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Study on friction and wear behavior of SAE 1045 steel, reinforced nylon 6.6 and NBR rubber used in clutch disks

Rosa,Avital Gabriel de Almeida; Moreto,Jéferson Aparecido; Manfrinato,Marcos Dorigão; Rossino,Luciana Sgarbi
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2014 EN
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The friction and wear properties of AISI 1045 steel, nylon 6.6 composites with different types and percentages of reinforcement and a nitrile rubber, Alpha 66, were submitted to sliding wear tests. The five types of nylon 6.6 composites tested generated matching, low values for the coefficient of friction. This may be due to the greater influence of the nylon 6.6 matrix on the coefficient of friction. However, the wear in nylon composites showed wide variation, determined by the type of reinforcement added to the composite. The other two materials tested, nitrile rubber and 1045 steel, showed behavior different from that of the composites. The NBR (signifying a norm established by the Brazilian Association of Technical Norms) rubber showed a superior coefficient of friction and greater wear. On the other hand, the steel showed a high coefficient of friction and low wear, suggesting that the coefficient of friction has no direct connection to the wear resistance of the materials studied here.

Aqueous extracts of mango and orange peel as green inhibitors for carbon steel in hydrochloric acid solution

Rocha,Janaina Cardozo da; Gomes,José Antônio da Cunha Ponciano; D'Elia,Eliane
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2014 EN
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In this paper, aqueous extracts of mango and orange peels were shown to be good corrosion inhibitors for carbon steel in a 1 mol L- 1 HCl solution. The inhibition efficiency increased as the extract concentration increased over a concentration range of 200-600 mg L- 1, varying from 79 to 96% (mango) and 84 to 91% (orange) using Tafel plots and from 69 to 94% (mango) and 76 to 90% (orange) using electrochemical impedance. In the presence of 400 mg L- 1 of mango and orange peel extracts, the weight loss measurements showed an increase in the inhibition efficiency with immersion time, where the best results after 24 h of immersion were 97% and 95%, respectively. The adsorption of the extract components on the surface of the carbon steel follows the Langmuir adsorption isotherm. With the extraction procedure used in this work, it can be surmised that it is likely that the more polar heterosides in the extracts are responsible for the corrosion inhibition of carbon steel in an acid solution.

Effect of Continuous and Pulsed Current on the Metallurgical and Mechanical Properties of Gas Tungsten Arc Welded AISI 4340 Aeronautical and AISI 304 L Austenitic Stainless Steel Dissimilar Joints

Arivarasu,Moganraj; Ramkumar Kasinath,Devendranath; Natarajan,Arivazhagan
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2015 EN
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In this research work, the weldability of low alloyed AISI 4340 aeronautical steel and AISI 304L austenitic stainless steel joined by continuous current (CC) and pulsed current (PC) gas tungsten arc welding (GTAW) techniques, using ER309L and ERNiCr-3 filler metals was investigated. The main focus of the study involves the investigation on the effect of continuous and pulsed current mode of GTA welding process on the metallurgical and mechanical properties of these dissimilar weldments. Microstructure studies revealed the formation of different zones across the weldments, vis-à-vis martensite at the HAZ of AISI 4340, vermicular δ - ferrite /ferrite stringers at the HAZ of AISI 304L, pearlite colonies at the parent metal of AISI 4340 and equi-axed cellular and/or columnar dendrites at the weld zone. Tensile results showed that current pulsing accrued better tensile properties. The structure - property relationships of these weldments were established based on the current modes employed by utilizing combined techniques of optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).

Corrosion and Wear Resistance of Carbon Films Obtained by Electrodeposition on Ferritic Stainless Steel

Cardoso,Henrique Ribeiro Piaggio; Falcade,Tiago; Kunst,Sandra Raquel; Malfatti,Célia Fraga
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2015 EN
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In improving the corrosion and hardness proprieties of ferritic stainless steel, the use of protective coatings becomes an interesting alternative. In this study, a carbon layer was deposited on AISI 430 by electrodeposition using N,N-dimethylformamide with the addition of an organic dopant as the electrolyte. The AISI 430 stainless steel was pretreated by anodization aiming to optimize the film anchoring. The obtained films were characterized by atomic force microscopy, by scanning electron microscopy and by optical interferometry. The microstructural characterization of the films was obtained by Raman Spectroscopy. The corrosion resistance was evaluated by open circuit potential and by potentiodynamic polarization. The friction test and the scratch test were performed to evaluate the mechanical properties. The Raman spectroscopy showed the presence of an amorphous carbon film. The films improved the corrosion resistance of stainless steel. In addition, on the wear analysis the coating showed a good adhesion on the substrate.

