O presente trabalho avalia a evolução das microestruturas e das propriedades mecânicas em tubos API 5L X65 soldados por fricção com auxílio de um anel centralizador na posição de topo. A soldagem foi realizada em tubos de 114,3 mm (4,5’’) de diâmetro nominal e 8 mm de espessura. A avaliação mecânica foi realizada segundo normas ASTM para os ensaios de tração, dobramento de raiz, dobramento de face, ensaio de impacto Charpy V e perfis de microdurezas. Os ensaios de fadiga foram realizados para análise da vida em fadiga das juntas soldadas. Os ensaios mecânicos realizados comprovam que houve a união metalúrgica dos materiais, sendo registradas regiões com defeitos de falta de adesão o que prejudicou as propriedades mecânicas ocasionando rupturas com baixa ductilidade nas interfaces de soldagem nestes locais. Nos resultados dos ensaios de microdurezas houve um pequeno aumento das microdurezas registradas próximo às interfaces de soldagem e uma redução nas microdurezas registradas nas regiões de ZACs. Os resultados do ensaio de impacto Charpy -20 °C foi aceitável segundo a norma API 5L. As microestruturas formadas nas interfaces de soldagem são compostas por ferrita de Widmanstätten e ferrita poligonal com crescimento de grão quando comparado com o tamanho de grão do material de base. Nas regiões de ZACs houve um reordenamento de carbonetos aliado a refino de grão sendo registrada uma redução nas microdurezas destas regiões. / This paper assesses the evolution of microstructures and mechanical properties in pipes API 5L X65 welded by friction with the aid of centering ring on top position. The welding was performed in tubes of 114.3 mm (4.5'') nominal diameter and 8 mm in thickness. The mechanical evaluation was performed according to ASTM standards for tensile, root bending, face folding, Charpy V impact test and microhardness profile. Fatigue tests were performed to analyze the fatigue life of the welded joints. The mechanical tests prove that there was a metallurgical union of the materials, regions with lack of adhesion defects being recorded which affected the mechanical properties causing fractures with low ductility in the weld interfaces in these places. Microhardness test results registered a small increase in the microhardness near the weld interfaces and a reduction in the microhardness recorded in the HAZ regions. The results of the Charpy impact test at -20°C was acceptable according to API 5L. The microstructures formed at the weld interfaces are composed of Widmanstatten ferrite and polygonal ferrite with grain growth when compared to the grain size in the base material. In HAZ regions there was a reorganization of carbides combined with grain refinement, with a reduction in microhardness of these regions being registered.

O presente trabalho avalia a evolução das microestruturas e das propriedades mecânicas em tubos API 5L X65 soldados por fricção com auxílio de um anel centralizador na posição de topo. A soldagem foi realizada em tubos de 114,3 mm (4,5’’) de diâmetro nominal e 8 mm de espessura. A avaliação mecânica foi realizada segundo normas ASTM para os ensaios de tração, dobramento de raiz, dobramento de face, ensaio de impacto Charpy V e perfis de microdurezas. Os ensaios de fadiga foram realizados para análise da vida em fadiga das juntas soldadas. Os ensaios mecânicos realizados comprovam que houve a união metalúrgica dos materiais, sendo registradas regiões com defeitos de falta de adesão o que prejudicou as propriedades mecânicas ocasionando rupturas com baixa ductilidade nas interfaces de soldagem nestes locais. Nos resultados dos ensaios de microdurezas houve um pequeno aumento das microdurezas registradas próximo às interfaces de soldagem e uma redução nas microdurezas registradas nas regiões de ZACs. Os resultados do ensaio de impacto Charpy -20 °C foi aceitável segundo a norma API 5L. As microestruturas formadas nas interfaces de soldagem são compostas por ferrita de Widmanstätten e ferrita poligonal com crescimento de grão quando comparado com o tamanho de grão do material de base. Nas regiões de ZACs houve um reordenamento de carbonetos aliado a refino de grão sendo registrada uma redução nas microdurezas destas regiões. / This paper assesses the evolution of microstructures and mechanical properties in pipes API 5L X65 welded by friction with the aid of centering ring on top position. The welding was performed in tubes of 114.3 mm (4.5'') nominal diameter and 8 mm in thickness. The mechanical evaluation was performed according to ASTM standards for tensile, root bending, face folding, Charpy V impact test and microhardness profile. Fatigue tests were performed to analyze the fatigue life of the welded joints. The mechanical tests prove that there was a metallurgical union of the materials, regions with lack of adhesion defects being recorded which affected the mechanical properties causing fractures with low ductility in the weld interfaces in these places. Microhardness test results registered a small increase in the microhardness near the weld interfaces and a reduction in the microhardness recorded in the HAZ regions. The results of the Charpy impact test at -20°C was acceptable according to API 5L. The microstructures formed at the weld interfaces are composed of Widmanstatten ferrite and polygonal ferrite with grain growth when compared to the grain size in the base material. In HAZ regions there was a reorganization of carbides combined with grain refinement, with a reduction in microhardness of these regions being registered.

