With the growth in pipeline installations all over the world, there is a great demand for highly productive and robust welding systems. Mechanised pipe welding has been developed over the last 50 years and the present focus is towards development of automated pipeline welding systems. Pipeline welding automation is aimed at reducing costs and improving the installation quality. To attain fully automated pipe welding systems there is a need to rely on sensors and controls systems to mimic human like capabilities, such as visual inspection, in real time. The key aim of this work is to develop and evaluate methods of automatic assessment of weld bead shape and quality during narrow gap GMAW of transmission pipelines. This implies that the measured bead profile will be assessed to determine whether the bead shape will cause defects when the subsequent pass is deposited. Different approaches have been used to conquer the challenge that is emulating human reasoning, all with different objectives in mind. In spite of extensive literature research performed, very little information was found concerning the real time determination and assessment of bead shape quality and none of it was reported to be applied successfully to the pipeline industry. Despite the continuous development of laboratory laser vision systems commercial ones have been on the market for decades, some specifically developed for the welding application. Laser vision sensor systems provide surface profile information, and are the only sensors which can satisfactorily measure bead profile on a narrow groove. In order to be able to use them to automatically assess weld bead shape and quality, a deep understanding of their characteristics and limitations needs to be achieved. Once that knowledge was attained it was then applied to determine the best sensor configuration for this purpose. After that the development of human like judgment algorithms were developed to accomplish the aim that was set. Empirical rules were obtained from an experienced welder regarding the acceptability of bead shapes and were then applied in the developed system with good results. To scientifically evaluate and determine the rules to use in this system, further experiments would be required. The output of the system developed showed very accurate, reliable and consistent results that were true to the external measurements and comparisons performed. The developed system has numerous applications in the pipeline industry and it could easily be implemented on commercial systems.

This research is aimed at understanding the effect of thermal cycles on the metallurgical and microstructural characteristics of the heat affected zone of a multi-pass pipeline weld. Continuous Cooling Transformation (CCT) diagrams of the pipeline steel grades studied (X65, X70 and X100) were generated using a thermo mechanical simulator (Gleeble 3500) and 10 mm diameter by 100 mm length samples. The volume change during phase transformation was studied by a dilatometer, this is to understand the thermodynamics and kinetics of phase formation when subjected to such varying cooling rates. Samples were heated rapidly at a rate of 400°C/s and the cooling rates were varied between t8/5 of 5.34°C/s to 1000°C/s. The transformation lines were identified using the dilatometric data, metallographic analysis and the micro hardness of the heat treated samples. Two welding processes, submerged arc welding (SAW) and tandem Metal Inert Gas (MIG) Welding, with vastly different heat inputs were studied. An API-5L grades X65, X70 and X100 pipeline steels with a narrow groove bevel were experimented with both welding processes. The welding thermal cycles during multi-pass welding were recorded using thermocouples. The microstructural characteristics and metallurgical phase formation was studied and correlated with the fracture toughness behaviour as determined through the Crack Tip Opening Displacement (CTOD) tests on the welded specimens. It was observed that SAW process is more susceptible to generate undesirable martensite-austenite (M-A) phase which induce formation of localised brittle zones (LBZ) which can adversely affect the CTOD performance. Superimposition of the multiple thermal cycles, measured in-situ from the different welding processes on the derived CCTs, helped in understanding the mechanism of formation of localised brittle zones. Charpy impact samples were machined from the two X65 and X70 grades, for use in thermal simulation experiments using thermo mechanical simulator (Gleeble). The real thermal cycles recorded from the HAZ of the SAW were used for the thermal simulations, in terms of heating and cooling rates. This is to reproduce the microstructures of the welds HAZ in bulk on a charpy impact sample which was used for impact toughness testing, hardness and metallurgical characterisation. The three materials used were showing different response in terms of the applied thermal cycles and the corresponding toughness behaviours. The X65 (a) i.e. the seamless pipe was showing a complete loss of toughness when subjected to the single, double and triple thermal cycles, while the X65 (b), which is a TMCP material was showing excellent toughness in most cases when subjected to the same thermal cycles at different test temperatures. The X70 TMCP as well was showing a loss of toughness as compared to the X65 (b). From the continuous cooling transformation diagrams and the thermally simulated samples results it could be established that different materials subjected to similar thermal cycle can produce different metallurgical phases depending on the composition, processing route and the starting microstructure.

