Werkstoff-, Prozess- und Bauteiluntersuchungen zum Laserdurchstrahlschweißen von Kunststoffen
Laser transmission beam welding is only possible, if one joining part is transparent for the laser beam. The other part is non-transparent and thus absorbs the light. Within the absorbing part light energy is altered into heat energy. In order to start the welding process, both parts have to be in contact with each other. As a general finding of this research, the welding process itself can be divided into three different phases. During the transmission of the laser beam through the transparent part the polymer scatters the laser beam and also absorbs a small amount of the laser light. Thermographic evaluations are able to show the amount of scattering. In the experiments laser beam transparent parts were heated up locally and the temperature image of the front and the rear side of the sample were evaluated. Calculations, done before the welding process, are a method to predict the welding temperature. A comparison between calculated and actual temperatures show that there is a difference between the two temperature curves. Thus, it is not possible to exactly pre-calculate the temperature curves of the process. The surface structure of the welding parts significantly influences the welding process. As a result, different surface roughness generally leads to reduced tractive force, when compared to polished surfaces. Additionally, welding is only possible with the right geometry of the component parts, which means these parts have to be specially designed. Photoelasticity and transmission detection with an infrared beam can be used for non-destructive welding line tests. The photoelasticity test revealed the additional presence of isochromates directly beneath the welding line of a transparent PC sample. Former research has not been able to provide a method to investigate the welding line of two laser transmission beam welded black parts. This problem has successfully been solved by using an infrared light emitting and detecting camera.
info:eu-repo/classification/ddc/620, Ingenieurwissenschaften, Kunststoff, Laser, Schweißen, optische Eigenschaften, Temperatur, Oberfläche, Geometrie
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