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X-Ray diffraction technique applied to study of residual stresses after welding of duplex stainless steel plates

Monin,Vladimir Ivanovitch; Lopes,Ricardo Tadeu; Turibus,Sergio Nolêto; Payão Filho,João C.; Assis,Joaquim Teixeira de
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2014 EN
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Duplex stainless steel is an example of composite material with approximately equal amounts of austenite and ferrite phases. Difference of physical and mechanical properties of component is additional factor that contributes appearance of residual stresses after welding of duplex steel plates. Measurements of stress distributions in weld region were made by X-ray diffraction method both in ferrite and austenite phases. Duplex Steel plates were joined by GTAW (Gas Tungsten Arc Welding) technology. There were studied longitudinal and transverse stress components in welded butt joint, in heat affected zone (HAZ) and in points of base metal 10 mm from the weld. Residual stresses measured in duplex steel plates jointed by welding are caused by temperature gradients between weld zone and base metal and by difference of thermal expansion coefficients of ferrite and austenite phases. Proposed analytical model allows evaluating of residual stress distribution over the cross section in the weld region.

Mechanical, structural and tribological properties of superaustenitic stainless steel submitted at solution heat treatment

Borges,Fabiana Cristina Nascimento; Oliveira,Willian Rafael de; Kublitski,Jonas
Fonte: Rede Latino-Americana de Materiais Publicador: Rede Latino-Americana de Materiais
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2015 EN
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The superaustenitic stainless steel presents several technological applications, mainly in corrosive environments. The different phase precipitation might alter some of its mechanical properties. Such alterations affect several factors, including the working life of the material under adverse working conditions. In this study, Instrumented Indentation techniques, Tribology and X-ray diffraction (XRD) were used to evaluate alterations in regions close to the surface. The parameters analyzed were: hardness and elastic modulus (instrumented indentation), friction coefficient (tribology) and structural alterations of the unit cell of the identified phases (XRD - Rietveld Refinement). All properties analyzed were compared with those of common austenitic steel. The presence of σ-phase (space group P42mnm) and γ-austenite (space group Fm3m) were detected. Data analyzed indicated that the presence of σ-phase caused small alteration in properties such as hardness in regions close to the surface. In the regions farther from the surface (material bulk) data can be compared to that of conventional austenitic steel.

Structural analysis of guyed steel telecommunication towers for radio antennas

Oliveira,Marcel Isandro R. de; Silva,José Guilherme S. da; Vellasco,Pedro Colmar G. da S.; Andrade,Sebastião Arthur L. de; Lima,Luciano R. O. de
Fonte: Associação Brasileira de Engenharia e Ciências Mecânicas - ABCM Publicador: Associação Brasileira de Engenharia e Ciências Mecânicas - ABCM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2007 EN
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The usual structural analysis models for telecommunication and transmission steel tower design tend to assume a simple truss behaviour where all the steel connections are considered hinged. Despite this fact, the most commonly used tower geometries possess structural mechanisms that could compromise the assumed structural behaviour. A possible explanation for the structure stability is related to the connections semi-rigid response instead of the initially assumed pinned behaviour. This paper proposes an alternative structural analysis modelling strategy for guyed steel towers design, considering all the actual structural forces and moments, by using three-dimensional beam and truss finite elements. Comparisons of the above mentioned design models with a third alternative, that models the main structure and the bracing system with 3D beam finite elements, are made for three existing guyed steel telecommunication towers (50m, 70m and 90m high). The comparisons are initially based on the towers static and dynamic structural behaviour later to be followed by a linear buckling analysis to determine the influence of the various modelling strategies on the tower stability behaviour.

Steel fiber reinforced concrete pipes: part 1: technological analysis of the mechanical behavior

