In different innovative markets, such as electro mobility and flexible electronics, among others, the mechanical joining processes based on sheet metal forming technologies are gaining a significant relevance due to their low cost and ease of automation as compared to traditional joining techniques of riveting, bolting, fastening, welding, etc. In lightweight hybrid constructions, where a high production rate is required, clinching technology demonstrates a sustainable method to join hybrid metal-composite parts. However, the basic mechanisms of this hybrid joining process are not well studied at present and an accepted design theory in this area has not yet been established. The current contribution presents a parametric study of the hybrid clinching joining process. The Taguchi’s design of experiments method is used to investigate the effects of tools’ geometry on hybrid clinching joints’ quality characteristics, i.e. neck thickness, undercut and final bottom thickness. For this purpose, a 2D axisymmetric modelling approach was adopted for its simplicity. The study results are analyzed using the mean response and signal-to-noise ratio approaches. Accordingly, the relevant geometrical parameters of the tools with the highest influence on the accurate shaping of hybrid clinching joints are determined numerically.
Multi-material and hybrid constructions are increasingly used in the automotive industry with the aim of achieving significant weight reductions of conventional car bodies, and thereby lead to effective reductions of fuel consumption. In this respect, the use of aluminum and short fiber reinforced plastics represents an interesting material combination. A full exploitation of such a material combination requires a suitable joining technique. Among different joining techniques, clinching represents one of the most appealing alternatives for automotive applications. This contribution deals with the experimental tests for determination of material behaviour of two representative materials PA6GF30 and EN AW 5754, which are used for parameterization of material models needed for numerical analysis of the clinching process using the FE software LS-DYNA. With regard to the material modeling of the aluminum sheet, an isotropic material model based on the von Mises plasticity implemented in LS-DYNA was chosen. For the description of the strain hardening behaviour of the aluminum sheet at high equivalent plastic strains, the hydraulic bulge test was carried out in addition to the uniaxial tensile test. For modeling of the short fiber reinforced thermoplastic a semi-analytical model for polymers (SAMP-1) available in LS-DYNA was taken. This material model uses an isotropic pressure dependent yield surface for the description of homogeneous materials. Finally, the FE model of clinching process is presented and an outlook of planned activities is given in terms on determination of the yield surface and hardening behaviour of PA6GF30 at high plastic strains.
A 3D FEM-based virtual test-rig tool for the hybrid metal-composites clinching technology is developed and built in the commercial finite element software Abaqus. The proposed tool consists of two modules: a module to simulate the hybrid clinching process and another to predict the strength of the clinched joints. At first, experimental results concerning the hybrid metal-composites (EN AW-5754-PA6GF30) clinching are presented. Then, the developed virtual tool is described in detail outlining the constitutive models implemented for the hybrid pairing sheets as well as illustrating the proposed FE numerical procedures. Later, the developed tool is applied to the hybrid pairing EN AW-5754-PA6GF30. In comparison to the conducted experiments, the simulation results obtained show the applicability and accuracy of the developed virtual testing tool.
Keywords: Metal / composites / multi-material design / hybrid clinching / virtual testing / finite element method (FEM) Ein dreidimensionales FEM-basiertes Simulationsmodell zur virtuellen Prüfung von hybriden Clinchverbindungen aus Faser-Kunststoff/Metall-Verbunden wurde entwickelt und in der kommerziellen Finite-Elemente-Software Abaqus aufgebaut. Das Simulationsmodell besteht aus zwei Berechnungsmodulen: Einem zur Simulation des hybriden Clinchprozesses, und einem weiteren zur numerischen Vorhersage der Festigkeit der hybriden Clinchverbindung. Zunächst werden experimentelle Ergebnisse zum hybriden Clinchen der Faser-Kunststoff/Metall-Verbunde (EN AW-5754 / PA6GF30) vorgestellt. Anschließend wird das entwickelte Berechnungsmodell detailliert beschrieben, wobei hier insbesondere auf die konstitutiven Materialmodelle, die für die einzelnen Fügeparameter in Abaqus implementiert worden sind, sowie auf das Simulationsverfahren eingegangen wird. Nach Berechnung des hybriden Clinchprozesses und erfolgreicher Modellvalidierung wird das Berechnungsmodul zur virtuellen Prüfung der Verbindungsfestigkeit angewandt. Durch den Vergleich der Simulationsergebnisse mit den experimentellen Daten wird die Anwendbarkeit und Genauigkeit des hier entwickelten virtuellen Prüfstands aufgezeigt.
A structural concept in multi-material design is used in the automotive industry with the aim of achieving significant weight reductions of conventional car bodies. In this respect, the specific use of steel foils and continuous fiber-reinforced thermoplastics represents an interesting material combination for the production of hybrid parts in sandwich design. This contribution deals with the experimental and numerical analysis of a conventional sheet metal forming process using a composite material based on Polyamide 6 (PA6) with unidirectional endless glass fiber reinforcement and HC220Y+ZE steel foil. A unidirectional composite plate is positioned between two steel foils in sandwich design and formed under appropriate temperature conditions. For the numerical analysis of the forming process the software LS-DYNA is used.
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