O câncer de próstata é um problema de saúde pública no Brasil, sendo a segunda causa de óbitos por câncer em homens, superado apenas pelo câncer de pulmão. Entre os possíveis tratamentos disponíveis para o câncer de próstata encontra-se a braquiterapia, onde, pequenas sementes contendo o radioisótopo 125I são implantadas na próstata. A semente consiste de uma cápsula de titânio selada de 0,8 mm de diâmetro externo e 4,5 mm de comprimento, contendo um fio de prata com 125I adsorvido. A soldagem por arco plasma é uma das técnicas viáveis para selagem, o equipamento tem um custo menor que o de outros processos. Constituem os objetivos deste trabalho o desenvolvimento e a validação do procedimento de selagem utilizando processo de soldagem plasma e a elaboração de rotinas para selagem segundo as Boas Práticas de Fabricação. O desenvolvimento do trabalho apresentou as seguintes fases: corte e limpeza do material, determinação dos parâmetros de soldagem, desenvolvimento de dispositivos para fixação do tubo de titânio durante o processo de soldagem, ensaios de validação de fontes seladas conforme norma ISO 2919 Sealed Radioactive Sources General Requirements and Classification, ensaios de estanqueidade conforme norma ISO 9978 Sealed Radioactive Sources Leakage Test Methods e ensaio metalográfico. O procedimento desenvolvido para a selagem das sementes de 125I mostrou-se eficiente, atendendo a todos os requisitos estabelecidos na norma ISO 2919. Os resultados apresentados neste trabalho possibilitaram a elaboração de rotinas de fabricação segundo as orientações apresentadas na resolução RDC nº 59 Boas Práticas de Fabricação de Produtos Médicos da ANVISA - Agência Nacional de Vigilância Sanitária. / The prostate cancer, which is the second cause of death by cancer in men, overcome only by lung cancer, is a problem of public health in Brazil. Brachytherapy is among the possible available treatments for prostate cancer, in which small seeds containing 125I radioisotope are implanted in the prostate. The seed consists of a titanium sealed capsule with 0.8 mm external diameter and 4.5 mm length, containing a central silver wire with adsorbed 125I. The plasma arc welding is one of the viable techniques for the sealing process. The equipment used in this technique is less costly than in other processes. The main objective of this work was the development and the validation of the welding procedure using plasma welding process and the elaboration of a sealing routine according to Good Manufacturing Practices. The development of this work has presented the following phases: cut and cleaning of the titanium material, determination of the welding parameters, development of a device for holding the titanium tube during the welding process, validation of sealed sources according to ISO 2919 Sealed Radioactive Sources - General Requirements and Classification, leakage test according to ISO 9978 Sealed Radioactive Sources - Leakage Test Methods and metallographics assays. The developed procedure, to seal 125I seeds using plasma welding process, has shown to be efficient, satisfying all the established requirements of ISO 2919. The results obtained in this work have given the possibility to establish a routine production process according to the orientations presented in resolution RDC nº 59 - Good Manufacturing Practices to Medical Products of the ANVISA - National Agency of Sanitary Surveillance.