Figueiredo,A. D. de; Fuente,A. de la; Aguado,A.; Molins,C.; Chama Neto,P. J.
Fonte: IBRACON - Instituto Brasileiro do Concreto Publicador: IBRACON - Instituto Brasileiro do Concreto
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2012 EN
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This paper is the first part of an extensive work focusing the technological development of steel fiber reinforced concrete pipes (FRCP). Here is presented and discussed the experimental campaign focusing the test procedure and the mechanical behavior obtained for each of the dosages of fiber used. In the second part ("Steel fiber reinforced concrete pipes. Part 2: Numerical model to simulate the crushing test"), the aspects of FRCP numerical modeling are presented and analyzed using the same experimental results in order to be validated. This study was carried out trying to reduce some uncertainties related to FRCP performance and provide a better condition to the use of these components. In this respect, an experimental study was carried out using sewage concrete pipes in full scale as specimens. The diameter of the specimens was 600 mm, and they had a length of 2500 mm. The pipes were reinforced with traditional bars and different contents of steel fibers in order to compare their performance through the crushing test. Two test procedures were used in that sense. In the 1st Series, the diameter displacement was monitored by the use of two LVDTs positioned at both extremities of the pipes. In the 2nd Series, just one LVDT is positioned at the spigot. The results shown a more rigidity response of the pipe during tests when the displacements were measured at the enlarged section of the socket. The fiber reinforcement was very effective...

Ligações em estruturas de aço utilizando emendas com parafusos de alta resistência solicitadas na flexão simples; Connections in steel structures using emendations with high strength screws requested in simple bending

Pereira, Ronivon Soares
Fonte: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Engenharia Civil (EEC); Escola de Engenharia Civil - EEC (RG) Publicador: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Engenharia Civil (EEC); Escola de Engenharia Civil - EEC (RG)
Tipo: Dissertação Formato: application/pdf
POR
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Structure is designed to have satisfactory performance given the quality standards and requirements in the construction of which designers need. Increasingly, large metal structures are developing in this competitive market, where performance and quality of the project depend on manufacturing processes of materials, assembly, inspection and maintenance. The metal structures, especially those of type I profiles of parallel laminated tabs depend on the quality control in your bolted splices. This study aimed to analyze the bearing capacity of steel beams supported by profiles consist of type I rolled parallel flanges with two axes of symmetry, being endowed with seams with high strength bolts type ASTM A325, diameter 19 mm. Eight beams with a length of 3000 mm, two reference beams were tested. In the remaining six beams splices were made at different positions varying the amount of seams. All models have been efforts required by simple bending to failure, by analyzing the vertical displacement, torsional displacement relative and specific deformations of steel. The connections of the beams withstood the test flexural not being observed and no break on the bolts or the connecting plate...

Design for moment redistribution in RC beams retrofitted with steel plates

Haskett, M.; Oehlers, D.; Mohamed Sadakkathulla, M.
Fonte: Multi-science Publishing Publicador: Multi-science Publishing
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
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It is now common practice to retrofit reinforced concrete members by adhesively bonding steel or fibre reinforced polymer plates to their surfaces. However, tests have shown that these plated RC structures tend to have less member ductility, or rotational capacity, than the unplated structure because of premature plate debonding. In this paper, structural mechanics approaches are described for both: quantifying the moment rotation capacity, or member ductility, of steel plated RC flexural members; and quantifying the moment redistribution capacity from the moment rotation capacity. It is shown how the moment redistribution structural mechanics model can be used to design for member ductility directly and, furthermore, it is applied to both externally bonded and near surface mounted steel plates. As would be expected, it is shown that steel plating produces more ductile members than fibre reinforced polymer plating.; Matthew Haskett, Deric John Oehlers and M. S. Mohamed Ali

Predictors of serum chromium levels after stainless steel posterior spinal instrumentation for adolescent idiopathic scoliosis

Rackham, M.; Cundy, T.; Antoniou, G.; Freeman, B.; Sutherland, L.; Cundy, P.
Fonte: Lippincott Williams & Wilkins Publicador: Lippincott Williams & Wilkins
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
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OBJECTIVE. To determine the predictors of serum chromium levels after stainless steel posterior spinal instrumentation for adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA. Abnormally elevated serum chromium levels have been detected in patients with adolescent idiopathic scoliosis after stainless steel instrumentation. To date, the relationship among serum chromium levels, time of implantation, and implant characteristics (including surface area, rod length, numbers of hooks, screws, and cross connectors) has not been studied. METHODS. Thirty patients with adolescent idiopathic scoliosis undergoing posterior instrumented spinal arthrodesis using stainless steel implants between 1998 and 2002 were prospectively studied. Serum chromium levels were measured between October 2006 and June 2007. Postoperative radiographs were used to measure rod lengths, number of hooks, screws, cross-connectors, and cables. The surface area of each component and the total surface area for each patient were calculated. Possible associations between serum chromium levels, time of implantation, and implant characteristics were investigated. RESULTS. Implant exposure, whether expressed in the form of total metal implant surface area, rod length...

