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1
Harris, I. D. "High-speed GMAW and laser GMAW hybrid welding of steel sheet." Thesis, Cranfield University, 2009. http://dspace.lib.cranfield.ac.uk/handle/1826/4571.
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Arc welding is the most widely used set of joining technologies in industry today. The automotive tier supplier network and light manufacturing are significant users of arc welding, particularly gas metal arc welding (GMAW) and pulsed GMAW (GMAW-P). For sheet metal welding the majority of welds are single pass fillet welds on T-butt, lap, or edge joints. A fundamental problem and limitation to the use of higher travel speeds in GMAW is the phenomenon of weld bead humping, a weld profile defect with a wavelike profile to the weld bead that has peaks and troughs in the longitudinal direction.
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Egerer, Johannes. "The Golgin GMAP-210." Diss., lmu, 2008. http://nbn-resolving.de/urn:nbn:de:bvb:19-88207.
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SILVA, Eduardo Pereira da. "Avaliação comparativa dos processos de soldagem GMAW convencional e GMAW-STT® em aço inoxidável duplex UNS S32205." reponame:Repositório Institucional da UNIFEI, 2018. http://repositorio.unifei.edu.br/xmlui/handle/123456789/1624.
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Este trabalho se propôs a investigar a influência dos parâmetros de soldagem do processo GMAW derivativo STT (Surface Tension Transferᵀᴹ) na soldagem do aço inoxidável duplex (AID) UNS S32205, comparando seus resultados ao processo GMAW convencional. Para tanto, foi realizado o planejamento experimental possibilitando a interação dos fatores estudados em todos os seus níveis, posteriormente foram realizadas as soldas, seguida da preparação dos corpos de prova para caracterização microestrutural, ensaios de tração mecânica, ensaios de impacto e ensaio de microdureza. As soldas foram realizadas emjuntas em chanfro utilizando aporte de energia entre 1,48 e 3,17 kJ/cm. A variação dos parâmetros nos níveis de trabalho adotados mostrou-se significativa quanto a influência nas propriedades microestruturais, geométricas e mecânicas da junta soldada. As soldas realizadas pelo processo GMAW-STT® apresentou melhores características geométricas e microestruturais do que o processo convencional com a mesma energia de soldagem, resultando em melhores propriedades mecânicas, em contrapartida algumas condições propiciaram a precipitação de fases intermetálicas na zona termicamente afetada (ZTA) e adjacências. O resultado tanto da caracterização microestrutural como dos ensaios mecânicos evidenciou a alteração de características fundamentais do material em estudo em função do tipo de processo utilizado, destacando os benefícios do processo GMAW-STT® em relação ao convencional, não somente no controle preciso das variáveis de entrada, mas também na qualidade final das juntas soldadas dentro dos limites trabalhados nesta pesquisa.
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Prakki, Anuradha. "Influência de aditivos nas propriedades de comonômeros, copolímeros e compósitos a base de Bis-GMA, diluído com TEGDMA ou análogos sintetizados do Bis-GMA (CH3Bis-GMA e CF3Bis-GMA)." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/25/25131/tde-11102007-093822/.
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O objetivo deste estudo foi avaliar a influência de dois aditivos, propionaldehyde (propanal aldeído) e 2,3-butanedione (diquetona diacetil), nas propriedades de comonômeros, copolímeros e resinas compostas à base de Bis-GMA, quando diluído com TEGDMA, Bis-GMA propoxilado (CH3Bis-GMA) e Bis-GMA propoxilado fluorinado (CF3Bis-GMA). Comonômeros, copolímeros e compósitos experimentais foram preparados combinando Bis-GMA com TEGDMA, CH3Bis-GMA, CF3Bis-GMA e, aldeído (24 e/ou 32 mol%) e diquetona (24 e/ou 32 mol%). No caso dos compósitos, partículas híbridas silanizadas (bário aluminosilicato; 60 peso%) foram adicionadas aos comonômeros. Para a fotopolimerização, adicionou-se canforoquinona (0,2 peso%) e N,N-dimetil-p-toluidina (0,2 peso%). Os comonômeros e copolímeros experimentais tiveram as seguintes propriedades avaliadas: viscosidade, contração de polimerização, grau de conversão, ângulo de contato (em esmalte, dentina e vidro), temperatura de transição vítrea (DSC e equação de Fox), microdureza, alteração de rugosidade superficial e desgaste por abrasão. Os compósitos experimentais, tiveram avaliadas as seguintes propriedades: resistência flexural, módulo de elasticidade, tração diametral, módulo de resiliência, microdureza, alteração de rugosidade superficial e desgaste por abrasão. Os sistemas Bis-GMA/TEGDMA e Bis-GMA/CH3Bis-GMA tiveram suas propriedades significantemente alteradas pela incorporação de aditivos (propanal ou diquetona). Os aditivos (propanal/diquetona) não influenciaram de forma significante as propriedades do sistema Bis-GMA/CF3Bis-GMA. O efeito dos aditivos nas propriedades dos materiais analisados relaciona-se à sua abilidade em aumentar o grau de conversão de alguns sistemas resinososThe purpose of this study was to evaluate the effect of two additives, propionaldehyde (aldehyde) and 2,3-butanedione (diketone), on the properties of Bis-GMA based comonomer, copolymer and composites when diluted with TEGDMA, propoxylated Bis- GMA (CH3Bis-GMA) and propoxylated fluorinated Bis-GMA (CF3Bis-GMA). Experimental comonomer/copolymer/composites were prepared combining Bis-GMA and TEGDMA, CH3Bis-GMA, CF3Bis-GMA, with aldehyde (24 and/or 32 mol%) and diketone (24 and/or 32 mol%). For composites, hybrid treated filler (barium aluminosilicate glass; 60 wt%) was added to monomer mixtures. Photopolymerization was effected by using camphorquinone (0.2 wt%) and N,N-dimethyl-p-toluidine (0.2 wt%). Experimental comonomer/copolymers viscosity, polymerization shrinkage, degree of conversion, contact angle (enamel, dentin and glass surfaces), glass transition temperature (DSC and Fox equation), microhardness, surface roughness changes and wear were evaluated. Experimental composites, flexural strength, modulus of elasticity, diametral tensile strength, modulus of resilience, microhardness, surface roughness changes and wear were also assessed. Bis-GMA/TEGDMA and Bis- GMA/CH3Bis-GMA systems had properties significantly influenced by incorporation of additives (either propanal or diketone). Additives (propanal/diketone) did not significantly influence on Bis-GMA/CF3Bis-GMA system properties. The effect of additives on the evaluated material properties is mainly attributed to their ability in improving some resin systems degree of conversion
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Santana, Ivan Jose de. "Modelamento matemático do processo de soldagem GMAW." Universidade Federal de Minas Gerais, 2010. http://hdl.handle.net/1843/BUDB-8DRHR9.
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This thesis describes the development and validation of a mathematical model that describes the electrical and operational behavior of GMA welding. Initially it was developed a static model that was able to simulate welding conditions characterized by small current and tension variation usually found with free-flight metal transfer. Afterwards, a dynamic model capable to simulate abrupt current and voltage changes usually observed in short-circuit welding was developed. These models were based on aset of equations that describes the power source characteristics, the voltage drop along the electric arc and the welding circuit and the energy balance on the wire tip. Despite the large number of variables of GMA welding and the complex relation among them, the results from the models agreed well with data from the literature and to experimentalresults. The dynamic model was able to simulate the welding parameters values (with less 10% of error) and to predict transitions in metal transfer mode. The mean current and voltage and their waveform variation, arc length, short circuit frequency and metal transfer transition were obtained as a function of wire feed rate, contact tip-to-work distance and open circuit voltage. The results indicate that the developed models,specially the dynamic one, are able to estimate welding parameters for specific welding conditions and can contribute to a more fundamental understanding of this welding process.Este trabalho descreve o desenvolvimento e validação de modelos matemáticos elaborados para simular o processo de soldagem GMAW, particularmente em seus aspectos elétricos e operacionais. Inicialmente, foi desenvolvido um modelo capaz de simular o processo sem grandes variações de corrente e tensão (definido, neste trabalho,como modelo estático), como por exemplo, com o processo operando em transferência metálica por vôo livre. Na sequência, foi desenvolvido um novo modelo (definido como dinâmico), que de forma mais abrangente simula, também, o processo frente a variações bruscas de corrente e tensão, um exemplo seria, quando o processo opera comtransferência metálica por curtos-circuitos. Estes modelos foram baseados em um conjunto de equações, que descrevem as características operacionais da fonte de energia, as quedas de tensão que ocorrem no arco elétrico e nos componentes do circuito de soldagem, e em um balanço de energia na ponta do arame. De uma forma geral, e levando-se em conta o grande número de variáveis envolvidas e a complexa inter-relação entre estas, os parâmetros simulados pelos modelos quando comparados com dados experimentais provenientes de testes de soldagem (deposição de cordão sobre chapa) e dados obtidos da literatura apresentaram bons resultados. O modelo dinâmico, por exemplo, foi capaz de simular com erros inferiores a 10% o comportamento de diferentes parâmetros do processo, assim como a transição de modos de transferência metálica. Os parâmetros e os aspectos do processo, que foram analisados, incluem, por exemplo, os valores médios de corrente e tensão, assim como seus oscilogramas, o comprimento de arco, a frequência de curtos-circuitos e a mudança de modo de transferência metálica em função da velocidade de alimentação, da distância entre o bico de contato e a peça e da tensão em vazio. Os resultados indicam que os modelos desenvolvidos, sobretudo o dinâmico, sejam capazes de facilitar o entendimento fundamental deste processo e determinar de maneira mais conveniente os parâmetros de soldagem mais adequados para uma situação específica de soldagem.
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De, Luca Stefano. "Studio orbitale di missione CubeSat con applicativo GMAT." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
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La missione per cui questo elaborato è stato redatto è relativa allo studio orbitale di un satellite CubeSat con lo scopo di garantire una navigazione nello spazio autonoma con l’aiuto dei satelliti GPS. E' stata studiata, in particolare, la natura di un nanosatellite, sempre più utilizzato ai giorni nostri per missioni di lancio nello spazio. Si è fatto uso di software quali GMAT e Matlab che hanno permesso di studiare i dati dei sottosistemi di telecomunicazione e di controllo termico utili ai fini della missione.
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Quintino, L. "Fusion characteristics in P-GMAW of mild steel." Thesis, Cranfield University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.483022.
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Neto, João Teles de Carvalho. "Descrição analítica da magnetização induzida pela metodologia GMAX." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-07092007-035436/.
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A metodologia GMAX, (Gradient-Modulated Adiabatic Excitation), caracteriza-se pelo uso de pulsos adiabáticos para localização de volumes em espectroscopia e seleção de fatias em MRI. A sua utilidade surge do interessante perfil de inversão da magnetização transversal induzido ao longo da amostra. Entretanto, a interpretação desse comportamento tem sido dada apenas de forma qualitativa, através da utilização da condição de adiabaticidade como ponto de partida. Neste trabalho é apresentada uma descrição analítica partindo da solução em termos da função hipergeométrica para os pulsos sech e tanh. A partir desse procedimento encontramos um conjunto de resultados com os quais é possível inferir analiticamente o comportamento característico da magnetização, tendo como objetivo obter um maior controle da magnetização a partir dos parâmetros da metodologia que proporcionam interpretação física.The Gradient-Modulated Adiabatic Excitation (GMAX) methodology is characterized by the use of adiabatic pulses for volume localization in spectroscopy and slice selection in MRI. Its use derives from the interesting nodal point transverse magnetization profile induced throughout the sample. Nevertheless, the interpretation of such behavior for the magnetization has been of qualitative purpose only, using the adiabatic condition as a starting point. Here, we present an analytical description, starting from the solution in terms of the hypergeometric functions for sech and tanh pulses. From this procedure we found a set of results with which is possible to infer analytically the characteristic behavior of the magnetization. This is on the purpose of obtaining greater control of the magnetization from parameters of the methodology that carry physical interpretation.
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Scotti, A. "Process modelling to establish control algorithms for automated GMAW." Thesis, Cranfield University, 1991. http://dspace.lib.cranfield.ac.uk/handle/1826/10518.
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The feasibility of fully automatic GMAW processes may rely on the
development of sophisticated equipment to emulate the manual welding
torch oscillation pattern or on the development of high level methods of
control to prevent the appearance of defects, especially the lack of sidewall
fusion. An intermediate solution is to optimise the weaving
parameters of a conventional pattern oscillator in such a way as to
minimise the level of rejection.
A prototype of a computerised system to work with Pulsed-GMAW
equipment, in the vertical-up position, was proposed to produce a minimal
level of rejection for welds in plates up to 25 mm thick. The system
basically consists of optimised mode control algorithms, based on
theoretical and experimental models of weld pool behaviour. Three tasks
are performed by the system; the selection of parameters for an optimum
working point, an off-line simulation of the operation and real-time error
monitoring of the process.
