Made available in DSpace on 2014-10-09T12:41:06Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:09Z (GMT). No. of bitstreams: 1 04673.pdf: 4338286 bytes, checksum: 9b40b59ddc2764691461410ae0194329 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

This master's thesis deals with the selection and evaluation of the appropriate welding technology for stainless steel and titanium alloys. Describes advantages and disadvantages of selected technologies. The experiment compares the mechanical properties, the heat input and the resulting surface structure of the welded samples. In conclusion, the thesis deals with the technical - economic evaluation of selected welding technologies.

The topic of this diploma thesis is the design of a MIG/MAG welding machine, suitable for locksmiths and workshops. The diploma thesis includes the analysis of existing products from the design and technical point of view and deals with the design of welding machine. The proposed concept focuses on interactive and modern look of the machine and comfortable manipulation and easy operation. The design itself offers a possible direction of morphology of welding machines in the future.

Due to increasing demands on component integration, functionalization, saving weight or material, the density and weight of thermoplastic parts could be influenced significantly by using the thermoplastic foam injection molding process. The characteristic three-layer structure offers numerous advantages for applications, such as weight reduction, increasing the specific bending stiffness with a simultaneous low tendency to warp and optimizing thermal and acoustic properties. For a subsequent joining process, however, difficulties arise due to the thin solid skin layer. Minimum joining distances during welding can no longer be met geometrically and the mechanical properties of the components are reduced. The present study is intended to analyze the interaction between the microcellular structure of the injection molded parts, the influence on the joining process and the resulting mechanical properties. Therefore, a cooperation of Chemnitz University of Technology and University of Bayreuth was founded to investigate the correlation between injection molding and welding by vibration and infrared for microcellular polypropylene and polyamide materials. In addition to various materials with and without fiber reinforcement, the influence of storage time and different joint types were investigated in this study. The aim was to improve the knowledge of process - material - structure - properties as well as to prepare guidelines for the transfer to industrial applications. The results have shown that the characteristic three-layer structure has a considerable inhomogeneity, depending on the used material, the foaming process and the process parameters. However, the weldability of foamed thermoplastics strongly depends on the internal structure due to the injection molding parameters, the storage time between foam injection molding and welding process, the joint type and the welding process itself.

Through a series of carefully designed experiments, characterization and some modeling tools, this work is aimed at studying the role of thermal profiles on different microstructural zones and associated properties like strength and corrosion through a variation of weld parameters, thermal boundary conditions and material temper. Two different alloys belonging to the Al-Cu and Al-Cu-Li system in different temper conditions- peak aged (T8) and annealed (O) were used. A 3D-thermal pseudo mechanical (TPM) model is developed for the FSW process using heat transfer module in COMSOL Multiphysics and is based on a heat source wherein the temperature dependent yield shear stress is used for the heat generation. The precipitation and coarsening model is based on the Kampmann and Wagner theoretical framework and accounts for the competition between the various nucleation sites for both metastable and equilibrium precipitates. The model predicts different precipitate mean radius and volume fraction for the various zones in the friction stir welded material. A model for the yield strength is developed which considers contributions from different strengthening mechanisms. The predictions of the each models have been verified against experimental data and literature. At constant advance per rotation, the peak temperature decreases with a decrease in traverse speed and increases with an increase in tool rotation. Weld properties were significantly affected by choice of thermal boundary conditions in terms of backing plate diffusivity. Weld conditions with a higher peak temperature and high strain rate results in more dissolution of precipitates and fragmentation of constituent particles resulting in a better corrosion behavior for the weld nugget. For a peak aged temper of 2XXX alloys, the weld nugget experiences dissolution of strengthening precipitates resulting in a lower strength and the Heat affected zone (HAZ) experiences coarsening of precipitates. For an annealed material, both the weld nugget and HAZ experiences dissolution of precipitates with an increase in strength in the weld nugget.