Este trabalho tem por objetivo simular a zona de grãos grosseiros da ZAC através da simulação computacional em software de elementos finitos e submeter amostras de um aço microligado API 5L X100M a ciclagens térmicas na Gleeble para representar a região de estudo e, dessa forma, caracterizar e comparar o comportamento mecânico e microestrutural do material frente a diferentes aportes térmicos. Foram realizadas simulações de soldagem por arco submerso (SAW) em software computacional de elementos finitos para os aportes térmicos 2.0, 2.5, 3.0, 3.5, 4.0, 4.5 e 5.0 kJ/mm e obtidos os ciclos térmicos de um local correspondente à zona de grãos grosseiros da zona afetada pelo calor (ZAC). Em seguida, o ciclo obtido para cada aporte simulado foi utilizado como fonte para a simulação térmica na Gleeble de amostras do metal de base de um tubo produzido para a norma API 5L grau X100M. Em seguida, foram realizados ensaios de microdureza nos corpos de prova após simulações térmicas na Gleeble e no material de base como recebido, para efeitos de comparação dos resultados. Para cada aporte de calor simulado, um corpo de prova foi destinado para avaliação de microdureza e posterior análise microestrutural. As amostras remanescentes foram submetidas a ensaio de impacto charpy em temperatura de 0°C para as amostras de aporte de calor 2.5, 3.0, 4.0 e 4.5 kJ/mm e, para os demais aportes térmicos foi feito levantamento de curva de transição entre as temperaturas de -60 a 24°C. Os resultados obtidos demonstraram que existe uma correlação entre tenacidade, aporte de calor e morfologia do constituinte MA gerado na região de estudo, de maneira que foram obtidos menores valores de energia absorvida conforme maior o aporte de calor simulado. Também, nessas condições foi observado que o constituinte MA apresentou uma maior tendência ao formato globular que ao alongado. / The objective of this study is to simulate the coarse grain from the heat affected zone (CGHAZ) through computer simulation in finite element software and to submit samples of an API 5L X100M micro alloyed steel to thermal cycling in Gleeble to replicate this region and thus characterize and compare the mechanical and microstructural behavior of the material face to different heat inputs. Submerged Arc Welding (SAW) simulations were performed in finite elements software for heat inputs of 2.0, 2.5, 3.0, 3.5, 4.0, 4.5 and 5.0 kJ/mm. Afterwards, the thermal cycle curve obtained for each simulated heat input was used as the source for the thermal simulation in Gleeble of samples taken from the base metal of a pipe produced for API 5L standard and X100M grade. Subsequently, microhardness tests were performed in the Gleeble simulated samples and in as received material for the purpose of comparing the results. For each heat input simulated, one test specimen was used for microhardness and microstructural analysis. The remaining samples were subjected to a charpy V notch impact test at the temperature of 0°C for the 2.5, 3.0, 4.0 e 4.5 kJ/mm heat inputs and a transition curve was plotted between -60 up to 24°C for heat inputs 2.0, 3.5 and 5.0 kJ/mm. The obtained results demonstrates that there is a correlation between toughness, heat input and the MA constituent morphology, in a way that lower values of absorbed energy were obtained as the simulated heat input increased. In this condition, it was also observed that the MA constituent showed a greater tendency to become more globular than elongated.

A utilização do eletrodo tubular no processo de soldagem a arco submerso leva a um aumento na produtividade com um custo relativamente baixo, pois não requer investimentos complementares em equipamentos. A mudança do eletrodo sólido para o tubular acarreta variações microestruturais no metal de solda que influenciam as propriedades mecânicas, tais como dureza, tração e tenacidade ao impacto. Este trabalho tem como objetivo principal estudar a tenacidade à fratura dinâmica do metal de solda, mostrando que o uso do eletrodo tubular diminui a propagação de trincas ao impacto, além de melhorar as propriedades de dureza e tração. Para a confecção da junta soldada foi utilizado o aço ASTM-A516 com espessura de 37,5 mm; para o metal de solda, o eletrodo sólido AWS EM12K, com diâmetro de 4,0 mm, e fluxo AWS F6A4 e o eletrodo tubular AWS E71T-5, com diâmetro de 4,0 mm, fabricado em caráter experimental, untamente com os fluxos AWS F6A4 e AWS F7A8 (Fluxo Neutro). Os ensaios de impacto, dureza e tração foram realizados em corpos de prova com e sem alívio de tensão, e o ensaio Charpy instrumentado em corpos de prova entalhados e em corpos de prova entalhados e com trinca por fadiga, nas temperaturas de 25, 200, 400 e 600OC. O metal de solda utilizando eletrodo sólido foi o que mostrou menor percentual de ferrita acicular (54%), enquanto que o utilizando eletrodo tubular e fluxo AWS F6A4 foi o que mostrou maior percentual de ferrita acicular (89%). Os ensaios de dureza mostraram uma influência do microconstituinte ferrita acicular: maior dureza para o maior percentual de ferrita acicular. Os limites de resistência e de escoamento também sofreram o efeito deste microconstituinte, apresentando maiores valores quando os percentuais de ferrita