Statistical experimental modelling was applied in order to build
most of the optimised models, because of the large number of variables
to be treated and their complex inter-correlation. The welding variables
were correlated with single responses. Partial and Correlation Analysis
techniques were used to discover the relationship between the variables
and the responses. Regression Analysis was then applied as a means of
obtaining the 'weight' of the most significant variables. Finally, since
some variables were found to be collinear, a corrective technique for
biased variables was employed.
Acceptance criteria for bead shapes were proposed and assessed.
The effect of the oscillation parameters and other welding variables on
the bead formation was analyzed and an operational 'envelope' for the
parameters determined. A theoretical approach to predict the occurrence
of poorly shaped beads, due to the lack of metal bridge between the joint
walls, was successfully developed and applied in parallel with the
statistical experimental methods. Equations for optimising the bead shape
and for determining the operational envelope contours were subsequently
generated and evaluated.
An extension of the system to an actual adaptive control scheme
was discussed and sensors and signals to be used were evaluated. Finally,
a process instability phenomenon in long test plates was identified and
investigated. This instability may prevent the use of GMA W in some
conditions in the vertical-up position.
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Tschirner, Simon. "The GMOC Model : Supporting Development of Systems for Human Control." Doctoral thesis, Uppsala universitet, Avdelningen för visuell information och interaktion, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-246719.
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Train traffic control is a complex task in a dynamic environment. Different actors have to cooperate to meet strong requirements regarding safety, punctuality, capacity utilization, energy consumption, and more. The GMOC model has been developed and utilized in a number of studies in several different areas. This thesis describes GMOC and uses train traffic control as the application area for evaluating its utility. The GMOC model has its origin in control theory and relates to concepts of dynamic decision making. Human operators in complex, dynamic control environments must have clear goals, reflecting states to reach or to keep a system in. Mental models contain the operator’s knowledge about the task, the process, and the control environment. Systems have to provide observability, means for the operator to observe the system’s states and dynamics, and controllability, allowing the operators to influence the system’s states. GMOC allows us to constructively describe complex environments, focusing on all relevant parts. It can be utilized in user-centred system design to analyse existing systems, and design and evaluate future control systems. Our application of GMOC shows that automation providing clear observability and sufficient controllability is seen as transparent and most helpful. GMOC also helps us to argue for visualization that rather displays the whole complexity of a process than tries to hide it. Our studies in train traffic control show that GMOC is useful to analyse complex work situations. We identified the need to introduce a new control strategy improving the traffic plan by supporting planning ahead. Using GMOC, we designed STEG, an interface implementing this strategy. Improvements that have been done to observability helped the operators to develop more adequate mental models, reducing use of cognitive capacity but increasing precision of the operative traffic plans. In order to improve the traffic controllers’ controllability, one needs to introduce and share a real-time traffic plan, and provide the train drivers with up-to-date information on the surrounding traffic. Our studies indicate that driver advisory systems, including such information, reduce the need for traffic re-planning, improve energy consumption, and increase quality and capacity of train traffic.KAJT
FTTS
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Kondety, Ramaiah. "The welding of multilayer wrappers using the NG-GMAW process." Thesis, Cranfield University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284913.
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Kolodziejczak, Gregory Conrad. "Pulsed GMAW parameter variation to minimize interference form tack welds." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14610.
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Arancibia, Orrego Marcos Enrique. "Desarrollo de plataforma de localización GMLC en red GSM/UMTS." Tesis, Universidad de Chile, 2016. http://repositorio.uchile.cl/handle/2250/140678.
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Magíster en Tecnologías de la InformaciónTelefónica Móviles de Chile lanza un servicio de localización en conjunto con una empresa local de mapas, este servicio permitía a los dueños de números de telefonía móvil localizar los teléfonos contratados mediante el uso de una página web donde se mostraba en un mapa la ubicación aproximada en la que ese móvil se encontraba. Con el pasar del tiempo otros proveedores de servicios de localización quisieron entrar en el mercado en asociación con Telefónica, sin embargo no se les pudo integrar porque no se disponía de una plataforma que permitiera una rápida integración. Esto da origen a la necesidad de desarrollar un Gateway de localización basado en los estándares de la industria. Al asumir la tarea de desarrollar se determinó que se implementaría las funciones básicas que permitieran prestar el servicio comercialmente usando la información disponible en la red sin tener que hacer inversiones en infraestructura. Para ello se determinó que se usaría la información de Cell-id disponible en la red y se complementaría con la información de ubicación de las antenas y el ángulo respecto del norte que define el centro del arco de cobertura de la celda. Además se definiría una arquitectura donde se usaría un servidor de localización que se encargaría de entregar la información y un Gateway de localización que se encargaría de integrar a los proveedores y clientes de localización. Esta tesis documenta y describe desde el punto de vista de la tecnología de la información las características del desarrollo realizado para disponer de un Gateway de Localización en Telefónica. Estas características tienen que ver con las partes de la arquitectura estándar que se implementan, las funciones y mensajes implementados. Además ilustra las mejoras y ventajas que se logran al implementar una solución estándar respecto de la solución inicial que al ser tan particular no permitía integrar a los nuevos proveedores de servicio de localización
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Volant, Karine. "Les sécrétions intestinales GMPc-dépendantes chez le rat, in vivo." Lyon 1, 1997. http://www.theses.fr/1997LYO1T066.
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Kameni, Tcheudji Jacques Fulber. "Etude comparative des phosphodiestérases spécifiques du GMPc : relation structure-fonction." Université Louis Pasteur (Strasbourg) (1971-2008), 2001. http://www.theses.fr/2001STR13754.
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Harwig, Dennis D. "Arc behaviour and metal transfer of the VP-GMAW process." Thesis, Cranfield University, 2003. http://dspace.lib.cranfield.ac.uk/handle/1826/11375.
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This project evaluated the metal transfer behaviour of the variable polarity (VP) GMAW process. Analysis was performed using high speed video that was synchronised with high speed data acquisition. Melting rate measurements were found to be very dependent on current waveform, polarity, and droplet size, and metal transfer if it occurred, for each waveform period. The transient conditions of current waveform and metal transfer produced rapid changes in arc behaviour which influenced the melting at the electrode tip and growing droplet. The concentrated melting theory was developed to explain the significant increase in electrode extension burnoff and droplet growth rate that occurred at short EN time as a function of current, and during EP peak pulse when the pre-pulse droplet volume was small. The highest electrode extension burnoff and droplet growth rate occurred when the arc was permitted to climb over the solid electrode tip producing rapid concentrated melting. Likewise, large molten droplets were found to promote a negative electrode extension burnoff and a decreased droplet growth rate. The arc rooted on large droplets providing additional heating but limited electrode melting. The droplet burnoff rate (DBR) method was developed and found to yield good experimental measurements for the arc and resistive heating coefficients used in a 2nd order melting rate equation developed for a complex waveform process, like VP-GMAW. For the EN period, the EN time affected the melting rate as a function of EN current. The greater melting rate that occurred at low EN time was measured by the changes in the resistive heating coefficient. Concentrated arc melting of the electrode extension at low EN time caused the slope of the burnoff diagram to increase, which represented the resistive heating coefficient. The melting rate of the EP pulse was related to the pre-pulse droplet volume. Large pre-pulse droplets decreased the arc heating coefficient, which could be negative, which meant the electrode extension was increasing and the arc length was decreasing in that waveform period. VP-GMAW power supplies offered stable operation for welding sheet structures on both carbon steel and stainless steel. Higher travel speeds were required as the %EN of the waveform increased to produce acceptable constant deposit area fusion. Welding speeds were up to 300% higher with VP-GMAW compared to the GMAW-P process when welding lap joints on 1.8 mm thick material with a 1.8 mm gap. VP-GMAW heat input was up to 47% less than GMAW-P for the same melting rate.
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Reis, Ronald Izidoro. "Anomalias na velocidade de fusão do eletrodo na soldagem GMAW." Universidade Federal de Minas Gerais, 2004. http://hdl.handle.net/1843/BUOS-8DVFLW.
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Wire melting rate in GMA welding with constant voltage power suplies is well described by a parabolic model that links the melting of the wire with electrical resistance and arc heating. However, tests performed with constant current power supplies indicate that the melting rate can deviate from the values predicted by this model when welding current is close to the globular to spray transition. Although the causes of these irregularities have not been well established yet, most authors consider them to be related to variations in liquid metal temperature close to the metal transfer transition current. This thesis evaluates the effect of welding parameters on the wire melting rate obtained in trials using a constant current power supply. A numerical model that consideres the contribution of both Joule and arc heating and includes the effect of temperature on the physical properties of the wire was developed to calculate the temperature distribution in the wire and its meltingrate. The experimental results were used with the model to assess the changes in either arc heating or metal vaporisation capable to explain the melting irregularities. High speed cinematography was used to analyse metal transfer in the current range associated with the melting irregularities.A velocidade de fusão do eletrodo na soldagem GMAW com fonte de tensão constante é bem descrita por um modelo parabólico que associa a fusão do arame com o aquecimento por resistência elétrica e do arco. Entretanto, testes realizados com fonte de corrente constante indicam que a velocidade de fusão pode se desviar dos valores preditos por este modelo quando a corrente está próxima da transição globular- spray. Embora as causas dessas irregularidades não tenham ainda sido bem estabelecidas, muitos autores consideram que elas estejam relacionadas com variações na temperatura do metal líquido próximo a corrente de transição de modo de transferência. O presente trabalho avalia os efeitos dos parâmetros de soldagem na velocidade de fusão obtidos com testes usando uma fonte de corrente constante. Um modelo numérico que considera a contribuição tanto do aquecimento por efeito Joule quanto do arco e inclui os efeitos da temperatura nas propriedades físicas do arame foi desenvolvido para calcular a distribuição de temperatura no arame e para simular a sua velocidade de fusão. Os resultados experimentais foram usados com o modelo para avaliar as mudanças no aquecimento do arco ou na vaporização do metal capazes de explicar as anomalias na velocidade de fusão. Filmagem de alta velocidade foi usada para analisar a transferência de metal na região de corrente associada com as anomalias na velocidade de fusão.
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Planckaert, Jean-Pierre Brie David Djermoune El-Hadi. "Modélisation du soudage MIG/MAG en mode short-arc." S. l. : Nancy 1, 2008. http://www.scd.uhp-nancy.fr/docnum/SCD_T_2008_0024_PLANCKAERT.pdf.
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Mohsin, AKM. "AUTOMATED Gmax MEASUREMENT TO EXPLORE DEGRADATION OF ARTIFICIALLY CEMENTED CARBONATE SAND." University of Sydney, 2008. http://hdl.handle.net/2123/5003.
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Doctor of Philosophy(PhD)Soil Stiffness is an important parameter for any geotechnical engineering design. In laboratory tests it can be derived from stress-strain curves or from dynamic measurement based on wave propagation theory. The second method is a more accurate and direct method for measuring stiffness at very small strains. Until now dynamic measurements have usually been obtained manually from the triaxial test. Attempts have been made to automate the procedure but have apparently failed due to the high level of variability in dynamic measurements. Moreover, triaxial tests of soil can be very lengthy and manual dynamic measurements can be very tedious and impractical for long stress-path tests. In this research a computer program has been developed to automate the stiffness measurement (using bender elements) based on the cross- correlation technique. In this method the program records all the peaks and corresponding arrival times in the cross-correlation signal during the test. The stiffness is calculated and displayed on the screen continuously. The Bender Element enabled to get the small strain shear modulus. An arbitrary “Chirp” waveform of 4 kHz frequency was used for this purpose. Subsequently Bender Element test results were checked by ‘Sine’ waveforms of frequencies 5kHz to 20kHz, as well as by manual inspection of the arrival time. This thesis discusses the method and some of the difficulties in truly automating the process. Finally some results from a number of stress path tests on uncemented and cemented calcareous sediments are presented. Bender elements have been used by many researchers to determine the shear modulus at small strain. Most previous studies have used visual observation of arrival time, which is time consuming and often requires some judgement from the operator. This thesis will describe the use of cross-correlation as a method for automation of Gmax measurement. Cross-correlation has been claimed to be unreliable in the past. However, it will be shown that provided several peaks in the cross-correlation signal are monitored it is possible to follow the variation of Gmax throughout consolidation and shearing. The measurement can be made at regular intervals within the software controlling a stress-path apparatus. Details of the apparatus used and practical considerations including selection of waveform and frequency are discussed. A series of drained cyclic triaxial tests was carried out on artificially cemented and uncemented calcareous soil of dry unit weights 13, 15, and 17 kN/m3 and sheared with constant effective confining stress 300 kPa. Gypsum cement contents of 10%, 20% and 30% of the dry soil weight were used. In addition a series of stress path tests were performed on Toyuora sand samples. Results will be presented for two uncemented and one cemented sand. In addition to the bender elements, all tests had internal instrumentation to monitor axial and lateral strains. Results will be presented for Toyura sand to show that the measurements are consistent with those obtained by other methods. Results will also be presented for carbonate sand subjected to a wide range of stress paths. Finally, results will be presented for the carbonate sand cemented with gypsum. The degradation of Gmax of the cemented soil subjected to variety of monotonic and cyclic stress-paths is presented. Analysis of the results includes assessment of the factors influencing Gmax for uncemented sand. Preliminary analysis indicates that in order of importance these are the mean effective stress, the stress history, void ratio and stress ratio. For cemented sand, Gmax is initially constant and independent of stress path. After yielding the modulus degrades, becoming increasingly stress level dependent and eventually approaches the value for uncemented sand. Factors influencing the rate of degradation are discussed. For the Toyuora sand samples the effects of end restraint on the stress-strain response at small strains were investigated. The conventional method of mounting triaxial specimen has the effect of introducing friction between sample and end platen during a compression test. This inevitably restricts free lateral movement of the specimen ends. Frictional restraint at the sample ends causes the formation of 'dead zones' adjacent to the platens, resulting in non-uniform distribution of stress and strain (and of pore pressure if undrained). On the other hand the specimen with 'free' ends maintain an approximate cylindrical shape instead of barrelling when subjected to compression, resulting in a more uniform stress distribution.
