Congressos

Resumo: The objectives of this work is to determine the elemental distribution map in reference samples and prostate tissue samples using X-Ray Fluorescence Microtomography (XRFCT) in order to verify concentrations of certain elements correlated with characteristics observed by the transmission microtomography. The experiments were performed at the X-Ray Fluorescence Facility of the Brazilian Synchrotron Light Laboratory. A quasi-monochromatic beam produced by a multilayer monochromator was used as an incident beam. The transmission CT images were reconstructed using filtered-back-projection algorithm, and the XRFCT images were reconstructed using filtered-back-projection algorithm with absorption corrections.

Resumo: Este trabalho tem por objetivo principal analisar a capacidade da técnica não destrutiva de termografia ativa pulsada para a inspeção de materiais compósitos poliméricos reforçados por fibra de carbono (CFRP) e detecção de defeitos que podem ocorrer nestes materiais. Foram confeccionados corpos de prova, extraídos a partir de um corte de secção reta de um tubo CFRP, onde foram usinados defeitos com diferentes diâmetros e profundidades. Além disso, foi construído um modelo de sólido virtual correspondente para simulação computacional da técnica, a fim de reproduzir numericamente os fenômenos físicos presentes nos ensaios termográficos. Através da validação do modelo de simulação computacional e do conjunto de dados obtidos experimentalmente, foi possível analisar a influência dos parâmetros geométricos dos defeitos no contraste térmico dos mesmos e também estimar o limite de detecção da técnica de termografia ativa pulsada para inspeção destes materiais pelo lado oposto dos defeitos.

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Resumo: This work aims the evaluation of the Layered Double Hydroxide (LDH) treatment and characterization for molybdate storage, focusing on smart organic coatings use. Commercial hydrotalcite (HT), which underwent several treatments, was the used LDH. First, HT was calcined and then reconstructed in water, terephthalic acid or glycerol followed by an interlamellar anion substitution with molybdate. The reconstruction was tried also directly in a molybdate aqueous solution. The LDHs SEM analyses have evidenced a lamellar morphology. The XRD have shown that the lamellar structure reconstruction, after calcination, was more efficient when terephthalic acid and glycerol were used, showing the structure memory effect. The molybdate release concentration was monitored by ion chromatography in double-distilled water and NaCl solution. The higher molybdate release, in solutions containing chlorides, indicates an anionic exchange property with different kinetics in terephthalic acid (HTCTe-Mo) and glycerol (HTCGl-Mo) reconstructed LDHs. Furthermore, the release process was accelerated by solution temperature, doubling the molybdate amount released at 85°C in comparison with 150 C. Electrochemical impedance spectroscopy (EIS) and anodic polarization curves of carbon steel, in aqueous extracts of molybdate loaded LDHs, have shown moderate inhibitory efficiency of the molybdate in 3.5 wt. % NaCl.

Resumo: Ballistic helmets are individual armor equipment designed to protect a soldier's head from projectiles and fragments. Although very common, these helmets are responsible for several causalities due to their low ballistic resistance and large back face deformation to stop the projectile. Therefore, to enhance helmet performance, studies have focused on the development of new materials and new ballistic protection solutions. The purpose of this study was to develop and evaluate a new ballistic solution using thermoplastic-based matrices. The first matrix was based on high-density polyethylene (HDPE). The second matrix was based on HDPE modified with ex-foliated montmorillonite (MMT). The main manufacturing processes of a thermoplastic-based ballistic helmet are presented, along with its ballistic performance, according to the National Institute of Justice (NIJ) standard 0106.01 and an investigation of its failure mechanisms via a non-destructive technique. All the helmets resulted in level III-A ballistic protection. The postimpact helmets were scanned to evaluate the back face deformation dimensions, which revealed that the global cone deformation was deeper in the HDPE than in the HDPE/MMT. The failure analysis revealed an overall larger deformation area in the HDPE and HDPE/MMT helmet delamination zones in regions with a large radius of curvature than in zones with the lowest radius, which is in accordance with previous simulations from the literature.

Resumo: Many elements play an essential role in a number of biological processes as activators or inhibitors of cellular and enzymatic activity. The topographic and quantitative elemental analysis of pathologically changed tissues may shed some new light on processes leading to the degeneration of cells in case of selected diseases. Zinc concentration in a prostate gland is much higher than that in other human tissues. The high concentration of zinc in the prostate suggests that zinc may play a role in prostate health. The aim of this work was to study the elemental distribution for Zinc in prostate tissues from patterns of relative fluorescence intensities. The measurements were performed in standard geometry of 45o incidence, exciting with a white beam and using a conventional system collimation (orthogonal slits) in the XRF beam line at the Synchrotron Light National Laboratory (Campinas, Brazil). The prostate glands were cut into pieces (slice) with thickness of 0.5 mm. The results showed the zinc distribution was not uniform for different zones of the prostate analyzed. INAC 2009, Rio de Janeiro, RJ, Brazil.

Resumo: The Rotating Cage (RC) system is a well-known laboratory tests methodology to evaluate the materials corrosion resistance and inhibitors under flow conditions, but does not allow to perform electrochemical measurements. The adaptation of the conventional RC to an Electrochemical RC in Autoclave (ERCA) allows following the corrosion process, as well as the performance of the corrosion inhibitors throughout the immersion time. The specimens tested can be monitored by impedance measurements, linear polarization resistance and polarization curves. The results presented herein shows that with ERCA assembly was possible estimate correctly the inhibitor efficiency and the influence of inhibitor concentration by electrochemical data once similar efficiency values were obtained by corrosion rates estimated from weight loss measures. It was possible to track the inhibitor action, film forming and consequent increase on X65 polarization resistance at 0.16% NaCl, 8.5 bar of CO2 in 170 Bar of total pressure, rotation speed of 540 RPM.

Resumo: An eddy current method was applied to evaluate amount of a sigma phase in a duplex stainless steel. In the preliminary experiments several transducers configuration were considered. The performance of the transducers were verified utilizing samples having different amount of sigma phase. The configurations presenting the greatest possibility of evaluation of the sigma phase were chosen for further experiments. In this paper a dedicated transducer operating in differential mode is presented. The results are shown and discussed.

Resumo: CO 2 corrosion is a complex process and a large number of variables are involved, such as: pH, temperature, chloride concentration, fugacity and system total pressure. This work presents electrochemical impedance spectroscopy and gravimetric results of tests carried out at pH 4, which was controlled within the whole experiment time. The impedance diagrams obtained with and without CO 2 presented the same interfacial process, suggesting the same corrosion mechanism for both. Therefore, no evidence was found for a direct reaction of CO 2 on Fe surface in the experimental conditions presented herein. In specific test conditions, local pH measurements demonstrated huge pH shifts whereas bulk pH remained constant. Thus, a strict controlled pH is mandatory to study corrosion mechanisms. For the same pH, comparing solutions with and without carbon dioxide, the weight loss was six times higher in environments containing CO 2 and eight times higher in CO 2 /brine conditions. The CO 2 buffering effect, previously reported in the literature, was only observed in brine condition. The results suggest a very good correlation between electrochemical and gravimetric data obtained at the same pH.

Resumo: The corrosion mechanism of X65 carbon steel was evaluated in water environment by increasing CO 2 partial pressure from 1 bar at 24 °C to 110 bar at 40 °C, reaching conditions that include water saturated with supercritical CO2. To perform this kind of investigation, the experimental tests were conducted only with CO2, eliminating any other influence of anions present in the solution. Electrochemical impedance measurements and weight loss tests were performed at pH 4, monitored within the whole experiment time. In addition, optical and confocal microscopy analyses were carried out to assess the carbon steel specimens after the immersion tests. The gravimetric results indicated that the corrosive process was not accelerated by increasing the pressure in H2O-CO2 systems. Concerning CO2 participation in the iron dissolution mechanism, electrochemical impedance results did not evidence a direct reaction of CO2 on the free iron surface, even when exposed to water saturated with supercritical CO2. If CO2 has any influence in the anodic mechanism, it must be detect by further experiments, however it certainly will not act directly on the free iron surface.

