Página 18 dos resultados de 11359 itens digitais encontrados em 0.015 segundos

Influence of joint slippage on the seismic response of steel frames

Nogueiro, Pedro; Silva, Luís Simões da; Bento, Rita
Fonte: EuroSteel Publicador: EuroSteel
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.58%
The present paper presents an evaluation of the influence of joint slippage on the seismic response of steel frames. Using three alternative hysteretic joint models to simulate the connections of a representative low-rise steel frame, and a series of dynamic time-history analyses for a typical seismic record, it is found that slippage affects the response of the structure and should be allowed for in design.

Residual strength of a steel-concrete composite structure subjected to a design seismic event by fire

Nogueiro, Pedro; Santiago, Aldina; Silva, Luís Simões da; Bento, Rita; Vila Real, P.M.M.
Fonte: IABSE Publicador: IABSE
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.58%
This paper presents a numerical investigation of the residual strength of a typical PR momentresistant multi-storey steel framed structure, subjected to a design seismic event followed by fire. In order to allow a calibration with some real results from fire tests on a natural scale, the architectural and structural definitions of the eight-storey steel Cardington building were chosen as the reference case, adapted to deal with basic seismic requirements. The seismic action was simulated with an artificial accelerogram with PGA of 0.6g, chosen to achieve significant energy dissipation in the joints. The adopted fire event is limited to an isolated compartment and it is defined as the natural fire observed during a full-scale fire test carried out at the BRE. Finally, the results are discussed in terms of robustness requirements for extreme events.

Fire behaviour of composite steel truss and concrete beam

Piloto, P.A.G.; Roque, Sergio; Vila Real, P.M.M.; Plizzari, Giovanni
Fonte: INEGI Publicador: INEGI
Tipo: Conferência ou Objeto de Conferência
POR
Relevância na Pesquisa
36.58%
This work compares the thermal behaviour on four different Composite Steel Truss and Concrete Beam (CSTCB), when submitted to two different fire conditions (one side and four sides of fire exposure). This analysis aims to be a preliminary assessment of a series of experimental tests. CSTCB with concrete plate delay temperature evolution on the steel truss and reinforcement, increasing fire resistance.

Fire behaviour of composite steel truss and concrete beam

Piloto, P.A.G.; Roque, Sérgio P. P. A.; Vila Real, Paulo M. M.; Plizzari, Giovanni A.
Fonte: INEGI Publicador: INEGI
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
36.58%
This work compares the thermal behaviour on four different Composite Steel Truss and Concrete Beam (CSTCB), when submitted to two fire conditions (one side and four sides). This analysis aims to be a preliminary assessment of a series of experimental tests. CSTCB with pre-cast plate delay temperature evolution on the steel truss and reinforcement, increasing fire resistance.

Influence of process parameters on the deep drawing of stainless steel

Padmanabhan, R.; Oliveira, M. C.; Alves, J. L.; Menezes, L. F.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
Relevância na Pesquisa
36.58%
Optimization of process parameters in sheet metal forming is an important task to reduce manufacturing cost. To determine the optimum values of the process parameters, it is essential to find their influence on the deformation behaviour of the sheet metal. The significance of three important process parameters namely, die radius, blank holder force and friction coefficient on the deep-drawing characteristics of a stainless steel axi-symmetric cup was determined. Finite element method combined with Taguchi technique form a refined predictive tool to determine the influence of forming process parameters. The Taguchi method was employed to identify the relative influence of each process parameter considered in this study. A reduced set of finite element simulations were carried out as per the Taguchi orthogonal array. Based on the predicted thickness distribution of the deep drawn circular cup and analysis of variance test, it is evident that die radius has the greatest influence on the deep drawing of stainless steel blank sheet followed by the blank holder force and the friction coefficient. Further, it is shown that a blank holder force application and local lubrication scheme improved the quality of the formed part.; http://www.sciencedirect.com/science/article/B6V36-4P83CYC-1/1/e6960497333623161079dd55519205bd

Non-linear dynamic analysis of stayed steel columns

Araujo, Ricardo R. de; Silva, José G. S. da; Vellasco, Pedro C. G. da S.; Andrade, Sebastião A. L. de; Lima, Luciano R. O. de; Silva, Luís A. P. Simões da
Fonte: Federal University of Rio de Janeiro; State University of Rio de Janeiro Publicador: Federal University of Rio de Janeiro; State University of Rio de Janeiro
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
36.58%
This work describes non-linear finite element simulations made on stayed system subjected to sudden impact loads. The study aimed to determine the influence of the prestress forces magnitude and its response with and without damping effects. Various cases where the load magnitude varied from 10% up to 100% of the stayed column load bearing capacity were investigated. The performed analyses enabled an evaluation of the structural system amplification factor to be later compared to allowing horizontal deflection limits usually adopted in steel design standards.

