Flexible Manufacture of Lightweight Frame Structures, 2006

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Authors: Alexander Klaus, Matthias Kleiner
Abstract: This paper presents the focus of research and the structure of the Collaborative Research Centre SFB/TR10 „Integration of Forming, Cutting, and Joining for the Flexible Production of Lightweight Structures” funded in 2003 by the German Research Foundation (DFG). Driven by the demands of low volume production. The aim of the Research Centre is to investigate the scientific basis and methods to design integrated process chains for the flexible manufacture of space frame structures.
Authors: Alexander Klaus, Dirk Becker, Matthias Kleiner
Abstract: This paper presents and discusses the latest achievements in the manufacture of threedimensionally curved aluminum profiles using an integrated bar extrusion process. While the conventional process chain lacks applicability and quality especially in low volume production, the new technology is promising, but still needs research to understand the correlation between the product to be manufactured and the contour accuracy to be achieved. This paper shows first results on the manufacture using a robot-guided second guiding tool and direct air quenching. The results will have an impact on further processing steps
Authors: Matthias Kleiner, Alexander Klaus, Michael Schomäcker
Abstract: 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.
Authors: Kay André Weidenmann, Eberhard Kerscher, Volker Schulze, Detlef Löhe
Abstract: Compound-extruded unidirectionally reinforced lightweight profiles are a novel class of materials for the realisation of load-bearing structures. They may be fabricated in a flexible and rapid near-net-shape process. The authors present investigations of the reinforcing effect of wires in compound-extruded aluminum profiles under quasi-static tension and compression. In particular, the compounds were characterized by metallographic examinations focusing on the fracture morphology. Furthermore, specimens subject to compression tests were examined using micro computer tomography (µ-CT) and light microscopy (LM). It is shown, that the mechanical properties of wire-reinforced profiles are improved under both positive and negative quasi-static loads in comparison to non-reinforced profiles.
Authors: Christian Munzinger, Jürgen Fleischer, Gregor Stengel
Abstract: The innovative process of curved profile extrusion facilitates the cost-effective production of lightweight structures with spatially curved profiles even for small series. Due to the extrusion process a continuous flow of material is unavoidable. The profiles have to be separated reactionlessly during the extrusion following the complex trajectory of the cut-off point in space. This paper discusses the challenges for a flying cut-off device. In addition to a concept to generate the trajectories and control the movements, the main parameters for dimensioning a cut-off device are presented. A specially designed clamping device permits to generate high accelerations. Further on, cutting results are shown especially for extruded sections with continuous reinforcing elements of steel.
Authors: Jürgen Fleischer, Steffen Kies, Christian Munzinger, Raphael Rilli
Abstract: Due to economical, ecological and functional reasons, lightweight-construction is continuously gaining importance. Therefore, lightweight space frames made of pipe profiles are subsequently of higher importance in today’s technology. Today, the lower limits of the production range of lightweight space frames are set by joining processes that require jigs. For a flexible variation in a small-scale production, the use of latching elements for the pre-attachment in the jigfree assembly of frame structures serves as a good approach. In consideration of the analysis of the actual situation this article takes up this approach and points out the potential enabled by latching elements. Subsequently, the implementation of laser cutting will be motivated and the results of the first experiments on reinforced and unreinforced profiles will be discussed. To conclude this article, the challenges and approaches for the integration of this procedure to an existing handling and machining kinematics will be pointed out, and finally the implementation potentials of the procedure within an entire process-chain will also be mentioned.
Authors: Klaus Weinert, Niels Hammer, Jens Rautenberg
Abstract: Innovative composite extrusions consisting of an aluminium matrix material with steel fibres for reinforced lightweight constructions require adapted cutting technologies. Due to the resulting tool wear when machining such composite materials, new tools and processes have to be developed. The following article describes experimental investigations concerning conventional drilling operations in comparison to helix milling operations for the manufacturing of holes in these materials. Therefore especially wear and quality aspects are discussed. Furthermore a flexible cutting process for thin walled lightweight frame connector elements to combine profiles is described. To obtain detailed process knowledge also FEA-Simulations of the thermo-mechanical loads affecting the workpiece during the process are performed.
Authors: Andreas Trautmann, Michael F. Zäh
Abstract: This paper renders research into the fundamentals governing the melt pool dynamics of a hybrid bifocal laser welding system consisting of an Nd:YAG and a high power diode laser (HPDL). The resulting superposition of keyhole by heat conduction mode welding is assayed for extruded aluminum. In particular the diffusion of the surface oxygen layer is considered. By comparing the results attainable by bifocal laser hybrid welding to the constituent laser processes synergetic effects of the laser hybrid can be demonstrated. These are namely the doubling of the welding speed from 2.0 min-1 to 4.0 m min-1, the reduction of the roughness of the weld surface from 60 om to approximately 10 om and an increase in energy transfer efficiency. The experimental investigations verifying these synergies are outlined and discussed.
Authors: Volker Schulze, Pablo Barreiro, Detlef Löhe
Abstract: Electromagnetic Compression of tubular profiles with high electrical conductivity is an innovative joining process for light weight structures. The components are joined 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. This process avoids any surface’s damage of the workpiece because there is no contact between the components and the forming tool. The load, which the joints can transmit, strongly depends on the process parameters. Of them, the charging energy and initial gap between components are the most important. In the present article, the influence of these two parameters on the joint’s characteristics, material’s microstructure and the mechanical properties is analyzed. The strength of the joint is determined by tensile tests and by measurements of the residual stresses. Finally, conclusions for the joint design are given.
Authors: Werner Homberg, Michael Marré, Charlotte Beerwald, Matthias Kleiner
Abstract: Joining of lightweight frame structures in small quantities is subject to specific conditions, which are exemplarily determined for joining by forming processes. Experimental investigations have been carried out to evaluate both feasibility and capability of joining by forming processes. Joining has been accomplished by compressing or expanding cylindrical profiles using rigid tools for rolling-in processes, fluid active medium for hydro-forming as well as active energy for electromagnetic forming.

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