Resumo: Quantificação de confiabilidade de ensaios não destrutivos pode ser realizada através de curvas de probabilidade de detecção (POD). Estudos de confiabilidade através de curvas de probabilidade de detecção dependem, como toda análise estocástica, de parte determinística e parte probabilística. A parte probabilística da geração de curvas POD são representadas basicamente por de parâmetros de incerteza. Tais parâmetros, no caso de curvas de probabilidade de detecção PoD simuladas, são determinados pelo usuário na própria configuração da simulação. Para a geração e propagação dos parâmetros de incerteza, métodos de Monte Carlo são utilizados de modo ser possível gerar uma PoD com o mínimo de aleatoriedade. O intuito do presente trabalho é determinar se existe a aleatoriedade requerida na geração e propagação de parâmetros de incerteza no que tange a construção de curvas PoD simuladas à luz da escolha do tipo de distribuição de probabilidade (PDF) de tais parâmetros. Para tanto, o software CIVA será utilizado para a inspeção virtual e para a simulação das curvas POD. Após realizados testes estatísticos, foi possível concluir que, tanto para distribuição de probabilidade do tipo normal quanto para distribuição do tipo uniforme, os parâmetros de incerteza gerados são satisfatoriamente aleatórios

Resumo: Harsh conditions in petroleum industry include temperature variation during service of in-side coated equipments. Ranking coatings for this purpose is a hard task, demanding expensive and long-term testings. The aim of this paper is to study the behavior of composite anticorrosive coatings when subjected to temperature variations. The methodology consists in comparing the performance of coatings provided by recognized brands subjected to corrosion test with immersion at room temperature and immersion with variation of temperature. During corrosion testing EIS, pull-off adhesion measurements and SEM are made to characterize performance. Mechanical dynamic analysis was employed to compare thermo-mechanical properties of new and aged coatings, seeking relationship between these properties and performance in corrosion testing. It is observed that the classification of performance is related with the relative change of the complex modulus magnitude between glassy and rubbery states for each coating. This result suggests that this can be one source of damage generation in the studied composite coatings and can justify the inclusion of this methodology in the selection criteria of coatings to be used in conditions involving thermal variations.

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Resumo: Os efeitos da combinação de meios corrosivos com carregamentos cíclicos exigem o uso de uma metalurgia especial para produção de petróleo e gás em ambiente offshore. Nesse contexto, os dutos fabricados com material cladeado vêm ganhando espaço no cenário nacional. Os dutos cladeados são constituídos de um substrato de aço carbono de alta resistência e baixa liga com um revestimento interno de uma liga resistente à corrosão, combinando assim, excelentes propriedades de resistência mecânica e tenacidade do material de base à resistência à corrosão do revestimento. Devido ao risco do surgimento de trincas de corrosão-fadiga nos dutos é importante que se tenha uma ferramenta de inspeção capaz de identifica-las, principalmente nas regiões mais críticas, caso das soldas circunferenciais. Amostras com juntas soldadas foram fabricadas com entalhes de eletroerosão inseridos na raiz das juntas. Os resultados alcançados com o sistema de inspeção, eletrônica e sensores, desenvolvido no trabalho, demonstraram a viabilidade de aplicar a tecnologia de correntes parasitas para detectar trincas de fadiga em juntas soldadas de dutos cladeados.

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Resumo: O ensaio de Correntes Parasitas (CP) tem ampla aplicação na inspeção em serviço de feixes tubulares dos trocadores de calor modelo casco e tubo. Entretanto, devido à alta sensibilidade do ensaio às diversas variáveis, nem sempre a confiabilidade dos resultados do ensaio tem sido satisfatória. Em função da sua geometria, a análise dos sinais na região dentro do espelho fica ainda mais complexa, dificultando diferenciar os sinais dos defeitos dos sinais espúrios característicos desta região, gerados simultaneamente durante o ensaio. No presente trabalho, utilizando um software de simulação computacional, foram construídos sólidos virtuais simulando os tubos, a região do espelho e as sondas, com as características geométricas e dimensionais similares a condição real. Os resultados preliminares da simulação revelaram que a metodologia se mostra promissora para diferenciar a origem dos diferentes sinais permitindo uma maior confiabilidade na análise do problema.

Resumo: Duplex stainless steels (DSS) are two-phase materials whose microstructure consists of grains of ferrite (δ) and austenite (γ). DSS exhibit attractive properties only when δ and γ phases are in equal proportions. For this reason, it is worthwhile, for industrial applications, to have a NDE technique that could reliably determine the δ/γ ratio. The goal of the present work is to develop an eddy current (EC) method to accomplish this task. Four samples were prepared with different ratios of δ/γ Previous works have shown that the conventional EC technique was unable to distinguish different amounts of these phases. In order to inspect the samples, a detailed study of the magnetic behavior using magnetic hysteresis loop measurements of materials with different δ/γ ratios was accomplished, and, it was verified that the different δ/γ ratios become detectable around the magnetic flux density saturation level. The current work cares about DSS inspection using EC methods in the saturation level. Simulations using commercial software were performed to check the capability to saturate the samples using permanent magnets, and a gaussmeter to find the best configurations for the magnets. Experimentally the samples were brought to saturation as previously designed in the simulations and the EC inspection was able to successfully separate samples with different δ/γ ratio.

Resumo: his paper evaluates the tensile properties in the axial direction of GFRP pipes aged under high pressure (73 and 89 bar) and high temperatures (60°C and 93°C) through time. The tests were performed according to ASTM D3039-17. The modulus of elasticity showed the highest degradation compared to the condition without aging. The aging affected the tensile modulus of elasticity much more significantly than the tensile strength. The aging conditions at 89 bar were the most aggressive, generating macroscopic delaminations and the greatest losses in tensile properties.

Resumo: O presente trabalho se baseia no estudo da recuperação de marcações adulteradas, em placas metálicas ferrosas, pela técnica de correntes parasitas (CP) /magnetografia (M) /visualização magneto-óptica (VMO) em comparação com o método destrutivo de restauração por ataque químico, utilizado pelos peritos criminais. Para tal, foram analisadas três amostras extraídas da sessão dianteira da estrutura do chassi de um veículo, as quais foram identificadas com caracteres impressos por indentações. Após a remoção das marcações por desgaste, as amostras foram analisadas pela inspeção CP/M/VMO e por ataque químico. Segundo os resultados obtidos, foi possível recuperar todas as identificações por ambos os métodos, além de compara-los segundo suas performances. Por conseguinte, a técnica não destrutiva demonstrou satisfatório desempenho na recuperação de marcações adulteradas.

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Resumo: The recommended standard technique for monitoring the degradation of polyamide 12 (PA-12) is viscosimetry, through measurements of inherent viscosity (IV) to obtain the values of Corrected Inherent Viscosity (CIV). The CIV values were used as reference to correlate with Raman and IR results. PA-12 pristine samples and those submitted to ageing in reactors with controlled pressure and supercritical CO2 conditions were analyzed. The specimens were immersed in mineral water (pH 4.0), at a temperature of 120 °C for a period of up to 45 days. From the Raman spectra the νasCH2 vibration at 2924 cm– 1 seems to be a sensitive spectral probe of PA-12 hydrolytic degradation, therefore the relative intensity decrease of pristine and aged samples was used to compare RAMAN and CIV results. From FTIR spectra, a variation in the intensity of the bands attributed to the α and γ phases, at ~ 1560 and 1545 cm– 1, respectively, was observed, which might be related to the degradation/ageing of the polymer. After analyzing samples submitted to different ageing conditions, there are good evidences that an analyses protocol of Raman and FTIR give consistent qualitative information on the degradation of PA-12, and therefore, is a new alternative for monitoring the hydrolytic degradation of PA-12, thus eliminating the use of toxic organic solvents, reducing the analysis time and bringing information about the degradation mechanism.

Resumo: Os aços inoxidáveis austeníticos são materiais utilizadas nos ramos petroquímico, nuclear e aeroespacial cujas demandas se resumem essencialmente à: boa resistência mecânica, excelente soldabilidade e elevada resistência à corrosão. Apesar destes metais atenderem a estes requisitos, não raro são submetidos a etapas de conformação para elaboração de peças, o que pode modificar as suas propriedades originais. Basicamente, a causa desta mudança são alterações metalúrgicas induzidas por deformação, como a transformação da austenita (paramagnética) em martensita-α’ (ferromagnética). Tendo em vista que tais mudanças são acompanhadas de variações nas propriedades elétricas/ magnéticas destes aços, uma maneira de monitorá-los de maneira não destrutiva é através da técnica de correntes parasitas. Para este estudo, diversas amostras de aço inoxidável AISI 321 foram solubilizadas e deformadas por laminação a fim de produzirem diferentes frações volumétricas de martensita. Em seguida, submetidas à microscopia ótica, magnetômetro de amostra vibrante e correntes parasitas. De acordo com os resultados, percebe-se que toda a transformação martensítica se passa no intervalo entre 0,10 e 0,55 de deformação verdadeira. Além disso, com os dados de magnetização de saturação, foi possível estabelecer uma curva de calibração de comportamento exponencial, permitindo a quantificação da martensita de maneira não destrutiva.

