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  • 1
    In: Revista de Sistemas Experimentales, ECORFAN
    Abstract: Inverse heat conduction problems are categorized by the solution technique or algorithm (Function Specification, Regularization, Laplace Transform, Conjugate Gradient, Mollification), by the solution method (Duhamel's Theorem, Difference Method Finite, Finite Element Method), and by the time domain (Stoltz Method, Sequential Method, and Complete Domain). In the direct approach, the unique solution of an effect due to a cause is obtained. From the cause-effect view, inverse problems are characterized by not meeting the existing criteria and the uniqueness of determining the cause when analyzing an effect. However, this has promoted the implementation of robust methods to optimize the stability of a solution. In this work, the study system consists of a long solid cylinder at an elevated temperature that is cooled. The implemented methodology allowed the creation of data trends through linear extrapolation to improve estimation accuracy for abrupt changes in the function (boundary condition). The results show an acceptable increase in punctual precision in the estimation, and it is a consequence of the solution that the calculated thermal histories already contain an implicit degree of error.
    Type of Medium: Online Resource
    ISSN: 2410-3950
    Language: English
    Publisher: ECORFAN
    Publication Date: 2022
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  • 2
    In: Key Engineering Materials, Trans Tech Publications, Ltd., Vol. 711 ( 2016-9), p. 12-20
    Abstract: This work is part of the DURACON Ibero-American project, which seeks to characterize concrete durability under environmental conditions, based on reinforced concrete sample exposure in at least two different atmospheres (marine and urban), for each of the 11 countries in the project. Specimens were exposed to the environmental conditions of 13 Mexican sites (8 urban and 5 marine atmospheres). Concrete specimens were 15 x 15 x 30 cm, with 6 rebars each, and three concrete covers (15, 20 and 30 cm). Two concrete mixtures were used with water/cement ratios of 0.45 and 0.65, respectively. Six reinforced and six plain concrete specimens were placed on each exposure site. Environmental data was collected on each exposure site, including rainfall, relative humidity, time of wetness, temperature, wind velocity, and carbon dioxide/chloride concentrations. Corrosion rates and potentials, as well as concrete resistivity were measured in the reinforced samples. Carbonation depths were measured on the plain ones. The present work focused on the measurements of environmental parameters during the first two years of exposure to analyze the potentiality and the probability of carbonation-induced corrosion, and the evaluation of the corrosion initiation period for the reinforcing steel on the 13 Mexican exposure sites.
    Type of Medium: Online Resource
    ISSN: 1662-9795
    URL: Issue
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2016
    detail.hit.zdb_id: 2073306-9
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  • 3
    Online Resource
    Online Resource
    Alconpat Internacional ; 2019
    In:  Revista ALCONPAT Vol. 9, No. 2 ( 2019-04-30), p. 200-214
    In: Revista ALCONPAT, Alconpat Internacional, Vol. 9, No. 2 ( 2019-04-30), p. 200-214
    Abstract: Este artículo describe propiedades referentes a la durabilidad de cinco mezclas de concreto con distintos contenidos de ceniza volante activada (CVA) y cemento portland tipo CPC 40. Los ensayos realizados fueron: velocidad de pulso ultrasónico, resistividad eléctrica aparente, permeabilidad rápida al ión cloruro y resistencia mecánica a la compresión. Los resultados indicaron que la calidad de todas las mezclas resultó durable, el desarrollo de la resistividad eléctrica y disminución del nivel de permeabilidad al ión cloruro fue favorecido por el contenido de CVA. En cuanto a las resistencias a la compresión, se notó que a mayor contenido de CVA estas resultaron menores. El porcentaje máximo de sustitución de CVA para cumplir con los criterios de durabilidad actuales resultó del 65%.