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Knutsen, Mirjam. "On Determination of Gmax by Bender Element and Cross-Hole Testing." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bygg, anlegg og transport, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-27232.
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The small-strain shear modulus, G<sub>max</sub>, is an important parameter in geodynamic problems and for advanced modelling. G<sub>max</sub> is influenced by several factors, which complicates the assessment and interpretation of test results. Due to sample disturbance, values measured in the laboratory may be lower than in the field. The use of G<sub>max</sub> as a measure of sample disturbance has previously been investigated. Different testing methods for determination of G<sub>max</sub> are described in this thesis, with a presentation of advantages and limitations on the basis of literature. Field tests can be performed either from the ground surface or in boreholes. For determination of G<sub>max</sub> in the laboratory, the use of bender elements in conventional test devices, such as the triaxial apparatus, has become a common procedure. With bender elements, several repetitive tests can be performed, and the sample can subsequently be tested for other soil characteristics. The initial part of this study concerned implementation of bender elements in a triaxial apparatus at the NTNU geotechnical laboratory. Subsequently, determination of G<sub>max</sub> by bender element testing was emphasized. Clay samples from three different sites were used, the Stjørdal, Tiller and Esp sites. At the Esp site, a limited field testing program was also performed, using a cross-hole method for determination of in situ G<sub>max</sub>. Laboratory measurements on two samples of Esp clay gave G<sub>max</sub> of 27 MPa and 30 MPa, after long-term consolidation. In situ measurements gave consistent results, with an average G<sub>max</sub> of 47 MPa. Values measured in the laboratory are seen to be about 40 % lower than values measured in the field. However, it should be noted that in the bender element test, the direction of propagation of the s-wave is vertical, while in the cross-hole test, it is horizontal. Consequently, due to anisotropy, a direct comparison may be somewhat erroneous.Factors influencing G<sub>max</sub> are presented on the basis of literature. Void ratio, plasticity index and soil structure are seen to be important factors. G<sub>max</sub> also show a stress dependency, increasing with increasing overburden pressure. Literature regarding G<sub>max</sub> as a measure of sample disturbance is also presented. For evaluation of the development of G<sub>max</sub> with time, long-term consolidation was performed. An evident increase in G<sub>max</sub> with time of consolidation was observed, with a correlation to axial strain. This is assumed to be due to aging effects, bringing the sample closer to its in situ state. Observations also showed a larger increase for 54 mm tube samples than for block samples, indicating some correlation between sample quality and G<sub>max</sub>. Reconsolidation seems to compensate for some effects of disturbance. However, it is suggested that destructuration of the soil is an important factor of sample disturbance which is not eliminated by reconsolidation. Bender element testing of the Esp clay was also performed on a sample of half height (5 cm). The results showed G<sub>max</sub> values about 25 % lower than those of the full-height samples. This indicates the existence of some near-field effects influencing the shear wave velocity close to the elements.Interpretation of cross-hole results revealed some difficulties regarding identification of the shear wave. The equipment should be further developed so that receivers are in direct contact with the soil. Lack of knowledge regarding an assumed complex environment in the triaxial cell, may have been a limitation when interpreting laboratory results. A model of the bender element test in a finite element method program, such as Plaxis, may be of interest for investigation of the actual condition of wave propagation. Further work is also proposed regarding the use of Gmax as a measure on sample disturbance.
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Cayo, Eber Huanca. "Modelagem e controle da soldagem orbital através do processo GMAW-S." reponame:Repositório Institucional da UnB, 2013. http://repositorio.unb.br/handle/10482/14444.
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Tese (doutorado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2013.Submitted by Albânia Cézar de Melo (albania@bce.unb.br) on 2013-10-25T14:26:10Z No. of bitstreams: 1 2013_EberHuancaCayo.pdf: 11106092 bytes, checksum: 32db1b7db30838656b3f458b6c65e047 (MD5)
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A soldagem orbital é um processo de fabricação que consiste da união de tubos metálicos e que tem diversas aplicações, tais como na indústria alimentar, farmacêutica, petroquímica e aeroespacial. Estas aplicações, em sua maioria, limitam-se à união de dutos de pequeno porte e de espessura fina, nos quais os efeitos gravitacionais sobre a transferência de calor e massa são ínfimos. Quando se pretende unir dutos de maior espessura, entretanto, é comum utilizar processos de soldagem com adição de material, o que incrementa as dimensões da poça de fusão. Em consequência, o efeito gravitacional altera a transferência de calor e massa, podendo acarretar escoamentos e deformações da solda se os parâmetros de soldagem são inadequados. O objetivo do presente trabalho é desenvolver um regulador de parâmetros de soldagem em função da posição de soldagem, objetivando obter soldas uniformes através do processo GMAW-S. Estudos iniciais mostraram que as oscilações da poça de fusão têm relação direta na formação da solda. Estas oscilações estão governadas pelo balanço das forças, eletromagnética, tensão superficial e gravitacional sobre a massa da poça. Considerando que em soldagem orbital há uma constante mudança de posição, o escoamento da poça causado pelo efeito gravitacional é inevitável, portanto é preciso regular adequadamente os parâmetros de soldagem em função da posição de soldagem ?. Para isto, em primeiro lugar, desenvolveu-se o modelo de transferência de massa a fim de estimar a quantidade de massa e a força com que esta massa é transferida do eletrodo arame à poça segundo a posição ?. Em segundo lugar desenvolveu-se o modelo de oscilações da poça a fim de estimar o valor final da oscilação em função da posição ?, o que permitiu estimar a localização do escoamento da poça assim como a localização da deformação do cordão de solda. Finalmente foi desenvolvido o modelo de regulação dos parâmetros de soldagem em função da posição ?, considerando a uniformidade das forças sobre a massa transferida, bem como a uniformidade da resistência do circuito de soldagem, do aporte térmico e da taxa de deposição. A partir da simulação de este conjunto de modelo foi possível prever o conjunto de parâmetros visando à uniformidade do valor final das oscilações da poça, o que implica na redução do escoamento da poça e consequentemente a relativa uniformidade do cordão de solda. Por meio de experimentos conseguiu-se verificar a uniformidade relativa das soldas a partir da regulação dos parâmetros de soldagem em função da posição ? utilizando os modelos propostos. Concluiu-se que o escoamento da poça é inevitável, porém, é possível reduzir seus efeitos através do controle do valor final das oscilações através da regulação dos parâmetros de soldagem em função da posição ?. ______________________________________________________________________________ ABSTRACT
Orbital welding is a manufacturing process that composes the union of metallic pipes which is largely applied in various industries such as food, pharmaceutical, petrochemical and aerospace industry. These applications are mostly limited to the union of small and thin ducts, on which the gravitational effects over heat and mass transference are minimal. When union of larger pipes is intended, however, welding processes with material addition are commonly applied, leading to an increased welding pool dimension. In consequence, gravitational effect alters heat and mass transference, what can cause outflows and deformations of the welding if welding parameters are inadequate. The aim of this work is to develop a regulator welding parameters according to the welding position, aiming to obtain uniform welds through the GMAW-S. Initial studies showed that the oscillations of the weld pool have a direct relation in the formation of the weld. These oscillations are governed by the balance of forces, electromagnetic, surface tension and gravity on the mass of the pool. Whereas that in orbital welding there is a constant change of position, the pool outflow caused by the gravitational effect is inevitable; therefore, it is necessary to regulate properly the welding parameters according to the welding position ?. For this, in first place it was developed the modeling of the mass transference to estimate the amount of mass and force with which this mass is transferred from the wire electrode to the welding pool according to position ?. In second place, it was developed the model of the welding pool oscillations in order to estimate the final value of the oscillation depending on the position ?, which allowed estimating the location of the pool outflow as well as the location of weld deformation. Finally the model of regulating of welding parameters according to the position ? was developed, considering the uniformity of forces on the mass transfer, as well as the uniformity of the welding loop resistance and the uniformity of the heat input and deposition rate. From the simulation of hese set of models, was possible to estimate the welding parameter set aiming to reach the uniformity of the final value of the pool oscillations, which implies the reduction of the pool outflow and consequently the relative uniformity of the weld bead. Through experimentation it was possible to verify the relative uniformity of welds from the adjustment of the welding parameters according to the position ? by using the proposed models. The obtained conclusion is that the outflow of the pool is unavoidable; however, their effects can be reduced by controlling the final value of the oscillations by regulating the welding parameters according to welding position ?.
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Clerc, Armel. "Mécanisme d'activation de la phosphodiestérase spécifique du GMPc du bâtonnet rétinien." Grenoble 1, 1991. http://www.theses.fr/1991GRE10119.
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Le mecanisme d'activation de la pde specifique du gmpc (pde) par la proteine g (g) a ete etudie en utilisant trois approches differentes: 1) par des mesures d'activite en systemes reconstitues dans lesquels la concentration de g et de pde varient, nous avons montre que l'activation totale de la pde necessite l'intervention de deux molecules d'activateurs (sous-unite alpha de la g avec un gtp lie). Le premier activateur se fixe sur la pde avec une forte affinite (kd voisin de 100 mm), entrainant une faible activation de la pde, tandis que le second se fixe avec une plus faible affinite (kd voisin de 600 nm), mais active de facon totale la pde (la vitesse d'hydrolyse du gmpc est alors 10 a 20 fois superieure a celle obtenue lors de la fixation du premier activateur). Les deux etats actives de la pde ont le meme km pour le gmpc, mais different par leur sensibilite vis-a-vis du gmp; 2) des experiences de fixation aux membranes de disques d'activateurs, en presence de pde et/ou de sous-unites inhibitrices de la pde (pde gamma) ont ete realisees, afin de preciser la nature des etats activites de la pde: complexe regroupant la pde et l'activateur ou sous-unites catalytiques de la pde (alpha et beta) liberees des sous-unites inhibitrices (gamma). Les resultats obtenus lors de la fixation d'activateurs aux membranes en presence de pde gamma (absence de fixation) et de pde native (fixation de 2 activateurs par pde), nous incitent a penser que l'activation de la pde native (fixation de 2 activateurs par pde), nous incitent a penser que l'activation de la pde se fait au sein d'un complexe stable membranaire, compose de pde et de g alpha; 3) des esperiences de reticulation de g alpha et de pde ont permis de mettre en evidence des complexes composes de pde alpha et beta avec une ou deux molecules de g alpha. Ces complexes correspondent aux deux etats actifs de la pde decrit en (1). L'ensemble de ces resultats prouve que la pde active est sous la forme d'un complexe membranaire stable compose de pde (alpha-beta-gamma) et de un ou deux activateurs (g alpha avec un gtp lie). L'activation de la pde se ferait par modification des interactions entre les sous-unites gamma et alpha beta de la pde au sein du complexe
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Silva, Fabio Gonçalves da. "Resistência ao desgaste por cavitação de diferentes ligas aplicadas pelo processo GMAW com e sem adição de arame frio." Universidade Federal de Uberlândia, 2014. https://repositorio.ufu.br/handle/123456789/14763.
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Fundação de Amparo a Pesquisa do Estado de Minas GeraisThe phenomenon of cavitation on the metal surface causes erosion decaying components in operation, in particular the blades of turbines for power generation, accounting for maintenance costs and losses in electricity generation resulting from periodic stops. The blades of these turbines, particularly those manufactured by C-Mn steel (carbon - manganese) are coated by arc welding for stainless steel protective order to present more uptime or longer intervals between maintenance periods. Among the materials used to coat these blades are austenitic stainless steels, and stainless steels featured in the Co and Cobased alloys (commercially Stellites). However, the latter have a high cost. Among the welding processes applied to the coating, the technique of adding cold wire (GMAW and GMAW-CW-AF) is presented as an advantageous tender in relation to other techniques currently existing special and conventional welding. Given the context, this work seeks to study, apply and evaluate the effect of alloy and austenitic stainless steel alloys Co (CoCrMo and CoCrW) deposited by GMAW-CW for the purpose of characterization, comparison, formulation and deposition of new alloys from commercial wire correlating with resistance to mass loss. The adjustments of welding technique have focused on obtaining the manufacture of coatings suitable welding parameters. The cavitation wear resistance was evaluated according to ASTM G 32, correlating microstructure and phases by optical microscopy, SEM-EDS, chemical composition and optical emission spectrometry analyzes of the phases present by XRD. The qualities of the welded surfaces have been analyzed by visual examination and Penetrant Liguid according to standard NT (Nondestructive Testing). It was found that the coatings showed good weldability without discontinuities or defects with good surface finish. In the analysis of the coatings of cobalt, the alloy H (Stellite electrode 21 and 309LSi as cold wire) and M (Stellite 6 and 309LSi electrode as cold wire) showed good performance in resistance to cavitation in similar levels of surface roughness and hardness when compared to coatings Stellites 21 and 06, made by conventional GMAW process.