Resumo: This work aimed to characterize the anticorrosive performance of HDLs with and without encapsulated imidazole. Also, the role of HDL is examined. Two HDLs were studied. One was calcined and reconstructed in imidazole solution (HTC-Im). The other was calcined, reconstructed with terephthalate and dopped with imidazole (HTCTe-Im). Hexagonal lamellar morphology was observed with transmission electron microscopy. DRX showed more crystalline and organized structure for HTC-Im, which also presents slower imidazole releasing kinetics, when compared to HTCTe-Im, as monitored by UV-Vis spectroscopy. Mass loss tests clearly showed that Mg-Al-HDL is more than an inert container. It has sinergic anticorrosive activity with the interlamallae imidazole. The chloride-inhibitor anion exchange can be considered as an important aspect for corrosion control, but there is also contribution of aluminum and/or magnesium specimens from HDL structure itself.

Resumo: Aços inoxidáveis austeníticos fundidos por centrifugação, da classe HP, são comumente utilizados na indústria de óleo e gás para a fabricação de tubos usados em fornos de reforma e pirólise. Essas ligas possuem uma elevada resistência à oxidação, elevada estabilidade térmica e elevada resistência à fluência em altas temperaturas, sendo esses requisitos necessários para aplicação nos fornos. Mudanças microestruturais, conhecidas como envelhecimento, podem ocorrer durante a operação, influenciado na resistência à fluência. Desta forma, a caracterização dos estados de envelhecimento de uma liga HP torna-se necessária para avaliar a sua vida remanescente. O objetivo deste estudo é caracterizar duas condições microestruturais de uma liga HP com a microscopia eletrônica de varredura e o ensaio não destrutivo de ultrassom. O processamento do sinal ultrassônico, utilizando a Transformada Rápida de Fourier (Fast Fourier Transform – FFT), foi realizado sobre o segundo eco de fundo do sinal ultrassônico, permitindo correlacionar a análise espectral do sinal com a microestrutura do aço HP. De acordo com a metodologia proposta, os dois estados de envelhecimento foram caracterizados através do processamento do sinal ultrassônico.

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Resumo: Adsorption of imidazole, 4-methylimidazole and guanine on copper in chloride solutions was investigated by a combination of weight loss tests with electrochemical and Raman techniques to understand their inhibition efficiency and interaction with the metal. Results revealed that imidazole and 4-methyimidazole are inefficient while guanine was an efficient inhibitor (86 %) due to formation of a passive film. Guanine was not efficient towards API 5L X65 steel corrosion in HCl (~22 %) and the low efficiency was due to physisorption. The insights obtained with the combination of spectroscopic and electrochemical results should aid selecting new efficient nontoxic inhibitors.

Resumo: The effect of salt concentration was investigated on general CO2 corrosion of X65 carbon steel. The corrosion process was monitored by weight loss and potentiodynamic sweeps for NaCl (0,1;3 and 10)wt% at pH 4, 22°C keeping dissolved CO2concentration constant.Experiments were performed in Na2SO4 solutions maintaining the same ionic strength as brine in order to evaluate the chloride or sulfate influence on corrosion. Experimental results showed different behaviors for carbon steel corrosion in chloride and sulfate environments. The weight loss in NaCl slowed down in concentrations ≥ 3 wt%. The weight loss in Na2SO4 enhanced with increasing salt concentration.That result was supported by an increase incathodic current density when sodium sulfate concentration was increased.

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Resumo: O papel das montmorilonitas (MMTs) como pigmentos em revestimentos anticorrosivos é investigado nesta tese. Foram avaliados revestimentos epóxi novolac pigmentados com aproximadamente 60% p/p de óxido de ferro micáceo, e 1 ou 5% p/p de diferentes MMTs. A metodologia experimental envolveu titulações de filtrados e suspensões das argilas, testes gravimétricos, como absorção de água e permeabilidade ao vapor de água através do filme polimérico, testes de corrosão a longo prazo, observando a cinética de envelhecimento dos revestimentos com análises de impedância eletroquímica. A ênfase na literatura é que as MMTs melhoram as propriedades de barreira desses, no entanto, foram observadas inibição ativa da corrosão e controle de pH para filtrados e suspensões das argilas. Nos revestimentos, observou-se que as MMTs foram capazes de controlar a permeação do H+ corrosivo através do filme de tinta, dependendo da afinidade da argila pela água. Foi verificado que com 5% das MMTs, houve ação inibidora de corrosão sob a película de todos os revestimentos. Os tratamentos de organofilização podem ter efeitos colaterais, como a MMT organofilizada com sebo hidrogenado metil dihidroxietilamônio que melhorou as propriedades de barreira, mas prejudicou a aderência. O conjunto de resultados revelou que as MMTs não são pigmentos inertes. Em vez disso, elas podem atuar como pigmentos inteligentes, com propriedades complementares às de barreira, que são ativadas à medida que o revestimento é encharcado com o eletrólito.

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Resumo: The objective of this work is to illustrate the importance of some experimental aspects about measurements of organic coatings adhesion by pull-off method. The issues addressed in this work are: surface preparation of the dollies, surface preparation of the coating where the dollies are glued and choice of adhesive. These procedures are not standardized leading to difficulties in industrial and laboratory practice. It is hoped that this work encourages regulatory agencies to address these issues in future revisions.

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Resumo: A integridade estrutural das tubulações existentes em plantas de extração de óleo e gás é um dos grandes desafios na área de ensaios não destrutivos, visando garantir a segurança e eficiência da produção. Os dutos de plástico reforçados com fibra de vidro (PRFV) tem, progressivamente, substituído as ligas metálicas tradicionais por apresentarem alta resistência mecânica e a corrosão além de baixo peso específico. Todavia as conexões de vários trechos desses dutos, realizadas por juntas adesivas, podem apresentar defeitos como a falta de adesão e a falta de adesivo, tornando-se pontos propícios ao colapso. Até o momento ainda não há uma metodologia de ensaio não destrutivo consolidada capaz de avaliar a integridade das juntas adesivas. O presente trabalho apresenta a caracterização qualitativa e quantitativa dos defeitos típicos encontrados em juntas adesivas do tipo “ponto e bolsa” utilizando as técnicas de ultrassom e microtomografia. Os resultados mostraram que a técnica de ultrassom é promissora no que tange a detecção de defeitos em juntas adesivas, ainda que com limitações. A microtomografia mostrou-se adequada para caracterização qualitativa e quantitativa dos defeitos visto que esta permite analisar a estrutura interna do material.

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Resumo: The purpose of this paper was to evaluate how different surface treatments of carbon steel influence the performance of a painting system with zinc rich primer. The surface treatments were applied to pre-corroded samples until degrees Sa3 as reference, St3 and SP11. Afterwards, the samples were painted with zinc rich primer, intermediate epoxy and polyurethane top coat. The specimens were subjected to cyclic corrosion test. The performance evaluation considered adhesion loss, blistering and corrosion advance around scribe. Electrochemical tests were carried out, including monitoring of open circuit potential and anodic polarization curves. The advantages of SP11 treatment compared to St3 were evidenced for the adherence and service-life of the painting system. However, consistent with previous results, a more important corrosion advance occurred around the risks in samples with SP11 treatment. Directly related to this greater advance, is the higher surface anodic activity detected by scanning vibrating electrode technique. Hypotheses justifying this behavior are heterogeneities in residual surface tension, as detected by X-ray measurements, and fouling with metallic material from the rotating brush.

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Resumo: The objective of this work is to evaluate the anticorrosive properties of epoxy novolac coatings, pigmented with micaceous iron oxide, to which 1% and 5% w / w of three types of montmorillonites (MMTs) were added: a natural calcium (bentonite), a sodium and a sodium with chemical treatment. The literature presents MMT as an inert pigment that would be capable of improving the barrier properties of anticorrosive coatings. In the studied epoxy coating the contribution of MMTs to the barrier action depends on the type and content. The experimental methodology consists of tests of permeability to water vapor, water absorption, immersion test and salt spray. Complementary tests include Foster swelling, mass loss and electrochemical impedance. It was seen that the chemical treatment improved the barrier effect but impaired the adhesion of the coating. It was found that with 5% of any type of MMT, the epoxy coating had underfilm corrosion inhibiting action. It is a moderate action as it does not extend to incision areas. Therefore, MMTs are not inert pigments and, even at low levels such as 5%, can contribute to further improve coating performance that is already considered noble; the epoxy novolac pigmented with micaceous iron oxide.