O presente trabalho avalia a evolução das microestruturas e das propriedades mecânicas em tubos API 5L X65 soldados por fricção com auxílio de um anel centralizador na posição de topo. A soldagem foi realizada em tubos de 114,3 mm (4,5’’) de diâmetro nominal e 8 mm de espessura. A avaliação mecânica foi realizada segundo normas ASTM para os ensaios de tração, dobramento de raiz, dobramento de face, ensaio de impacto Charpy V e perfis de microdurezas. Os ensaios de fadiga foram realizados para análise da vida em fadiga das juntas soldadas. Os ensaios mecânicos realizados comprovam que houve a união metalúrgica dos materiais, sendo registradas regiões com defeitos de falta de adesão o que prejudicou as propriedades mecânicas ocasionando rupturas com baixa ductilidade nas interfaces de soldagem nestes locais. Nos resultados dos ensaios de microdurezas houve um pequeno aumento das microdurezas registradas próximo às interfaces de soldagem e uma redução nas microdurezas registradas nas regiões de ZACs. Os resultados do ensaio de impacto Charpy -20 °C foi aceitável segundo a norma API 5L. As microestruturas formadas nas interfaces de soldagem são compostas por ferrita de Widmanstätten e ferrita poligonal com crescimento de grão quando comparado com o tamanho de grão do material de base. Nas regiões de ZACs houve um reordenamento de carbonetos aliado a refino de grão sendo registrada uma redução nas microdurezas destas regiões. / This paper assesses the evolution of microstructures and mechanical properties in pipes API 5L X65 welded by friction with the aid of centering ring on top position. The welding was performed in tubes of 114.3 mm (4.5'') nominal diameter and 8 mm in thickness. The mechanical evaluation was performed according to ASTM standards for tensile, root bending, face folding, Charpy V impact test and microhardness profile. Fatigue tests were performed to analyze the fatigue life of the welded joints. The mechanical tests prove that there was a metallurgical union of the materials, regions with lack of adhesion defects being recorded which affected the mechanical properties causing fractures with low ductility in the weld interfaces in these places. Microhardness test results registered a small increase in the microhardness near the weld interfaces and a reduction in the microhardness recorded in the HAZ regions. The results of the Charpy impact test at -20°C was acceptable according to API 5L. The microstructures formed at the weld interfaces are composed of Widmanstatten ferrite and polygonal ferrite with grain growth when compared to the grain size in the base material. In HAZ regions there was a reorganization of carbides combined with grain refinement, with a reduction in microhardness of these regions being registered.

