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1	Analytical Prediction of Three-Dimensional Fusion Zone Shape in Penetration Welding Chiang, Cheng-chia 17 July 2008 (has links) Analytical three-dimensional temperature field in the liquid and heat-affected zones and prediction of the three-dimensional fusion zone shape around the keyhole produced by a moving high-intensity beam are provided. Determination of the fusion zone shapes is of fundamental and practical importance to understand properties and microstructures of joints. In this work, the keyhole is idealized by a paraboloid of revolution in a finite workpiece subject to an incident flux of a Gaussian distribution.Introducing analytical solutions of three-dimensional analytical temperature field, the dimensionless width, leading and rear edges, and depth of the fusion zone are analytically found to be a function of the dimensionless parameters governing beam power per unit penetration, location of the workpiece surface and shape of the keyhole. The dimensionless parameters governing the keyhole shape can be evaluated from a force balance at the keyhole base. The results show the effects of welding parameters, such as the dimensionless beam power, Peclet number, cavity opening radius, Biot number, thickness of workpiece, and the parameter approximating convection, on the shape of the fusion zone and the temperature of keyhole surface. A significant difference in the fusion zone shapes predicted between the line-source solution and this work indicates the strong effects of three-dimensional heat transfer. Agreement between the prediction from this work and available experimental data is achieved. steady state deep penetration Keyhole
2	Simulace geometrie key hole v závislosti na svařovacích parametrech při laserovém penetračním svařování / Simulation of geometry of key hole depending on the welding parametrs in laser deep penetration welding Křivan, Miloš January 2013 (has links) The diploma thesis is focused on simulation of keyhole creation in laser deep penetration welding and on the effect of welding parameters on the geometry of keyhole (weld). With reference to this issue theories of keyhole creation are described. 2D simulation model that is created in mathematical software Matlab is verified pursuant welding results of non-alloy constructional steel 1. 0122 and stainless steel 1.4301. Effect of welding parameters on the geometry of keyhole and on the quality of weld is investigated through the welds in non-alloy steel 1.0122.
3	Método espectro-nodal linear para problemas de transporte de nêutrons na formulação de ordenadas discretas em geometria bidimensional cartesiana / Spectral greens function-linear nodal method for problems of neutrons transport in the discrete ordinates formulation in X, Y Cartesian geometry Dany Sanchez Dominguez 17 February 2006 (has links) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nesta tese o método espectro-nodal linear (SGF-LN) é desenvolvido para a solução numérica de problemas de penetração profunda na formulação de ordenadas discretas (SN) e regime estacionário com fonte de espalhamento isotrópica a uma velocidade em geometria cartesiana bidimensional. Este método é baseado em análise espectral das equações SN integradas transversalmente onde os termos de fonte de espalhamento são tratados analiticamente e apenas os termos de fuga transversal são aproximados, por polinômios de primeira ordem. Resolvemos as equações SGF-LN usando o esquema de inversão nodal total, cf. blinking iterative scheme (BIS), onde as grandezas emergentes da célula espacial em todas as direções são estimadas em função de todas as grandezas incidentes e a fonte interior prescrita. Resultados numéricos são apresentados com o objetivo de ilustrar a precisão e a eficiência computacional do método desenvolvido. / In this dissertation we present the Spectral Greens Function - Linear Nodal method (SGF-LN) for numerically solving one-speed deep penetration problems in the static discrete ordinates (SN) formulation with isotropic scattering, in X, Y Cartesian geometry. This method is based on a spectral analysis of the transverse integrated SN nodal equations, wherein the scattering terms are analytically treated, and only the transverse leakage terms are approximated by first degree polynomials. We solve the SGF-LN equations using fully nodal block inversions, that we refer to as the blinking iterative scheme (BIS), where the node exiting quantities in all angular directions are estimated as a function of all the node ingoing quantities and interior source. Numerical results are presented to illustrate the accuracy and the computational efficiency of the SGF-LN method. Métodos nodais Problemas de penetração profunda Ordenadas discretas Equação de transporte Discrete ordinates Transport equation Nodal methods Deep penetration problems