Resumo: Camadas de conversão de molibdato têm sido avaliadas como possível alternativa às de cromato. O ácido utilizado no ajuste do pH dos banhos de conversão exerce grande influência nas propriedades anticorrosivas dessas camadas. O objetivo deste trabalho foi verificar o papel dos ácidos fosfórico e sulfúrico no processo de conversão de zinco com molibdato. As técnicas utilizadas foram: cronopotenciometria, espectroscopia de impedância eletroquímica (EIE) e medidas de pH interfacial. A caracterização superficial foi feita com microscopia eletrônica de varredura (MEV) e espectroscopia de raios-X por dispersão de energia (EDS). Os resultados de cronopotenciometria mostraram que a influência da velocidade de rotação do eletrodo no processo de conversão depende do ácido: o ácido influencia o transporte de massa durante a conversão. As medidas de EIE sugeriram que o mecanismo de conversão não varia com o ácido, sendo as camadas mais espessas quando H2SO4 é usado do que as obtidas com H3PO4. Os resultados de pH interfacial mostraram um aumento de pH mais significativo para o banho com H2SO4, indicando uma cinética de dissolução do zinco mais rápida. Foi identificada a presença de Mo em todas as camadas analisadas, para ambos os ácidos, e P naquelas obtidas com H3PO4.

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Resumo: The microstructural evolution of a variant of a Super Martensitic Stainless Steel was investigated using in-situ high temperature X-ray diffraction (HT-XRD). The tempering of this alloy is required for adjustment of strength and toughness, and such treatment is performed at intercritical temperatures. The stability of austenite formed during this treatment depends on a number of factors, such as the local chemical composition, temperature and soaking time. After cooling, some amount of this reversed austenite may transform into untempered martensite while other part stay retained. To achieve better properties, it is essential to know the evolution and the relationship between these microstructures during tempering. Thus, in present work the formation of reversed austenite was analyzed by means of HT-XRD at different temperatures and times. Specimens were also characterized using scanning electron microscopy (SEM). It was observed that there is a critical tempering temperature in which reverted austenite tends to stabilize and remain untransformed during cooling.

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Resumo: The vast majority of fiber-reinforced polymer (FRP) composites are known to exhibit stiffness degradation during fatigue life. Based on this phenomenon, predictive models have been developed to evaluate the residual life of FRP components and structures subjected to cyclic loading. However, some researchers reported an increase in residual stiffness of laminated composites under different experimental conditions (fiber orientations, loading types, stress ratios, etc.), representing a gap in the FRPs fatigue theory. To understand this phenomenon, unidirectional laminates of carbon and glass fiber-reinforced polymer (CFRP and GFRP) were tested by tension- tension fatigue up to 10⁴ cycles. The experimental procedure followed the ASTM D3479-19 standard and employed a stress ratio (R) of 0.1 and a frequency of 1 Hz. Residual stiffness was monitored using extensometers in quasi- static and cyclic conditions. The GFRP specimens were also characterized by computed tomography (CT) to detect the fiber realignment. The mechanical testing showed a decrease in residual stiffness, confirming the degradation theory. CT images did not reveal significant changes in fiber alignment.

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Resumo: Flow accelerated corrosion (FAC) is a steel degradation that occurs in heat recovery steam generators in the power industry. The mechanism of this corrosion comprises an electrochemical dissolution of the semi-protective magnetite layer (Fe3O4) that is formed within the pipes employed in the boilers. The FAC is influenced by different factors such as fluid velocity, pH and dissolved oxygen concentration. In this context, Rotating Cage tests were used to evaluate the influence of pH and dissolved oxygen content on FAC of A210, P11 and P22 steels. General corrosion was lower for P11 and P22 steels, an effect consistent with the presence of chromium in their compositions. General corrosion was most critical at pH 8.5. The corrosion intensity decreased for the three steels when the dissolved oxygen concentration increased, at 2 m/s. This behavior is coherent considering the most effective precipitation of Fe2O3 inside the pores of the Fe3O4 layer in a more oxidizing environment. For 3 m/s, the corrosion intensity increased for both materials when oxygen increased, showing the shear stress effect. These behaviors were more significant at pH 8.5. About pitting corrosion, the analyzes show localized attack in the majority of coupons, however with very low number of pits.

Resumo: O presente trabalho teve o objetivo de avaliar a aplicabilidade das técnicas magnéticas não destrutivas de partículas magnéticas e visualização magneto-óptica na prática de investigação veicular, especificamente na área de recuperação de marcações adulteradas. As amostras utilizadas nesse estudo foram extraídas de partes do chassi de dois veículos desconhecidos. Com a finalidade de determinar os materiais estudados foi necessária a caraterização prévia dos mesmos através de análise química, magnética, mecânica e microestrutural. Em seguida, as amostras foram identificadas por estampagem e adulteradas por remoção e remarcação. As técnicas não destrutivas foram avaliadas de acordo com a definição dos códigos revelados e o tempo de análise. Com base nos resultados obtidos, as técnicas magnéticas não destrutivas apresentaram desempenho satisfatório na recuperação das marcações originais das amostras adulteradas por remoção e remarcação. Entretanto, do ponto de vista de aplicação prática, a técnica de recuperação por visualização magneto-óptica se mostrou superior em comparação com a técnica de revelação por partículas magnéticas

Resumo: A evolução da microestrutura de um aço inoxidável bifásico com estrutura martensítico-ferrítica (AIMF) desenvolvido pela Vallourec Tubos do Brasil S.A. foi estudada durante o tratamento térmico de revenimento através de medições in situ das frações de fase por difração de raios X. Para a liga de AIMF o revenimento é realizado para ajuste das propriedades do material e assim como ocorre com as ligas de aço inoxidável supermartensítico (AIS), este tratamento é realizado em temperaturas intercríticas. Após o resfriamento, uma quantidade da austenita revertida pode se transformar novamente em martensita enquanto outra pode permanecer retida na estrutura. Para conhecer melhor a ocorrência deste fenômeno para a liga de AIMF é essencial avaliar a sua evolução microestrutural durante o revenimento. Neste trabalho, a reversão da austenita em diferentes temperaturas de revenimento foi analisada através de difração de raios X in situ. As amostras foram também caracterizadas por microscopia eletrônica de varredura. A propriedade mecânica após diferentes condições de revenimento foi avaliada em ensaio de tração. Foi observado que há uma temperatura crítica em que a austenita revertida se torna mais estável e não se transforma durante o resfriamento subsequente.

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Resumo: O objetivo deste trabalho é pesquisar sobre as principais falhas apresentadas por revestimentos anticorrosivos modernos comumente empregados para proteção interna de tanques de armazenamento de produtos petroquímicos e avaliar a capacidade da técnica de correntes parasitas para a inspeção não destrutiva deste material. Nesse contexto, as vantagens e limitações da técnica são analisadas. A aquisição de dados foi realizada considerando as propriedades isolantes dos revestimentos nas condições como aplicado e também após o envelhecimento. Amostras foram preparadas com defeitos controlados inseridos no substrato de aço carbono a fim de simular defeitos de corrosão localizada sob o revestimento. A detecção dos defeitos foi avaliada nas amostras com diferentes espessuras e também com a presença de óxido de ferro no interior dos defeitos a fim de simular áreas de corrosão localizada. Através da comparação entre os resultados obtidos no C-Scan original e após o processamento de imagem, foi possível observar uma melhoria significativa na eliminação dos falsos defeitos relacionados a variação da espessura inerente do revestimento pela limiarização multilevel. Também foi possível através do efeito do lift-off distinguir os defeitos reais e falsos defeitos. Nesse aspecto, a técnica de correntes parasitas se mostrou capaz de detectar defeitos neste tipo de material.

Resumo: Duplex stainless steel (DSS) is a two-phase (ferrite and austenite) material, which exhibits an attractive combination of mechanical properties and high corrosion resistance, being commonly employed for equipment of petrochemical plants, refining units and oil & gas platforms. The best properties of DSS are achieved when the phases are in equal proportions. However, exposition to high temperatures (e.g. welding process) may entail undesired consequences, such as deleterious phases precipitation (e.g. sigma, chi) and different proportion of the original phases, impairing dramatically the mechanical and corrosionproperties of the material. A detailed study of the magnetic behavior of DSS microstructure with different ferrite austenite ratios and deleterious phases content was accomplished. The non destructive method evaluates the electromagneticproperties changes in the material and is capable to identify the presence of deleterious phases into DSS microstructure.

Resumo: Several Brazilian offshore pipelines are made of duplex stainless steel. In the welding processes, the oxygen content in back purging gas is controlled to prevent oxidation on the inner surface of welded joints. Understanding how the pitting corrosion resistance is affected by a higher oxygen level and how a post-weld surface treatment by pickling and passivation can improve the corrosion resistance is important in situations where the control of oxygen content is limited. In the present study, specimens welded with back purging gas containing 100 ppm and 200 ppm of oxygen and without back purging gas were investigated through ASTM(1) G48 A, and through corrosion tests under field simulated conditions. In these two last weld conditions, the specimens were also investigated after pickling and passivation treatments. No significant mass loss was observed and no pit was verified for 100 ppm. Without back purging gas and for 200 ppm of O2, the pitting resistance were improved after post-weld surface treatment.