Magnetic properties and retained austenite quantification in SAE 4340 steel

Ajus,C.; Tavares,S.S.M.; Silva,M.R.; Corte,R.R.A.
Fonte: Rede Latino-Americana de Materiais Publicador: Rede Latino-Americana de Materiais
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
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Magnetic properties (coercive force and saturation magnetization) of SAE 4340 steel, heat treated in different ways, were measured in a Vibrating Sample Magnetometer. Four soaking temperatures were investigated: 860°C, 960°C, 1060°C and 1160°C. The oil-quenched samples were tempered at different temperatures between the range of 200°C and 650°C. The increase of the soaking temperature promotes the decrease of the saturation magnetization, which is mainly due to the retained austenite in the steel. This austenite transforms into bainite during tempering between 200°C and 300°C. The saturation magnetization measurements were used to quantify the amount of retained austenite in the different samples. The coercive force of the steel varied from 115.0 Oe (9151.7 A/m) to 133.0 Oe (10584.1 A/m), depending on the heat treatment condition.

Processing and characterization of dual phase steel foam

Gruttadauria,A.; Mombelli,Davide; Castrodeza,E. M.; Mapelli,C.
Fonte: Rede Latino-Americana de Materiais Publicador: Rede Latino-Americana de Materiais
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 EN
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36.66%
Porous materials featuring cellular structures are known to have many interesting combinations of physical and mechanical properties. Some of them have been extensively used in the transportation field (i.e. balsa wood). Steel foams presented promising theoretical properties for both functional and structural applications in transportation, but processing of such a kind of foams is complex due to their high melting point. Recently a technique for processing Cu-based alloys open-cell foams through the molten metal infiltration of a leachable bed of amorphous SiO2 particles was proposed. A variation of the proposed technique that uses SiC particles as space holder is now presented and was recently successfully applied for dual phase steel foam processing. Results from a processing of dual phase DP500 steel foams, including some morphological, micro-structural and mechanical characterization, are here presented.

Stress-strain curves for steel fiber-reinforced concrete in compression

Oliveira Júnior,Luiz Álvaro de; Borges,Vanessa Elizabeth dos Santos; Danin,Alice Ribeiro; Machado,Daiane Vitória Ramos; Araújo,Daniel de Lima; El Debs,Mounir Khalil; Rodrigues,Paulo Fernando
Fonte: Rede Latino-Americana de Materiais Publicador: Rede Latino-Americana de Materiais
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 EN
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36.66%
This paper presents a study on the compressive behavior of steel fiber-reinforced concrete. In this study, an analytical model for stress-strain curve for steel fiber-reinforced concrete is derived for concretes with strengths of 40 MPa and 60 MPa at the age of 28 days. Those concretes were reinforced with steel fibers with hooked ends 35 mm long and with aspect ratio of 65. The analytical model was compared with some experimental stress-strain curves and with some models reported in technical literature. Also, the accuracy of the proposed stress-strain curve was evaluated by comparison of the area under stress-strain curve. The results showed good agreement between analytical and experimental data and the benefits of the using of fibers in the compressive behavior of concrete.

Formation of biofilms by Staphylococcus aureus on stainless steel and glass surfaces and its resistance to some selected chemical sanitizers

Marques,Simone Cristina; Rezende,Jaíne das Graças Oliveira Silva; Alves,Lizandra Aparecida de Freitas; Silva,Belami Cássia; Alves,Eduardo; Abreu,Luiz Ronaldo de; Piccoli,Roberta Hilsdorf
Fonte: Sociedade Brasileira de Microbiologia Publicador: Sociedade Brasileira de Microbiologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2007 EN
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The objectives of this work were to verify the capability of Staphylococcus aureus of forming bio-film on stainless steel and glass surfaces; to evaluate the efficiency of sodium dichloroisocyanurate, hydrogen peroxide and peracetic acid in inactivating Staphylococcus aureus cells adhered onto these surfaces; and to visualize biofilm development by scanning electron microscopy before and after sanitizer treatment. The surfaces studied consisted of 10x20mm chips immersed in Petri dishes containing BHI broth inoculated with S. aureus ATCC 25923. Biofilm formation was observed after 15-day incubation, when the cells were removed using the swab technique, followed by Baird Parker agar plating. Also, the efficiency of the chemical sanitizers on the chip surfaces was tested and the non-removed cells were counted on the Baird-Parker agar. After biofilm formation and use of sanitizers, the chips were respectively observed by scanning electronic microscopy following a pre-existing protocol. The obtained results showed biofilm formation on both surfaces, with bacterial count in the order of 10(7) CFU/cm² on and 10(8) CFU/cm² on stainless steel and glass surfaces, respectively. Peracetic acid was the most efficient in removing adhered cells...