acicular foram maiores. Para a análise da tenacidade para o início de propagação da trinca foram utilizados os métodos da variação da taxa da flexibilidade elástica, o método da energia da carga máxima revisada e o método da energia da carga máxima. Foram calculados os valores de JId e de KJd (K derivado de J). Os únicos valores validados, de acordo com a norma, foram os de JId calculados pelo método da variação da taxa da flexibilidade elástica. Os resultados encontrados, utilizando este método, mostraram, à 600OC, a influência da ferrita acicular, sendo que o metal de solda com maior percentual deste microconstituinte forneceu maior valor de tenacidade. Os valores de JId utilizando o método da variação da taxa da flexibilidade elástica para os corpos de prova com trinca por fadiga ficaram próximos aos resultados encontrados quando o ensaio foi realizado em corpos de prova somente entalhados. Os resultados mostraram que a substituição do eletrodo sólido pelo tubular levou à maior tenacidade e a propriedades mecânicas superiores. / The cored wire application in the submerged arc welding process leads to a increase productivity with relative low cost, because it doesn’t require complementary investments in equipments. Changing from solid to cored wire promotes microstructural modification in the weld metal that enhances mechanical properties, such as hardness, stretching and impact toughness. The principal aim of this work is to study the dynamic fracture toughness of the weld metal. The use of cored wire reduces the impact crack propagation, as well as hardness and strength properties. The welded plate was composed of ASTM-A516 steel with 37.5 mm thickness and for making the weld metal was utilized AWS EM12K wire, with 4.0 mm diameter, and AWS F6A4 flux, and AWS E71T-5 cored wire, with 4.0 mm diameter, making in experimental mode, with AWS F6A4 and AWS F7A8 (Neutral Flux) fluxes. Impact, hardness and tensile tests were carried out in specimens with and without stress relief. The instrumented Charpy tests were carried out at notch and notch plus fatigue crack specimens, at 25, 200, 400 and 600OC temperatures. The solid wire weld metal produced 53.9% of acicular ferrite, while the cored wire weld metal and AWS F6A4 flux produced 88.8% of acicular ferrite. The hardness values were influenced by acicular ferrite and showed higher hardness for acicular ferrite higher values. Tensile strength and yield stress data suffered the same effect of this micro constituent also, they had bigger amount when the acicular ferrite percentiles were bigger. For toughness analysis to crack propagation start were utilized the compliance changing rate method, the energy revised method, and the maximum load energy method. JId and KJd (K derived of J) values were calculated according to the standards. The results met for this method had acicular ferrite influence at 600OC, where the weld metal with the biggest micro constituent had bigger toughness value. The JId values utilized the compliance changing rate method for the precracked specimen got values near to the notched specimen. The change solid wire by the cored wire had better toughness, and it gets better the other mechanical properties.

Continuing an investigation on using FSP to heal stress corrosion cracks (SCC) in welds on nuclear reactors, this study seeks to use AM in addition to FSP to aid crack repair. Previous studies address that current repair technology on nuclear reactors involves the use of TIG welding which can allow helium atoms to aggregate and form voids at the grain boundaries. This weakens the material and renders the repair ineffective. Another previous study evaluated the effectiveness of FSP alone in repairing SCC which did have defects depending on the parameters used during FSP. This study evaluated the use of AM in addition to FSP. Literature is available on FSP and AM separately and literature is available on technologies that used both them together. However, the current processes that are available that use both AM and FSP can be expensive and may be impractical for some purposes. This study shows a new process that is both less expensive and more practical in SCC repair. Initial proof of concept trials was performed on 1018 mild steel using both wire fed additive and insert additive technologies. A slot would be removed and filled in with an additive process and processed using FSP. Because of poor repeatability, substantial distortion, and voids present this study went forward using insert technologies in further experiments rather than wire wed additive technologies. In addition, the depth and width of the insert or area where the added material would be placed was varied in initial trails. Tensile testing was performed on initial steel trials and the stainless steel experiments and it demonstrated a correlation between depth of the added material and the tensile strength. Micro-hardness mapping performed on initial steel trials also showed hardening in the FSP stir zone. Three-point bend tests were performed to show that an existing crack underneath the FSP zone would not propagate through the nugget. All evaluations supported a substantial increase in yield strength increased after FSP.