    Type of Medium: Online Resource
    ISSN: 2007-6835
    URL: Issue
    Language: Unknown
    Publisher: Alconpat Internacional
    Publication Date: 2019
    detail.hit.zdb_id: 3093244-0
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  • 4
    In: ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2014-02, No. 13 ( 2014-08-05), p. 761-761
    Abstract: The main objective of this work is to study the electrochemical behavior of galvanic coupling between carbon steel, CS, and stainless steel, SS, in an alkaline environment simulating the conditions prevailing in a repaired structure in which stainless steel rebar’s will be an option. Previously research conducted in different parts of the world on this subject reach agreement with the fact that AISI 304 SS and 316 SS embedded in concrete offers high corrosion resistance in aggressive environments but only for the case of new structures, and no further explanation has been given on the behavior of SS when in contact with CS. Galvanic coupling between these two metals should increase the corrosion process of the more anodic, CS in this case, but this phenomenon does not occur in practice. Galvanic coupling was investigated by means of the electrochemical coulostatic technique. Tests performed allow determining the Tafel slopes of anodic and cathodic processes. The Tafel slope values obtained show that the process is being controlled by the reduction of oxygen, O 2 in the environment where the samples were placed. On the basis of these kinetic parameters, a mechanism for the corrosion process is proposed in which the rate determining step would be O 2 mass transfer process. The diffusion of O 2 would take place through a formed oxide film, passivating in nature. Due to the formation of this oxide film, the cathodic oxygen reduction reaction, ORR, on stainless steel surface would be very slow. The high polarization of ORR rate would be the factor controlling the whole process, then minimizing the risk of damage by galvanic corrosion, demonstrating the feasibility of using stainless steel in the repairing of concrete structures.
    Type of Medium: Online Resource
    ISSN: 2151-2043
    Language: Unknown
    Publisher: The Electrochemical Society
    Publication Date: 2014
    detail.hit.zdb_id: 2438749-6
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  • 5
    In: Revista ALCONPAT, Alconpat Internacional, Vol. 9, No. 2 ( 2019-04-30), p. 167-184
    Abstract: In this study, the corrosion performance of dissimilar welded joints between ASTM A615 and AISI 304 stainless steel with and without buttering using Inconel 182 was evaluated. In both cases, the filler metal was ER-309L and the base metals were prepared with a 45° single bevel. One half of the specimens were welded with “buttering” using Inconel 182. The electrochemical results showed that despite welding defects, the welded specimens formed a passive layer in alkaline environments. The specimens welded with buttering exhibited the best corrosion resistance and mechanical properties.
    Type of Medium: Online Resource
    ISSN: 2007-6835
    URL: Issue
    Language: Unknown
    Publisher: Alconpat Internacional
    Publication Date: 2019
    detail.hit.zdb_id: 3093244-0
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  • 6
    In: MRS Advances, Springer Science and Business Media LLC, Vol. 7, No. 2-3 ( 2022-02), p. 33-38
    Type of Medium: Online Resource
    ISSN: 2731-5894 , 2059-8521
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2022
    detail.hit.zdb_id: 2858562-8
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  • 7
    In: ECORFAN Journal Bolivia, ECORFAN
    Abstract: This work shows the influence of the normal anisotropy (“r” value) in the deep drawing of AISI 439 ferritic stainless steel sheets. In order to do so, quantitative chemical analysis, metallographic analysis, tensile mechanical properties, and the determination of the “r” value and the “n” value were carried out in two different AISI 439 steel sheets of two different suppliers. In recent years, this ferritic stainless steel has been applied in a deep drawing process of automotive components. In this way, it must be said that one of these ferritic stainless steel sheets cracked due to exhaustion of formability during deep drawing after few steps. On the other hand, the second ferritic stainless steel sheet showed neither cracking nor other type of defects. The results of the tests, which were carried out in this work, probed that the“r” value has a strong influence on the forming behaviour of ferritic steel during deep drawing. This information is very relevant because the AISI 439 standard does not consider the planar anisotropy or the strain hardening coefficient as relevant for designation, but this type of steel is being applied in many forming operations of different components.
    Type of Medium: Online Resource
    ISSN: 2410-4191
    Language: English
    Publisher: ECORFAN
    Publication Date: 2019
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  • 8
    In: Soldagem & Inspeção, FapUNIFESP (SciELO), Vol. 21, No. 2 ( 2016-06), p. 137-145
    Abstract: Resumo Em aços inoxidáveis o dano microestrutural é causado pela precipitação de carbonetos de cromo ou de fase sigma. Estes microcomponentes são prejudiciais em soldas de aço inoxidável, porque eles levam a corrosão intergranular. No entanto, eles são propensos a aparecer na microestrutura da zona afetada pelo calor de soldas em aço inoxidável. Isto é particularmente importante para reparos de componentes industriais feitos de aço inoxidável austenítico. Réplica metalográfica pode ser aplicada para identificar a necessidade de reparos em componentes de aço AISI304 inoxidável onde é difícil assegurar que tal fase está presente na microestrutura da ZTA. A necessidade de inspeção microestrutural não destrutiva no aço inoxidável AISI 304 está associada a impossibilidade de se obter corpos de prova para análise via técnicas convencionais. Neste trabalho, propõe-se a aplicação de réplica metalográfica, a fim de identificar danos microestruturais em soldas de aço inoxidável AISI 304. Os resultados deste estudo mostraram que as micrografias da superfície externa do conjunto de peças soldadas representam a microestrutura da ZTA do componente de aço inoxidável porque mostram a presença de carbonetos metálicos precipitados nos contornos de grão ou de fase sigma.
