Buch, Englisch, 167 Seiten, PB, Format (B × H): 148 mm x 210 mm, Gewicht: 251 g
Reihe: Dortmunder Umformtechnik
Buch, Englisch, 167 Seiten, PB, Format (B × H): 148 mm x 210 mm, Gewicht: 251 g
Reihe: Dortmunder Umformtechnik
ISBN: 978-3-8440-2041-0
Verlag: Shaker
Polymer Injection Forming (PIF) is a new production technique to manufacture plastic-metal hybrid components. The most distinctive advantage of the PIF-process is that the injected polymer melt can be simultaneously used as a pressure medium to form the sheet metal blank. Contrary to the conventional hydroforming process, the pressure and temperature in PIFprocess are non-uniformly distributed. To predict the forming behavior in PIF, it is essential to have knowledge of the local pressure and local temperature. So far, the main weakness of the previous studies is the failure to address the impact of local pressure and temperature on the forming process. The inherent complexities of the forming problem in PIF-process demand an in-depth analysis through experiments, analytical, and simulation means.
In this work, experiments are conducted to realize three different forming processes namely free forming, cup forming and concentric ring forming process. Different alloys of aluminium and steel with molten thermoplastic Polypropylene as an injected medium are used as processing materials. For experiments, a special injection mold has been developed and integrated with the necessary instrumentation for the real-time observation of the process variables. The most significant contribution of the experiments in present work is the evidence of the non-uniform pressure and temperature in PIF-process which has never been reported before. The experiment results have shown that the thickness of the flow channel has a decisive role on the development of the pressure gradients. The impact of these pressure gradients on the local forming depends on the mechanical properties of the sheet metal blank such as sheet thickness and hardening behavior. Another important finding of this work is that the forming process in PIF is mainly a cold forming process since the temperature of the sheet metal blank remained approximately 100°C, which is insufficient even for the warm forming of the aluminium alloy.
Another contribution of this work is the provision of simple closed-form analytical solutions of the process which can be used as a quick solution for the prediction of the local cavity pressure, local blank temperature, and local formed shape. These solutions are supported well with the tendencies of the experimentally obtained results.
The numerical modeling of the PIF-process is realized by Finite Element Method. The limitations of the existing simulation models are addressed by proposing a new simulation approach which offers the Multi-Physics modeling of the PIF-process by single simulation code. The key is to treat the flow field of the polymer melt as a Lagrangian flow field instead of Eulerian flow field. The non-Newtonian behavior of the polymer melt is modeled through viscoplastic relations. The simulation results indicate that the core of melt in PIF-process remains at the initial temperature and the distinguishing temperature gradients lie only near the melt-blank contact regions. The highest forming pressure occurs near the injection gate. Moreover, the pressure gradients in PIF process are nonlinear function of the location and the thickness of the flow channel whereas the thickness of the flow changes locally once the forming is initialized. The simulation model is validated over the local and temporal domain of the process by comparing the computed pressure, temperature and sheet displacement with experimentally recorded and analytically calculated result. In general, the simulation results are in good agreement with the experiments and analytical results.
