Anton Schmailzl, Johannes Käsbauer, J. Martan, P. Honnerová, F. Schäfer, Maximilian Fichtl, T. Lehrer, L. Prušáková, J. Tesař, J. Skála, M. Honner
Measurement of core temperature through semi-transparent polyamide 6 using scanner-integrated pyrometer in laser welding
International Journal of Heat and Mass Transfer, vol. 146, no. January
Predicting the core temperature during welding is an ambitious aim in many research works. In this work, a 3D-scanner with integrated pyrometer is characterized and used to measure the temperature during quasi-simultaneous laser transmission welding of polyamide 6. However, due to welding in an overlap configuration, the heat radiation emitted from the joining zone of a laser transmission weld has to pass through the upper polymer, which is itself a semi-transparent emitter. Therefore, the spectral filtering of the heat radiation in the upper polymer is taken into account by calibrating the pyrometer for the measurement task. Thermal process simulations are performed to compare the temperature field with the measured temperature signal. The absorption coefficients of the polymers are measured, in order to get precise results from the computation. The temperature signals during welding are in good agreement with the computed mean temperature inside the detection spot, located in the joining area. This is also true for varying laser power, laser beam diameter and the carbon black content in the lower polymer. Both, the computed mean temperature and the temperature signal are representing the core temperature. In order to evaluate the spatial sensitivity of the measurement system, the emitted heat radiation from both polymers is calculated on basis of the computed temperature field. Hereby it is found, that more than 90 percent of the detected heat radiation comes from the joining area, which is a crucial information for contact-free temperature measurement tasks on semi-transparent polymers.
Johannes Käsbauer, Anton Schmailzl, J. Prehm, T. Loose, S. Hierl
Simulation of Quasi-Simultaneous Laser Transmission Welding of Plastics: Optimization of Material Parameters in Broad Temperature Range
Procedia CIRP, vol. 94, pp. 737-741
Thermo-mechanical simulation offers great opportunities to optimize welding processes of plastics. For realistic simulation, the temperature dependent mechanical properties need to be implemented from ambient temperature to temperatures above the flow temperature. Standard test methods are insufficient for characterization in the entire temperature range because close to the flow temperature the material is too soft for tensile tests and too stiff for rheometry. Therefore, an optimization strategy is developed, that determines unknown material parameters by testing in welding simulations. The unknown parameters are iteratively adjusted to minimize the mismatch between computed and measured set-paths. Thus, important process characteristics are calculated realistically, enabling the computer aided assessment of the weld quality.
Beitrag (Sammelband oder Tagungsband)
Anton Schmailzl, S. Hüntelmann, T. Loose, Johannes Käsbauer, F. Maiwald, S. Hierl
Potentials of the ALE-Method for Modeling Plastics Welding Processes, in Particular for the Quasi-Simultaneous Laser Transmission Welding
Mathematical Modelling of Weld Phenomena 12, Graz, Österreich, vol. 12
The Arbitrary-Lagrangian-Eulerian-Method (ALE-Method) offers the possibility to model the quasi-simultaneous laser transmission welding of plastics, in which a squeeze-flow of molten plastic occurs. It is of great interest to get a deeper understanding of the fluid-structure-interactions in the welding zone, since the occurring squeeze-flow transports heated material out of the joining zone, causing a temperature decrease inside. In addition, the numerical modelling offers the possibility to investigate the flow conditions in the joining zone. The aim of this article is to show the potentials of the ALE-Method to simulate the quasi-simultaneous laser transmission welding with the commercially available software LS-DYNA. The central challenge is to realize a bi-directional thermo-mechanically coupled simulation, which considers the comparatively high thermal expansion and calculates the interactions of solid and melted plastic correctly. Finally, the potentials of the ALE element formulations for the mathematical description of welding processes are shown, especially for those with a squeeze-flow.
Simulationsgestützte Prozessentwicklung beim Laser-Durchstrahlschweißen von Thermoplasten ohne absorbierende Füllstoffe
36. CADFEM ANSYS Simulation Conference, Leipzig
Beitrag (Sammelband oder Tagungsband)
Johannes Käsbauer, Anton Schmailzl, S. Hierl
Simulationsgestützte Prozessentwicklung beim Laser Durchstrahlschweißen von Thermoplasten ohne absorbierende Füllstoffe
Tagungsband zur 36. CADFEM ANSYS Simulation Conference (10.-12.10.2018; Leipzig)