Flexible Manufacture of Lightweight Frame Structures, 2008

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Authors: Dirk Becker, Marco Schikorra, A. Erman Tekkaya
Abstract: Curved Profile Extrusion (CPE) is an extension of the common extrusion process and offers the possibility to manufacture three-dimensionally curved profiles. Due to the flexibility of the process different curvatures can be produced with the same setup, which makes this technique efficient especially for low volume production. The process is characterized by a controlled lateral deflection of the strand which influences the material flow in the die and causes the profile curvature. In this paper, a direct comparison of the power rating between warm bending and CPE is presented. Furthermore, the investigations concerning the choice of support strategy of the surmounting profile by a robot to increase the curvature accuracy are continued. Finally, some extensions of the equipment are explained to increase the level of process integration.
Authors: Daniel Pietzka, Marco Schikorra, A. Erman Tekkaya
Abstract: Extruded aluminum profiles are essential for lightweight constructions in contemporary transport and automotive applications. The reinforcement of such aluminum-based profiles with high-strength materials offers a high potential for weight reduction and an improvement of functional and mechanical properties. In comparison to conventional composite extrusion using fiber or particle reinforced billets, the alternatively developed process for the embedding of endless reinforcing elements provides enormous advantages regarding extrusion forces, load-adapted reinforcement, and tool abrasion. In this extrusion process with conventional billets, modified tools with portholes are used to position reinforcing elements from outside the pressing tool and to embed them into the material flow during the pressing operation. This composite extrusion process is part of the research work started in 2003 and carried out within the scope of the Collaborative Research Center SFB/TR10. To increase the potential of composite extrusion with endless reinforcing elements, the manufacture of composite extrusion profiles with high-strength non-metallic alumina wires is planned. Due to the wires’ specific properties, e.g. high stiffness, their deflection behavior must be analyzed to guarantee a stable feeding-in process. In this paper the specific behavior of alumina reinforcing elements regarding the feeding-in process is analyzed by experimental investigations. The main influencing factors are determined and a process window is deduced.
Authors: Matthias Merzkirch, Kay André Weidenmann, Eberhard Kerscher, Detlef Löhe
Abstract: A possibility to increase both stiffness and strength of aluminium-based structures for the application in lightweight profiles for vehicle space frames is the use of composite extrusions in which high-strength metallic reinforcements are incorporated. Within the scope of the present investigations, composite-extruded profiles with wire-reinforcements made of austenitic spring steel 1.4310 (X10CrNi18-8), in an aluminium matrix AA6060 (AlMgSi0.5), which were exposed to different corrosive media for different times, were characterised in terms of the debonding shear strength using the push-out-technique. The formation of a galvanic couple could be conceived mathematically in regard of terms describing the formation of a shear-impeding layer and the corrosive attack. Thereby the parameters for the different media could be determined.
Authors: Christian Munzinger, Jürgen Fleischer, Gregor Stengel, Markus Schneider
Abstract: The prototype for the flying cutting of spatially curved extrusion profiles developed as part of the Collaborative Research Center Transregio 10 (SFB/TR 10) was tested as an integrated part of the overall system in first test runs. The profiles resulting from this process give proof of the potential involved in both, the novel curved profile extrusion (CPE) and the automatic supporting and cutting device. For subsequent automated processing to become possible, however, the reliably achievable accuracy of extruded profiles needs to be further improved. By the example of the extruded profiles produced so far, this article discusses potential factors that may impair profile accuracy and presents approaches and methods for the improvement of accuracy.
Authors: Dirk Biermann, Klaus Weinert, Andreas Zabel, T. Engbert, Jens Rautenberg
Abstract: Lightweight frame components made of aluminum and load optimized connecting elements allow the reduction of weight and energy consumption as well as the increase of payload. Complex frame structures which nowadays can be designed and optimized with the help of modern simulation technologies require the use of adapted manufacturing technologies. Especially the flexible machining of single or limited products on the basis of common machining strategies is still inefficient and economically unacceptable. This article describes the development of adequate strategies for a high quality machining using simultaneous five-axis milling. Consequently, the machining of composite extruded aluminum profiles with continuously embedded steel-wire elements and the preparation of joining areas on nodes and commonly extruded profiles for innovative joining by forming processes have been analyzed.