Adhesion and biocides inactivation of Salmonella on stainless steel and polyethylene

Tondo,Eduardo Cesar; Machado,Taís Raquel Marcon; Malheiros,Patrícia da Silva; Padrão,Débora Kruger; Carvalho,Ana Lyl de; Brandelli,Adriano
Fonte: Sociedade Brasileira de Microbiologia Publicador: Sociedade Brasileira de Microbiologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2010 EN
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The adhesion of Salmonella (S.) strains to stainless steel and polyethylene and their inactivation by biocides used in food industry was investigated. Coupons of stainless steel and polyethylene were immersed in bacterial suspensions of S. Enteritidis, S. Typhimurium, and S. Bredeney during 15, 30, and 60 minutes, and submitted to different concentrations of peracetic acid (PAA), sodium hypochlorite (NaOCl), and quaternary ammonium (Quat) sanitizers. Hydrophobicity of the surfaces was evaluated by contact angle measurements using the sessile drop method and bacterial adhesion was accompanied through bacterial counts and scanning electron microscopy (SEM). Results indicated that the three serovars of Salmonella presented similar adhesion to both materials (5.0 to 6.5 log cfu cm-2). The time of exposure did not influence the counts of adhered cells on both surfaces, however SEM revealed larger clusters of S. Enteritidis on both materials, not found for the other serovars. S. Enteritidis presented lower sessile drop angle on polyethylene, indicating hydrophilic properties of this material. The biocides were not able to inactivate all the microorganisms adhered on both surfaces. At least 1 log cfu cm-2 of all serovars tested remained viable after the exposure to different biocide concentrations. In general...

An effective thickness proposal for strength evaluation of one-side pitted steel plates under uniaxial compression

Nouri,Zorareh Hadj Mohammad Esmaeil; Khedmati,Mohammad Reza; Sadeghifard,Shokoufeh
Fonte: Associação Brasileira de Ciências Mecânicas Publicador: Associação Brasileira de Ciências Mecânicas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2012 EN
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This paper presents the results of an investigation into the post-buckling behaviour and ultimate strength of imperfect pitted steel plates used in ship and other marine-related structures. A series of elastic-plastic large deflection finite element analyses is performed on pitted steel plates. The effects of pitting corrosion on one side of the plates are introduced into the finite element models. The effects on plate compressive strength as a result of parametric variation of the pitting corrosion geometry are evaluated. A proposal on the effective thickness is concluded in order to estimate the ultimate strength and explore the post-buckling behaviour of pitted steel plates under uniaxial compression.

Finite element implementation for the analysis of 3D steel and composite frames subjected to fire

Caldas,R. B.; Fakury,R. H.; Sousa Jr.,João Batista M.
Fonte: Associação Brasileira de Ciências Mecânicas Publicador: Associação Brasileira de Ciências Mecânicas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 EN
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This paper presents a finite element formulation for the numerical analysis of three-dimensional framed steel, reinforced concrete or composite steel and concrete structures subjected to fire. Several specialized and commercial programs may be used for the analysis of structures in fire condition. Within this context, the purpose of this work is to present the steps taken to extend a previously developed static analysis procedure with beam elements in order to cope with the thermal and structural analysis of structures under fire action. Physical nonlinearity and material property degradation considering the temperature distribution are taken into account at the cross section level, which is divided into quadrilateral or triangular finite elements. Thermal strains are considered through the effective strain concept, and the resulting nonlinear system of equations is solved by the Newton-Raphson scheme. The accuracy and capability of the formulation to simulate the behavior of framed structures under fire action are assessed through comparison with various numerical and experimental results.