    Type of Medium: Online Resource
    ISSN: 0104-9224
    Language: Unknown
    Publisher: FapUNIFESP (SciELO)
    Publication Date: 2016
    detail.hit.zdb_id: 2436756-4
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  • 9
    In: Coatings, MDPI AG, Vol. 10, No. 3 ( 2020-02-25), p. 199-
    Abstract: In an impressed current cathodic protection system (ICCP) to protect structures against corrosion, the efficient operation depends on the proper selection of the electrodes, particularly the anode, chosen considering the structure to be protected and the environment in which it is located. The nature and overpotential of the anodic reaction determine the operation costs of an ICCP system so that proper anode selection is critically important for an ICCP system to function efficiently. Commercial anodes based on titanium substrates coated with iridium–tantalum oxide mixtures (IrO2-Ta2O5/Ti) are frequently used for this purpose due to low operating overpotentials. However, the gradual passivation of its surface limits its useful life and increases its operating costs, so it is necessary to seek competitive alternatives for its replacement. This study aimed to determine the feasibility of using carbon steel substrates coated with nickel/cobalt/boron (NiCoB/CS) as a viable low-cost alternative to replace IrO2-Ta2O5/Ti anodes in ICCP systems. Comparison between the electrochemical behavior and the corrosion resistance of both types of electrodes shows that the NiCoB/CS anode shows a good electrocatalytic activity and a higher corrosion resistance than IrO2-Ta2O5/Ti coated anodes, indicating that the NiCoB/CS anodes are promising low-cost candidates for ICCP systems.
    Type of Medium: Online Resource
    ISSN: 2079-6412
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2662314-6
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  • 10
    In: Anti-Corrosion Methods and Materials, Emerald, Vol. 62, No. 2 ( 2015-3-2), p. 69-76
    Abstract: – The purpose of this paper was to characterize the surface of steel reinforcement of concrete under cathodic protection (CP), submerged in seawater, to understand the surface changes due to the application of CP and their consequences on cathodic current requirements. Design/methodology/approach – Reinforced concrete specimens with applied CP were immersed in natural seawater. The experimental methodology included monitoring of corrosion potential (E corr ); measurement of galvanic current (Igalv), protection potential (E protection ) and the depolarization potential of steel during the time of exposure; and electrochemical impedance spectroscopy (EIS). The chemical composition of the steel surface was assessed using X-ray diffraction (XRD). Findings – The application of CP leads to the formation of a deposit on the steel surface that according to XRD results, Pourbaix diagram and physical characteristics, is a protective oxide: magnetite (Fe 3 O 4 ). This oxide causes a decrease in the corrosion rate and requires application of the protection current. It was found that the surface remained protected even after eight days when the CP system was interrupted. Research limitations/implications – It is necessary to carry out analysis of the chemical composition of deposits formed on the steel surface, perhaps using X-ray photoelectron spectroscopy, Mössbauer, to verify the presence of the magnetite. Practical implications – Determination of the main cause of the decrease in current required for protection and deposit formation conditions will enable the design of a CP system to be optimized and economized. At present, the CP design considers only a constant current value for the duration of the protection time. Originality/value – CP is a technique that has proven effective for the protection of metal structures. However, little attention has been devoted to the surface changes that occur under applied CP and their impact on the electrochemical behavior of the system. This paper describes the phenomena produced at the metal surface and determines kinetic parameters and their consequences on the CP behavior.
    Type of Medium: Online Resource
    ISSN: 0003-5599
    Language: English
    Publisher: Emerald
    Publication Date: 2015
    detail.hit.zdb_id: 1477132-9
    detail.hit.zdb_id: 2419228-4
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