Auf Grund ähnlicher spezifischer Steifigkeits‐ und Festigkeitseigenschaften von Aluminium und Stahl lassen sich in der Anwendung bei leichten Rahmenstrukturen durch gegenseitige Werkstoffsubstitution nur geringe Leichtbaugewinne erzielen. Lediglich die Verwendung von z. B. Kohlefaserwerkstoffen oder Höchstleistungsstählen lässt eine Gewichtsreduktion für den Einsatz von Rohren oder Profilen in ultraleichten Strukturen erwarten. Am Lehrstuhl für Umformtechnik (LFU) der Universität Dortmund ist ein Verfahren entwickelt worden, das durch ein modifiziertes Strangpressen zur Herstellung von Verbundprofilen geeignet ist. Ausgehend von konventionellen Aluminium‐Pressblöcken werden hierbei verschiedenartige endlose Verstärkungselemente innerhalb der Wandstärke der Profilmatrix eingebettet. Für das Verfahren, das im Rahmen des Sonderforschungsbereiches SFB/TR10 erforscht wird, ist die Entwicklung neuartiger Strangpresswerkzeuge erforderlich. Durch experimentelle Untersuchungen auf einer 2,5 MN Laborstrangpresse wurden erfolgreich erste Verbundprofile hergestellt. Zur Vertiefung des Prozessverständnisses und der Prognose der Wirksamkeit neuer Werkzeugkonzepte wurden parallel FEM‐Simulationen durchgeführt. Die mit Hilfe des Verfahrens hergestellten geraden Verbundprofile lassen sich auf Grund möglicher Gefügeschädigungen nicht biegen. In Kombination mit dem ebenfalls am LFU entwickelten Verfahren Runden beim Strangpressen werden diese Verbundprofile jedoch auch mit gekrümmter Kontur herstellbar sein.

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In order to manufacture a workpiece fulfilling specified requirements with the lowest possible weight, it is crucial to be able to work with a variety of materials and to combine them accordingly. The production of profiles based on hybrid materials demonstrates such an approach. The continuous and selective reinforcement of aluminum profiles with metallic elements like steel wire and steel wire ropes by composite extrusion is being investigated within the scope of research of the Transregional Collaborative Research Center (SFB/TR10). A stable production process for composite profiles with embedded continuous reinforcing elements was developed during the research work. In this paper, the process principle is shown and an overview of the special tools is given. Furthermore, the temperature and the strand speed as influencing factors on the final state of the composite are analyzed, based on real size experiments using a 2.5MN and a 10 MN extrusion press.

The decrease of the bearing length in extrusion processes results in increasing of the material flow and offers, through this, the possibility for manipulation and optimization. This paper presents a simulation based optimization technique which uses this effect for optimizing the material flow in direct extrusion processes. Firstly, the method is used in a multi-extrusion process with equal pitch circle profiles, then in an extrusion process of an asymmetric profile. Furthermore, a composite extrusion process is analyzed where endless wires of high strength steel are embedded in a base material of aluminum. The insertion of reinforcement elements into the base material flow, especially within the small ratio between profile thickness and the reinforcement diameter, can lead to significant local disturbances inside the die, which result in undesirable profile defects. Hence, the simulation-based optimization method is especially used to optimize inhomogeneous wall thicknesses in composite profiles.

The production of continuously reinforced profiles by use of aluminum as base material and a reinforcement made of steel or carbon offers a great potential for modern lightweight constructions. Within this scope, they present the potential for an increase in usage of space frame constructions in automotive or aerospace engineering. But the insertion of reinforcement in the material flow of the extrusion process leads to a significant local perturbation inside of the forming tool: while the velocity of the base material increases due to the increasing press ration the velocity of the reinforcement remains constant at the profiles out-coming velocity. These effect leads in the compound zone to the induction of tensile stresses into the reinforcement which result in failures like cracking during the extrusion process. By use of a coupled thermo-mechanical finite element simulation with the commercial fe-codes Superform from MSC and HyperXtrude from Altair the velocity fields of an extrusion process with and without reinforcement were calculated and the resulting stress components were analysed. Based on these results, a process optimisation to reduce stresses on the reinforcement has been carried out, for example by a modification of the tool geometry. The numerical results went along with experiments to verify the calculated failures and the optimised process.