Numerical study of confinement in short concrete filled steel tube columns

Gupta,P.K.; Singh,Heaven
Fonte: Associação Brasileira de Ciências Mecânicas Publicador: Associação Brasileira de Ciências Mecânicas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2014 EN
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This study presents a numerical investigation into the behaviour of short concrete filled steel tubular (CFST) columns. Three Dimensional Nonlinear finite element analysis of the compression process is performed using commercial software ABAQUS v6.9 (2009). Steel tubes of different geometries and in-filled with different grades of concrete are chosen for modelling from literature. The proposed FE model is validated by comparing its results with those of the corresponding experimental specimens. The model is further used to study the variation of radial confining pressure f cp provided by the steel tube to the concrete core. It is observed that the value of f cp varies widely throughout the length of the CFST, with the values in the area adjacent to top and bottom platens being markedly higher than the values in-between due to the end restraint provided by the machine platens. This is in contrast to the present confined concrete model which uses a uniform value of confining pressure throughout the height. Effect of effective length of column and interfacial friction present between the platen and specimen are found to be negligible on behaviour of short CFST column.

Avaliação experimental do comportamento do concreto fluido reforçado com fibras de aço : influência do fator de forma e da fração volumétrica das fibras nas propriedades mecânicas do concreto; Experimental evaluation of the behavior of fluid concrete reinforced steel fibers : influence of shape factor and volumetric fraction of fibers on the mechanical properties of concrete

Góis, Fernanda Alves Pinto
Fonte: Universidade Federal de Alagoas; BR; Estruturas; Programa de Pós-Graduação em Engenharia Civil; UFAL Publicador: Universidade Federal de Alagoas; BR; Estruturas; Programa de Pós-Graduação em Engenharia Civil; UFAL
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
36.66%
The development of new technologies in the production of concrete over time is allowing increase its compressive strength, workability and durability. Despite their many advantages, concrete has limitations related to its fragile behavior in the presence of tensile loads. An alternative to solve this problem is the use of fibers in the concrete, getting a composite material that has different characteristics of the original material. Seeking collaborate with the evaluation about the efficiency of different fiber types, this work analyses the behavior of fluid concrete reinforced with steel fibers, subjected to tensile loads, evaluating the influence of shape factor and volumetric fraction. The ability of flow has served as a reference for concrete can be used on parts with high rates of reinforcement, whose compacting is not fully efficient. However, because it is a cementitious matrix, the concentration of tensile strength on these points of high rates of reinforcement, may trigger a harmful process of cracking. Are analyzed in this work the effects of the incorporation of steel fibers in the workability, the incorporated air content, the compressive strength, the tensile strength and modulus of elasticity. Additionally, a comparison is made between the relationship of the compression strength and tensile of the experimental results with the theoretical relationships of the tensile strength found in the literature ...

O uso do sistema light steel framing associado a outros sistemas construtivos como fechamento vertical externo n?o-estrutural

Santiago, Alexandre Kokke
Fonte: Programa de P?s Gradua??o em Engenharia Civil. Departamento de Engenharia Civil, Escola de Minas, Universidade Federal de Ouro Preto. Publicador: Programa de P?s Gradua??o em Engenharia Civil. Departamento de Engenharia Civil, Escola de Minas, Universidade Federal de Ouro Preto.
Tipo: Dissertação
PT_BR
Relevância na Pesquisa
36.66%
A constru??o civil brasileira ? marcada pelos sistemas construtivos artesanais, por?m, diante da crescente demanda e da disponibilidade t?cnica de alternativas, v?rias correntes deste setor t?m se mostrado abertos ao emprego de solu??es industrializadas. Sistemas construtivos com concep??o racionalizada t?m ganhado espa?o conforme cresce a aceita??o da tecnologia por parte dos setores produtivos e principalmente dos consumidores. O sistema construtivo Light Steel Framing (LSF), que se apresenta como uma solu??o industrializada e racionalizada, vem ganhando espa?o no Brasil em constru??es dos mais diversos usos e j? conta com todos os insumos necess?rios para sua execu??o dispon?veis no pa?s. Os fechamentos verticais industrializados s?o utilizados no Brasil com certa freq??ncia, sendo o dry-wall (internamente) e os pain?is met?licos e de concreto pr?-moldado (externamente) suas formas mais comuns. Entretanto, os fechamentos externos em LSF para edif?cios com estrutura principal portante, que s?o comuns em pa?ses de cultura construtiva mais industrializada, ainda s?o raros em nosso pa?s. A utiliza??o deste sistema representa maior rapidez de execu??o com perdas m?nimas; menor emprego de m?o-de-obra; e a redu??o consider?vel no peso pr?prio comparado a materiais convencionais. Nesse contexto...

