guest ::
%0 Thesis %A Nguyen, Nam-Phong Andrej %T Laserdurchstrahlschweißen von transparenten Kunststoffen mit Thulium-Faserlaserstrahlung %I RWTH Aachen University %V Dissertation %C Aachen %M RWTH-2023-08822 %@ 978-3-98555-172-9 %B Ergebnisse aus der Lasertechnik %P 1 Online-Ressource : Illustrationen, Diagramme %D 2023 %Z Druckausgabe: 2023. - Auch veröffentlicht auf dem Publikationsserver der RWTH Aachen University. - Weitere Reihe: Edition Wissenschaft Apprimus %Z Dissertation, RWTH Aachen University, 2023 %X In contrast to classic joining processes, laser transmission welding of plastics offers technological advantages such as a contactless and precise energy input. This enables the generation of highly complex and fine seam geometries, which is why this process is used in particular for the encapsulation of sensitive components in the electronics, automotive or medical industries. The absorption behaviour can be induced by adding additives such as carbon black. In areas like the medical technology, the use of additives is often not permitted. The reason for this is the high requirements regarding the transparency and biocompatibility of the plastics. One possible solution is absorber-free laser transmission welding: By using beam sources that emit radiation in the natural absorption range of the plastics, the use of absorption-enhancing additives is no longer necessary. This makes it possible to join transparent plastics as well. Since both joining partners have identical optical properties, the incident laser radiation is absorbed in the entire irradiated volume. This creates heat-affected zones that extend along the entire cross-section of the material. The increased melt formation causes a higher thermal load on the plastic, which can lead to cracking and distortion especially in flat components. The absorption processes and the influence of energy deposition on the formation of the heat-affected zone are investigated in this work by using contour and quasi-simultaneous welding. The aim is to develop a joining technique in which seam geometries with seam widths between 50 - 400 µm can be produced. In this way, the thermal load on the plastic can be kept low. First, the temperature distribution and development during the welding process are analysed with the help of a thermal simulation model in order to generate a basic understanding regarding the energy deposition. In addition to the irradiation strategy, the influence of the material structure on the formation of the heat-affected zone is investigated. The simulation model is evaluated with the help of experimental tests and the energy deposition mechanisms in contour and quasi-simultaneous welding are compared. In order to be able to establish absorber-free laser transmission welding in the industrial environment, damages in the weld seam must be identified during the production process. For this purpose, two different approaches are investigated and compared: With the help of a pyrometer, the heat radiation emitted during the welding process is measured. Furthermore, a camera-based analysis using deep learning algorithms is investigated as a novel approach to process monitoring. %F PUB:(DE-HGF)11 ; PUB:(DE-HGF)3 %9 Dissertation / PhD ThesisBook %R 10.18154/RWTH-2023-08822 %U https://publications.rwth-aachen.de/record/968817