Abstract not available

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2005. / This study involved the modelling and verification of the Shielded Metal Arc Welding of mild steel with the focus on displacement and temperature distribution prediction of welded plates. The project was divided into three phases namely; the literature survey into finite element modelling of welding processes, the modelling of a welding process and verification of the modelling with experimental results. A working welding model was created using a commercial finite element software package with the capabilities to model welding processes. The welding model was systematically developed from a two-dimensional model into a threedimensional full physics process model. Experimental measured welding heat input parameters were applied in the model, temperature dependent material properties were applied and actual structural restraints from the experiments were modelled. Displacement and temperature distributions were measured on mild steel plates welded with the Shielded Metal Arc Welding process. The plate temperature was measured at various locations with K-type thermocouples spot welded onto the plates. Plate deformation was measured at various stages of the manufacturing process. Tendencies in plate displacement were investigated with a change in certain welding parameters. The finite element model was verified and good correlations were found, especially for the temperature distribution in the welded plates.

Atlikus projekto analizę, buvo pasirinktas optimalus, ekonomiškiausias ir racionaliausias projekto variantas, padėsiantis užtikrinti mažiausias statybos ir eksploatavimo sąnaudas, taip pat ilgiausią tilto eksploatavimo laiką. Ruošiant suvirinimo procedūrų aprašus atlikti ardomieji ir neardomieji bandymai virintinėms jungtims. Bandymai užtikrina, kad virintinės jungties kokybė atitiks standartų keliamus reikalavimams. Neardomieji tyrimo metodai: apžiūrimoji kontrolė, skvarbiųjų dažalų kontrolė, ultragarso kontrolė. Ardomieji tyrimo metodai: tempimas, lenkimas, smūginis tąsumas, kietumas, mikroskopinis ir makroskopinis tyrimai. Darbą sudaro 6 dalys: įvadas, literatūros šaltinių apžvalga, tilto techninio projekto apžvalga, medžiagų skaičiuotiniai stipriai, išvados, literatūros sąrašas. Darbo apimtis – 74 p. teksto be priedų, 43 iliustr., 12 lent., 4 grafikai, 49 bibliografinių šaltinių. / After completing the project analysis, the most optimal, economical and rational project option was chosen, which will secure the lowest construction and manufacturing costs as well as the longest exploitation time. Making welding procedure specification, destructive and non destructive parts were tested for welding joints. The tests showed that the quality of welded joints will be sufficient for the standard requirement. Non destructive research methods: visual testing, penetrant testing, ultrasonic testing, destructive research methods: tensile test, bend test, impact test, hardness test, microscopic and macroscopic tests. The structure of work : introduction, theory research, overview of the bridges' project, calculated strengths of the materials, conclusions, bibliography. Thesis consist of - 74 pages of text, 43 illustrations, 12 tables, 4 graphs, 49 sources.

Automotive structures contain hundreds of welds. Most of the time, failure occurs at the weld ends (weld toe or weld root). Thus, welds affect the structural integrity of an entire structure. Thus, the modeling of welded joints is very important from a design point of view. In this research, the primary aim is to develop a weld model to assess the structural integrity of welded joints based on stress analysis by using a finite element method (FEM) and through experimental validation. The stress distribution in welded joints mainly depends on the geometry, loading type and material properties. Therefore, it is greatly challenging to develop a weld model that can predict the behavior of stress distribution and weld stiffness in joints. There are several approaches for modeling welded structures by using FEM. However, the effective notch stress approach has been used for weld joint modeling in this research which is gaining in popularity in the automotive industry. The effective notch stress approach calculates the local stress at a notch (weld toe or root) assuming that there is linear-elastic material behavior. Parameter tuning of the weld model has been done to obtain the lowest validation error with the experimental results. The effective notch radius is chosen as the only tuning parameter in this weld model. Through this investigation, the weld model based on the effective notch stress has been experimentally validated for the first time through parameter tuning. Two different types of welded joints are investigated. Both types of joints are analyzed with a fine meshed 3D finite element model by using the effective notch stress approach. The FEM model of these two joints is validated with the experimental results. The calculated FEM results show a good agreement with the experimental results (obtained by using strain gages) for the ASTM model. This modeling technique is also validated with real world data of a bus window pillar. The model of the bus window pillar shows a close approximation with the experimental results. / October 2016