Resumo: Several offshore pipelines in Pre-salt fields, Brazil, are made of Super Duplex stainless steel. When welded, in general, these materials present a decrease in its corrosion resistance. Welding procedures, materials properties, surface conditions and post-weld treatment have influence on the resistance to local corrosion Although there is a strict control regarding the contamination of back purging gas with oxygen, sometimes, this control may fail and the oxygen content may exceed this limit. Understanding if the pitting corrosion resistance is affected by a higher oxygen level and how a post-weld surface treatment by pickling and passivation can improve the corrosion resistance is important in situations where the control of oxygen content is limited. In the present study, specimens welded with back purging gas containing 100 ppm and 200 ppm of oxygen and without back purging gas were investigated through ASTM(1) G48-A, and through ASTM G48 method E6. The pitting resistance was improved after post-weld surface treatment for super duplex stainless steel.

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Resumo: The effects of pressure cycles and CO2 were characterized for three commercial anticorrosive composite coatings. N2 was also used for comparison purposes. The temperature and pressure range include CO2 supercritical state. The coatings performance was evaluated by visual inspection, pull-off adhesion measurements, impedance and microscopy. The aim is not ranking performance, but to evidence modes of failure and highlight the importance of a protocol including thermo-mechanical evaluation, whenever CO2 and pressure cycles are concerned. Complementary techniques include permeability to CO2, water absorption measured by gravimetry and viscoelastic properties measured by dynamic mechanical analysis. The coatings viscoelastic properties are closely related with performance in such experimental conditions. The presence of water enhanced the pressure cycles effects. The coatings performance becoming more impaired by CO2 than by N2, could be justified by change of physical state of CO2 during the pressure cycles and its cryogenics. Voids within the coating layer seem to enhance cracking during pressure cycles and must be minimized by formulation development and proper coating application methods.

Resumo: O comportamento de ligas NiFe é objeto de intensa investigação devido ao grande número de aplicações desses materiais no meio industrial. A eletrodeposição é um dos processos mais utilizados para produção dessas ligas devido ao seu baixo custo e sua capacidade de recobrir geometrias complicadas. Variáveis do processo como pH, densidade de corrente e composição do banho podem afetar a morfologia, a estrutura e a cinética de deposição da liga. O objetivo do presente trabalho foi estudar o efeito do pH sobre a cinética, composição e a morfologia dos filmes. Os resultados das curvas de polarização e analise química mostraram duas regiões (I e II), a primeira refletindo a redução de H+ . Com aumento da polarização a corrente passa a variar linearmente com o potencial (II) e a redução metálica é observada com boa eficiência. A morfologia dos filmes varia com o pH da solução, em pH 5 os depósitos são homogêneos e compactos, em menores pH (pH 1), a boa aparência dos filmes diminui e trincas são observadas ao longo da superfície.

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Resumo: Heat exchangers are equipments with high relevance in the petrochemical plants, refining units and oil & gas platforms. The heat exchangers consist of a series of tubes that contains the fluid that must be heated or cooled. These tubes are the most critical element in the system, since are typically used for high-pressure applications, with pressures greater than 30 bar and temperatures greater than 260 °C. For in service inspection the eddy current testing (ECT) is the non destructive technique most applied to evaluate the tubes integrity. However, depending on the defects position and orientation the ECT signal related to the defect can be complicated to decode. The present work shows a finite element modeling of a heat exchanger tube inspection. The goal is obtain a representative model to simulate the in service inspection, and with a validated model improve the ECT inspection results.

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Resumo: A avaliação da integridade estrutural de materiais compósitos através da aplicação de métodos não destrutivos é preocupação corrente, uma vez que tais materiais têm sido progressivamente mais aplicados em ambientes agressivos. Este trabalho avalia a detecção, localização e dimensionamento de defeitos tipicamente apresentados por juntas laminadas em material plástico reforçado por fibra de vidro (PRFV) através da inspeção por phased array. Corpos de prova com defeitos artificiais representando delaminações entre mantas e descolamento duto/laminado foram investigados neste estudo. Diversas leis focais foram avaliadas nas inspeções por phased array, através do uso de um transdutor matricial de 32 elementos e 500 kHz de frequência em um equipamento de 64 canais paralelos. Os resultados indicaram que a metodologia proposta é adequada para a detecção dos defeitos, destacando-se o desempenho de leis focais com focalização no fundo da junta. Palavras-chave: Phased array; PRFV; Inspeção não-destrutiva

Resumo: Este trabalho tem por objetivo principal avaliar a capacidade da técnica de termografia ativa como uma técnica não destrutiva a ser utilizada na inspeção de materiais com revestimentos compósitos anticorrosivos de baixa espessura. As três modalidades mais utilizadas de termografia ativa (Pulsada, Fase Pulsada e Lockin) foram analisadas na detecção dos principais defeitos, como a perda de espessura devido a corrosão localizada no substrato e falhas decorrentes de uma aderência incompleta do revestimento. De acordo com os resultados obtidos, todos os defeitos foram detectados nas três modalidades de termografia, no entanto, o pós-processamento nos dados de temperatura adotados nas modalidades Fase Pulsada e Lockin permitiu uma melhoria significativa no contraste dos defeitos apresentados na imagem de fase.

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Resumo:  THIS WORK PROPOSES METHODOLOGY TO DESIGN AND SYNTHESIZE A HIGH ENTROPY ALLOY (HEA) WITH REFRACTORY PROPERTIES IN THE FORM OF A PROTECTIVE THIN FILM. THE GOAL IS TO DEPOSIT A FILM WITH CHARACTERISTIC MICROSTRUCTURE OF HEA, WITH THE PRESENCE OF A DISORDERED SOLID SOLUTION MATRIX. TO PERFORM THE ALLOY DESIGN, A MINIMUM SET OF TARGET PROPERTIES OF INTEREST FOR THE ALLOY WAS DEFINED, IN THIS CASE THE YIELD STRENGTH, OXIDATION RESISTANCE AND RAW MATERIAL COST. FROM THESE PROPERTIES, SIX CONSTITUENT ELEMENTS WERE CHOSEN. AN ARTIFICIAL INTELLIGENCE MODEL WAS DEVELOPED TO DETERMINE THE OPTIMAL CHEMICAL COMPOSITION FROM PUBLIC DATA MINED FROM THE LITERATURE. ONCE DESIGNED, THE ALLOY WAS DEPOSITED OVER A SUBSTRATE, BY MAGNETRON SPUTTERING TECHNIQUE, USING POWER BALANCING TO ACHIEVE THE OPTIMAL COMPOSITION ON THREE CHOSEN TARGETS. TWO SAMPLES WERE DEPOSITED, ONE WITH HOMOGENEOUS DEPOSITION, AND ANOTHER WITH STATIC SAMPLE CARRIER. CHARACTERIZATION OF THE SAMPLES CONCLUDED THAT A CHEMICAL AND MORPHOLOGICAL HOMOGENEOUS SINGLE-PHASE BCC MICROSTRUCTURE WAS ACHIEVED, AND REVEALED THE PRESENCE OF THE HIGH MIXING ENTROPY AND SEVERE LATTICE DISTORTION HEA’S FUNDAMENTAL EFFECT.

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Resumo: A descoberta de óleo e gás no Pré-Sal transformou o Brasil em um dos grandes possuidores de reservas de petróleo no mundo e aumentou as expectativas de produção em águas profundas. Apesar da euforia, alguns desafios têm o potencial de inviabilizar a exploração do Pré-Sal: a complexa logística offshore, as dificuldades de acesso ao reservatório, as condições físico-químicas do poço e de subsuperfície. As condições impostas pelo ambiente são relevantes, devido aos altos teores de contaminantes, alta temperatura e pressão, que exigem materiais de alto desempenho. O objetivo deste trabalho é revisar os avanços que podem contribuir para superar as condições físico-químicas do Pré-Sal. Verificou-se que a solução deste problema pode envolver três tipos de abordagem: O desenvolvimento de ligas resistentes à corrosão (LRC), a adição de agentes modificadores do meio corrosivo (inibidores) e modificações no projeto dos equipamentos. Espera-se, portanto, que a utilização conjunta das diferentes abordagens proporcione a viabilidade de longo prazo da produção no Pré-Sal.