The effect of steel yielding on CFRP plated steel member by partial interaction theory

Akbar, I.; Oehlers, D.; Mohamed Sadakkathulla, M.
Fonte: Penerbit Universiti Teknologi Malaysia Publicador: Penerbit Universiti Teknologi Malaysia
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
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The reliability in strengthening concrete or steel structures using Carbon Fibre Reinforced Polymer (CFRP) depends on the success of the stress transfer between the two materials. This paper presented a simple numerical approach to simulate the stress transfer by applying partial interaction theory. The numerical approach uses a local bond–slip (τ–δ) model obtained from a previous experimental work. Pull tests were conducted on a dog–bone shaped steel specimens to initiate yielding of the steel. Results from the tests and published data compared with the numerical values show good correlations. These provide useful insights in the existence of full and partial interaction regions along the bonded length of the CFRP.; Ibrisam Akbar, Deric Oehlers, Mohamed Ali Sadakkathulla

Estudo da evolução microestrutural e das propriedades magnéticas do aço inoxidável austenítico AISI 201 laminado a frio; Study of the microstructural evolution and magnetic properties of a cold rolled AISI 201 austenitic stainless steel

Souza Filho, Isnaldi Rodrigues de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 20/08/2015 PT
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Nos últimos anos, devido ao elevado preço do níquel, uma nova série de aços inoxidáveis austeníticos com um menor teor de níquel foi criada. A essa nova série foi dado o nome de série 200. Dentre os aços dessa classe, o AISI 201 tem sido utilizado em aplicações onde a elevada resistência à corrosão não é tão necessária. Neste trabalho de Mestrado investigou-se a formação e a reversão da martensita induzida por deformação em um aço inoxidável austenítico AISI 201 laminado a frio em 20, 40 e 60% de redução em espessura. Das chapas laminadas foram retiradas amostras que foram recozidas em várias temperaturas (200-800oC) por 1 hora. Amostras do material laminado em 60% de redução em espessura também foram recozidas por várias temperaturas (200-800oC) e por vários tempos (5-180min). Com isso, avaliou-se a evolução microestrutural do material durante a laminação frio e durante o recozimento por meio de medidas de microdureza Vickers, microscopias óptica, eletrônica de varredura e eletrônica de transmissão, difração de elétrons retroespalhados, difração de raios X e medidas de magnetização. Além disso, foram realizados cálculos termodinâmicos para a previsão da formação de fases nesse material. Constatou-se que o material de partida não era completamente austenítico...

Investigation into the mechanism of acicular ferrite nucleation in steel weld metal

Mahony, Michael F.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: xi, 85 p.;28 cm.
EN_US
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Approved for public release; distribution is unlimited; Although steel with its high strength and toughness has been used extensively in all facets of construction, the joining of steels through welding has been problematic at best. The weld itself is the weakest part in any structure. This belief has been pervasive until recently when a microstructure called acicular ferrite was discovered. Acicular ferrite forms on non-metallic inclusions found within the weldment and when significant amounts are "grown", the weldment's toughness and strength approaches that of the steel-base plate. Unfortunately, the mechanism by which high level of acicular ferrite is nucleated in steel weld metal is unknown. This thesis is ground-breaking work in understanding this process and factors that can influence acicular ferrite formation. The present work has found that titanium-rich inclusions are the strongest acicular ferrite formers available, and goes on to suggest a new, undocumented compound may form if the proper amounts of titanium and aluminum within the weld are produced. The applications are far reaching as steel is used by all services for most all equipment; http://www.archive.org/details/investigationint00maho; Captain, United States Army