Buckling of concrete filled steel hollow columns in case of fire

Pires, Tiago A. C.; Rodrigues, João P. C.; Silva, J. Jéfferson Rêgo
Fonte: Federal University of Rio de Janeiro; State University of Rio de Janeiro Publicador: Federal University of Rio de Janeiro; State University of Rio de Janeiro
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
36.58%
The use of concrete filled steel hollow sections (CSHS) in building construction has increased in the last decade. This type of columns has several advantages linked to their high load bearing capacity and good fire performance. However, when the columns are inserted in a building structure, the effect of the restraining to their thermal elongation, change significantly their fire behavior. The high restraining forces developed during the fire, associated to the degradation of the mechanical properties, will lead to their buckling sooner than they are isolated. In order to study these phenomena a series of fire resistance tests on CSHS columns was carried out in University of Coimbra. Several parameters expected to have influence in the fire resistance of these columns were studied: the slenderness of the column, the load level, the stiffness of the surrounding structure, the percentage of steel reinforcement and the thickness of the concrete layer inside the column. This paper presents some results of the fire resistance tests and analyzes the different buckling phenomena observed in the tested columns.

Reliability analysis of I-section steel columns designed according to new Brazilian building codes

BECK, André T.; DÓRIA, André S.
Fonte: Associação Brasileira de Engenharia e Ciências Mecânicas - ABCM Publicador: Associação Brasileira de Engenharia e Ciências Mecânicas - ABCM
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.58%
This paper presents an evaluation of the safety of I-section steel columns designed according to the new revision of the Brazilian code for design of steel buildings (NBR8800) and to the code for loads and safety of structures (NBR8681). The safety evaluation is based on structural reliability analysis of columns designed to comply with these codes, and on advanced (FE-based) analysis of actual column resistance. The effects of geometrical imperfections and residual stresses in column resistance are taken into account. The uncertainty in yield stress, elasticity modulus, geometrical imperfections and dead and live loads are considered in the reliability evaluation. Reliability indexes are obtained for several column configurations. These indexes reflect the safety of the columns designed according to the two building codes. Reliability indexes are compared with target reliability indexes used in calibration of the ANSI code and with indexes proposed in the new EUROCODE.; (CNPq) Brazilian Council for Research and Development

Synergistic Effect of Nizoral and Iodide Ions on the Corrosion Inhibition of Mild Steel in Sulphuric Acid Solution

Obot,Ime B.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
Relevância na Pesquisa
36.66%
The corrosion rates in the presence of nizoral (NZR), an antifungal drug, as mild steel corrosion inhibitor in 0.1 M H2SO4 was measured by the weight loss method in the temperature range from 30 - 50 ºC. Results obtained revealed that NZR acts as an inhibitor for mild steel in sulphuric acid solution. Inhibition efficiency increased with increase in concentration of the inhibitor but decreased with increase in temperature. The addition of KI increased the inhibition of NZR to a considerable extent. The experimental results suggest that the presence of iodide ions in the solution stabilized the adsorption of Nizoral molecules on the mild steel surface thereby improving the inhibition efficiency of Nizoral. The adsorption characteristics of the inhibitor were approximated by Langmuir adsorption isotherm and kinetic/thermodynamic adsorption model of El-Awady et al. Mechanism of physical adsorption is proposed from the activation and thermodynamic parameters calculated.

Inhibitive Performance of Gemini Surfactants as Corrosion Inhibitors for Mild Steel in Formic Acid

Ansari,Farhat A.; Quraishi,M. A.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 EN
Relevância na Pesquisa
36.66%
Three new gemini surfactants referred to as n-2-n (where n= 6, 12, 16) were developed as corrosion inhibitors for mild steel. Their critical micelle concentration (cmc) at equilibrium in water at 30ºC was determined. Corrosion inhibition studies of mild steel in formic acid by gemini surfactants were conducted by using weight loss, electrochemical polarisation and electrochemical impedance spectroscopy (EIS) measurements. Scanning electron microscopic study (SEM) was also used to investigate the surface morphology of inhibited and uninhibited metal samples. The results obtained show that the surfactants studied are good mixed type inhibitors. The result was also correlated with several factors, including the chain length of the hydrophobic chains, critical micelle concentration (cmc) and adsorption free energy of these inhibitors. The adsorption of all the gemini surfactants was found to follow Langmuir adsorption isotherm. EIS results indicate that the change in the impedance parameters (Rt and Cdl) with concentration of inhibitors was due to the formation of a protective layer on the surface of mild steel.