O fenômeno da cavitação sobre a superfície metálica provoca à erosão que deteriora componentes em operação, em particular as pás de turbinas hidráulicas de geração de energia, sendo responsável por custos da manutenção e perdas em geração de energia elétrica decorrente das paradas periódicas. As pás dessas turbinas, em especial as fabricadas pelo aço C-Mn (carbono manganês) são revestidas por soldagem a arco por aços inoxidáveis a fim de proteção para que apresentem maior tempo de operação ou maior intervalo entre os períodos de manutenção. Entre os materiais aplicados para revestir essas pás estão os aços inoxidáveis austeníticos, e em destaque os aços inoxidáveis ao Co e as ligas à base de Co (comercialmente Stellites). No entanto, estes últimos apresentam alto custo. Entre os processos de soldagem aplicados para o revestimento, a técnica de adição de arame frio (GMAW-CW ou GMAW-AF) se apresenta como uma proposta vantajosa em relação às outras técnicas especiais de soldagem existentes atualmente e convencionais. Diante do contexto, este trabalho buscou estudar, aplicar e avaliar o efeito das ligas de aço inoxidáveis austeniticos e ligas de Co (CoCrMo e CoCrW) depositadas pelo processo GMAW-CW com a finalidade de caracterização, comparação, formulação e deposição de novas ligas a partir de arame comerciais, relacionando com a resistência à perda de massa. As adequações da técnica de soldagem têm como foco a obtenção dos parâmetros de soldagem adequados à confecção dos revestimentos. A resistência ao desgaste por cavitação foi avaliada segundo a Norma ASTM G 32, correlacionando com a microestrutura e fases por microscopia óptica, MEV-EDS, composição química por espectrometria de emissão óptica e análises das fases presentes por DRX. As qualidades das superfícies soldadas foram analisadas por análise visual e Líquido Penetrante de acordo com a norma de END (Ensaio Não Destrutivo). Verificou-se que os revestimentos apresentaram boa soldabilidade, sem descontinuidades ou defeitos, com bom acabamento superficial. Na análise dos revestimentos de cobalto, as ligas H (eletrodo Stellite 21 e 309LSi como arame frio) e M (eletrodo Stellite 6 e 309LSi como arame frio) apresentaram bom desempenho de resistência a cavitação em semelhantes níveis de rugosidade e dureza quando comparados aos revestimentos de Stellites 21 e 6, feitos pelo processo GMAW convencional.
Doutor em Engenharia Mecânica
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Wang, Zhenzhou. "Automated monitoring of high-speed metal transfer for real-time control." Lexington, Ky. : [University of Kentucky Libraries], 2007. http://lib.uky.edu/ETD/ukyelen2007d00642/Disseration.pdf.
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Thesis (Ph. D.)--University of Kentucky, 2007.Title from document title page (viewed on August 30, 2007). Document formatted into pages; contains: xv, 183 p. : ill. (some col.). Includes abstract and vita. Includes bibliographical references (p. 172-181).
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Gallardo, Galdames Christian E. "Rol del sistema No-GMPc en la antinocicepción orofacial experimental del ketorolaco." Tesis, Universidad de Chile, 2011. http://repositorio.uchile.cl/handle/2250/132096.
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Trabajo de Investigación Requisito para optar al Título de Cirujano DentistaAutor no autoriza el acceso a texto completo de su documento
Introducción: Los fármacos más ampliamente usados en el manejo del dolor son los corticoides, AINEs y analgésicos opioides. Otros fármacos moduladores de neurotransmisores, algunos de uso experimental, se han desarrollado como alternativa en analgesia. En este estudio se evaluará la actividad antinociceptiva de ketorolaco (AINE pirrolacético) en presencia y ausencia de LNAME (modulador nitridérgico) en el ensayo de la formalina orofacial en ratones. Material y método: Se utilizaron 120 ratones machos Mus musculus cepa CF/1 a los cuales se les administró i.p. soluciones salinas de ketorolaco en dosis de 10-200 mg/kg, L-NAME 1-5 mg/kg, y la combinación de ambos fármacos (6-8 muestras por cada dosis de los fármacos) 30 minutos previo al test algesiométrico de la formalina, que consiste en la inyección subcutánea en labio superior de formalina al 1%. Se realizó la observación y registro con cronómetro digital del tiempo total de frotamiento perinasal posterior a la inyección de la noxa en fase I algésica y fase II inflamatoria. Posteriormente se realizó análisis de regresión lineal mediante curvas dosisrespuesta para cada fármaco independiente para evaluar el efecto antinociceptivo; para la combinación de fármacos se utilizó el método de potenciación de Zelcer para evaluar la interacción sinérgica o antagónica de la coadministración farmacológica. Los resultados para el análisis estadístico fueron expresados como promedio ± EEM con límite de confianza al 95% (LC =95%) y los cálculos fueron realizados mediante programa computacional del laboratorio (Pharm Tool Pro, versión 1.27, McCary Group Inc.). La significancia estadística considerada fue de un 5% (p<0,05) a través de análisis de varianza y pruebas t de Student. Resultados: El análisis algesiométrico y de las dosis efectivas al 50% (DE ) determinó efecto antinociceptivo dosis-dependiente de ketorolaco y L-NAME al administrarse aislados, respecto al grupo control. La coadministración de ketorolaco con L-NAME 1 mg/kg dio como resultante DE 50 50 de 18,63 ± 1,20 mg/kg en fase I y de 25,47 ± 2,88 mg/kg en fase II; la coadministración de ketorolaco con L-NAME 5 mg/kg dio como resultante DE de 4,90 ± 2,07 mg/kg en fase I y 15,42 ± 2,89 mg/kg en fase II, comparadas con las DE 50 50 de ketorolaco aislado de 22,08 ± 3,08 mg/kg en fase I y de 20,56 ± 4,96 mg/kg en fase II. El análisis estadístico determinó un efecto antagónico de L-NAME sobre la antinocicepción generada por ketorolaco. Conclusiones: La administración i.p. de ketorolaco y de L-NAME aislados produce un efecto antinociceptivo dosis-dependiente en el test de la formalina orofacial. La coadministración de LNAME produce un efecto antagónico en la antinocicepción generada por ketorolaco, respecto a la administración de ketorolaco de manera aislada.
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Fischer, Alexander. "Estudo da influência dos parâmetros no processo de soldagem GMAW - arco pulsado." Universidade Federal de Minas Gerais, 2011. http://hdl.handle.net/1843/BUOS-8S7H6T.
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Pulsed gas metal arc welding describes the metal transfer mode involving oscillation (pulsing) of the welding current from a high pulse current in which level drop growth, necking of wire tip and detachment occur, and a low background current, which is applied to maintain the arc.The advantages of the process are: metal transfer without spatter formation and a wide range of welding power. The disadvantages are: noise pollution (pulse frequency), the cost of the equipment is much higher and the process is slightly more complex as compared to standard GMAW because a number of variables are required to be controlled to achieve good results. This study investigated the effect of the weld polarity on the metal transfer at the pulsed GMAW process, the effect of arc self-regulation with the current modulation mode IP-UB, theinfluence of the base parameters at the metal transfer and the limits of application. Experiments were carried out on an automated GMAW platform. The base metal was mild steel ASTM-A36 with a thickness of 4mm and 2,5mm. The filler wire was ER70S-6 with a diameter of 1,2mm. It was used as shielding gas 82% argon with 18% CO2. During trials,a high speed camera was used to record the metal transfer process. During welding the arc voltage and the welding current were continuously measured and synchronized with the high speed images. The high speed camera used a sampling speed of 4000 frames per second (fps).The study of the metal transfer with different electrode polarities showed that a controlled metal transfer was only possible when the electrode is connected to the positive pole. The current modulation mode IP-UB demonstrated self regulation properties to maintain the arc length steady during welding. As advantages of this modulation mode where indentifiedthe constant droplet formation conditions during pulsing (constant current mode) and the self regulation effect during the base level (constant voltage mode). The study of the base parameters showed, the arc length was regulated with the base voltage, pulse duration and pulse current influenced the droplet formation and pulse frequency was coupled directly with the wire feed speed. At the low power level, the application of the pulsed GMAW process was limited by the lack of penetration and by the arc instability. At the high power level, the application was limitedby the high base voltage, what provoked during the different phases similar arc lengths.O processo MIG/MAG - Arco Pulsado descreve-se como o processo onde o modo de transferência do metal caracteriza-se por apresentar a transferência em queda livre com a alteração entre dois níveis da corrente da soldagem, sendo um nível baixo, conhecido como corrente de base e outro nível alto, conhecido como corrente de pulso ou pico. As vantagens do processo são: a transferência do metal sem formação de respingos e uma larga faixa de potência de soldagem. As desvantagens são o barulho excessivo (devido a freqüência de pulsação), o custo muito mais alto do equipamento e a complexidade dos parâmetros.No presente trabalho foi investigada a influência da polaridade do eletrodo na transferência do metal, o efeito da auto-correção na modulação da corrente de pulso tensão de base (IP-UB), a influência dos parâmetros principais da pulsação e as limitações do processo. Para os ensaios foi utilizado o metal de base ASTM-A36, o metal de adição ER70S-6 e a mistura de gás de proteção 82% argônio e 18% CO2. A análise dos resultados foi feita pelas imagens capturadascom uma câmera de alta velocidade. As imagens capturadas foram sincronizadas com os valores de corrente e tensão de soldagem. As características geométricas foram analisadas pelas seções transversais de cordões. O diagrama de tensão-corrente (U-I) foi utilizado para apresentar as características do processo. A variação da polaridade mostrou que, no modo arco pulsado, a transferência do metal só foi controlada com o eletrodo consumível no pólo positivo.A modulação IP-UB mostrou um efeito de auto-correção suficiente para manter o comprimento do arco constante durante a soldagem. Como vantagem da modulação foi identificado que a corrente constante na fase de pulso provocou um estrangulamento uniforme da gota e a tensão constante na fase de base provocou o efeito de auto-correção.O estudo dos principais parâmetros da pulsação apresentou como resultado que a tensão de base como uma ferramenta para manipular o comprimento do arco controlado; que o tempo de pulso atuou junto com a corrente de pulso, que o tempo da descida da corrente não influenciou na transferência do metal e que a freqüência de pulsação foi dependente da velocidade de alimentação do arame. O processo foi limitado por baixo (inferiormente) pela falta de penetração e instabilidade do arco na fase de base. Por cima (superiormente) ele foi limitado pela alta tensão na fase de base que provocou um comprimento do arco parecido como na fase de pulso.
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MELO, Leonardo Gadêlha Tumajan Costa de. "Influência de parâmetros de soldagem GMAW no cálculo de tensões residuais através do método de Deslocamento de Pontos Coordenados (DPC) em chapas navais." Universidade Federal de Pernambuco, 2017. https://repositorio.ufpe.br/handle/123456789/20178.
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CAPES
A escolha de parâmetros de soldagem é uma etapa importante do processo de soldagem, influenciando diretamente no aporte térmico fornecido às juntas soldadas. Neste trabalho, alguns parâmetros de soldagem foram escolhidos para analisar suas influências nas tensões residuais, obtidas através do método de Deslocamento de Pontos Coordenados (DPC) em chapas de aço naval ASTM A-131 grau AH-36. Chapas de teste com dimensões de 200 mm x 70 mm e 13,7 mm de espessura foram soldadas através do processo Gas Metal Arc Welding (GMAW) seguindo o sentido de laminação. Para análise das tensões, foram escolhidas as condições de referência como: velocidade de soldagem de 6 mm/s, ângulo de bisel de 25° e tensão de soldagem média de 19,63 V. Posteriormente, cada um desses parâmetros foi variado, porém mantendo-se constantes os demais. Deste modo, foi possível estabelecer comparações entre um parâmetro dito padrão e suas variações. Para a chapa padrão, as médias das tensões residuais obtidas foram 138,13 MPa e 153,65 MPa, medidas a 3 mm e 2 mm da borda do cordão de solda, respectivamente. Para as amostras nas quais houve redução da velocidade de soldagem de 6mm/s para 3,5mm/s, as médias das tensões residuais medidas foram 34,67 MPa e 42,32 MPa, a 3 mm e 2mm da borda do cordão de solda, respectivamente. Para as amostras soldadas nas quais o ângulo de bisel foi aumentado de 25° para 35°, as médias das tensões residuais medidas foram 28,29 MPa e 31,96 MPa, a 3 mm e 2 mm da borda do cordão de solda, respectivamente. Por fim, para o aumento da tensão de soldagem média de 19,63 V para 26,48 V, as média das tensões residuais calculadas foram 50,81 Mpa e 47,39 MPa, a 3 mm e 2 mm da borda do cordão de solda, respectivamente. As tensões residuais calculadas apresentaram comportamentos esperados. Assim, foi evidenciado como a mudança de parâmetros de soldagem influencia de forma significativa as tensões residuais na peça soldada.