A parallel finite element code with adaptive meshing was developed and used to study three dimensional, time-dependent fluid flows caused by thermocapillary convection as well as temperature and dopant distribution in fusion welding and floating zone crystal growth. A comprehensive numerical model of the three dimensional time-dependent fluid flows in a weld pool had been developed. This model considered most of the physical mechanisms involved in gas tungsten arc welding. The model helped obtaining the actual chaotic time-dependent melt flow. It was found that the fluid flow in the weld pool was highly complex and influenced the weld pool’s depth and width. The physicochemical model had also been studied and applied numerically in order to simulate the surfactant adsorption onto the surface effect to the surface tension of the metal liquid in a weld pool. Another model, a three dimensional time-dependent, with adaptive mesh refinement and coarsening was applied for simulating the effect of weak flow on the radial segregation in floating zone crystal growth. The phase change equation was also included in this model in order to simulate the real interface shape of floating zone. In the new parallel code, a scheme that keeps the level of node and face instead of the complete history of refinements was utilized to facilitate derefinement. The information was now local and the exchange of information between each and every processor during the derefinement process was minimized. This scheme helped to improve the efficiency of the parallel adaptive solver. / QC 20100527

Modern arc welding machines utilize controllable high frequency DC/DC power supply with high dynamic and steady state current regulation performance. In the design robustness, small size and low weight, low complexity, and high efficiency are the defining criteria. The most suitable approach for a 5 kW arc welding machine power supply application is the high frequency Full-Bridge Phase-Shifted Zero Voltage Switching (FB-PS-ZVS) DC/DC converter with an isolation transformer. This converter not only gives the advantage of zero voltage switching for a wide load current range, it also provides reduced Electromagnetic Interference (EMI) and reduced component stress compared to standard PWM converters. In this thesis a FB-PS-ZVS DC/DC converter with 5 kW power rating is designed for modern arc welding machine applications. IGBTs are utilized at 50 kHz switching frequency for high efficiency and control bandwidth. The output current of the DC/DC converter is controlled via a Digital Signal Processor (DSP) control platform. The performance of the designed DC/DC converter is evaluated via the computer simulations and the experimental study of the constructed prototype.

Gas Metal Arc Welding (GMAW) is one of the main methods used to join structural members. One of the largest challenges involved in production of welds is ensuring the quality of the weld. One of the main factors attributing to weld quality is penetration depth. Automatic control of the welding process requires non-contact, non-destructive sensors that can operate in the presence of high temperatures and electrical noise found in the welding environment. Inspection using laser generation and electromagnetic acoustic transducer (EMAT) reception of ultrasound was found to satisfy these conditions. Using this technique, the time of flight of the ultrasonic wave is measured and used to calculate penetration depth. Previous works have shown that penetration depth measurement performance is drastically reduced when performed during welding. This work seeks to realize in-process penetration depth measurement by compensating for errors caused by elevated temperature. Neuro-fuzzy models are developed that predict penetration depth based on in-process time of flight measurements and the welding process input. Two scenarios are considered in which destructive penetration depth measurements are or are not available for model training. Results show the two scenarios are successful. When destructive measurements are unavailable, model error is comparable to that of offline ultrasonic measurements. When destructive measurements are available, measurement error is reduced by 50% compared to offline ultrasonic measurements. The two models can be effectively applied to permit in-process penetration depth measurements for the purpose of real-time monitoring and control. This will reduce material, production time, and labor costs and increase the quality of welded parts.