Avaliação tribomecânica via esclerometria retilínea e indentação instrumentada do aço abnt 8550; Tribomechanical evaluation of ABNT 8550 steel by using scratch and indentation tests

Ferreira, Fernando Martins
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Dissertação
POR
Relevância na Pesquisa
36.66%
Em sistemas de bombeamento multifásico de petróleo o aço ABNT 8550 é empregado na construção de rotores de bombas de extração de petróleo. Esses rotores são solicitados basicamente por desgaste erosivo/abrasivo. O conhecimento do comportamento desse material mediante ao desgaste é de fundamental importância. Assim, para avaliar as propriedades tribomecânicas desse aço nas condições temperada/revenida e recozida, foram realizados ensaios de microesclerometria retilínea, bem como de indentação instrumentada. Assim, foi realizado um estudo do efeito da velocidade de riscamento, do raio de ponta do penetrador Rockwell C e da carga normal de riscamento. Nos ensaios de esclerometria foram obtidas: dureza ao risco, coeficiente de atrito aparente e energia específica de riscamento. Os mecanismos de desgaste foram avaliados por meio do fator fab e microscopia eletrônica de varredura. O material beneficiado mostrou uma maior dureza ao risco quando comparado com o recozido. A variação da velocidade de riscamento em duas ordens de grandeza praticamente não apresentou influência no comportamento tribológico do material no estado beneficiado. O aumento do raio de ponta do penetrador resultou em pouca influência nos valores de dureza ao risco para o material beneficiado...

Polibilidade de aços para moldes de plásticos; Polishing steel for plastic molds

Domingues Júnior, Gilberto
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Tese de Doutorado
POR
Relevância na Pesquisa
36.66%
A polibilidade é uma característica fundamental para seleção do material para fabricação de moldes e matrizes para plásticos. Esta característica está associada, principalmente à necessidade do acabamento superficial final da peça fabricada, como por exemplo lente de óculos ou faróis de carros. Este trabalho tem o objetivo de caracterizar a polibilidade de materiais e comparar o resultado para três diferentes tipos de aços utilizados na fabricação de moldes de injeção de plásticos. A caracterização da polibilidade foi feita através da avaliação da rugosidade da superfície medida através de diferentes procedimentos. Os materiais avaliados foram os aços VP20 ISO, VP80 e 304 UF, produzidos pela Villares Metals. Foram preparadas 45 amostras para cada um dos três aços. As amostras foram submetidas a diferentes níveis de acabamento utilizando lixamento e polimento. Medidas de rugosidade foram realizadas utilizando interferômetro a laser, rugosímetro com apalpador mecânico e medidas de refletividade pela técnica de fotoluminescência. Diante dos resultados fez-se uma comparação e avaliação dos três métodos de medição do acabamento superficial. Nesta comparação, tentou-se mostrar a relação entre a rugosidade e refletividade da técnica de fotoluminescência. Os resultados obtidos na comparação dos métodos demonstraram uma boa correlação para o aço VP80. Quanto maior a rugosidade medida pelo rugosímetro e interferômetro...

Usinabilidade do aço de corte-fácil baixo carbono ao chumbo ABNT 12L14 com diferentes níveis de elementos químicos residuais (cromo, níquel e cobre); N. Machinability of low carbon free-machining leaded steel ABNT 12L14 with different levels of residual elements (chromium, nickel and cooper)

Luiz, Nelis Evangelista
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Tese de Doutorado
POR
Relevância na Pesquisa
36.66%
O objetivo desta tese foi estudar a usinabilidade do aço de corte fácil baixo carbono ao chumbo (ABNT/AISI 12L14) com diferentes níveis dos elementos residuais cromo, níquel e cobre. Foram produzidas nove corridas de aço com composição química controlada e alterações nos níveis de residuais citados de forma a conduzir planejamentos fatoriais a dois níveis. A técnica de Planejamento e Análise de Experimentos (DOE) foi usada nos experimentos quantitativos. A caracterização dos materiais estudados envolveu: análise de composição química, dureza e inclusões; ensaios de resistência à tração. A usinabilidade foi avaliada levando-se em consideração a variação das condições de usinagem. As variáveis de usinagem de interesse foram a forma do cavaco, a rugosidade superficial, o grau de recalque do cavaco, a força de corte e a temperatura de usinagem. A conjugação das variáveis de composição química (residuais) com as variáveis de corte (velocidade, profundidade e avanço) permitiu, para os ensaios quantitativos, a construção de planejamentos fatoriais em que todas as influências e interações puderam ser quantificadas. Todos os ensaios foram feitos em operação de torneamento cilíndrico sem fluído de corte. Os ensaios de temperatura de usinagem foram feitos com ferramentas de aço rápido. Os outros ensaios foram feitos com ferramentas de metal duro. Amostras da raiz do cavaco e da superfície de saída de ferramentas...