Choosing welding parameters is an important step of the welding process, which may influence directly in the heat input provided. In this study, some welding parameters were selected in order to analyze their influences in calculating residual stresses through Displacement of Coordinated Points (DCP) method in ASTM A-131 grade AH36 naval steel sheets. Samples with 200 mm x 70 mm and 13,7 mm thickness were welded through Gas Metal Arc Welding (GMAW) process according to rolling direction. To analyze the stresses, standard conditions were defined, such as welding speed of 6 mm/s, bevel angle of 25°, average welding voltage of 19,63 V. Then, each parameter was switched, however, only one at a time, keeping the rest of them constant. This way it was possible to establish comparisons between a standard parameter's value and its variation. For the standard sample, the average residual stresses found were 138,13 MPa and 153,65 MPa, by 3 mm and 2 mm from bead margin, respectively. For the samples in which welding speed was lowered from 6 mm/s to 3,5 mm/s, the average measured residual stresses were 34,67 MPa and 42,32 MPa, by 3 mm and 2 mm from bead margin, respectively. For the welded samples in which bevel angle was increased from 25° to 35°, the average measured residual stresses were 28,29 MPa and 31,96 MPa, by 3 mm and 2 mm from bead margin, respectively. Finally, for an increase in average welding voltage from 19,63 V to 26,48 V, the average calculated residual stresses were 50,81 MPa and 47,39 MPa, by 3 mm and 2 mm from bead margin. The calculated residual stresses presented as expected. It was evidenced how changing welding parameters would influence the residual stresses in a welded component in a significant way.
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Dean, Gary. "Optimization of metal transfer and fusion using current control in dip transfer GMAW." Access electronically, 2003. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20041029.140918/index.html.
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Eliasson, Rikard. "Design of a balanced X-band low-noise amplifier using a GMIC process." Thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-97089.
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This report is the result of a master thesis work done at SAAB Bofors Dynamics AB between September 2005 and January 2006. The purpose of the work was to design a balanced low-noise amplifier covering the X-band (8 . 12 GHz) using the GMIC (Glass Microwave Integrated Circuit) process provided by M/A-COM, Tyco Electronics UK Limited. This thesis work has resulted in an approved and functional balanced low-noise amplifier design. The manufacturer, M/A-COM, reviewed the design for manufacturability only and takes no responsibility for the electrical performance. The amplifier has been designed to have a flat frequency response and low reflections on the input and output. Of course, the noise performance has also been taken into consideration during the design process. This thesis report covers the whole design flow in a chronological order. The layout work and most of the simulations were accomplished by using the design tool Microwave Office from Applied Wave Research. For complex structures such as Lange couplers and spiral inductors, more accurate simulation models were obtained by using HFSS (High Frequency Structure Simulator) from Ansoft.
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Hurtado, Meneses Lissy Yojana. "Modelagem e simulação da transferência metálica no processo GMAW-S em soldagem orbital." reponame:Repositório Institucional da UnB, 2013. http://repositorio.unb.br/handle/10482/15103.
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Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2013.Submitted by Albânia Cézar de Melo (albania@bce.unb.br) on 2014-01-29T11:48:48Z No. of bitstreams: 1 2013_LissyYojanaHurtadoMeneses.pdf: 4186055 bytes, checksum: 15a188905f0b7aed4b12cf678924755d (MD5)
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A procura por processos de soldagem versáteis e de alta produtividade é uma necessidade contínua, em especial na união de dutos que representam o cerne no escoamento dos mais diferentes fluidos na área de petróleo e gás. A soldagem orbital refere-se ao processo de união de dutos e tubulações. A soldagem fora da posição plana e a própria geometria da peça de trabalho tornam o processo complicado, devido à variação contínua da posição de soldagem, o que constitui uma constante mudança no comportamento das forças que atuam sobre a gota de metal fundido e altera a dinâmica da transferência de metal. Este evento faz com que a solda apresente problemas de qualidade, pelo escoamento da poça de fusão e a instabilidade na transferência metálica. O presente trabalho propõe o desenvolvimento e implementação de um modelo híbrido que representa o processo GMAW na soldagem orbital, construído sob a aplicação de um tratamento físico e matemático específico para a modelagem dos períodos de formação, crescimento e transferência da gota, que compõem o modo de transferência por curto circuito, a fim de compreender os fenômenos físicos e dinâmicos envolvidos no processo. As respostas obtidas pelo modelo foram complementadas com o estudo da estabilidade da transferência de metal em experimentos reais, para ter uma visão global que combine o conhecimento obtido pela análise de experiências reais conduzidas, com os resultados gerados por ferramentas computacionais. Após a análise das respostas obtidas, os procedimentos desenvolvidos nesta pesquisa foram expostos a uma regra de regulação de parâmetros, para mitigar os efeitos da variação da posição de soldagem e melhorar a estabilidade da transferência metálica. Os resultados apresentados foram satisfatórios e se refletem na melhoria da aparência e qualidade do cordão de solda. Destaca-se que o modelo pode ser utilizado para o estudo do controle da transferência de metal, bem como para o estudo da escolha de parâmetros adequados para soldagem, com o objetivo de alcançar um elevado nível de qualidade da junta soldada em diferentes condições. ______________________________________________________________________________ ABSTRACT
Demand for welding versatile processes and high productivity is an ongoing need, particularly in the union of ducts that represent the core in the flow of the different fluids in in the field of oil and gas. The orbital welding refers to the process of union of ducts and pipes. The welding outside the plane position and the own geometry of the work piece make the process complicated, due to the continuously variation in the welding position, which is a constant change in the behavior of the forces acting on the molten metal droplet, and changes the dynamics of metal transfer. This event causes the solder present quality problems by runoff of the molten pool and the instability in metal transfer. This paper proposes the development and implementation of a hybrid model that represents the GMAW process in the orbital welding, built under the application of specific physical and mathematical treatment for the modeling of periods of formation, growth and transfer of the drop, which compose mode transfer by short circuit, in order to understand the physical and dynamical phenomena involved. The responses obtained by the model were complemented with the study of stability of metal transfer in real experiments, to have a global vision that combines the knowledge gained by analyzing real experiments with the results generated by computational tools. After the analysis of responses, the procedures developed in this study were exposed to a regulation rule of parameters, in order to mitigate the effects of the variation of welding position and improve the stability of metal transfer. The results were satisfactory and were reflected in the improvement of the appearance and quality of the weld. It is noteworthy that the model can be used to study the control of metal transfer, as well as to study the choice of appropriate parameters for welding, in order to achieve a high level of quality of the welded joint in different conditions.
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Hassas, Salima. "Gmal : un modèle d'acteurs réflexif pour la conception de systèmes d'intelligence artificielle distribuée." Lyon 1, 1992. http://www.theses.fr/1992LYO10201.
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Concevoir et réaliser des systèmes intelligents nécessite un outil qui fournisse un cadre favorable pour la mise en oeuvre des propriétés de cette intelligence. Outre son aspect massif et complexe, une des caractéristiques importantes de l'intelligence est son aspect évolutif et adaptatif permettant ainsi une capacité d'adaptation à son environnement (et/ou a des situations nouvelles). Le modèle d'acteurs, qui est un modèle de calcul concurrent, propose pour la première fois en 1977 par C. Gewitt au MIT, semble être un bon outil pour la mise en oeuvre de tels systèmes. De plus pour pouvoir offrir un système qui soit capable de s'adapter à son environnement, il est primordial qu'un tel système puisse avoir une représentation de lui-même qu'il puisse observer et manipuler au cours de son évolution. Cet aspect nécessite donc un outil qui puisse offrir une architecture réflexive. C'est ce que nous proposons avec GMAL (Gosseyn Machine Actor Language) qui est un modèle d'acteurs réflexif. La réflexivité dans GMAL est fondée sur l'éxistence d'un met́a-modèle de représentation et d'éxécution qui soit lui-même un modèle d'acteurs. Cette modélisation au méta-niveau fait que GMAL est un outil pour la concéption de systèmes intelligents qui est lui-même doté de propriétés intelligentes. . .
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Resende, Amadeu das Dores. "Mapeamento paramétrico da soldagem GMAW com arames de aço inoxidável ferrítico e austenítico." Universidade Federal de Minas Gerais, 2007. http://hdl.handle.net/1843/MAPO-7R5LYA.
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The use of stabilized ferritic stainless steel wires for GWAW welding in the industry has been increasing in the last years, replacing austenitic stainless steel wires for the welding of stabilized ferritic stainless steel. Besides its lower costs, the ferrític stainless steel weld present a similar, or even superior quality compared to austenitic welds. Considering that this development is relatively recent, there is still a small number ofpublications related to it, particularly in our country, and this may be a factor hindering a broader application of this consumable in the industry. The present work intents to contribute to increase the knowledge related to the application of these wires to the welding of the stabilized ferritic stainless steels. Two stabilized ferritic stainless steel wires, one of them stabilized with Ti (430Ti) and the other with Nb (430LNb), and oneaustenitic (308LSi), with nominal diameter of 1,00mm, were utilized for bead-on-plate welding tests of bistabilized ferritic stainless steel (439) plates 5.0 mm thick. Firstly, the wires were characterized in terms of their chemical analysis, surface quality, mechanical properties, cast and helix and electrical resistivity. In the welding trials, the wire feed rate was varied from 2 to 12 m/min and the voltage from 12 to 32 V to obtain the threemain kinds of metal transfer (short circuit, globular and spray). The shielding gas mixture was Ar2%O2 and the flow rate 15l/min. The current and voltage were monitored by a data acquisition system. The data were analyzed by the SINAL program which was developed in the LABSEND (UFMG). Several aspects like current, current standard deviation, short circuit time, and others were compared for the three wires in order to analyze different aspects of the process, including its relative stability. Metal transfer maps were built in terms of voltage and feed rate. The results were verified through high speed filming. It was verified that welding with the 430Ti wire tends to present less stability. The weld beads obtained with this wire showed a poorer bead aspect when compared with the others. One possible reason is its significant inferiorsurface quality.A utilização de arames de aços inoxidáveis ferríticos para soldagem MIG/MAG tem aumentado cada vez mais na indústria em substituição aos consumíveis austeníticos para a união de aços inoxidáveis ferríticos. Além do menor custo, tem-se verificado que as soldas obtidas apresentam uma qualidade tão boa, ou mesmo melhor, que aquelas obtidas com arames austeníticos. Como se trata de uma aplicação relativamente nova, um número reduzido de trabalhos sobre essa aplicação foi publicado, o que é um fator limitador de uma utilização mais intensa desses arames na indústria, particularmente em nosso país. Dentro deste escopo, o presente trabalho explora a aplicação desses arames na soldagem MIG de um arame inoxidável ferrítico estabilizado, com enfoque nas características operacionais do processo e em comparação com a soldagem com arames de aço austenítico. Dois arames de aço inoxidável ferrítico estabilizado, um ao titânio (430Ti) e outro ao nióbio (430LNb), e um austenítico (308LSi), de diâmetro nominal 1,00mm, foram utilizados em testes de soldagem em chapas de aço inoxidável ferrítico estabilizado ao titânio e nióbio (439) de 5,00mm de espessura. Primeiramente, os arames foram caracterizados em termos de qualidade superficial, composição química, propriedades mecânicas e elétricas. Nos testes de soldagem, a velocidade de alimentação foi variada de 2 a 12m/min e a tensão de soldagem entre 12 e 32V de modo a varrer todos os campos onde é possível se obter os três tipos principais de transferências (curto circuito, globular e aerossol). Utilizou-se o gás de proteção Ar2%O2 na vazão de 15L/min e distância bico de contato peça de 20mm. A corrente e a tensão foram monitoradas com sistema de aquisição e depois analisadas com a ajuda do programa SINAL, desenvolvido no LABSEND (UFMG). Os valores obtidos da corrente média de soldagem, os desvios padrão da corrente e da tensão e de parâmetros derivados dos sinais de tensão para caracterizar a transferência por curto circuito foram comparados para os três arames. Procurou-se caracterizar, assim, diferenças no processo de soldagem, inclusive a estabilidade operacional, associadas com os arames e tentou-se definir campos de predominância de cada tipo de transferência metálica em termos de tensão, velocidade de alimentação e arame usado. Os resultados foram verificados através de filmagem em alta velocidade. A soldagem com o arame 430Ti apresentou uma estabilidade inferior à soldagem com os arames 430LNb e 308LSi em todas as formas de transferência, apresentando desvios padrão de corrente mais altos. Apesar disto, com transferência por curto circuito, este arame parece operar com valores de tensão menores que os outros. O aspecto dos cordões de solda obtidos com o arame 430Ti apresentou uma qualidade inferior, com uma maior convexidade. Uma possível explicação para o pior desempenho do arame 430Ti é sua qualidade superficial significativamente inferior com uma rugosidade muito maior que poderia provocar agarramentos do arame no conduíte causando problemas de alimentação.