Objectif : Examiner la relation entre une exposition professionnelle aux fumées de soudage au gaz et à l’arc et le risque de développer un cancer du poumon, chez des travailleurs provenant de différents milieux de travail et exposés à de nombreuses substances de différentes concentrations. Méthodes : Nous avons mené deux études cas-témoins basés sur la population montréalaise (1979-86 et 1996-2001), incluant respectivement 857 et 736 cas, ainsi que des témoins appariés selon la fréquence des cas, le sexe et le lieu de résidence. Un historique détaillé des emplois occupés fut obtenu par entrevue et évalué par une équipe d’experts afin d’estimer l’intensité, la durée ainsi que l’exposition cumulative à un grand nombre de substances. Les fumées de soudage au gaz et à l’arc sont parmi les substances évaluées et nous avons pu calculer un rapport de cote (RC) et son intervalle de confiance de 95% (IC 95%) pour le risque de cancer du poumon en utilisant la régression logistique et en ajustant pour l’historique de tabagisme et plusieurs autres covariables pertinentes. Des analyses subséquentes ont permis d’explorer d’autres voies, comme la modification des effets observés par le tabagisme. Résultats : Les résultats obtenus à partir des deux études étant assez similaires, nous avons donc pu les combiner pour former une seule étude. Aucune association statistiquement significative n’a été trouvée entre le cancer du poumon et les fumées de soudage au gaz (RC=1,13; IC 95%=0,90-1,42) et les fumées de soudage à l’arc (RC=1,01; IC 95%=0,80-1,26). Par contre, dans le sous-groupe des non-fumeurs et fumeurs très légers, nous avons trouvé un risque accru de cancer du poumon en relation avec les fumées de soudage au gaz (RC=2,78; IC 95%=1,66-4,65) et à l’arc (RC=2,20; IC 95%=1,32-3,70). En se concentrant sur ce sous-groupe, nous avons trouvé un risque encore plus élevé de développer un cancer du poumon pour ceux exposé à des doses plus substantielles, pour le soudage au gaz (RC=4,63; IC 95%=2,14-10,03) et à l’arc (RC=3,45; IC 95%=1,59-7,48). Discussion : Globalement, aucun excès de risque causé par une exposition aux fumées de soudage n’a été détecté, mais un excès a été trouvé chez les non-fumeurs et fumeurs légers uniquement et ce, pour les deux types de fumées de soudage. L’effet des fumées de soudage peut être voilé chez les fumeurs, ou bien les non-fumeurs pourraient être plus vulnérables. / Objective: To investigate the relationship between occupational exposure to gas and arc welding fumes and the risk of lung cancer among workers exposed to various agents at various concentrations and over a wide range of occupations. Methods: We conducted two population-based case-control studies in Montreal (1979-1986 and 1996-2001), including 857 and 736 cases respectively and frequency-matched controls. Detailed job histories were obtained by interview and evaluated by an expert team of chemist-hygienists to estimate intensity, duration and cumulative exposure to multiple substances for each job. Gas and arc welding fumes were among the agents evaluated, and we estimated odds ratios (ORs) and 95% confidence intervals (CIs) for lung cancer using logistic regression, adjusting for smoking history and other relevant covariates. Subsequent analyses allowed us to explore other avenues, such as effect-measure modification by smoking. Results: The results from both studies were similar, so a pooled analysis was conducted. No significant association was found between lung cancer and gas welding fumes (OR=1,13; 95% CI=0,90-1,42) or arc welding fumes (OR=1,01; 95% CI=0,80-1,26). However, when restricting attention to light and non-smokers, we found an increased risk of lung cancer in relation to gas welding fumes (OR=2,78; 95% CI=1,66-4,65) and arc welding fumes (OR=2,20; 95% CI=1,32-3,70). When we further narrowed attention to workers with the highest cumulative exposures, we found even higher risk of lung cancer for gas (OR=4,63; 95% CI=2,14-10,03) and arc welding fumes (OR=3,45; 95% CI=1,59-7,48). Discussion: There was no detectable excess risk due to welding fumes among smokers; but among light and non-smokers there were excess risks related to both types of welding fumes. The effect of welding fumes may be masked in smokers or light and non-smokers may be more vulnerable.