4	Método espectro-nodal linear para problemas de transporte de nêutrons na formulação de ordenadas discretas em geometria bidimensional cartesiana / Spectral greens function-linear nodal method for problems of neutrons transport in the discrete ordinates formulation in X, Y Cartesian geometry Dany Sanchez Dominguez 17 February 2006 (has links) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nesta tese o método espectro-nodal linear (SGF-LN) é desenvolvido para a solução numérica de problemas de penetração profunda na formulação de ordenadas discretas (SN) e regime estacionário com fonte de espalhamento isotrópica a uma velocidade em geometria cartesiana bidimensional. Este método é baseado em análise espectral das equações SN integradas transversalmente onde os termos de fonte de espalhamento são tratados analiticamente e apenas os termos de fuga transversal são aproximados, por polinômios de primeira ordem. Resolvemos as equações SGF-LN usando o esquema de inversão nodal total, cf. blinking iterative scheme (BIS), onde as grandezas emergentes da célula espacial em todas as direções são estimadas em função de todas as grandezas incidentes e a fonte interior prescrita. Resultados numéricos são apresentados com o objetivo de ilustrar a precisão e a eficiência computacional do método desenvolvido. / In this dissertation we present the Spectral Greens Function - Linear Nodal method (SGF-LN) for numerically solving one-speed deep penetration problems in the static discrete ordinates (SN) formulation with isotropic scattering, in X, Y Cartesian geometry. This method is based on a spectral analysis of the transverse integrated SN nodal equations, wherein the scattering terms are analytically treated, and only the transverse leakage terms are approximated by first degree polynomials. We solve the SGF-LN equations using fully nodal block inversions, that we refer to as the blinking iterative scheme (BIS), where the node exiting quantities in all angular directions are estimated as a function of all the node ingoing quantities and interior source. Numerical results are presented to illustrate the accuracy and the computational efficiency of the SGF-LN method. Métodos nodais Problemas de penetração profunda Ordenadas discretas Equação de transporte Discrete ordinates Transport equation Nodal methods Deep penetration problems
5	Entwicklung und Evaluation eines Gewichtsfenstergenerators für das Strahlungstransportprogramm AMOS Jakobi, Christoph 19 March 2018 (has links) (PDF) Effizienzsteigernde Methoden haben die Aufgabe, die Rechenzeit von Monte Carlo Simulationen zur Lösung von Strahlungstransportproblemen zu verringern. Dazu gehören weitergehende Quell- oder Geometrievereinfachungen und die Gewichtsfenstertechnik als wichtigstes varianzreduzierendes Verfahren, entwickelt in den 1950er Jahren. Die Schwierigkeit besteht bis heute in der Berechnung geeigneter Gewichtsfenster. In dieser Arbeit wird ein orts- und energieabhängiger Gewichtsfenstergenerator basierend auf dem vorwärts-adjungierten Generator von T.E. BOOTH und J.S. HENDRICKS für das Strahlungstransportprogramm AMOS entwickelt und implementiert. Dieser ist in der Lage, die Gewichtsfenster sowohl iterativ zu berechnen und automatisch zu setzen als auch, deren Energieeinteilung selbstständig anzupassen. Die Arbeitsweise wird anhand des Problems der tiefen Durchdringung von Photonenstrahlung demonstriert, wobei die Effizienz um mehrere Größenordnungen gesteigert werden kann. Energieabhängige Gewichtsfenster sorgen günstigstenfalls für eine weitere Verringerung der Rechenzeit um etwa eine Größenordnung. Für eine praxisbezogene Problemstellung, die Bestrahlung eines Personendosimeters, kann die Effizienz hingegen bestenfalls vervierfacht werden. Quell- und Geometrieveränderungen sind gleichwertig. Energieabhängige Fenster zeigen keine praxisrelevante Effizienzsteigerung. / The purpose of efficiency increasing methods is the reduction of the computing time required to solve radiation transport problems using Monte Carlo techniques. Besides additional geometry manipulation and source biasing this includes in particular the weight windows technique as the most important variance reduction method developed in the 1950s. To date the difficulty of this technique is the calculation of appropriate weight windows. In this work a generator for spatial and energy dependent weight windows based on the forward-adjoint generator by T.E. BOOTH and J.S. HENDRICKS is developed and implemented in the radiation transport program AMOS. With this generator the weight windows are calculated iteratively and set automatically. Furthermore the generator is able to autonomously adapt the energy segmentation. The functioning is demonstrated by means of the deep penetration problem of photon radiation. In this case the efficiency can be increased by several orders of magnitude. With energy dependent weight windows the computing time is decreased additionally by approximately one order of magnitude. For a practice-oriented problem, the irradiation of a dosimeter for individual monitoring, the efficiency is only improved by a factor of four at best. Source biasing and geometry manipulation result in an equivalent improvement. The use of energy dependent weight