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Shrestha, Amit. "Optimal Strategic Plan for Sustainable Urban Transport System in Kathmandu City Centre : Using Decision Support Systems." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-176159.
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There are many factors associated with an urban environment that enrich or diminish the experience of the environment. These factors have a significant influence on how an urban morphology is appraised within the social, economical, and environmental framework. One of such factors is the urban transport system that represents the mobility of the people and accessibility to public services. This thesis is an assessment of a current transport system in Kathmandu city centre in comparison to Kathmandu Sustainable Urban Transport Project (KSUTP) promoted by Ministry of Physical Planning and Works in cooperation from Asian Development Bank (ADB). The study aims to find the optimal strategic alternative between the current system and KSUTP. The focus area is the historic city centre, because of its cultural, historical, architectural, and aesthetical significance. Two methods are used for two different purposes; first to measure people’s appraisal and second, to evaluate action alternatives. Measurement of Experience in Environment from Results of Core affect Investigation (MEERCI) is used to measure people’s appraisal and experience of the urban characters of Kathmandu city centre. The results from this survey will provide a background on people’s assessment of the city environs, and collected data from field work will be used in Generic Multi-Attribute Analysis (GMAA) model to determine the best strategic plan for developing sustainable urban transport system for Kathmandu city centre. The hard facts and figures are collected from authorities, ministries, and previous researches, which is then entered into the model to evaluate the optimal alternative. It is concluded that improvements in the current transport system in Kathmandu city centre, with the implementation of KSUTP, will result in better environment for the local population, local economy, public services, and transport facilities. In short, the quality of life will be enhanced with an upgrade in the urban transport system.
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Harper, Richard Eugene. "Development of novel synthetic turf infill materials." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54346.
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Mitigation of health and heat-build-up issues related to black, granulated crumb rubber infill (GCRI) in synthetic turf fields (STF) while maintaining acceptable impact absorption properties was the central goal of this study. The first step was establishing a STF baseline performance of GCRI samples that originated from several sources while elucidating the synergistic parameters between infill and turf that promulgate acceptable impact performance. Based on the knowledge base built on the GCRI-STF standard, three polymeric waste streams selected for their benign chemical contents, non-black colors and competitive low costs were evaluated as alternate turf infill materials: post-consumer carpet broadloom (PCCB), post-consumer carpet tile (PCCT) and recycled polyethylene terephthalate (PET) drink bottles. For ground PCCB carcass (the base on the carpet construction remaining after the face fibers were removed), the heterogeneous composition of unconfined fine particles and remaining short fibers prevented sufficient material integration to allow sufficient impact energy absorption. The ground PET homogeneous particles alone lacked sufficient impact absorption capabilities, and their synergistic interactions with the turf blade yarns were not sufficient to meet specified levels of impact performance. Only the PCCT infill crumb possessed a heterogeneous structure that effectively filled the STF to yield sufficient impact cushioning comparable to standard GCRI. In conclusion, PCCT was shown to be a technically-viable candidate for GCRI infill replacement, warranting further development to bring it into closer cost competitiveness to GCRI and ensure long-term wear and weathering performance in synthetic turf.
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Valensi, Flavien. "Contribution à l’étude des phénomènes liés aux effets anodiques et cathodiques en soudage MIG-MAG." Orléans, 2007. http://www.theses.fr/2007ORLE2067.
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Le procédé de soudage MIG-MAG repose sur l’utilisation d’un arc électrique pour transférer des gouttes de métal fondu d’une électrode consommable (l’anode) vers la pièce à souder (la cathode) sous protection gazeuse contrôlée. Différents régimes de transfert peuvent exister, selon le choix notamment du courant et la composition du gaz de protection : le régime pulvérisation axiale, préféré par les utilisateurs, est obtenu pour un courant suffisamment élevé sous argon seul ; Pour un courant plus faible ou lorsque du CO2 est ajouté en quantité suffisante dans le gaz, le transfert devient globulaire, de moindre qualité. L’objectif du travail présenté dans ce mémoire est de définir les conditions permettant d’obtenir le régime de pulvérisation axiale pour le taux de CO2 dans le gaz de protection le plus élevé possible et/ou un courant d’arc le plus faible possible. Les travaux réalisés sont basés sur l’observation de l’arc par imagerie rapide pour déterminer les conditions de la transition entre les deux régimes de soudage. Le diagnostic de la colonne de plasma a été réalisé par spectroscopie optique d’émission en utilisant une méthode originale donnant accès à la température et la densité électronique sans hypothèse sur l’état d’équilibre du milieu. Les résultats obtenus ont permis de déterminer la répartition des vapeurs métalliques dans la colonne pour différents régimes de fonctionnement. L’analyse en microscopie électronique à balayage de l’électrode consommable a permis de comprendre les phénomènes se produisant aux électrodes lors de la transition entre les régimes globulaires et de pulvérisation axiale. En particulier, il s’avère que les éléments minoritaires de l’acier constituant l’électrode consommable ont une grande influence sur les résultats obtenus, et que leur contrôle permet une amélioration significative des performances du procédé de soudage.
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Adolfsson, Stefan. "Quality monitoring in pulsed GMA welding using signal processing methods." Licentiate thesis, Luleå tekniska universitet, 1995. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18082.
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BARBOZA, FILHO Lúcio da Silva. "Estudo da técnica de enchimento de chanfro do aço naval pelo processo GMAW-CW." Universidade Federal do Pará, 2011. http://repositorio.ufpa.br/jspui/handle/2011/5107.
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FAPESPA - Fundação Amazônia de Amparo a Estudos e Pesquisas
Nesse trabalho estudou-se a viabilidade operacional e as características econômicas e geométrica da técnica do processo de soldagem GMAW-CW (alimentação adicional de um arame frio) em comparação Gas Metal Arc Welding (GMAW). O sistema de alimentação de arame frio foi projetado e adaptado a pistola de soldagem MIG/MAG. Utilizou-se uma fonte eletrônica de múltiplos processos ajustada em tensão constante e CC+, a proteção gasosa foi uma mistura 75%Ar+25%CO2 e CO2 comercialmente puro. O arame utilizado foi o da classe ER70S-6 com diametro de 1,2 mm para o arame eletrodo e 1,0 mm para o arame frio, os dois arames foram alimentados em cabeçotes independentes. As variáveis operacionais de entrada foram: a velocidade de alimentação de arame energizado, em três níveis, 4, 6 e 8 m/min e a velocidade de alimentação do arame frio em 50%, 60% e 70% da velocidade de alimentação do arame energizado. As soldagens foram automatizadas em simples deposição no sentido empurrando e o posicionamento do arame frio, em um único nível, Tandem em chanfro em “U” de chapas de aço ASTM 1020. As variáveis de resposta utilizadas foram: inspeção superficial dos cordões; análise da geometria (largura, penetração, reforço e diluição) da solda e econômicas (taxa de fusão, taxa de deposição, rendimento e custo operacional). Os resultados indicaram que para a análise superficial, com o uso do gás Ar25%CO2 a superfície dos cordões mostraram-se mais homogêneas em relação ao CO2 e com menor índice de salpicagem, para a análise das características econômicas, o processo GMAW-CW sempre foi superior ao processo convencional, quanto aos custos operacionais o processo convencional mostrou-se menor, porém não houve o preenchimento do chanfro, o que ocorreu com a utilização do processo GMAW-CW.
In this work studied the operational viability and the characteristics economic and geometric of technique of the process welding GMAW -CW (additional alimentation of a cold wire) in comparison Gas Metal Arc Welding (GMAW). The alimentation system of cold wire was designed and adapted to welding gun GMAW. Used an electronic source of multiple processes adjusted in constant voltage and DC +, the gas shield was a mixture 75% Ar+25% CO2 and commercially pure CO2. The wire used was Class ER70S-6 with diameter of 1.2 mm for the electrode wire and 1.0 mm for the cold wire, the both wires were fed in heads independent. The input operating variables were the feed speed of wire energized at three levels, 4, 6 and 8 m / min and the wire feed speed in cold 50%, 60% and 70% of the wire feed speed energized . The welds were automated in simple deposited in the pushing direction and the positioning of the cold wire in a single level, Tandem in chamfer "U" steel plate ASTM 1020. The variables of response used were: superficial inspection of the cords, analysis of the geometry (width, penetration, reinforcement and dilution) and economic solder (melting rate, deposition rate, yield and operating cost). The results indicated that for surface analysis, using the AR25% CO2 gas to the surface of the strands were more homogeneous with respect to CO2 and less splash index for the analysis of economic characteristics, the process always GMAW-CW was superior to the conventional process, the operating costs the conventional process was lower, but without filling of the chamfer, which occurred with the use of GMAW-CW.
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CARVALHO, Márcio Corrêa. "Análise microestrutural e de propriedades mecânicas de revestimentos soldados por SAW e GMAW-CW." Universidade Federal do Pará, 2016. http://repositorio.ufpa.br/jspui/handle/2011/8250.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
FAPESPA - Fundação Amazônia de Amparo a Estudos e Pesquisas
Revestimentos depositados por soldagem tem sido largamente empregados em diversas areas da industria da mineração. Os processos de soldagem a arco, gas e metal ou metal inert/active gas (MIG/MAG) ou gas metal arc welding (GMAW), a arco, gas e metal com adição do arame frio ou gas metal arc welding and cold wire (GMAW-CW) e soldagem a arco submerso submerged arc welding (SAW), têm sido estudados com foco na aplicação de revestimentos resistentes ao desgaste. O uso de processos com alta produtividade e com exibilidade para alteração da composição química mostra-se no caso do processo SAW como viavel, e promissor no caso do processo GMAW-CW, na aplicação de revestimentos resistentes ao desgaste. Neste trabalho foram investigados a microestrutura e as propriedades mecânicas de revestimentos resistentes ao desgaste obtidos pelo processo SAW e GMAW-CW em revestimentos de carbetos de cromo primario (RCC) e revestimentos ferrticos de segunda fase (RFe-SF). As tecnicas de caracterização estrutural convencionais como microscopia optica (MO) e espectroscopia de emissão optica (EEO), e avancadas como difração de raios X (DRX) e difração de eletrons retroespalhados (DERE) ou electron backscattered di raction (EBSD), identicaram as fases (M7C3, M23C6, austenita e ferrita), defeitos (trincas, pos não-dissolvidos e porosidades) e mecanismos de formação de defeitos (trincas de solidicação e falhas de fabricação) nestes revestimentos. As tecnicas de caracterização de propriedade mecânicas convencionais como microdureza e não convencionais como o teste de impacto abrasão compacto (TIAC) apresentaram-se como importantes ferramentas no estudo do desgaste de revestimentos depositados por soldagem. Os RFe-SF's e RCC apresentaram um crescimento da perda de massa ao longo do tempo de ensaio. O RCC apresentou a menor taxa de perda massa, 48,1 % menor que o RFe-SF de maior razão de arame frio (rAF) e 61,4% menor que o RFe-SF de menor rAF. A taxa de perda de massa aumentou com a rAF. A taxa de perda de massa do RFe-SF de menor rAF e 34,6 % maior que a do do RFe-SF de maior rAF. A taxa de perda de massa em relação a rAF , comportou-se de forma inversa em relação a microdureza, ou seja, quanto maior a microdureza menor a perda de massa.
Welded deposited overlays have been widely used in various areas of the mining industry reltaed to wear. The welding processes as Metal Inert/Active Gas (MIG/MAG) or Gas Metal Arc Welding (GMAW), Gas Metal Arc Welding with Cold Wire (GMAW-CW) and Submerged Arc Welding (SAW) have been studied focusing on the application of wear resistant overlay's. The use of processes with high productivity and exibility that allow changes in chemical composition as SAW is viable, and promising in the case of GMAW-CW. The present study investigated the microstructure and mechanical properties of wear resistant overlays obtained by the SAW and GMAW-CW processes on primary chromium carbides overlay's (CCO's) and ferritic second phase overlays (Fe-SF). Conventional techniques of structural characterization as optical microscopy and optical emisson spectroscopy (OES) and advanced as X ray di raction (XRD) and electron backscatter di raction (EBSD), identied the main phase and defect formation mechanisms in these overlays. Characterization techniques of mechanical property such as microhardness and unconventional as the compact impact abrasion test (CIAT), were also presented as important tools, in the study of welded deposited wear resistant overlays. The Fe-SF and CCO showed an increase in mass loss over time CIAT testing. The CCO had the lowest mass loss rate, 48.1 % less than the Fe-SF higher cold wire rate (rAF) and 61.4 % less than the Fe-SF lower rAF. The mass loss rate raised as rAF increased. The mass loss rate for Fe-SF lower rAF is 34.6 % higher than the largest rAF Fe-SF. The mass loss rate compared to rAF, behaved in an inverse manner with respect to hardness, i.e. the higher the hardness the lower mass loss rate.
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Furini, Cristiane Regina Guerino. "Participação da via de sinalização NO/GMPc/PKG na memória de reconhecimento de objetos." Pontifícia Universidade Católica do Rio Grande do Sul, 2009. http://hdl.handle.net/10923/4609.