Resumo: O aço carbono é um material amplamente empregado na indústria petrolífera devido sua elevada resistência mecânica e baixo custo. Entretanto, este material não possui boa resistência à corrosão. Neste contexto a predição da taxa de corrosão é de extrema importância para estimar a durabilidade desses materiais. Atualmente isto é feito com base em dados de ensaios de perda de massa em um único tempo de imersão, estimando-se a taxa de corrosão. Contudo, para converter os dados de perda de massa em taxas de corrosão é imprescindível que os ensaios sejam conduzidos em diferentes tempos de imersão e que haja linearidade entre perda de massa e tempo. Neste trabalho a corrosão do aço carbono em meios saturados com CO2 foi investigada através de ensaios de perda de massa em três tempos de imersão diferentes, com o objetivo de avaliar essa linearidade. Dos quatro meios corrosivos estudados, um não apresentou linearidade entre PM e tempo de imersão, sendo portanto incorreto extrapolar os dados para taxa de corrosão. Os resultados comprovaram que a extrapolação de dados de PM para taxas de corrosão não pode ser aplicada sem uma prévia verificação da linearidade entre perda de massa e tempo de imersão.

Resumo: The quantification of intermetallic phases (σ, χ and Cr2N, mainly) and the influence on susceptibility to localized corrosion of super duplex stainless steels have a strong scientific and practical appeal. Mainly enable the reduction of costs in terms of unwanted stops, preventing failures of equipment and facilitate the estimated of remaining life of a component whose corrosive process is an imminent risk. Currently, the techniques of electrochemical potentiodynamic reactivation with double loop (DL-EPR, following the ISO 12732) and eddy current (EC) are presented as potentials tools for characterization of the susceptibility to localized corrosion of stainless steels. The application of these techniques in welded joints of stainless steels is a technical challenge, which basically involves the development of a methodology where aspects related to the limits of detection and characterization needs to be better analyzed. In this sense, this paper presents a comparison between techniques of DL-EPR and EC to quantification of intermetallic deleterious phases in super duplex stainless steel (UNS S32750) under different isothermal treatments (annealing and aging).

Resumo: The ultrasonic non-destructive evaluation is a valuable tool for materials characterization in the industry. It presents advantages such as high speed of testing, low operational cost and portability for field inspection. The great majority of engineering materials present microstructural heterogeneities such as pores, inclusions, second phase particles and precipitates, which may change their response to ultrasound. The Fast Fourier Transform is useful for converting signals from the time domain to the frequency domain in order to reveal information that is not evident in typical ultrasonic signals. The Fast Fourier Transform (FFT) is an important signal processing algorithms to obtain the Fourier Transform; its application in ultrasonic signals is already well established in the literature and has been subject of studies by several authors. Spectral analysis using the FFT of back wall echoes may allow the microstructural characterization of a material. The present study aims at the characterization of the aging condition of centrifugally cast heat-resistant HP stainless steels through the post-processing of ultrasonic signals. This material has been widely applied at the oil industry in reformer and pyrolysis furnaces tubes due to its high creep resistance and high mechanical performance while exposed to severe operational conditions. However, these conditions can cause microstructural changes in HP steels and may reduce their creep and mechanical resistance, leading the material to failure. Therefore, in order to ensure the reliability of these structures, the development of non-destructive techniques capable of monitoring the states of aging this steel is required. The FFT was applied on the ultrasonic signals obtained from three HP steel samples, each one presenting different states of aging. Spectral analysis was conducted in back wall echo of these specimens. The results indicate that it is possible to characterize different states of aging in HP steel samples through the proposed methodology.

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Resumo: Aços austeníticos HP atualmente são os materiais utilizados em tubos de fornos de reforma a vapor devido as suas propriedades superiores a altas temperaturas de operação. Por causa da exposição a ambientes oxidantes durante o serviço, na parede externa dos tubos é formada uma complexa camada de diferentes óxidos e, adjacente a esta, se forma região empobrecida de cromo. A presença de uma resposta magnética nesta região influencia diretamente o desenvolvimento de fermentas de inspeção não destrutiva para avaliação magnética da evolução microestrutural em fornos de reforma a vapor. Para caracterizar a resposta magnética desta camada transformada, foi utilizada uma amostra com estado de envelhecimento V utilizando-se a técnica de microscopia Kerr. Foram realizadas análises qualitativas por meio de imagens e análises quantitativas através do levantamento da curva de histerese. Os resultados permitiram identificar regiões com domínios magnéticos e correlacionar o seu comportamento com o valor do campo magnético aplicado.

Resumo: A composição química da camada de óxido formada durante operação em um forno de reforma a vapor por 70000 h em um aço inox resistente ao calor grau HP-Nb, foi analisada através da espectroscopia Raman confocal, com o objetivo de correlacionar as características químicas e morfológicas dos óxidos com os diferentes estados de envelhecimento. Os espectros Raman, adquiridos pontos aleatórios da camada de óxidos, revelam que os óxidos de Fe (-Fe2O3 e Fe3O4), bem como os óxidos mistos NiFe2O4 e NiFeMnO4 são as espécies predominantes no estado de envelhecimento I. Amostras envelhecidas dão origem a espectros característicos de Cr2O3, MnCr2O4, Fe3O4 e NiFe2O4, em consonância com estudos recentes reportados na literatura.

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Resumo: A deformação plástica de aços acompanha mudanças irreversíveis da microestrutura, que podem ser consideradas como o estágio inicial do processo de fratura. No entanto, detectar, monitorar e avaliar previamente, estados de dano e pequenos defeitos, de forma não destrutiva, ainda se mostra desafiador. Foi reportado na literatura o fenômeno do surgimento espontâneo de fracos campos magnéticos em aços estruturais e em oleodutos, que são originados devido a tensões mecânicas heterogêneas ou térmicas. Esta observação não é associada com transformações de fase induzidas por deformação e parece ser uma ferramenta promissora para a caracterização prévia de danos em aços ferromagnéticos. Para proporcionar uma melhor compreensão das bases físicas deste processo, foram observadas as microestruturas magnéticas de tais materiais e as mudanças ocorridas nos domínios magnéticos dos mesmos após sofrerem deformação plástica. Para isto foi utilizado um meio de solução coloidal com partículas superparamagnéticas na escala nanométrica (ferrofluido) que proporcionou, através da técnica Bitter, observar não apenas uma mudança de tamanho dos domínios magnéticos do material, mas também modificações em sua morfologia. Foram estudados neste trabalho aços ferríticos com as respectivas concentrações de carbono em sua composição: 0.08%; 0.22% e 0.45%.

Resumo: Os aços austeníticos HP são empregados na fabricação dos tubos de fornos de reforma a vapor, sobretudo pela manutenção de sua elevada resistência mecânica e à corrosão, a temperaturas superiores à 700°C. Contudo, intercorrências durante a operação podem causar o bloqueio do fluxo interno de matéria-prima, gerando um aumento rápido de temperatura na parede do tubo, muito superiores àquelas de projeto. Este tipo de falha é conhecido como surto de temperatura, e pode levar à formação de grandes trincas longitudinais no equipamento. As caracterizações das transformações ocorridas no surto são importantes para determinar os parâmetros de detecção dessa condição através de ensaios não destrutivos. Por isso, com a finalidade de analisar a resposta magnética de amostras que sofreram surto, foram avaliados dois casos. O primeiro corresponde a análise de uma amostra proveniente de um tubo de reforma a vapor que sofreu surto de temperatura durante operação. O segundo caso, corresponde a amostras com estado V de evolução microestrutural, que foram submetidas a um ciclo térmico para simular o surto. A análise foi realizada via microscopia de força magnética. Os resultados obtidos mostraram resposta magnética no contorno dos carbetos da amostra surtada em serviço e na amostra com simulação a 1050°C.

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Resumo: This work utilizes the electrochemical parameters proposed by the ISO 12732 standard to evaluate the susceptibility to localized corrosion of super duplex stainless steel UNS S32760. The relationship between these electrochemical parameters (ratio of peak currents or charge obtained with activation and reactivation during potentiodynamic polarization) and the percentage by weight of deleterious phases are evaluated. For the aging conditions, the deleterious effect of the phases has been satisfactorily detected by the DL-EPR technique. A new experimental protocol allowed the characterization of the attacks that occurred for each polarization range Neste trabalho, amostras de aço Lean Duplex UNS S32304 foram submetidas à temperatura de 800°C em um forno acoplado a um difratômetro de raios-x durante intervalos de tempo de 30, 60 e 90 minutos. Com o objetivo de analisar em tempo real a transformação das fases constituintes, foram realizadas várias varreduras insitu durante os diferentes tempos de permanência em 800°C deste material. Assim, observou-se a formação da fase sigma neste aço, tanto nos contornos de grão da ferrita como nas interfaces ferrita/austenita. Os valores de fase sigma obtidos para cada tempo de exposição foram calculados através do método de Rietveld sobre cada difratograma obtido e variaram de 11% a 17%. Notou-se que a fase sigma exibiu crescimento contínuo até 60 minutos e variação após este período. Todavia, observou-se que a formação de fase sigma a 800°C ocorre de forma significativa neste material após 30 minutos de aquecimento, o que pode comprometer as propriedades do mesmo.