STABILITY OF BURIED STEEL AND GLASS FIBRE REINFORCED POLYMER PIPES UNDER LATERAL GROUND MOVEMENT

Almahakeri, MOHAMED
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
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As vast networks of high pressure buried energy pipelines traverse North America and other continents, the stability of such essential buried infrastructure must be maintained under a variety of earth loading conditions. The pipe-soil interaction and the longitudinal behaviour of buried pipes due to relative ground movements is poorly understood. This thesis presents full scale testing and numerical modeling of steel and Glass Fibre Reinforced Polymer (GFRP) pipelines to better understand the flexural performance of buried pipes subjected to lateral earth movement. For the experimental phase of the study, a series of pipe bending experiments have been conducted on 102 mm nominal diameter and 1830 mm long steel and GFRP pipes buried in dense sand. Pipe loading was carried out by pulling pipe ends using two parallel cables attached to a spreader beam outside the test region, using a hydraulic actuator. The different tests covered burial depth-to-diameter (H/D) ratios of 3, 5 and 7. During the steel pipe testing phase, special consideration was given to assess the effect of boundary limits, friction within the pulling mechanism, and consistency of results using repeated tests. For the GFRP pipes, the experimental work investigated the effect of the laminate structure of the pipes...

Overload effects on a ferritic-baintic steel and a cast aluminium alloy: two very different behaviours

SAINTIER, Nicolas; PALIN-LUC, Thierry; EL DSOKI, C.; BIDOUARD, H.; KAUFMANN, Heinz; DUMAS, C.; VÖLLMECKE, F.J.; SONSINO, Cetin Morris
Fonte: Wiley Publicador: Wiley
EN
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Load controlled fatigue tests were performed up to 107 cycles on flat notched specimens (Kt =2.5) under constant amplitude and variable amplitude loadings with and without periodical overloads. Two materials are studied: a ferritic-bainitic steel and a cast aluminium alloy. These materials have a very different cyclic behaviour: the steel exhibits cyclic strain oftening whereas the Al alloy shows cyclic strain hardening. The fatigue tests show that, for the steel, periodical overload applications reduce significantly the fatigue life for fully reversed load ratio (Rr = – 1), while they have no influence under pulsating loading (Rr = 0). For the Al alloy over-loads have an effect (fatigue life decreasing) only for variable amplitude loadings. The detrimental effect of overloads on the steel is due to ratcheting at the notch root which evolution is overload's dependent.

In Situ Microstructure Observation Of Steel Grades In The Semi-Solid State For Thixoforging Process By Using Confoncal Laser Scanning Microscopy

GU, Guochao; PESCI, Raphaël; BECKER, Eric; LANGLOIS, Laurent; BIGOT, Régis
Fonte: Trans Tech Publications, Switzerland Publicador: Trans Tech Publications, Switzerland
EN
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The microstructure plays a crucial role for steel semi-solid forming process, and particularly for the steel thixoforging process, since it determines the thixotropic flow behavior of materials in the semi-solid state. Therefore, it is necessary to well understand the microstructure evolution during high speed heating and forming. Classically, it is investigated on a solid material quenched from semi-solid state by 2D characterization techniques. However, the semi-solid microstructure could probably not be preserved in the solid state by quenching due to complicated phase transformations or high diffusion rate of alloying elements during cooling, especially at low liquid fractions. In order to avoid this, a new in situ technique - high temperature Confocal Laser Scanning Microscopy (CLSM) - was developed and used for studying the microstructure evolution directly at high temperature. The present study aims at providing an experimental investigation of the microstructure evolution on several steel grades (M2, 100Cr6 and C38LTT) during heating from the as-received state to the semi-solid state (heating rate: ~200°C/min) and finally cooled to the solid state (cooling rate: ~200°C/min). It has been found that the temperature sensitivity of liquid fraction (ΔT/ Δfl) of these grades is much different. In addition...

A component model for the behaviour of steel joints at elevated temperatures

Silva, L. Simões da; Santiago, Aldina; Vila Real, Paulo
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
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Recent experimental evidence has shown that steel joints exhibit a distinct change in their moment-rotation response under increasing temperature. In terms of cold design, the component method is currently the widely accepted procedure for the evaluation of the various design values. It is the purpose of the present paper to extend the component method to the prediction of the response of steel joints under fire loading. Using typical mechanical models consisting of extensional springs and rigid links, whereby the springs exhibit a non-linear force deformation response (here taken as a bi-linear approximation), an analytical procedure is proposed capable of predicting the moment-rotation response under fire conditions that incorporates the variation of yield stress and Young's modulus of the various components as the temperature increases. An application to a cruciform flush end-plate beam-to-column steel joint is presented and compared to the experimental results obtained under various loading conditions.; http://www.sciencedirect.com/science/article/B6V3T-45SRS62-4/1/f4fa6b254370f846ea9388c17a5f6dbf