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Das Magnetpulsschweißen ermöglicht das stoffschlüssige Fügen verschiedenartiger Metalle, wobei die intermetallische Phasenbildung im Gegensatz zu herkömmlichen Schmelzschweißverfahren deutlich reduziert werden kann. Im Rahmen dieser Arbeit erfolgt die Entwicklung eines neuartigen optischen Messsystems, welches sich zum Bestimmen der axialen und radialen Kollisionsgeschwindigkeit eignet und die Berechnung des Kollisionswinkels ermöglicht. Es wertet das charakteristische Prozessleuchten aus, das bei der Fügepartnerkollision während dieses Pressschweißverfahrens entsteht. Experimente in Vakuumatmosphäre belegen, dass die Temperatur im Fügespalt bei kleinen Kollisionswinkeln deutlich über den Siedetemperaturen der beteiligten Werkstoffe liegen kann. Die aus dem Fügespalt strömende heiße Partikelwolke schmilzt die Fügepartneroberflächen an, bevor diese aufeinander treffen, sich stoffschlüssig verbinden und schließlich rasch abkühlen. Metallografische Analysen belegen die angeschmolzenen Bereiche in der Fügeverbindung und bilden den Ausgangspunkt für ein numerisches Modell, welches das Aufheiz- und Abkühlverhalten der Oberflächen abschätzt. Das patentierte Messsystem hilft außerdem bei der Prozesseinstellung und -überwachung mit möglichst geringer Impaktgeschwindigkeit, wobei der Einfluss verschiedener anlagenbedingter und geometrischer Faktoren untersucht wird. Der Wärmeeintrag in die Verbindungszone kann außerdem durch exotherm reagierende Zwischenschichten erhöht und dadurch die benötigte Impaktgeschwindigkeit reduziert werden. Die genannten Maßnahmen tragen dazu bei, die thermischen und mechanischen Belastungen auf die Werkzeugspulen zu reduzieren und damit ihre Lebensdauer zu erhöhen.:1 Einleitung 2 Stand der Kenntnisse beim Magnetpulsschweißen 2.1 Verfahrenseigenschaften und Anwendungsgebiete 2.2 Wirkprinzip und Einflussgrößen beim elektromagnetischen Umformen 2.3 Theorien zum Fügemechanismus beim Kollisionsschweißen 2.4 Erscheinungsbild und Eigenschaften der Verbindungszone 2.5 Messtechnisches Erfassen von Prozessparametern 2.6 Strategien für eine höhere Prozesseffizienz 2.7 Zwischenfazit zu Kapitel 2 3 Zielsetzung 4 Versuchsaufbau und Bewerten des Schweißvorgangs 4.1 Versuchsaufbau 4.2 Bewerten des Energieeinsatzes 4.3 Bewerten des Schweißergebnisses 4.4 Zwischenfazit zu Kapitel 4 5 Erfassen der kinetischen Kollisionsparameter 5.1 Entwickeln eines Messsystems zum Erfassen des Impaktblitzes 5.2 Numerisches Modell zum Bestimmen der Kollisionsparameter 5.3 Experimentelles Bestimmen der Impaktgeschwindigkeit 5.4 Experimentelles Bestimmen der Kollisionspunktgeschwindigkeit 5.5 Weitere Anwendungsmöglichkeiten der Blitzauswertung 5.6 Zwischenfazit zu Kapitel 5 6 Experimentelle Analyse der Partikelwolkeneigenschaften 6.1 Einfluss der Kollisionsbedingungen auf die Temperatur der Partikelwolke 6.2 Charakterisieren der Partikelwolke 6.3 Zwischenfazit zu Kapitel 6 7 Schweißmodell 7.1 Unterscheidung von Schweißmechanismen 7.2 Zwischenfazit zu den experimentellen Ergebnissen 7.3 Metallurgische Effekte 7.4 Aufbau des temperaturbasierten Schweißmodells 7.5 Einfluss der thermischen und kinetischen Prozessbedingungen 7.6 Zwischenfazit zu den numerischen Ergebnissen 7.7 Wellenbildung 7.8 Zwischenfazit zu Kapitel 7 8 Einstellen der kinetischen Kollisionsparameter 8.1 Frequenzeinfluss 8.2 Wandstärkeeinfluss 8.3 Fügespalt- und Wirklängeneinfluss 8.4 Prozessrobustheit bei geometrischen Abweichungen 8.5 Experimentelle Hinweise zum Ermitteln des Schweißfensters 8.6 Zwischenfazit zu Kapitel 8 9 Exotherm reagierende Zwischenschichten 10 Zusammenfassung / Magnetic Pulse Welding is a pressure welding process that enables material joints between dissimilar metals. Compared to conventional fusion welding processes, the intermetallic phase formation can be minimized to an uncritical minimum due to the reduced and localized heat input. Although the process is already applied in industrial production for hybrid parts, the underlying principle of the bond formation is not yet completely explored. One of the main reasons for this is the difficulty in process monitoring, which also hinders process adjustment or the targeted support of the joining mechanism. Both aspects are of great importance for an efficient welding process and increased life-times of the tool coils. In the present thesis, a new optical measurement system has been developed to get insights into the kinetic conditions during collision welding processes. It evaluates the characteristic flash that occurs during the high-speed collision of the joining partners above a certain impact velocity. Furthermore, the second velocity component of the collision front in axial direction can be measured, which enables the calculation of the collision angle. Experiments in vacuum atmosphere reveal for small collision angles, that the temperatures in the joining gap can exceed the vaporization temperatures of the involved materials. Since the ejected cloud of particles is very hot, the surfaces of the parts are melted before they are pressed together. Afterwards, the bond is formed and the joining zone is cooled down rapidly. Metallographic analysis evidenced melted regions in the joining zone, which serve as an input variable for the numerical model. This model predicts the heating and cooling behavior of the surfaces and shows for large collision angles, that the surfaces are already solidified before they come into contact. This fact inhibits the identified welding mechanism based on fusion. The patented measurement device helps studying the influence of certain machine-related and geometrical parameters during the process adjustment with low impact velocities and serves as a quality assurance system. Furthermore, exothermic reactive interlayers can increase the heat input in the joining zone and thus, decrease the minimum impact velocities. These strategies may contribute to a significant reduction of thermal and mechanical shock loading of the tool coils to increase their life-time.:1 Einleitung 2 Stand der Kenntnisse beim Magnetpulsschweißen 2.1 Verfahrenseigenschaften und Anwendungsgebiete 2.2 Wirkprinzip und Einflussgrößen beim elektromagnetischen Umformen 2.3 Theorien zum Fügemechanismus beim Kollisionsschweißen 2.4 Erscheinungsbild und Eigenschaften der Verbindungszone 2.5 Messtechnisches Erfassen von Prozessparametern 2.6 Strategien für eine höhere Prozesseffizienz 2.7 Zwischenfazit zu Kapitel 2 3 Zielsetzung 4 Versuchsaufbau und Bewerten des Schweißvorgangs 4.1 Versuchsaufbau 4.2 Bewerten des Energieeinsatzes 4.3 Bewerten des Schweißergebnisses 4.4 Zwischenfazit zu Kapitel 4 5 Erfassen der kinetischen Kollisionsparameter 5.1 Entwickeln eines Messsystems zum Erfassen des Impaktblitzes 5.2 Numerisches Modell zum Bestimmen der Kollisionsparameter 5.3 Experimentelles Bestimmen der Impaktgeschwindigkeit 5.4 Experimentelles Bestimmen der Kollisionspunktgeschwindigkeit 5.5 Weitere Anwendungsmöglichkeiten der Blitzauswertung 5.6 Zwischenfazit zu Kapitel 5 6 Experimentelle Analyse der Partikelwolkeneigenschaften 6.1 Einfluss der Kollisionsbedingungen auf die Temperatur der Partikelwolke 6.2 Charakterisieren der Partikelwolke 6.3 Zwischenfazit zu Kapitel 6 7 Schweißmodell 7.1 Unterscheidung von Schweißmechanismen 7.2 Zwischenfazit zu den experimentellen Ergebnissen 7.3 Metallurgische Effekte 7.4 Aufbau des temperaturbasierten Schweißmodells 7.5 Einfluss der thermischen und kinetischen Prozessbedingungen 7.6 Zwischenfazit zu den numerischen Ergebnissen 7.7 Wellenbildung 7.8 Zwischenfazit zu Kapitel 7 8 Einstellen der kinetischen Kollisionsparameter 8.1 Frequenzeinfluss 8.2 Wandstärkeeinfluss 8.3 Fügespalt- und Wirklängeneinfluss 8.4 Prozessrobustheit bei geometrischen Abweichungen 8.5 Experimentelle Hinweise zum Ermitteln des Schweißfensters 8.6 Zwischenfazit zu Kapitel 8 9 Exotherm reagierende Zwischenschichten 10 Zusammenfassung