Este trabalho apresenta uma análise teórica e experimental do desempenho de vigas de concreto armado com telas soldadas com relação à resistência, à força cortante e ao controle da fissuração. O programa experimental englobou cinco séries de vigas com variação dos seguintes parâmetros: largura e altura das vigas, taxa de armadura transversal, taxa de armadura lateral e tipo de ancoragem dos fios verticais da tela no bordo comprimido da viga. Os modelos experimentais foram constituídos por doze vigas VQ (15 x 40 x 305), relação a/d= 2,78 e sete vigas VS (20 x 70 x 540), a/d= 2,66, ambas com seção T (bf = 50 cm e hf = 10 cm). O esquema de ensaio foi de uma viga simplesmente apoiada, com duas forças concentradas aplicadas. A formulação proposta, elaborada com base na teoria do cisalhamento-atrito, considerando a contribuição da armadura lateral na resistência à força cortante, foi analisada mediante os resultados obtidos nos ensaios. Analisaram-se também as aberturas das fissuras de cisalhamento na alma. A contribuição da armadura lateral da tela soldada deve-se à alteração em dois mecanismos resistentes alternativos: aumento da parcela de engrenamento dos agregados afetada pelas menores aberturas das fissuras de cisalhamento na alma e pelo efeito de pino dos fios da armadura lateral nos pontos em que são interceptados pelas fissuras diagonais. De modo geral, as vigas armadas com telas soldadas apresentaram menores aberturas de fissuras de cisalhamento na alma, um panorama de fissuração mais sistemático e maior reserva de resistência nas proximidades do colapso. / This work presents a theoretical-experimental analysis of performance shear design and cracking control in reinforced concrete beams with welded wire mesh. The experimental program consisted of five series of beams with variation of the following parameters: width and depth of the beam, transversal reinforcement ratio, lateral reinforcement ratio and type of stirrup anchorage in beam compression zone. The tested specimens comprised of twelve beams VQ (15 x 40 x 305), shear span-to-depth a/d= 2,78 and seven beams VS (20 x 70 x 540), a/d= 2,66, both with T transversal section (bf = 50 cm e hf = 10 cm). The test setup was a simply supported beam, with two concentrated forces applied. The proposed model was based on shear friction, which took account of the lateral reinforcement contribution on shear design. This model was compared with the test results. It was also studied the shear crack widths on the web beam. The lateral reinforcement contribution is provided by two alternative strength mechanisms: the increasing of portion agreggate interlock affected by smaller diagonal crack widths and the dowel effect of lateral reinforcement wires intercepted by diagonal plane failure. Generally, the welded wire fabric beams presented smaller inclined shear cracks, a better cracking configuration and higher strength reserve close to colapse.