Colunas mistas esbeltas de aço preenchidas com concreto de alta resistencia em temperatura ambiente e em situação de incendio; Mixed slender steel columns filled with high strenght concrete in room temperature and fire situation

Geraldo Silveira Leite Junior
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 06/02/2009 PT
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Neste trabalho, foi investigado em laboratório o efeito do fogo em colunas esbeltas de aço sem preenchimento e preenchidas com concreto de alta resistência que foram submetidas a três diferentes níveis de carga (30%, 50% e 70%). O nível de carga é a razão entre a carga axial a ser aplicada em situação de incêndio e a carga última obtida no ensaio da coluna à temperatura ambiente. Assim sendo, colunas esbeltas de aço sem preenchimento e preenchidas com concreto de alta resistência também foram investigadas à temperatura ambiente, uma vez que os resultados obtidos nessa situação serviram de referência para o estabelecimento das cargas axiais que foram aplicadas em situação de incêndio. Ao todo, foram investigadas 32 colunas esbeltas, sendo 4 sem preenchimento e 4 preenchidas com concreto de alta resistência em temperatura ambiente. Além dessas colunas, 12 foram ensaiadas sem preenchimento e 12 preenchidas com concreto de alta resistência em situação de incêndio. Os valores experimentais de carga última obtidos com as colunas de aço sem preenchimento e preenchidas com concreto de alta resistência à temperatura ambiente e em situação de incêndio foram comparados a aqueles determinados a partir da formulação proposta respectivamente pelo EUROCODE 3 (prEN 1993-1-1:2001)...

Propriedades de fadiga em alto ciclo de um aço baixo carbono microligado com titanio e niobio em duas condiçoes microestruturais distintas; Fatigue properties of high cycle titanium and niobium microalloyed low carbon steel in two different microstructural conditions

Jairo Aparecido Martins
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 26/08/1997 PT
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Atualmente, grandes esforços tem sido direcionados no sentido de se obter aços de baixo custo, com rnicroestruturas que proporcionem as melhores combinações de propriedades mecânicas, sobretudo aquelas relacionadas com fadiga em alto ciclo. Este trabalho tem como objetivos analisar as propriedades mecânicas monotônicas e cíclicas do aço API 5L X65 aço de baixo teor de carbono e microligado com titânio e nióbio-, em duas condições microestruturais distintas; a primeira na condição como fornecida (CF) e a segunda na condição tratada termicamente (T77) (normalizada a 1193K + tratada na região intercrítica a 1043 K e resfriado em óleo a uma taxa de 30 'Ks POT. -1'). A primeira condição analisada, como fornecida (CF) apresentou microestrutura ferrítico-perlítica (84,9% de ferrita para 15,1% de perlita) enquanto a segunda condição (T77) apresentou microestrutura ferrítico-martensítica (82,7% de ferrita para 17,3% de martensita). Foram analisadas as propriedades de tração ('sigma' IND. t ), limite de escoamento ('sigma' IND. e) redução de área (RA) e o limite de resistência à fadiga ('S IND. f') para as duas condições. Verificou-se um aumento do limite de resistência à tração em 14% (de 615 MPa para 800 MPa)...

Plasma nitriding of CA-6NM steel: effect of H2 + N2 gas mixtures in nitride layer formation for low N2 contents at 500 ºC

Allenstein,Angela Nardelli; Lepienski,Carlos Maurício; Buschinelli,Augusto José de Almeida; Brunatto,Silvio Francisco
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2010 EN
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This work aims to characterize the phases, thickness, hardness and hardness profiles of the nitride layers formed on the CA-6NM martensitic stainless steel which was plasma nitrided in gas mixtures containing different nitrogen amounts. Nitriding was performed at 500 ºC temperature, and 532 Pa (4 Torr) pressure, for gas mixtures of 5% N2 + 95% H2, 10% N2 + 90% H2, and 20% N2 + 80% H2, and 2 hours nitriding time. A 6 hours nitriding time condition for gas mixture of 5% N2 + 95% H2 was also studied. Nitrided samples results were compared with non-nitrided condition. Thickness and microstructure of the nitrided layers were characterized by optical microscopy (OM), using Villela and Nital etchants, and the phases were identified by X-ray diffraction. Hardness profiles and hardness measured on surface steel were determined using Vickers hardness and nanoindentation tester, respectively. It was verified that nitrided layer produced in CA-6NM martensitc stainless steel is constituted of compound layer, being that formation of the diffusion zone was not observed for the studied conditions. The higher the nitrogen amounts in gas mixture the higher is the thickness of the nitrided layer and the probability to form different nitride phases, in the case γ'-Fe4N...