Authors: Pablo Barreiro, Volker Schulze, Detlef Löhe
Abstract: Electromagnetic compression of tubular profiles with high electrical conductivity is an innovative joining process for lightweight structures. The components are joint using pulsed magnetic fields which apply radial pressures of up to 200 MPa to tubular work pieces causing a symmetric reduction of the diameter with typical strain rates of about 104 sec-1. Since there is no contact between the components to be joined and the joining machine, any damage of component’s surface can be avoided. Friction stir welding (FSW) is a relatively new solid state joining technique and has been extensively developed for aluminum, magnesium, copper and titanium alloys as well as steels. The primal advantages of the process in comparison to conventional fusion welding are better mechanical properties, low residual stresses and distortion, and reduced occurrence of defects. In the present article, the influence of process and material parameters on the joint’s characteristics, material’s microstructure and the mechanical properties of electromagnetic compressed joints and friction stir welds using reinforced aluminum profiles is analyzed. The strength of the joint is determined by tensile tests. Finally, possible improvements of both techniques are outlined.
Authors: Michael Marré, Alexander Brosius, A. Erman Tekkaya
Abstract: One major objective of the Collaborative Research Center SFB/TR10 is the flexible and competitive production of frame structures which meet the requirements of lightweight design. The development of composite extrusion by embedding continuous reinforcing elements, like e.g. steel wires, in profiles during the extrusion process illustrates one approach to fulfill these conditions. To assemble such composite profiles, joining processes and strategies have to be developed taking into account the special composite material characteristics. In addition, the flexible production of lightweight frame structures in small quantities generates more requirements on the joining technology. The feasibility of joining by forming has been carried out investigating experimentally both conventionally extruded and reinforced profiles. Therefore, joining profiles to lightweight frame structures by both expansion and compression has been examined. The necessary forming pressure for the joining by forming processes was applied to tubular workpieces by a medium (hydroforming) and by a magnetic field (electromagnetic compression). Joints have been manufactured by these two processes to transmit axial loads either by force- or form-fit.
Authors: Michael F. Zaeh, Paul Gebhard, Sonja Huber, Markus Ruhstorfer
Abstract: On a global market, new products are subject to rising requirements regarding strength and quality. Simultaneously, the conservation of the environment and natural resources has become a key priority. One approach to these demands is the weight reduction of mechanical components by lightweight construction. The Transregional Collaborative Research Center (TR 10), funded by the German Research Foundation (DFG), is therefore working on the “Integration of forming, cutting and joining for the flexible production of lightweight space structures”. The use of light metals, like aluminium and composite materials is a main part in the TR10 process chain. This paper deals with the challenges of welding of light weight components made out of EN AW-6060. It shows the use and potentials of two innovative joining processes, particularly suited for welding aluminium. Especially developed for the fusion welding of aluminium components, BHLW (Bifocal Hybrid Laser Beam Welding), combines a Nd:YAG and a high power diode laser. The paper will give insight into the findings of the achieved results so far and line out the further proceedings with regard to critical parameters and their effect on the overall laser welding process. For the welding of aluminium composite materials, which play a big role in the TR10 process chain, Friction Stir Welding (FSW) is evaluated. As a solid state joining process, it can be used for the welding of materials that are hardly weldable with fusion welding techniques. In this paper, results of basic experiment for the joining of reinforced aluminium and the resulting process forces are presented.
Authors: Thomas Kloppenborg, Marco Schikorra, Jan P. Rottberg, A. Erman Tekkaya
Abstract: This paper presents the results of investigations on topology optimizations in extrusion dies. The change of material viscosity of finite elements in the numerical model is utilized to allow or to block the material flow through the finite elements in simplified two-dimensional extrusion models. Two different optimization procedures are presented. In the first part of the paper dead zones in a flat and in a porthole die were improved by enhance the streamlining of the extrusion die. In the second part an evolutionary optimization algorithm has been used to optimize the extrusion die topology in order to reduce the difference between the strand exit velocities in a multi extrusion process. Finally, both methods were sequentially combined.

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