A utilização de tubos de aços de alta resistência e baixa liga (ARBL) é comumente o mais indicado, segundo a norma American Petroleum Institute (API) 5L, para o transporte de óleo e de gás sob pressão. Em vista da necessidade de adequar as tubulações em campo de acordo com o relevo de cada região, são realizados curvamentos a quente em tubos. Durante este processo, o tubo sofre tratamentos térmicos, modificam sua microestrutura e propriedades mecânicas. Neste sentido, foram realizados, neste trabalho, tratamentos térmicos de têmpera e revenimento, com o objetivo de melhorar as propriedades mecânicas nas juntas soldadas. O material utilizado foi o tubo API 5L X80 com diâmetro de 40 polegadas e 16 mm de espessura. Foi realizada a soldagem circunferencial com passe de raiz pelo processo Metal Active Gas (MAG) com curto circuito controlado, gás de proteção 80% Ar e 20% CO2, passes de enchimento e acabamento pelo processo de soldagem com arame tubular (AT) e gás de proteção 75% Ar 25% CO2. Os consumíveis utilizados no passe de raiz foi arame sólido ER80S-G e nos passes de enchimento e acabamento o arame tubular E101T1GM-H8. Realizaram-se combinações de tratamentos térmicos de têmpera e revenimento com variações nas temperaturas de ambos. Para analisar a influência destes tratamentos térmicos foram realizados ensaios de tração, ensaios de microdureza e ensaios de impacto Charpy às temperaturas de -40 ºC e 0 ºC no metal de solda (MS) e na zona afetada pelo calor (ZAC). Alguns tratamentos térmicos realizados aumentaram a resistência à tração e a tenacidade em relação à condição como soldada, mas o melhor tratamento térmico foi o de tempera a partir de 900ºC seguindo de revenimento a 650 ºC. / The use of high strength low alloy steels tubes is commonly the most appropriate for transporting oil and gas under pressure, according to API 5L. In view of the need to adapt the pipes in the field according to the relief of each region, they are held hot bend in pipelines. During the process, the product undergoes thermal treatments which modify its microstructure and mechanical properties. It has been carried out, in this work, heat treatment of quenching and tempering, with the objective of obtaining the best mechanical properties in the welded joints. The material was API 5L X80 pipe with a 40 inch diameter and 16 mm thick. The circumferential welding pass root was done by GMAW with controlled short circuit transfer, shielding gas 80%Ar and 20% CO2. Filling and finishing passes were welded with FCAW using a shielding gas 75% Ar and 25% CO2. Consumables used in the root pass were ER80S-G and in the filling and finishing passes E101T1GM-H8. There were done four heat treatments of quenching and tempering for 2 hours. The results were analyzed by tensile test, hardness and Charpy V impact tests at temperatures of -40 °C and 0 °C in the weld metal and HAZ. The heat treatments influence statistically on the mechanical properties of welded joints related to as welded condition. The best result was quench heat treatment at 900°C followed by tempering at 650°C.

Este trabalho apresenta resultados de uma análise teórico-experimental sobre a resistência à compressão de perfis I soldados de aço, formados por chapas cortadas a maçarico. A construção metálica no Brasil utiliza os perfis I soldados formados por chapas cortadas a maçarico em virtude da pouca disponibilidade no mercado dos perfis laminados. Os perfis soldados brasileiros apresentam dimensões (altura, largura de mesa e espessura) diferentes das encontradas nos perfis laminados e soldados, fabricados em outros países. Apresentam-se os principais parâmetros envolvidos na formulação das curvas de resistência à compressão para perfis soldados de pequenas dimensões, tais como: tensões residuais, imperfeições geométricas iniciais e seus efeitos no cálculo da resistência à compressão dos perfis soldados compostos por chapas cortadas a maçarico. Os perfis ensaiados são das séries PS 200x25, PS 225x29 e CS 150x25, sendo que foram obtidos resultados experimentais da força normal crítica e das imperfeições geométricas iniciais para três modelos de cada série com quatro índices de esbeltez diferente. / This work presents results of theoretical and experimental analysis about the compressive strength of steel welded I-shapes manufactured from flame-cut plates. Steel construction in brazil uses these welded I-shapes because of the limited availabilily of hot-rolled shapes in the market. The brazilian welded shapes have dimensions (height, flange width and thickness) that differ from steel welded shapes manufactured in other countries. It presents the main parameters in the formulation of the compressive strength curves for welded shapes of small dimensions as: residual stresses, geometrical initial crookedness and their effects in the evaluation of the compressive strength of the welded shapes manufactured from flame-cut plates. The tested shapes are of PS 200x25, PS 225x29 and CS 150x25 series. Test results were obtained for the critical axial load and the geometrical initial crookedness to three models with four different slenderness ratio in each serie.