windows proved to be of no practical relevance. Effizienzsteigerung Monte-Carlo Monte-Carlo-Simulation AMOS Simulation Gewichtsfenster Gewichtsfenstertechnik Gewichtsfenstergenerator Strahlungstransport tiefe Durchdringung vorwärts-adjungiert Varianzreduktion Quellveränderungen Geometrieveränderungen Russisch Roulette Teilchensplitting Increasing efficiency Monte Carlo Monte Carlo simulation AMOS simulation weight windows weight window technique weight window generator radiation transport deep penetration forward-adjoint variance reduction source biasing geometry manipulation Russian roulette particle splitting ddc:530 rvk:UN 3020 Effizienzsteigerung Monte-Carlo Monte-Carlo-Simulation AMOS Simulation Gewichtsfenster Gewichtsfenstertechnik Gewichtsfenstergenerator Strahlungstransport tiefe Durchdringung vorwärts-adjungiert Varianzreduktion Quellveränderungen Geometrieveränderungen Russisch Roulette Teilchensplitting Increasing efficiency Monte Carlo Monte Carlo simulation AMOS simulation weight windows weight window technique weight window generator radiation transport deep penetration forward-adjoint variance reduction source biasing geometry manipulation Russian roulette particle splitting
6	Entwicklung und Evaluation eines Gewichtsfenstergenerators für das Strahlungstransportprogramm AMOS Jakobi, Christoph 13 March 2018 (has links) Effizienzsteigernde Methoden haben die Aufgabe, die Rechenzeit von Monte Carlo Simulationen zur Lösung von Strahlungstransportproblemen zu verringern. Dazu gehören weitergehende Quell- oder Geometrievereinfachungen und die Gewichtsfenstertechnik als wichtigstes varianzreduzierendes Verfahren, entwickelt in den 1950er Jahren. Die Schwierigkeit besteht bis heute in der Berechnung geeigneter Gewichtsfenster. In dieser Arbeit wird ein orts- und energieabhängiger Gewichtsfenstergenerator basierend auf dem vorwärts-adjungierten Generator von T.E. BOOTH und J.S. HENDRICKS für das Strahlungstransportprogramm AMOS entwickelt und implementiert. Dieser ist in der Lage, die Gewichtsfenster sowohl iterativ zu berechnen und automatisch zu setzen als auch, deren Energieeinteilung selbstständig anzupassen. Die Arbeitsweise wird anhand des Problems der tiefen Durchdringung von Photonenstrahlung demonstriert, wobei die Effizienz um mehrere Größenordnungen gesteigert werden kann. Energieabhängige Gewichtsfenster sorgen günstigstenfalls für eine weitere Verringerung der Rechenzeit um etwa eine Größenordnung. Für eine praxisbezogene Problemstellung, die Bestrahlung eines Personendosimeters, kann die Effizienz hingegen bestenfalls vervierfacht werden. Quell- und Geometrieveränderungen sind gleichwertig. Energieabhängige Fenster zeigen keine praxisrelevante Effizienzsteigerung.:1 Einleitung 2 Theoretische Grundlagen 2.1 Strahlungsfeldgrößen und Strahlungstransportgleichung 2.2 Monte Carlo Methoden 2.3 Effizienzsteigernde Methoden 3 Gewichtsfenstergenerator 3.1 Güte der Ergebnisse 3.2 Iterative Berechnung 3.3 Implementation in AMOS 4 Anwendungsbeispiele 4.1 Tiefe Durchdringung von Photonenstrahlung 4.2 Gestreute Photonenstrahlung 5 Zusammenfassung und Ausblick 6 Literatur Anhänge / The purpose of efficiency increasing methods is the reduction of the computing time required to solve radiation transport problems using Monte Carlo techniques. Besides additional geometry manipulation and source biasing this includes in particular the weight windows technique as the most important variance reduction method developed in the 1950s. To date the difficulty of this technique is the calculation of appropriate weight windows. In this work a generator for spatial and energy dependent weight windows based on the forward-adjoint generator by T.E. BOOTH and J.S. HENDRICKS is developed and implemented in the radiation transport program AMOS. With this generator the weight windows are calculated iteratively and set automatically. Furthermore the generator is able to autonomously adapt the energy segmentation. The functioning is demonstrated by means of the deep penetration problem of photon radiation. In this case the efficiency can be increased by several orders of magnitude. With energy dependent weight windows the computing time is decreased additionally by approximately one order of magnitude. For a practice-oriented problem, the irradiation of a dosimeter for individual monitoring, the efficiency is only improved by a factor of four at best. Source biasing and geometry manipulation result in an equivalent improvement. The use of energy dependent weight windows proved to be of no practical relevance.:1 Einleitung 2 Theoretische Grundlagen 2.1 Strahlungsfeldgrößen und Strahlungstransportgleichung 2.2 Monte Carlo Methoden 2.3 Effizienzsteigernde Methoden 3 Gewichtsfenstergenerator 3.1 Güte der Ergebnisse 3.2 Iterative Berechnung 3.3 Implementation in AMOS 4 Anwendungsbeispiele 4.1 Tiefe Durchdringung von Photonenstrahlung 4.2 Gestreute Photonenstrahlung 5 Zusammenfassung und Ausblick 6 Literatur Anhänge info:eu-repo/classification/ddc/530 ddc:530

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