Pericarp of the Fruit of Garcinia Mangostana as Corrosion Inhibitor for Mild Steel in Hydrochloric Acid Medium

Kumar,K.P. Vinod; Pillai,M.S. Narayanan; Thusnavis,G. Rexin
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 EN
Relevância na Pesquisa
36.66%
The corrosion inhibition effect of acid extract of the pericarp of the fruit Garcinia mangostana on mild steel in hydrochloric acid medium is studied. Using weight-loss data, corrosion rate (CR) and thermodynamic parameters such as energy of activation for corrosion of mild steel (E), heat of adsorption of the inhibitors on the metal surface (Q) and change in free energy (∆G) are calculated. Adsorption isotherm is also recorded between log C and θ. Electrochemical parameters are evaluated from AC impedance and Tafel polarization studies in the presence and absence of different concentrations of inhibitor. Infra-red spectra are recorded for the extract and the adsorption product to find out the changes in the functional group frequencies of the organic components of the extract. The surface morphological changes are analysed using the SEM images. The entire study shows that the pericarp extract of the fruit G. mangostana is a non-toxic, cost-effective corrosion inhibitor for mild steel in acid medium.

Surface Analysis of Inhibitor Film Formed by Poly(Vinyl Alcohol) on Stainless Steel in Sodium Chloride Solution

Samide,A.; Ciuciu,A.; Negrila,C.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 EN
Relevância na Pesquisa
36.66%
The corrosion inhibition of stainless steel in 0.9% NaCl solution in presence of poly(vinyl alcohol) (PVA) is discussed according to electrochemical measurements, such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS).The morphology of the surface was analyzed using Scanning Electron Microscopy (SEM). The composition of the layer formed on stainless steel surface was estimated using X-ray Photoelectron Spectroscopy (XPS) technique. Electrochemical measurements indicated that the presence of PVA in NaCl solution decreases the corrosion current and increases the polarization resistance. The values of inhibition efficiency obtained from polarization curves and EIS measurements are in good agreement. In absence and in presence of PVA, SEM images showed that the stainless steel surface was covered with a non-uniform layer and a uniform adsorbed film, respectively. XPS analysis indicated that the surface layer consists of PVA containing a small amount of other elements, such as Na and Cl.

Corrosion Inhibition of Aqueous Extract of Cocos nucifera - Coconut Palm - Petiole Extract from Destructive Distillation for the Corrosion of Mild Steel in Acidic Medium

Vijayalakshmi,P.R.; Rajalakshmi,R.; Subhashini,S.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 EN
Relevância na Pesquisa
36.66%
The inhibitive effect and adsorption properties of petiole extract obtained from destructive distillation of cocos nucifera for the corrosion of mild steel in 0.5 M H2SO4 and 1 M HCl were investigated using mass loss, polarization and electrochemical impedance techniques of monitoring corrosion. The results obtained indicate that petiole extract of cocos nucifera behaves as good inhibitor for the corrosion of mild steel in 0.5 M H2SO4 and 1 M HCl. Activation energy of thermodynamic parameter was evaluated from temperature studies result. The adsorption of the inhibitor on mild steel surface was found to be spontaneous, endothermic and consistent with the assumptions of Langmuir adsorption isotherm. The electrochemical measurements reveal that the petiole extract behaved like mixed type inhibitor. Efforts are made to analyze the effectiveness of petiole extract of coconut palm in industrial processes.

