Refine
Document Type
- Article (7)
- Monograph/Edited Volume (4)
Is part of the Bibliography
- yes (11)
Keywords
- Außenpolitik (1)
- Deutschland (1)
- Kongress (1)
- Strukturreform (1)
- Vereinte Nationen (1)
As a non-contact process laser beam melt ablation offers several advantages compared to conventional processing mechanisms. During ablation the surface of the workpiece is molten by the energy of a CO2-laser beam, this melt is then driven out by the impulse of an additional process gas. Although the idea behind laser beam melt ablation is rather simple, the process itself has a major limitation in practical applications: with increasing ablation rate surface quality of the workpiece processed declines rapidly. With different ablation rates different surface structures can be distinguished, which can be characterised by suitable surface parameters. The corresponding regimes of pattern formation are found in linear and non-linear statistical properties of the recorded process emissions as well. While the ablation rate can be represented in terms of the line-energy, this parameter does not provide sufficient information about the full behaviour of the system. The dynamics of the system is dominated by oscillations due to the laser cycle but includes some periodically driven non-linear processes as well. Upon the basis of the measured time series, a corresponding model is developed. The deeper understanding of the process can be used to develop strategies for a process control.
As a non-contact process laser beam melt ablation offers several advantages compared to conventional processing mechanisms. During ablation the surface of the workpiece is molten by the energy of a CO2-laser beam, this melt is then driven out by the impulse of an additional process gas. Although the idea behind laser beam melt ablation is rather simple, the process itself has a major limitation in practical applications: with increasing ablation rate surface quality of the workpiece processed declines rapidly. With different ablation rates different surface structures can be distinguished, which can be characterised by suitable surface parameters. The corresponding regimes of pattern formation are found in linear and non-linear statistical properties of the recorded process emissions as well. While the ablation rate can be represented in terms of the line-energy, this parameter does not provide sufficient information about the full behaviour of the system. The dynamics of the system is dominated by oscillations due to the laser cycle but includes some periodically driven non-linear processes as well. Upon the basis of the measured time series, a corresponding model is developed. The deeper understanding of the process can be used to develop strategies for a process control.
Towards a better understanding of laser beam melt ablation using methods of statistical analysis
(2002)
Laser beam melt ablation, as a contact free machining process, offers several advantages compared to conventional processing mechanisms. Although the idea behind it is rather simple, the process has a major limitation: with increasing ablation rate surface quality of the workpiece processed declines rapidly. The structures observed show a clear dependence of the line energy. In dependence of this parameter several regimes of the process have been separated. These are clearly distinguishable as well in the surfaces obtained as in the signals gained by the measurement of the process emissions which is the observed quantity chosen.
Am 25. und 26. Juni 2004 fand die sechste Konferenz des Forschungskreises Vereinte Nationen an der Universität Potsdam statt. Die Konferenz befaßte sich mit dem Thema „Integrative Konzepte in der Reform der Vereinten Nationen". Kennzeichnend für die „Potsdamer UNO-Konferenzen", die traditionell am letzten Wochenende im Juni veranstaltet werden, sind die Verbindung von Wissenschaft und Praxis auf der einen Seite und die Beteiligung unterschiedlicher Disziplinen auf der anderen. Sieben Referate beschäftigten sich mit bisher nicht oder nicht genügend in der Arbeit der Vereinten Nationen einbezogenen Aspekten bei der Struktur-Reform. Die nachstehend abgedruckten sechs Beiträge - von Dr. Jochen Prantl, der zum Thema „Informelle Staatengruppen als Instrument zur Konfliktregulierung: Auswirkungen auf die Arbeitsweise des Sicherheitsrates der Vereinten Nationen" referiert hatte, lag bei der Drucklegung der Broschüre kein Manuskript vor - und die zugehörigen Diskussionen, die hier zusammengefaßt wiedergegeben werden, geben ein anschauliches Bild von der Komplexität der Aufgabe „UN-Reform". Die damit verbundenen Fragen, die für das zukünftige Funktionieren der Vereinten Nationen, aber auch für das Klima innerhalb der internationalen Gemeinschaft sehr wichtig sind, werden in dieser Dokumentation diskutiert. Die im Forschungskreis vertretene deutschsprachige UN-Forschung machte auf der Konferenz deutlich, daß man zu kurz greift, wenn sich die Reformdiskussion auf den ständigen Sitz für die Bundesrepublik Deutschland im Sicherheitsrat beschränkt. Der Forschungskreis möchte mit dieser Broschüre allen Interessierten die Möglichkeit geben, andere, nicht minder wichtige Aspekte dieser Diskussion kennenzulernen. Der Forschungskreis dankt der Juristischen Fakultät der Universität Potsdam für die Gastfreundschaft und dem MenschenRechtsZentrum der Universität Potsdam für die Kooperation bei der Organisation der Konferenz.
Laser beam melt ablation - a contact-free machining process - offers several advantages compared to conventional processing mechanisms: there exists no tool wear and even extremely hard or brittle materials can be processed. During ablation the workpiece is molten by a CO2-laser beam, this melt is then driven out by the impulse of a process gas. The idea behind laser ablation is rather simple, but it has a major limitation in practical applications: with increasing ablation rates surface quality of the workpiece processed declines rapidly. At high ablation rates, depending on the process parameters different periodic-like structures can be observed on the ablated surface. These structures show a dependence on the line energy, which has been identified as a fundamental control parameter. In dependence on this parameter several regimes with different behaviours of the process have been separated. These regimes are distinguishable as well in the surfaces obtained as in the signals gained by the measurement of the process emissions. Further aim is to identify the different modes of the system and reach a deeper understanding of the dynamics of the molten material in order to understand the formation of these surface structures. With this it should be possible to influence the system in the direction of avoiding structure formation even at high ablation rates. Relying on the results on-line monitoring and control of the process should be studied.