Resumo: This work utilizes the electrochemical parameters proposed by the ISO 12732 standard to evaluate the susceptibility to localized corrosion of super duplex stainless steel UNS S32760. The relationship between these electrochemical parameters (ratio of peak currents or charge obtained with activation and reactivation during potentiodynamic polarization) and the percentage by weight of deleterious phases are evaluated. For the aging conditions, the deleterious effect of the phases has been satisfactorily detected by the DL-EPR technique. A new experimental protocol allowed the characterization of the attacks that occurred for each polarization range 

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Resumo: This paper concentrates in defining an equation for crack length of a specimen Single Edge Notch Bend – Four Point (SENB-4P), applying the so-called Back-face Strain (BFS) method for a large extension and precision. The specimen type SENB-4P is well known and used in fatigue testing. The standard (ISO 12108) 1,(1) provides a complete description of the specimen SENB-4P, however, this standard does not specify how SENB-4P could be used applying a BFS method to measure crack growth during a fatigue test. Moreover, there is lack of the literature concerning with BFS method applied to SENB-4P specimen for measuring crack propagation 2. The existing work presents a relative short crack length with high level of imprecision. It is noteworthy that the majority of fatigue tests have a crack monitoring via Direct Current Potential Drop (DCPD), however its use in corrosive media is something still quite questionable and costly. In this work, two methods were used: simulation by Finite Elements Analysis and Fatigue Testing (air and in corrosive media), with monitoring of crack, a SENB specimen of API 5L X70 steel (2) , widely used in offshore pipelines. A methodology is presented herein, for using the technique of BFS in the specimen immersed in corrosive medium SENB. At the end of the test, the fatigue curves were compared to the curves of (BS 7910) 3,(3) ..

Resumo: Os aços inoxidáveis bifásicos superduplex estão presentes em diversos setores da engenharia devido a versatilidade oferecida em termos de propriedades mecânicas e resistência à corrosão. Para garantir a qualidade destes aços, avaliar o teor de ferrita presente na microestrutura é de grande relevância para indústria uma vez que diversas propriedades do material dependem do controle deste teor. Durante a fabricação de equipamentos ou inspeções de campo uma das formas mais viáveis de monitorar o teor de ferrita é através do ferritoscópio, dada sua portabilidade e fácil interpretação. No entanto, observou-se que a forma usual de calibração do
ferritoscópio pode levar a medidas imprecisas, principalmente na avaliação dos aços superduplex. A fim de analisar esta influência, foram realizados diferentes testes de
caracterização microestrutural através de microscopia ótica, difração de raio-x e o magnetômetro de amostra vibrante, para confrontar com medidas obtidas com ferritoscópio. Conclui-se que para elevados teores de ferrita, a calibração do ferritoscópio realizada a partir dos padrões fornecidos pelos fabricantes apresentam desvios significativos dos teores encontrados a partir da caracterização com equipamentos de laboratório. O presente trabalho apresenta uma solução para utilização do ferritoscópio para uma quantificação mais acurada do teor de ferrita nos aços inoxidáveis superduplex.

Resumo: Thermography is a non destructive technique that maps the heating distribution on a material’s surface. The advantages of the technique are the velocity and efficiency in superficial and internal defects detection, in addition to the fact that no specific treatment of the surface is needed due to its contact-free nature. The purpose of the present paper is to verify the possibility of using the infrared thermography as a non destructive technique in the inspection of the following organic coating defects: blistering, lack of adherence and undercoating corrosion. For the experimental procedure, thermography has been applied using the active approach; the Pulsed Thermography technique. The sample was submitted to a ten seconds thermal pulse, emitted by halogen lamps. Analyzing the originals thermographic images, all the three kinds of defects were detected. Samples with defects simulating localized corrosion were prepared with holes of six different dimensions. In some samples the holes were filled with iron oxide, simulating corrosion product. The results had shown the method capacity to detect and dimension corrosion flaws on organic coatings, including composite materials widely used in extreme conditions of the oil industry.

Resumo: This work aims to study the use of absolute probes as an alternative to detect sensitization of austenitic stainless steels by nondestructive eddy current testing. In contrast to the methodologies currently applied, this technique makes it possible to adapt inspections to promote the automation of processes, generated by advances in industry 4.0. In this study, a sample of AISI 304 austenitic stainless steel, sensitized in the laboratory, was inspected through eddy current equipment, using two different absolute probes, both produced at the laboratory, operating in a frequency range of 1 to 10 kHz. The results obtained prove the feasibility of using these probes to inspect sensitized structures, due to the variation in the responses obtained for the phase angle between the inspected specimens.

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Resumo: There is great industrial interest in developing non-destructive tests for the detection of deleterious phases in stainless steels. In this context, the Electrochemical Potentiodynamic Reactivation (EPR) technique, described by the standard ISO 12732, can be used as a tool for quantitative analysis of the degree of sensitization of austenitic stainless steels. Experimental parameters that influence directly the test results are not dealt with carefully in the literature. This study then performs a critical analysis of the standard usefulness, mainly evaluating the influence of potential scan rate and concentration of potassium thiocyanate (KSCN) in the test solution. Actually, the EPR method can be sensitive to the degree of sensitization of the studied material. However, the classification given by ISO 12732 can lead to errors whether standard curves previously established for the steel are not considered.

Resumo: In this study, three modalities of Thermography (Pulsed, Pulsed Phase and Lockin) were used to detect delamination defects in CFRP samples from the 4ENF test. The results obtained for each modality were compared in relation to the real delamination area in these samples. In addition to the experimental analysis, a computational simulation model was also created to evaluate the influence of defect parameters (depth and thickness) on its thermal contrast and thus estimate the detection limit presented by the Pulsed modality.

Resumo: The application of simulation methods in sciences has been a powerful tool for the solution of problems of varying degrees of complexity. Among the different simulation techniques applied to the field of engineering, molecular dynamics simulation features a prominent position. It consists of a set of computational techniques that calculate physical properties of atomic or molecular systems derived from the motion of atoms and molecules, i.e. from simulations of the dynamic evolution of the systems. This work applied the basic methodology of molecular dynamics for modeling two fundamental processes in materials science: solid state diffusion and adsorption of a gas in air metallic interface. The challenge was to reach compatibility between the modeling parameters and the nature of the phenomena itself, in order to accurately reproduce the experimental results reported in the literature. The calculated values for the diffusion in the solid state were close to those listed in the literature and the calculated values of potential energy presented the behavior commonly expected for the adsorption process, indicating the feasibility of molecular dynamics simulation for such phenomena.

Resumo: This paper presents a failure analysis of a CFRP mast of a racing sailboat that collapsed on duty and an evaluation of NDT techniques, for failure assessment in composite materials. Visual inspection, pulsed thermography, radiography, and computed tomography tests were performed to obtain information about the locations, types, and orientations of the damage. Based on these results, four samples were taken and analyzed in an SEM, revealing information about the propagation directions of the defects and the predominance of mode II fracture. The weak interface between the composite layers, manufacturing defects, and the stress concentration effect due to the abrupt geometry transition, possibly caused the failure. The severe damage made it difficult to reach a clear conclusion about the cause of the failure and its origin. However, the inspection and characterization techniques applied made it possible to identify defects and potential causes that led to or contributed to the failure.

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Resumo: Neste trabalho foi caracterizada a influência da evolução microestrutural e da composição química de aços austeníticos HP-Nb na resposta magnética detectada pela técnica de microscopia de força magnética (MFM). Além disso, também foi determinada a influência das forças eletrostáticas no sinal detectado por tal método, através da implementação da técnica de microscopia por força Kelvin (KPFM). Para este estudo, foram analisadas quatro amostras, que foram extraídas de dois tubos de reforma a vapor com diferentes composições químicas. Cada uma das amostras estudadas foi extraída de uma região do tubo exposta a diferentes temperaturas resultando em distintos estados de evolução microestrutural. Segundo os resultados obtidos, apenas as amostras com estado de envelhecimento I exibiram resposta magnética nas interfaces matriz-carbetos.