Adsorption and Corrosion Inhibition Behavior of C38 Steel by one Derivative of Quinoxaline in 1 M HCl

Elayyachy,M.; Hammouti,B.; El Idrissi,A.; Aouniti,A.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 EN
Relevância na Pesquisa
36.66%
The influence of 2-[3-(2-oxo-2-phenylethylidene)-1,4-dihydroquinoxaline-2(1H)-ylidene]-1-phenylethanone (Qx1) and amino-2-aniline (Diam1) on the corrosion of steel in 1 M HCl solution has been investigated by weight loss measurements, potentiodynamic polarisation and impedance spectroscopy (EIS) methods. The inhibiting action increases with the concentration of Qx1 and Diam1. The highest efficiency (85%) is obtained at the 10-4 M Qx1. There is good agreement between gravimetric and electrochemical methods (potentiodynamic polarisation and EIS). Polarisation measurements also show that Qx1 and Diam1 act as mixed inhibitors. The cathodic curves indicate that the reduction of proton at the steel surface happens with an activating mechanism. Qx1 adsorbs on the steel surface according to Langmuir adsorption model. Effect of temperature is also studied between 308 and 353 K.

Performance of conductive pre-primers applied on galvanized steel sheets for automotive bodies

Santos,D.; Raminhos,H.; Costa,M.; Diamantino,T.; Goodwin,F.
Fonte: LNEG - Laboratório Nacional de Energia e Geologia, I.P. Publicador: LNEG - Laboratório Nacional de Energia e Geologia, I.P.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2008 EN
Relevância na Pesquisa
36.66%
The main driving forces concerning the use of pre-primed automotive sheet are corrosion protection increase and cost reduction during vehicle manufacturing. In this work, the behaviour of two conductive primers, codified by 1 and 2, was studied and compared with that of a conventional electrophoretic primer. Primer 1 is an organic zinc rich silicate with a low thickness (near 4 µm) and primer 2 is a very thin (near 2 µm) water based primer filled with graphite. These primers were applied on electrogalvanized, hot dip galvanized and galvannealed steel sheets. Formability capabilities of pre-primed galvanized steel sheets were evaluated, through cupping and stone chipping tests, according to EN ISO 1520 and ASTM D3170, respectively. To evaluate corrosion protection, the samples were submitted to a corrosion cyclic test according to VDA procedure 621-415 contained in the SEP 1160. Corrosion mechanisms were studied by scanning electron microscopy (SEM) with X-ray microanalysis by dispersive energy spectrometry (EDS) associated. Primers 1 and 2 offer cathodic protection when exposed, however by different manners, and allow previous welding works. Primer 1 acts as a zinc rich primer and primer 2 acts as a sealer of metallic zinc coatings...

Corrosion of hot-dip galvanized steel reinforcement

Figueira,R. B.; Silva,C. J. R.; Pereira,E. V.; Salta,M. M.
Fonte: LNEG - Laboratório Nacional de Energia e Geologia, I.P. Publicador: LNEG - Laboratório Nacional de Energia e Geologia, I.P.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2014 EN
Relevância na Pesquisa
36.66%
In the past several years hot-dip galvanized steel (HDGS) has successfully been used to extend the service life of reinforced concrete structures, mainly due to its low cost and high corrosion resistance compared to mild steel. However, the initial corrosion behaviour of the galvanized coating when embedded in concrete and how that behaviour may be affected by the surface composition of the coating remains unclear. When HDGS is embedded in fresh concrete (a highly alkaline environment), the zinc coating corrodes vigorously until passivation occurs and the concrete hardens. This leads to two main concerns, namely, the high initial corrosion rate, which may remove so much zinc that this leads to insufficient galvanic protection of the underlying steel, and the hydrogen production (in the corresponding cathodic half-cell reaction) which may increase the porosity of the adjacent cement paste and reduce the bond strength between the bar and the concrete. To avoid, or at least minimize, this initial reaction the use of chromates has been implemented. However, due to the toxicity of hexavalent chromium, environmental and human health concerns have restrained their use and alternatives are being studied all over the world. In this paper, the coatings and pre-treatments studied at an academic level in the last few years (2001-2014) have been reviewed together with the corrosion mechanisms of HDGS in contact with high alkaline environments and the role of Cr(VI) in inhibiting the initial zinc corrosion process.