Soldagem A-TIG em aço inoxidável ferrítico; A-TIG welding in Ferritic Stainless Steel

Azevedo, Alessandra Gois Luciano de
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Tese de Doutorado
POR
Relevância na Pesquisa
36.66%
O uso de fluxo ativo no processo de soldagem TIG pode ser uma alternativa para aumentar a velocidade de soldagem do processo, pois esta técnica permite o aumento da profundidade de penetração do cordão de solda mantendo os mesmo parâmetros empregados no TIG convencional. A principal desvantagem desta técnica reside principalmente na propensão à formação de uma camada oxidada sobre o cordão de solda o que pode também acarretar num acabamento superficial ruim. Uma forma de tirar proveito desta técnica garantindo um bom acabamento do cordão é aplicar o fluxo de tal maneira que, ao invés de uma camada que cubra toda a superfície da chapa, sejam feitas duas faixas de fluxo, separadas por uma distância predeterminada, definida como parâmetro “a”. Esta técnica é chamada neste trabalho de Técnica da Constrição Controlada (TCC). Desta forma, a camada de fluxo isola eletricamente certas regiões da superfície da peça direcionando a região de incidência do arco e, como a diluição do fluxo na poça de solda é menor, alia-se a vantagem do aumento de penetração com o bom acabamento do cordão de solda. O objetivo desta pesquisa é verificar e analisar a influência do uso da Técnica da Constrição Controlada com o processo A-TIG na soldagem do aço inoxidável ferrítico; identificar e quantificar os principais fenômenos envolvidos como...

Evaluation of stability and integrity of a steel truss bridge in a forensic investigation

BRANDO, FRANCESCA
Fonte: La Sapienza Universidade de Roma Publicador: La Sapienza Universidade de Roma
Tipo: Tese de Doutorado
EN
Relevância na Pesquisa
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The studies presented in this Thesis have been developed in the frame of the forensic investigation into the causes of the collapse of the I-35West Bridge (I-35W) in Minneapolis, Minnesota, USA that occurred on August 1 st, 2007. The failure of the I-35W represents a major case-study for the evaluation of stability and integrity of a steel truss bridge. The Thesis has been developed at Columbia University and at the engineering firm Thornton Tomasetti (TT) which was hired by a national law firm, Robins, Kaplan, Miller & Ciresi, to perform a forensic investigation into the cause of the catastrophic collapse. According to the findings of the forensic investigation, the collapse was triggered by the buckling of an element of the main truss bottom chord in the main span close to the pier. The Thesis focused on technical aspects and did not attempt to assign responsibility among the involved parties. In the first part of the thesis, the background and motivation for the forensic investigation are presented together with a description of the I-35W Bridge. The definition of bridge safety and related classifications are given. The concept of structural stability and integrity of steel structures are discussed. The nature of structures and their complexity are considered as well as the methodologies used to study them. An extensive description of the structural decomposition method is presented and detailed for the case study. In this work...

Fractures of modern high nitrogen stainless steel cemented stems

Yates, P.; Quaraishi, N.; Kop, A.; Howie, D.; Marx, C.; Swarts, E.
Fonte: Churchill Livingstone Inc Medical Publishers Publicador: Churchill Livingstone Inc Medical Publishers
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
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We present 14 cases of fracture of modern, high-nitrogen, stainless steel stems. Our clinical and radiological data suggest that heavy patients with small stems and poor proximal support are at risk for fracturing their implants. “Champagne-glass” canals can lead to the use of smaller stems often placed in varus, which can lead to cantilever bending and fatigue failure in the distal half of the stem. Metallurgical assessment of the retrieved high-nitrogen, stainless steel stems reveals microstructural inconsistencies that may contribute to their failure. Based on our findings, careful consideration and attention to technique is required when using stainless steel stems in patients with high body mass index or high weight. Technique is particularly important in femurs with champagne-glass canals.; Piers J. Yates, Nasir A. Quraishi, Allan Kop, Donald W. Howie, Clare Marx and Eric Swarts; Copyright © 2008 Elsevier Inc. All rights reserved.