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Previous issue date: 2009Evidence suggests that the NO/cGMP/PKG pathway plays a key role in memory processing but the actual participation of this signaling cascade in the consolidation of declarative memory, such as object recognition (OR), remains unknown. Here we show that consolidation of long-term object recognition memory enhances the nitric oxide synthase neuronal activity (nNOS) in the CA1 region of the dorsal hippocampus of rats. Indeed, when infused immediately after but not 180 and 360 min after training in the OR task, the nNOS inhibitor, L-NN, hindered long-term memory retention without affecting locomotion, exploratory behavior, anxiety state or hippocampal functionality. The amnesic effect of L-NN was not due to statedependency and was equally produced by the hippocampal infusion of soluble guanylyl cyclase (sGC) inhibitor, LY83583, and by the protein kinase G (PKG) inhibitor, KT5823.Furthermore, post-training infusion of the non-hydrolysable analog of cGMP, 8Br-cGMP, reversed the L-NN and LY83583 effect but not that induced by KT5823. The noradrenaline (NA) regulate NO/sGC/PKG pathway activation in distinct preparations. In accordance with this fact, the amnesia induced by intrahippocampal administration of antagonist -adrenergic receptor, timolol, immediately after training in the OR task is not reversed by co-infusion of 8-Br-cGMP or of NO donator, SNAP. When administrated in the CA1 region of the dorsal hippocampus together with LY-83583, KT-5823 or L-NN, NA reversed the amnesic effect of these compounds. Our results indicate that the activation of NO/cGMP/PKG pathway in the CA1 region of the dorsal hippocampus is essential for consolidation of OR memory and suggests that the ß-adrenergic receptors, has a fundamental participation on regulation of these events.
Evidências sugerem que a via de sinalização NO/GMPc/PKG tem papel chave no processamento da memória, entretanto a atuação desta cascata de sinalização no hipocampo durante a consolidação de memórias declarativas, tais como a de reconhecimento de objetos (RO), permanece desconhecida. Aqui será mostrado que a aquisição da memória associada ao treino na tarefa de reconhecimento de objetos aumenta a atividade da óxido nítrico sintase neuronal (NOSn) na região CA1 do hipocampo dorsal de ratos. Ainda mais, quando infundido nesta região do cérebro imediatamente, mas não 180 ou 360 min após o treino na tarefa de RO, o inibidor da NOSn, L-NN, prejudica a retenção da memória em questão, sem afetar a locomoção, o comportamento exploratório, nem o estado de ansiedade dos animais ou causar lesão ao hipocampo. O efeito amnésico do L-NN não se deve a indução de dependência de estado e é mimetizado pela infusão intra-hipocampal do inibidor da guanilil-ciclase solúvel (GCs), LY83583 ou do inibidor da proteína cinase G (PKG), KT5823.Ainda, a infusão pós-treino do análogo não-hidrolizável do GMPc, 8- Br-GMPc, reverte o efeito de L-NN e LY5823, mas não o de KT5823. A noradrenalina (NA) regula a ativação da via NO/GMPc/PKG em distintas preparações. Em concordância com este fato a amnésia induzida pela administração intra-hipocampal do antagonista -adrenérgico, timolol, imediatamente após o treino na tarefa de RO não é revertida pela co-infusão de 8-Br-GMPc e do doador de NO, SNAP. Quando administrada na região CA1 do hipocampo dorsal juntamente com LY-83583, KT-5823 ou L-NN, a NA reverte o efeito amnésico destes agentes. Nossos dados indicam que a ativação da cascata de sinalização NO/GMPc/PKG na região CA1 do hipocampo dorsal é fundamental para a normal consolidação da memória de reconhecimento de objetos e sugerem que os receptores ß-adrenérgicos desempenham um papel fundamental na regulação destes eventos.
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Joseph, Andrew Paul. "Assessing the effects of GMAW-Pulse parameters on arc power and weld heat input /." Connect to resource, 2001. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1130521651.
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Baskova, Irina Mikhailovna. "Preparing Non-Native English Speakers for the Mathematical Vocabulary in the GRE and GMAT." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6684.
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The purpose of this study was to develop vocabulary materials to aid non-native English speakers, specifically Russian speaking test-takers, in their preparation for the mathematical sections of the General Record Examination (GRE) and the Graduate Management Admission Test (GMAT) in terms of English mathematical vocabulary. GRE and GMAT preparation materials and practice tests published by the Educational Testing Service, Kaplan, and Barron's were analyzed with the help of computer software. This data was then used to determine which key words to include in the vocabulary tool, which is now available on Quizlet (www.quizlet.com). The developed materials were further proofread by competent mathematics and English language professionals and assessed with the help of a questionnaire administered to them. The rationale of the materials development and the procedures used for the process are described in detail in this thesis project.
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Teixeira, Gustavo Simões. "Análise da influência dos parâmetros de soldagem sobre a geometria do cordão de solda depositado pelo processo de soldagem TIG - MAG em tandem." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/32025.
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O objetivo deste trabalho é analisar a influência dos parâmetros de um sistema mecanizado de soldagem, composto por uma tocha TIG e outra MAG em tandem, sobre a geometria do cordão de solda resultante. Os resultados obtidos foram comparados com soldas realizadas pelos processos TIG e MAG operando isoladamente. Os testes foram executados por meio de simples deposição de cordões sobre chapas de aço ao carbono AISI 1010 com espessura de 6,3 mm. Os parâmetros analisados foram: corrente de soldagem e distância da ponta do eletrodo até a peça no processo TIG, velocidade de alimentação de arame e tensão do arco no processo MAG, além de velocidade de soldagem e distância entre as tochas. Os cordões de solda foram executados em um dispositivo de soldagem mecanizado, que permite a variação da velocidade de soldagem, distância da ponta do eletrodo TIG e a distância entre as tochas. Os ajustes de corrente e tensão de soldagem foram feitos em duas fontes de potência separadas, ambas do tipo transformador-retificador, uma para cada tocha, devido às diferentes curvas características de cada processo. Através do projeto de experimento fatorial fracionado, foram avaliados os efeitos de dois níveis, um mínimo e outro máximo, mais quatro réplicas dos seus níveis intermediários, resultando em 20 experimentos para cada processo de soldagem. Os valores dos resultados finais indicam uma diferença ao utilizar uma tocha TIG para pré-aquecer o material base, porém, estatisticamente, essa diferença não é significativa entre os processos TIG e MAG em tandem e MAG convencional para a faixa de parâmetros de soldagem adotada.This study aims to investigate the influence of process parameters of a mechanized welding system, comprising a GTAW torch and a GMAW torch in tandem configuration, on the geometry of the resulting weld bead, performed using GTAW and GMAW welding processes in tandem. The results were compared with weld beads performed by conventional GTAW and GMAW welding processes. The tests were conducted performing bead-on-plate deposits over AISI 1010 6,3 mm thick carbon steel plates. GTAW current, GMAW wire feed speed, GTAW arc length, GMAW voltage, welding speed and the distance between GTAW and GMAW torches were the analyzed parameters. The weld beads were performed in a mechanized welding bench, which allows the variation of speed, distance between torches and arc length of the GTAW torch. Current and voltage adjustments were made in two separate transformer-rectifier power sources, one for each welding torch, due to their different characteristic curves of each process. Through the fractional factorial design of experiment, the effects of two different levels for each parameter were analyzed, plus four replicates of the average values of these levels, resulting in 20 experiments for each welding process. The results show a difference on the weld bead geometry using a GTAW torch to preheat the base metal, however, this difference is not statistically significant between GTAW and GMAW welding process in tandem and GMAW welding process for the adopted range of welding parameters.
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Rodrigues, Pardal Goncalo Nuno. "Joining of steel to aluminium and stainless steel to titanium for engineering applications." Thesis, Cranfield University, 2016. http://dspace.lib.cranfield.ac.uk/handle/1826/10007.
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Dissimilar welding has been subject of several investigations due to its potential importance in various industrial fields such as transportation, energy generation and management. Dissimilar welding can increase the design efficiency, by the use of complementary alloys with different properties, cost cutting and light weighting structures. The use of different materials within a component or structure to best suit a particular task, requirement or increase its life and performance has always been an ambition of several designers and engineers. This project investigated the joining steel and aluminium for the automotive industry and also stainless steel and titanium to be applied in the civil nuclear energy generation industry. These dissimilar metallic combinations are metallurgically incompatible and the formation of brittle intermetallic phases (IMC) need to be controlled or eliminated. To join steel to Al, laser spot welding process was selected, to avoid the bulk melting of steel and Al at the joint interface that enhance the formation of brittle IMC. This part of the work was focused in controlling the joining process to control the IMC formation of galvanized and uncoated steel to Al and verify if it was possible to have a sound and reliable joint in the presence of an IMC layer. In the second part of this study, stainless steel to titanium joining, a different approach was taken with the application of weld metal engineering to modify or eliminate the IMC formation. Several metals were evaluated as potential interlayers to use and laser welding with a Ni interlayer was evaluated with moderate success, due to the modified IMC with improved mechanical properties and the good compatibility between Ni and the stainless steel. A further improvement was achieved when Cu was brazed between stainless steel and Ti using CMT (Cold Metal Transfer) a low heat input MIG process. The final attempt was to use a different interlayer that was 3D printed and deposited in several layers. This interlayer was composed Cu and Nb that were selected as candidates to avoid the IMC formation between the stainless steel and Ti. With this approach it was possible to build an IMC free component and possibly improve and avoid IMC formation in several other dissimilar metallic combinations.
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Souza, Camila da Silva de. "Biodiversidade dos Loricariidae (Teleostei Siluriformes) das bacias costeiras do sudeste e sul do Brasil /." Botucatu, 2017. http://hdl.handle.net/11449/149931.
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Orientador: Claudio de OliveiraAbstract: The coastal drainages of Southern and Southeastern Brazil are part of the Eastern basin, currently composed by different drainages. The large distribution area and variety of habitats along these drainages have a direct influence on the species diversity and their high level of endemism. However, this region has been suffered intense exploration and loss of habitat due to anthropic actions. The present study aimed to identify Operational Taxonomic Units (OTUs) of the Loricariidae and to delimit ecoregions through their distribution patterns. A total of 499 partial sequences of the mitochondrial COI gene were analyzed, belonging to 47 Loricariidae species. 58 OTUs were delimited along 31 drainages of Southeastern and Southern coastal revealing a previously unrecognized genetic diversity for some groups. The 31 drainages based on Parsimony Analysis of Endemicity (PAE), were divided in five groups, characterizing areas that are favorable to the delimitation of ecoregions. The Jacuí, Ribeira de Iguape and Paraíba do Sul rivers presented fairly exclusive faunas in relation to morphological and genetic patterns, being essential for preservation. The stream capture and paleoclimatic events are largely responsible for the distribution of the Loricariidae along the drainages.
Resumo: Os rios costeiros da região Sul e Sudeste do Brasil fazem parte do complexo hidrográfico da bacia do Leste, que abriga diferentes drenagens isoladas atualmente, entre as quais destacamse, na região Sul e Sudeste as do Paraíba do Sul, Ribeira de Iguape, Itajaí e Jacuí. A grande área de distribuição e variedade de habitats ao longo dessas drenagens têm influência direta na diversidade de espécies e no seu alto nível de endemismo. No entanto, essa região vem sofrendo intensa exploração e perda de habitas por ações antrópicas. Trabalhos de zoneamento dessa região vêm sendo realizados com o intuito de fornecer melhores dados para a sua preservação. Nesse sentido, o presente trabalho teve como objetivo identificar unidades taxonômicas operacionais (OTUs) da família Loricariidae e delimitar ecorregiões através de seus padrões de distribuição. Foram analisadas 499 sequências parciais do gene mitocondrial Citocromo c Oxidase subunidade I (COI), representantes de 47 espécies de Loricariidae e encontradas 58 OTUs distribuídas ao longo de 31 drenagens da região costeira Sul e Sudeste do Brasil, revelando uma diversidade genética antes não reconhecida para alguns grupos. As 31 drenagens, com base na Análise de Parcimônia de Endemismo (PAE), foram divididas em cinco grupos, caracterizando áreas propícias à delimitação de ecorregiões. As drenagens Jacuí, Ribeira de Iguape e Paraíba do Sul, apresentaram faunas bastante exclusivas em relação a padrões morfológicos e genéticos, sendo imprescin... (Resumo completo, clicar acesso eletrônico abaixo)
Mestre
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Francis, Justin David. "Welding Simulations of Aluminum Alloy Joints by Finite Element Analysis." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/32250.
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Simulations of the welding process for butt and tee joints using finite element analyses are presented. The base metal is aluminum alloy 2519-T87 and the filler material is alloy 2319. The simulations are performed with the commercial software SYSWELD+®, which includes moving heat sources, material deposit, metallurgy of binary aluminum, temperature dependent material properties, metal plasticity and elasticity, transient heat transfer and mechanical analyses. One-way thermo-mechanical coupling is assumed, which means that the thermal analysis is completed first, followed by a separate mechanical analysis based on the thermal history.