Inhibition of Mild Steel Corrosion by some Phenyltetrazole Substituted Compounds in Hydrochloric Acid

Elkacimi,Y.; Achnin,M.; Aouine,Y.; Touhami,M. Ebn; Alami,A.; Touir,R.; Sfaira,M.; Chebabe,D.; Elachqar,A.; Hammouti,B.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2012 EN
Relevância na Pesquisa
36.66%
Phenyltetrazole substituted compounds, namely 5-phenyl-1H-tetrazole (PT), 5-(4chlorophenyl)- 1H-tetrazole (Cl-PT), 5-(4-methoxyphenyl)-1H-tetrazole (MO-PT) and 5-p-tolyl-1H-tetrazole (M-PT) were synthesized to study their inhibition behavior on mild steel in 1 M HCl by weight loss measurement, potentiodynamic polarization studies and electrochemical impedance spectroscopy (EIS). It has been observed that corrosion rate decreases and inhibition efficiency increases with increasing in phenyltetrazole substituted concentration and dependence on molecular structure. Polarization data indicate that these compounds act as very good cathodic inhibitors of mild steel in 1 M HCl. The result showed that the inhibition efficiency decreased with temperature and increased with immersion time. EIS has the same trend of inhibitive effect as that of the polarization data, which indicates the formation of a protective layer on mild steel surface by molecules adsorption.

Evaluation of Nicotiana Leaves Extract as Corrosion Inhibitor for Steel in Acidic and Neutral Chloride Solutions

Abd-El-Khalek,D.E.; Abd-El-Nabeyb,; Abdel-Gaberb,A.M.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/07/2012 EN
Relevância na Pesquisa
36.66%
The inhibition of steel corrosion in hydrochloric acid and sodium chloride solutions by Nicotiana leaves extract was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy measurements. Polarization curves showed that the extract behaves as a mixed type inhibitor in acidic medium, while it acts as anodic type in neutral medium. Impedance measurements indicated that the size of the semicircles obtained increased with increasing the concentration of the extract and decreasing the chloride ion concentration. Nicotiana leaves extract was found to be more effective in controlling corrosion of steel in acidic solution than in neutral one. The activation parameters of the corrosion reaction of steel in acid media in absence and presence of nicotiana leaves extract were also calculated and discussed.

Corrosion Inhibition of Steel in Phosphoric Acid by Phenacyldimethyl Sulfonium Bromide and some of its p-Substituted Derivatives

Arab,S.T.; Al-Turkustani,A.M.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2006 EN
Relevância na Pesquisa
36.66%
Corrosion inhibition of mild steel in 0.67 M H3PO4 by phenacyl dimethylsulfonium bromide and six of its p-substituted derivatives was studied using different chemical, electrochemical and scanning electron microscopy techniques. The order of increasing inhibition efficiency was correlated with its p-substituted through Hammett relation. Potentiodynamic polarization curves indicated that the compounds acted primarily as mixed-type inhibitors. Electrochemical impedance spectroscopy showed that the steel dissolution is controlled by charge-transfer mechanism. The kinetic-thermodynamic model of adsorption isotherm described the experimental findings. Number of active sites, binding constant and change of free energy were computed for all studied compounds. Depending on the inhibitor, it was found that each organic molecule replaced one or two adsorbed water molecules from the steel surface. The adsorption center was suggested to be the π electrons of the phenyl ring, and a flat configuration adsorption of the molecule may occur.

A mathematical model of laser surface heat-cooling treatment for medium carbon steel

Fedotov,I; Fedotova,T; Pityana,S.L; Labuschange,K; Shatalov,M; Potgieter,J.H
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2011 EN
Relevância na Pesquisa
36.66%
SYNOPSIS One of the most effective methods of metal surface heat treatment is through laser hardening. In most cases, laser parameters are determined experimentally, which is expensive and time-consuming. A mathematical model for the surface heat treatment process will allow a significant decrease in costs, and reduce the time required for optimization. In the present work, the authors present a mathematical model for laser heat treatment with forced cooling which can be applied to medium carbon steel. The model is based on a three-dimensional heat transfer equation using Green's function. The model allows one to calculate the temperature of the treated steel at different depths below the surface with and without cooling, for set values of the laser power and travelling speed, when the heat transfer coefficient is a known constant. It also takes variations in the radiation adsorption coefficient on the metal surface and laser beam spot size into account. The model was illustrated by comparing calculated and experimental temperature profiles of mild carbon steel with 0.5% C with and without cooling. A reasonably good agreement was achieved between experimental and predicted values to ensure that a high enough austenizing temperature with short enough cooling time was reached for direct martensite formation. It also predicted the depth of treatment accurately. The incorporation of cooling in the model substantially improves previous models based on heat transfer only. It delivers a tool that can with a reasonable accuracy predict the depth of surface heat treatment and cooling time required from operational parameters...