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Resumo: This paper addresses the design, implementation and experimental evaluation of a recently proposed force control scheme for fatigue testing machines. The phase shift between the desired force signal and the applied force to the specimen is irrelevant for keeping the force within the fatigue testing requirements considered here. Thus, the proposed approach relies only on an appropriate amplitude and mean value tracking control, disregarding the phase. An estimator for the amplitude and mean value of the output force signal is proposed based on a demodulation technique. Global exponential stability of the complete error system with respect to a small residual set is guaranteed via averaging analysis, for the plant operating at low frequencies. Experimental results and numerical simulations performed at the Non-destructive, Corrosion and Welding Laboratory (LNDC/COPPE/UFRJ) illustrate the remarkable behavior of the proposed scheme, considering real fatigue testing machines.

Resumo: In the present study, Raman spectroscopic characterization of the oxides formed on Ni-Cr-Mo alloys, stainless steels and carbon steel is presented, and the changes in these layers upon exposure to solutions containing high chloride concentrations and H2S/CO2 are discussed. This work also describes our experience characterizing corrosion products formed on carbon steel and corrosion resistant alloys (stainless steels and nickel chromium alloys) using Raman spectroscopy.

Resumo: This work proposes a method to test flexible pipe carcass samples by Sulfide Stress Cracking (SSC) C-Ring test. As flexible pipes are going to be used on the majority of new deep water oil & gas offshore fields and at most of pre-salt fields in Brazil where the conditions are sour or can eventually became sour due to H2S presence, SSC may occur. Therefore, a method to test SSC on samples made from flexible pipes is very important. In this context, the NACE Standard TM 01771, method C (C-Ring) test is presented as a good alternative to evaluate these components. However, the method as it is described in the standard does not contemplate the carcass geometry. The experimental procedure presented herein follows the standard NACE TM 0177 and proposes, in addition, a finite element simulation to find the main direction of applied stresses and also the use of a rosette strain gauge instead of the uniaxial one recommended in the standard. Reproducible results were obtained on loads performed following the procedure presented in this paper.

Resumo: In Quantitative Nondestructive Evaluation (QNDE), assessing the reliability of the NDT method is crucial. Technology advances and the development of new life estimation models based on the damage tolerance concept have led to the maturing of QNDE techniques. Nowadays, the concept is widely used for such models in fitness-for-service (FFS) assessments. As an input to these models, flaws size plays a very important role. In these concepts, Probability of Rejection (PoR) was introduced around 2007 and combined the concepts of Probability of Detection (PoD) with the need to accurately size flaws when using fracture mechanics-based acceptance criteria. Improvements in sizing techniques have been made and fracture-mechanics acceptance criteria are becoming more commonly accepted instead of the traditional workmanship criteria. However, experimental PoD campaigns are excessively time and money-consuming, rapidly making them almost prohibitive. On the other hand, recent advances in technology to accurately simulate nondestructive testing (NDT) processes made available new tools for reliability study. This paper uses CIVA’s ultrasonic inspection simulation to demonstrate how small changes on the flaw sizing characterization would affect probability of rejection.

Resumo: The 2015 World Federation of NDE Centers (WFNDEC) eddy current benchmark problem involves the inspection of two EDM notches placed at the edge of a conducting plate with a pancake coil that runs parallel to the plate’s edge line. Experimental data consists of impedance variation measured with a precision LCR bridge as a XY scanner moves the coil. The authors are pleased to present the numerical results obtained with commercial FEM packages (OPERA 3-D). Values of electrical resistance and inductive reactance variation between base material and the region around the notch are plotted as function of the coil displacement over the plate. The calculations were made for frequencies of 1 kHz and 10 kHz and agreement between experimental and numerical results are excellent for all inspection conditions. Explanations are made about how the impedance is calculated as well as pros and cons of the presented methods.

Resumo: The 2012 Eddy Current Benchmark Problem involves the inspection of an inconel pipe using an internal pancake coil situated with its axis perpendicular to the axis of the pipe. The experimental data were supported by the Benchmark Eddy Current 2012, as released by the World Federation of Non Destructive Evaluation Centers (WFNDEC). The software OPERA 3D and COMSOL were used by the authors to solve the proposed simulation problem. The simulated results were in good agreement with the experimental ones. However some simulated results exhibited a small variation in the impedance and electrical resistance between the base material and the region around the notch. The values of these changes were plotted as a function of the displacement of the sensor over the notch region. The calculations were made for frequencies of 25kHz to 200kHz. A good agreement was obtained at low frequency. However, the simulation at high frequencies presented differences, which can be attributed to the mesh refinement. The finite elements in both software should be adjusted to two regions: the change of the small notch region and its neighborhood. It is important to adjust the mesh size parameter to compensate the low skin depth inherent to eddy current testing at high frequencies.

Resumo: RIP2025-00099: It is common sense that all CCS wells must be designed for potential CO2 exposure. Cement integrity is essential to prevent migration of stored CO2 out of the storage zones. In this context, electrochemical techniques can give valuable information on electrolyte migration from outside through the cement barrier and eventually reaching the well casing. The challenge is to design an experimental setup to perform electrochemical measurements that mimic CCS wells conditions. Herein we present the results of electrochemical impedance measures performed at 65 oC and 10 MPa of CO2 and 0.02MPa of H2S/CO2 (balance) with 80,000 ppm of NaCl with setup specially developed to follow the changes on casing/cement interface. All tests were performed from the cement curing up to 30 days exposure to field conditions reproduced in laboratory. Two distinct cement paste were evaluated, C1 and C2, and carbon steel as casing metal. By the impedance diagrams, recorded periodically over the entire test, it was possible to follow the interface changes and correlate the results with cement paste performance and carbon steel corrosion resistance at CCS wells conditions. The analyses of electrochemical measures associated with Raman spectra interpretation of compounds formed on carbon steel after exposure to high pressure environments (10 MPa) gave valuable insights on cement paste role on casing corrosion performance. During the immersion period at high CO2 or H2S/CO2 pressure it was easy to identify any cracks on cement due to changes on electrochemical impedance response of carbon steel/cement interface. To both, C1 and C2, exposed to supercritical CO2 for 30 days the following compounds were identified on carbon steel surface by Raman analyses: Fe3O4, g-Fe2O3 e b-FeOOH(Cl). FeCO3 was present only when cement was physically damaged. These findings support the electrochemical results: open arcs on Nyquist diagrams, clear indication of resistive interface. Higher impedance values were observed to casing/cement interface with C2 compared to C1 in agreement with designed cement composition. On test carried out with H2S/CO2 the interface processes might be similar but happens faster once to the same frequencies the impedance components were lower. Within the test time CO2 and H2S only reach the casing surface when cement was physically damaged. The designed experimental setup was effective to evaluate casing/cement interface at CCS well condition and allowed to investigate the influence of cement paste and environment composition on casing corrosion, a valuable contribution to study the performance of new cement paste.

Resumo: RIP2025-00148: Corrosion models are crucial for estimating uniform corrosion. The understanding of CO2 corrosion mechanism has been extensively developed in the literature over the last 50 years. It is well known that CO2 enhanced corrosion of pipelines steel. The hydrogen evolution reaction increases in the presence of CO2 compared to a strong acid solution at the same pH. After years of discussions in the literature it was understood that CO2 acts as a buffering agent, where the dissociation of carbonic acid produces an additional H+ reservoir, which is the precursor of the cathodic reaction1-2. On the other hand, Almeida et al.3, using electrochemical impedance at OCP and calculation, demonstrated that, if CO2 was able to act on the free iron surface, producing (FeCO2)ads as reported in the literature4 its relaxations would appear as a capacitive loop. Thus, two consecutive capacitive loops should be seen. This diagram has never been observed since CO2 is not able to act on free iron surface. Nonetheless, if CO2are able to play any role in the corrosion mechanism, this can only be seen by polarizing the system.

Considering the above, electrochemical impedance was used to investigate the effect of CO2 on X65 carbon steel corrosion in different pH values. An experimental methodology was performed to polarize anodically and also cathodically the system, with small and fixed quantities of chloride, in the presence and absence of CO2.

The preliminary results at pH 3 and pH 4, show that in general, the impedance has two faradaic loops. The inductive loop is associated with relaxation of (FeOH)ads5. Hering, the diagrams clearly showed that CO2 does not act directly on the free iron surface, showing that the mechanism is not changed. However, a change in the characteristic frequency of the inductive loop in the medium containing CO2 was observed and highlight the role of CO2 in this corrosion mechanism. The mechanism of corrosion by CO2 will be discussed in this work, and a new reaction mechanism will be presented. These results and discussions bring new study perspectives to understand the effects of contaminants, such as SO2 and NO2, present in CO2 injection systems, and can elucidate the role of each contaminant in the carbon steel corrosion mechanism in CCS systems.