The residual stress state from a three-dimensional analysis of the butt joint is compared to previously published results. For the quasi-steady state analysis the maximum residual longitudinal normal stress was within 3.6% of published data, and for a fully transient analysis this maximum stress was within 13% of the published result. The tee section requires two weld passes, and both a fully three-dimensional (3-D) and a 3-D to 2-D solid-shell finite elements model were employed. Using the quasi-steady state procedure for the tee, the maximum residual stresses were found to be 90-100% of the room-temperature yield strength. However, the longitudinal normal stress in the first weld bead was compressive, while the stress component was tensile in the second weld bead. To investigate this effect a fully transient analysis of the tee joint was attempted, but the excessive computer times prevented a resolution of the longitudinal residual stress discrepancy found in the quasi-steady state analysis. To reduce computer times for the tee, a model containing both solid and shell elements was attempted. Unfortunately, the mechanical analysis did not converge, which appears to be due to the transition elements used in this coupled solid-shell model.
Welding simulations to predict residual stress states require three-dimensional analysis in the vicinity of the joint and these analyses are computationally intensive and difficult. Although the state of the art in welding simulations using finite elements has advanced, it does not appear at this time that such simulations are effective for parametric studies, much less to include in an optimization algorithm.Master of Science
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McNutt, Teresa M. "The effect of welding process on the microstructure of HY-130 steel weldments." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/23194.
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Approved for public release; distribution is unlimitedHY-130 is a high-strength, low-carbon steel used in the quenched and tempered condition . It is designed for high performance and marine applications where good weldability is a requirement. Optimum welding parameters are currently under investigation. In this study, 1/2 inch (12.7 mm) HY-130 steel weldments produced by submerged arc welding (SAW) and gas metal arc welding (GMAW) processes are compared by means of a systematic microstructural characterization of the base metal, weld metal, and heat affected zone (HAZ). The microstructures are characterized by optical and electron microscopy and microhardness measurements are performed in the weld metal and across the HAZ to relate the microstructure with the microhardness profiles. The weld metal microstructure of both weldments showed a predominantly martensitic structure. The GMAW weld metal had a finer lath martensite structure and contained more retained austenite and twinned martensite. The SAW weld metal had a less defined lath structure which was more bainitic. The microhardness values were higher in the GMAW weld metal. No significant differences in microstructure and hardness were observed in the HAZ of the two weldments.
http://archive.org/details/effectofweldingp00mcnu
Captain, Canadian Forces
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PEDROSA, Igor Rafael Vilarouco. "Influência do gás de proteção no modo de transferência do metal de adição e nas propriedades mecânicas das juntas soldadas pelos processos GMAW." Universidade Federal de Pernambuco, 2008. https://repositorio.ufpe.br/handle/123456789/5290.
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Previous issue date: 2008Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
A influência do gás de proteção no modo de transferência do metal de adição e nas propriedades mecânicas associadas foram estudadas neste trabalho. Considerando-se que o tema é pouco explorado no meio científico, a correlação microestrutura / propriedades mecânicas foi realizada para os diferentes processos GMAW. Para a realização deste estudo, foram utilizados gases de proteção disponíveis no mercado: Argônio Puro (Ar), Mistura Stargold Plus (75% Ar / 25% CO2) e o Dióxido de Carbono Puro (CO2). O metal de base utilizado foi o açocarbono de classificação ASTM A36 e o metal de adição utilizado foi o arame de classificação ER70-S6. Os resultados deste estudo mostraram que o modo de transferência do metal de adição passa de globular, quando soldado com o Dióxido de Carbono Puro (CO2), para spray (aerosol) na soldagem com a Mistura Stargold Plus (75% Ar / 25% CO2) ou com o Argônio Puro (Ar). As microestruturas associadas a estes diferentes processos foram caracterizadas macro e microestruturalmente por microscopia ótica (MO) e microscopia eletrônica de varredura (MEV). A microestrutura da junta soldada com o Argônio Puro (Ar) revelou falta de penetração e uma grande densidade de poros. A microestrutura da junta soldada com a Mistura Stargold Plus (75% Ar / 25% CO2) revelou uma pequena densidade de poros e uma completa fusão na raiz. A microestrutura da junta soldada com o Dióxido de Carbono Puro (CO2) revelou uma densidade de poros intermediária em relação às juntas soldadas com os outros gases de proteção. As propriedades mecânicas levantadas foram microdureza e resistência à tração. Os resultados das propriedades mecânicas ratificaram os resultados obtidos com a caracterização microestrutural. As melhores propriedades foram obtidas com a Mistura Stargold Plus (75% Ar / 25% CO2)
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Rose, Malcom Riley. "Assessing the Importance of Sequencing Laboratory Welding Practicums." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/1944.
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The effects of mastering 1F (flat position-fillet) welds on carbon steel using a sequenced pattern of welding was examined. Participants (N = 71) were randomly assigned a specific sequence of welding between Gas Metal Arc Welding (GMAW) and Shielded Metal Arc Welding (SMAW). The hypothesis of teaching beginning welders the GMAW process before the SMAW process to improve the ability to master American Welding Society (AWS) welds was tested. A welding pretest was administered to determine any prior welding knowledge. Sixty minutes of welding instruction taught proper welding safety, machine set-up, arc length, travel speed, work angle, and correct bead formation. Two practice sessions of 60 minutes were given for participants to become familiar with each welding process, followed by two testing sessions of ten minutes. During the testing period, individuals were assessed on their ability to produce an AWS 1F (flat position- fillet) lap weld in a given sequence. Welds were graded according to the AWS rubric for fillets with a total of four criteria categories based on the following criteria: a) presence of cracks or porosity, b) complete fusion, c) fillet leg size is specified minimum, and d) undercut - not to exceed 1/32 inches. The study indicate that students perform welds that meet AWS quality standards when using the GMAW process, however, the results were not statistically significant.
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Posinasetti, Praveen. "Process modelling and control of pulse gas metal arc welding of aluminum." Thesis, Queensland University of Technology, 2007. https://eprints.qut.edu.au/16530/1/Praveen_Posinasetti_Thesis.pdf.
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Recent developments in materials and material joining [specifically Aluminum and Pulse Gas Metal Arc Welding (GMAW-P) technology] have increased the scope and extent of their areas of application. However, stern market demand for the improved weld quality necessitates the need for automation of the welding processes. As a result, improvements in the process parameter feedback, sensing and control, are necessary to successfully develop the automated control technology for the welding processes. Hence, several aspects of the GMAW-P process have been investigated in this study in order to improve its control techniques.
Welding was conducted on 6XXX aluminium, using 1.2 mm diameter 4047 aluminum electrode and argon shielding gas. An extensive collection of high speed camera pictures were taken over a wide range of pulse parameters and wire feed rates using a xenon shadowgraph setup to improve understanding of the physics of GMAW-P process. Current and voltage signals were recorded concurrently too.
This investigation explores the effects of different process parameters namely pulsing parameters (Peak current (IP), Base Current (IB), Peak time (TP), Base Time (TB)) and wire feed rate on metal transfer phenomena in GMAW-P. Number of drops per pulse, arc length and droplet diameter were measured for aluminium electrodes by high speed videography. The pulsing parameters and wire feed rate were varied to investigate their effect on the metal transfer behaviour. Analysis showed that transition between the different metal transfer modes is strongly influenced by the electrode extension. Lower electrode extension reduced the number of droplets detached per pulse, while at higher electrode extension, spray mode is observed due to increased influence of the resistance heating.
Analysis of the current and voltage signals were correlated with the high speed films. A simple derivative filter was used to detect the sudden changes in voltage difference associated with metal transfer during GMAW-P. The chosen feature for detection is the mean value of the weld current and voltage. A new algorithm for the real time monitoring and classification of different metal transfer modes in GMAW-P has been developed using voltage and current signals. The performance of the algorithm is assessed using experimental data. The results obtained from the algorithm show that it is possible to detect changes in metal transfer modes automatically and on-line.
Arc stability in the GMAW-P has a close relationship with the regularity of metal transfer, which depends on several physical quantities (like voltage, current, materials, etc.) related to the growth and transfer of the metal droplet. Arc state in GMAW-P can be assessed quantitatively in terms of number of drops per pulse, droplet diameter and arc length. In order to assess the arc state in GMAW-P quantitatively, statistical and neural network models for number of drops/pulse, droplet diameter and arc length were developed using different waveform factors extracted from the current waveform of GMAW-P. To validate the models, estimated results were compared to the actual values of the number of drops per pulse, droplet diameter and arc length, observed during several welding conditions.
Determination of stable one drop per pulse (ODPP) parametric zone containing all the combinations of peak current (IP), base current (IB), peak time (TP), and base time (TB) that results in stable operation of GMAW-P, is one of the biggest challenges in GMAW-P. A new parametric model to identify the stable ODPP condition in aluminium which also considers the influence of the background conditions and wire feed has been proposed.
Finally, a synergic control algorithm for GMAW-P process has been proposed. Synergic algorithm proposed in this work uses the sensing and prediction techniques to analyse state of the arc and correct the pulsing parameters for achieving the stable ODPP. First arc state is estimated using the signal processing techniques and statistical methods to detect the occurrence of short circuit, unstable ODPP or multiple drops per pulse (MDPP) in GMAW-P system. If the arc state is not stable ODPP, then parametric model and genetic algorithm (GA) is used to assess the deviation of the existing pulsing parameters from the stable operation of GMAW-P process and automatically adjust pulsing parameters to achieve stable ODPP.
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Posinasetti, Praveen. "Process modelling and control of pulse gas metal arc welding of aluminum." Queensland University of Technology, 2007. http://eprints.qut.edu.au/16530/.
Full textAbstract:
Recent developments in materials and material joining [specifically Aluminum and Pulse Gas Metal Arc Welding (GMAW-P) technology] have increased the scope and extent of their areas of application. However, stern market demand for the improved weld quality necessitates the need for automation of the welding processes. As a result, improvements in the process parameter feedback, sensing and control, are necessary to successfully develop the automated control technology for the welding processes. Hence, several aspects of the GMAW-P process have been investigated in this study in order to improve its control techniques.
Welding was conducted on 6XXX aluminium, using 1.2 mm diameter 4047 aluminum electrode and argon shielding gas. An extensive collection of high speed camera pictures were taken over a wide range of pulse parameters and wire feed rates using a xenon shadowgraph setup to improve understanding of the physics of GMAW-P process. Current and voltage signals were recorded concurrently too.
This investigation explores the effects of different process parameters namely pulsing parameters (Peak current (IP), Base Current (IB), Peak time (TP), Base Time (TB)) and wire feed rate on metal transfer phenomena in GMAW-P. Number of drops per pulse, arc length and droplet diameter were measured for aluminium electrodes by high speed videography. The pulsing parameters and wire feed rate were varied to investigate their effect on the metal transfer behaviour. Analysis showed that transition between the different metal transfer modes is strongly influenced by the electrode extension. Lower electrode extension reduced the number of droplets detached per pulse, while at higher electrode extension, spray mode is observed due to increased influence of the resistance heating.
Analysis of the current and voltage signals were correlated with the high speed films. A simple derivative filter was used to detect the sudden changes in voltage difference associated with metal transfer during GMAW-P. The chosen feature for detection is the mean value of the weld current and voltage. A new algorithm for the real time monitoring and classification of different metal transfer modes in GMAW-P has been developed using voltage and current signals. The performance of the algorithm is assessed using experimental data. The results obtained from the algorithm show that it is possible to detect changes in metal transfer modes automatically and on-line.
Arc stability in the GMAW-P has a close relationship with the regularity of metal transfer, which depends on several physical quantities (like voltage, current, materials, etc.) related to the growth and transfer of the metal droplet. Arc state in GMAW-P can be assessed quantitatively in terms of number of drops per pulse, droplet diameter and arc length. In order to assess the arc state in GMAW-P quantitatively, statistical and neural network models for number of drops/pulse, droplet diameter and arc length were developed using different waveform factors extracted from the current waveform of GMAW-P. To validate the models, estimated results were compared to the actual values of the number of drops per pulse, droplet diameter and arc length, observed during several welding conditions.
Determination of stable one drop per pulse (ODPP) parametric zone containing all the combinations of peak current (IP), base current (IB), peak time (TP), and base time (TB) that results in stable operation of GMAW-P, is one of the biggest challenges in GMAW-P. A new parametric model to identify the stable ODPP condition in aluminium which also considers the influence of the background conditions and wire feed has been proposed.
Finally, a synergic control algorithm for GMAW-P process has been proposed. Synergic algorithm proposed in this work uses the sensing and prediction techniques to analyse state of the arc and correct the pulsing parameters for achieving the stable ODPP. First arc state is estimated using the signal processing techniques and statistical methods to detect the occurrence of short circuit, unstable ODPP or multiple drops per pulse (MDPP) in GMAW-P system. If the arc state is not stable ODPP, then parametric model and genetic algorithm (GA) is used to assess the deviation of the existing pulsing parameters from the stable operation of GMAW-P process and automatically adjust pulsing parameters to achieve stable ODPP.