Wet processing and characterization of ZrO2/stainless steel composites: electrical and mechanical perfomance.

Pecharromán, Carlos; Lopez-Esteban, S.; Bartolomé, J. F.; Moya, J. S.; Castanhob, S.R.H. Mello
Fonte: Universidade Federal de São Carlos Publicador: Universidade Federal de São Carlos
Tipo: Artículo
ENG
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Zirconia/stainless steel composites have been prepared by a wet processing method with metal volume concentration ranging from 15% to 30%. The composites were characterized by electrical andmechanicalmeasurements. The dependence of the electrical properties of these composites with themetal concentration presents a percolative behaviour with ametal-insulator transition, in addition to an increment of the capacity in the neighbourhood of a critical volume concentration. This value was found to be fc = 0.285, which is much higher than the theoretical value for randomly dispersed 3D composites (fc = 0.16). It has been found that the incorporation of stainless steel particles to zirconia matrix, increases the toughness and decreases both the hardness and the flexural strength. The enhancement of toughness is attributed to a crack deflection mechanism as a consequence of a weak ZrO2/stainless steel interface.; This work was supported by CICYT, Spain, under project number MAT97-0724, S.R.H. Mello Castanho acknowledges Mr. S. Kvist, from Höganäs for send the steel powder samples.; Peer reviewed

Calibrating the steel-members fatigue limit states of the AASHTO LRFD bridge design specifications

Berwick, Benjamin
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
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Mertz, Dennis R.; It is important to develop and incorporate the knowledge needed to design, construct, and maintain bridges to have the longest service life as possible. Consequently, the fatigue effects on bridges need to be considered and more accurately reflected within the proper bridge design specifications. This thesis describes the calibration process used to select the load and resistance factors for the fatigue limit states of steel bridge members within the AASHTO LRFD Bridge Design Specifications. The process presented within this thesis builds upon work completed as part of the Strategic Highway Research Program No. 2 including the determination of the fatigue load model. The resistance model was developed using available fatigue test data and statistically analyzed using specially developed techniques. Target reliability indices of 1.0 were chosen for all steel detail types based upon a procedure using Monte Carlo simulations and engineering judgment. Load and resistance factors were finally chosen for both Fatigue I and Fatigue II service limit states. The load and resistance factors for the Fatigue I limit state are 2.0 and 1.0 respectively. Similarly, the load and resistance factors are 0.80 and 1.0 for the Fatigue II limit state. We expect the new load and resistance factors for the fatigue service limit states to more accurately capture the fatigue effects of steel bridges and thus increase their service life.; University of Delaware...

Azo Dye Compounds as Corrosion Inhibitors for Dissolution of Mild Steel in Hydrochloric Acid Solution

Nagiub,A.M.; Mahross,M.H.; Khalil,H.F.Y.; Mahran,B.N.A.; Yehia,M.M.; El-Sabbah,M.M.B.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2013 EN
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The effect of some mono-, bis- and tris-azo dyes compounds on the dissolution of mild steel in 1.0 M HCl solution was studied using weight loss and potentiodynamic polarization measurements. The inhibition efficiency was found to increase with increasing concentration of the inhibitors and with decreasing temperature. The adsorption of different azo dyes on the mild steel surface obeys the Langmuir adsorption isotherm. Polarization studies indicate that the compounds used are mixed type inhibitors. The thermodynamic functions of adsorption processes were calculated from weight loss at different temperatures data and were used to analyze the inhibitor mechanism. The surface morphology of the mild steel specimens was evaluated using SEM and EDAX analysis. To provide an evidence for the formation of the complex, UV-VIS spectra of solutions were investigated. From previous results (I.E.%, ΔGads, SEM, EDAX and UV-VIS spectra) are likely to get into the possiblity of configure the complex on the mild steel surface.