The ability to make rational decisions based on the synthesis of various pieces of information and to eventually arrive at an integrated design plays a very important role in everyday engineering practice. In this paper, a conceptual framework for manufacturing design is obtained through a causal perspective. This framework is used in developing a knowledge-based system that gains insight into the process of arc welding from a few detailed analyses and experiments on simplified models and rationally arrives at an integrated design of the actual process using a hybrid axiomatic-algorithmic approach for design synthesis. The design strategy presented here may also be applied to any manufacturing process in general.

Predictive process control (PPC) is the use of predictive, physical models as the basis for process control [1]. In contrast, conventional control algorithms utilize statistical models that are derived from repetitive process trials. PPC employs in-process monitoring and control of manufacturing processes. PPC algorithms are very promising approaches for welding of small lots or customized products with rapid changes in materials, geometry, or processing conditions. They may also be valuable for welding high value products for which repeated trials and waste are not acceptable. In this research, small-lot braze-welding of UNS C22000 commercial bronze with gas metal arc welding (GMAW) technology is selected as a representative application of PPC. Thermal models of the welding process are constructed to predict the effects of changes in process parameters on the response of temperature measurements. Because accurate thermal models are too computationally expensive for direct use in a control algorithm, metamodels are constructed to drastically reduce computational expense while retaining a high degree of accuracy. Then, the feasibility of PPC of welding applications is analyzed with regard to uncertainties and time delays in an existing welding station and thermal metamodels of the welding process. Lastly, a qualitative residual stress model is developed to nondestructively assess weld quality in end-user parts. / text