with a lot of people who helped me to realize this work, mainly my Mum María Lily Barbosa and in general my family and friends in Colombia and Brazil who makes me believe in selfless friendship. I have a big debt with them and God for giving me as much love.Quero fazer um reconhecimento especial de gratidão ao Brasil e suas faces para mim como o Professor Waldek Wladimir Bosé Filho, o Departamento De Engenharia de materiais mesmo, a EMBRAER pelo fornecimento do material e a CNPq pela bolsa de estudos.Este trabajo es particularmente dedicado a mi Mamá María Lily Barbosa.Un beso enorme para todos los que me dieron la mano en los muchos momentos difíciles de este camino, por que como dijo Cerati si algo está enfermo, está con vida. Gracias de aquellas.....Totales RESUMO BARBOSA, J. F. C. Propagação de trinca por fadiga na liga AA7050-T7451 considerando o efeito do meio ambiente, razão de tensões, direção de laminação e forma de onda.. Dissertação (Mestrado) -Escola de Engenharia de São Carlos, Universidade de São Paulo, São Carlos, 2017.Os principais fatores modificadores extrínsecos e intrínsecos da taxa de propagação de trincas na liga AA7050-T7451 foram avaliados para fornecer subsídios para projetistas de estruturas aeronáuticas, com base na filosofía de tolerância ao dano. A metodologia experimental consistiu em ensaiar corpos de prova do tipo compact tension (CT) da liga nas direções de laminação TL e LT, para verificar seu comportamento sob diferentes razões de tensões, forma de onda e condição ambiente. Os valores de razão de tensão estudados foram 0,1 e 0,5, as formas de onda foram senoidal e trapezoidal ou de Dwell, em condições normais de laboratório, ao ar, e névoa salina 3,5% NaCl, em massa, para simular um ambiente marinho. No caso dos ensaios Dwell, os resultados foram conferidos pelo método de queda de potencial eléctrico (QPE), além do método de flexibilidade elástica.Usando os coeficientes de Walker calculados a partir dos resultados obtidos, pôde-se projetar com precisão o comportamento da propagação de trinca na região de Paris e prever a vida em fadiga usando os diagramas da/dN e S-N para diferentes valores da razão de tensões. O ambiente corrosivo aumenta tanto a taxa de propagação de trinca, quanto o valor de ΔKth por causa da formação de óxidos na trajetória da trinca, que geram um efeito de fechamento sobre a mesma. Quanto à forma de onda, verificou-se que o carregamento Dwell diminui a taxa de propagação de trinca, diminuindo a inclinação das curvas log (da/dN) versus log (ΔK) na região de Paris, ao invés de deslocá-la paralelamente como ocorre com ligas de titânio. A mudança da direção de laminação de LT para TL aumenta a taxa de propagação de trinca por fadiga (PTF) tanto na região de threshold, quanto na região de Paris, onde a mudança de taxa é pequena.Palavras-chave: -Propagação de trinca por fadiga (PTF), determinação da taxa de propagação de trinca, técnicas de medição de trinca, método de queda de potencial elétrico (QPE), corrosão por fadiga, carregame...

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“…Conforme já mencionado, a primeira constante de tempo a altas frequências (AF) é relacionada com o óxido passivo (R ox /C ox ) na superfície das ligas e da junta soldada; a segunda, a médias frequências (MF) é associada com processos de transferência de carga e o carregamento da dupla camada elétrica (R ct /CPE dl ) e a terceira, a baixas frequências (BF), a processos de corrosão na liga exposta ao meio corrosivo, nas regiões de defeito do filme óxido. A escolha do CEE em cascata foi feita a partir de modelos já propostos na literatura para a liga 2XXX e 7XXX (QUEIROZ, 2002;MORETO, 2012). dois MB e para a junta soldada obtidas a partir do PCA após 2 horas de imersão em solução 10 mM de NaCl.…”

Section: Circuito Elétrico Equivalente (Cee)unclassified

Estudo da resistência à corrosão das ligas de alumínio 2024-T3 e 7475-T651 soldadas por fricção e mistura (FSW)

Bugarin¹

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Friction stir welding (FSW) has roused great interest in recent years and it is now an alternative for joining materials of low weldability, such as the aluminum alloys of the 2XXX and 7XXX series, used in the aircrafts structure due to their high strength /weight ratio. However, FSW causes material microstructural changes, mainly in the stir zone (SZ), the heat affected zone (HAZ) or thermomechanically (TMAZ) affected zones of the materials welded. These generally interfere with the corrosive performance of the welded joint. In the present study, the corrosion resistance of the 2024-T3 and 7475-T761aluminum alloys, joined by FSW was investigated in 10 mM NaCl electrolyte. Agar-agar gel and immersion tests associated with microscopic techniques were performed to investigate the effect of galvanic coupling between the welded materials. Results from this test showed that, when galvanically coupled, the 2024 alloy acts as cathode and the 7475 as anode. Immersion tests revealed galvanic coupling between the alloys in the SZ. The zone most susceptible to corrosion was the TMAZ of the 7475. Intergranular corrosion was observed in this zone since the first hours of immersion. The influence of the welding process on the corrosion resistance of the alloys was also evaluated by electrochemical tests. The electrochemical tests adopted were open circuit potential measurements (OCP) as a function of time of exposure to the electrolyte, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves. The polarization tests showed high electrochemical activity in the stir zone indicated by the high current densities measured comparatively to the other tested zones. The global EIS results indicated that in the first few hours of exposure to the electrolyte the corrosion process was predominantly controlled by the 7475 alloy; however, with time of exposure to the electrolyte, the corrosion was controlled by alloy 2024.

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Estudo da corrosão e corrosão-fadiga em ligas de Al e Al - Li de alta resistência para aplicação aeronáutica

Abstract: estarem sempre ao meu lado nos momentos felizes e de dor. Sei que são meus amigos de verdade, pois, sempre suportaram minha felicidade.

Cited by 7 publications

References 27 publications

Effect of salt-water fog on fatigue crack nucleation of Al and Al-Li alloys

Effect of salt-water fog on fatigue crack nucleation of Al and Al-Li alloys

Fatigue crack propagation in AA 7050-T7451 alloy considering environment, stress ratio, rolling direction and waveform effects

Estudo da resistência à corrosão das ligas de alumínio 2024-T3 e 7475-T651 soldadas por fricção e mistura (FSW)

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