Laserendbearbeitung metallischer Werkstoffe

Koch, Jürgen GND

Die Laserendbearbeitung metallischer Werkstoffe fasst die Einzelprozesse der abtragenden Mikromaterialbearbeitung von Metallen mit Laserpulsen von ns-Dauer zusammen. Dabei wird erstmals die Strahlausbreitung in die Betrachtungen einbezogen. Somit gelingt es, ein Modell zu erarbeiten, das Vorhersagen zu Optimierungsbemühungen erlaubt und ein tieferes Verständnis dieser Abtragprozesse ermöglicht. Schließlich führen Optimierungsergebnisse auf Basis der entwickelten Modellvorstellung zu einer Verkürzung der Prozesskette. So gelingt einerseits die Aufteilung des Bearbeitungsprozesses in Schruppen und Schlichten, andererseits motiviert die Beobachtung von erstarrten Schmelzefilmen zur Erzeugung einer definierten Schmelzeschicht. Damit kann die Qualität der gefertigten Oberflächen bei reduzierter Bearbeitungszeit gesteigert werden, wobei sich die Fertigung in einer Aufspannung realisiert lässt.

The present work, laser finishing of metallic materials, summarizes the individual processes of ablative micromachining of metals with laser pulses of ns duration. Thus, synergetic effects between these erosive processes are revealed, serving a description of both, the stationary ablation, i.e. the mechanisms of material removal, when laser pulses are applied in a static superposition, as well as the dynamic erosion, i.e. laser machining at a relative motion between incident laser beam and work piece. In addition, investigations on beam propagation are leading to the development of a conceptual model that considers not only ablation mechanisms but also optical parameters at once. On that basis a simulation of pulse superposition for two-dimensional laser processing is created, which allows a prediction of the machining results and a visualization of optimization efforts as well. Results of own experimental studies and data from literature are used to develop the conceptual model. Moreover, the results serve for identification and verification of predominating parameters on the ablation process. They also confirm that the well-known mechanisms of stationary ablation remain to be valid in case of percussion drilling as well as for two-dimensional laser processing. However, for a complete description of the two-dimensional laser processing, also the radiation propagation and the resulting beam-material interaction are to be considered with respect to the overlapping use of a multiplicity at laser pulses. This is leading to the consideration of the iso-intensity lines along the beam propagation direction and to the definition of a limiting intensity, which depends on the ablation threshold, thus the thermo-physical properties of the material. Among other things, it allows the description of the resulting geometry along the drilling axis of holes produced by use of percussion drilling. Finally, optimization results lead on basis of the developed conceptual model to a shortening of the process chain. By dividing the process in rough and finish machining the quality of the manufactured surfaces can be increased. The observation of solidified melt films on these surfaces motivates additionally to the production of a defined melt layer. Hence, by applying continuous laser radiation in alteration with finish machining smooth or shiny surfaces are obtained in one setting.

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Zitierform:

Koch, Jürgen: Laserendbearbeitung metallischer Werkstoffe. Ilmenau 2011. Universitätsverlag Ilmenau.

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