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TRR 10:  Integration of Forming, Cutting and Joining for the Flexible Manufacture of Lightweight Frame Structures

Subject Area Mechanical and Industrial Engineering
Materials Science and Engineering
Term from 2003 to 2014
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 5485733
 
Final Report Year 2015

Final Report Abstract

An important result of the Transregio is the integrated process chain and the development of technologies for an automated and product-flexible small-series production of lightweight frame structures. Here, especially the flexibility in terms of applicability in different quantities, the applicability at a high diversity of variants, and the manufacturability have to be highlighted. Products for lightweight frame structures vary in shape, size and in their application and often possess customized properties. For small quantities and a high diversity of variants, processes with a tool-based form of production are usually uneconomical. For this reason processes with a kinematic shape generation should be enhanced and qualified so that they are suitable for the increased manufacturing complexity. In order to reduce the number of processes and component-related interfaces between the single manufacturing steps, the vertical range of manufacture has to be decreased by an increased technological integration. To achieve this, the large number of simple processes is replaced by less, but more complex manufacturing methods. For this purpose, the profile extrusion process was extended in the Transregio. Innovative manufacturing methods such as the curved profile extrusion, the extrusion of profiles with variable wall thicknesses, and the composite extrusion were developed. The composite extrusion process allows the use of metallic wires or hybrid ceramic fiber composite wires as reinforcing elements and glass fibers or insulated electrical conductors as functional elements. To predict the quality of the embedding by on quasi-stationary process simulations and to allows an automatic optimization, methods have been developed on the basis of algorithms such as the "Evolutionary Algorithms" from computer science. To provide an insight into the failure behavior of the new components, new methods for the material characterization such as micro-push-out tests, in-situ testing methods using acoustic emission analysis, and in-situ tensile tests with a computer tomography imaging were developed. The handling of the profiles was performed with a flexible and intelligent gripping technology, which can also be used for the measurement and arrangement of the profiles by means of a geometrydependent component system scale. The high qualitaty processing of these profiles was partly achieved through the use of real-time acoustic emission systems, which can identify material intersections. Due to that e.g. machining processes can be interrupted just before reaching the reinforcing elements inside a composite profile. For the prediction, process planning, and optimization of milling processes for the production of lightweight, reinforced structural and node components made of aluminum, a simulation framework was developed, which allows to predict the essential process variables including their influences. Due to the combination of YAG and high power diode lasers for bifocal-hybrid-laser-welding, a doubling of the welding speed compared to conventional methods could be achieved. Furthermore, a 25 % higher strength was obtained in a benchmark on flat samples at quasi-static as well as at dynamic loads in comparison to the WIG process. For the bifocal-hybrid-laser-beam-welding and for the friction stir welding a flexible heat source model was developed that can predict the process-specific distortion and the residual stresses of the considered component geometries by means of numerical calculations. In addition, for force-fit joining methods of profile-profile connections, the internal-high-pressure-joining and for sheetprofile connections the magnetic pulse welding were analyzed. Methods for integrated consideration of structural mechanics and production engineering aspects were developed for the design optimization of extruded (composite) components and structures. Due to these methods, construction designs for any semi-finished products and components can be derived. The developed methods of the design optimization were used for dynamic impact processes (crash) and were extended to verify the robustness of deviations from the nominal of the determined design. On the material and the structural mechanics level, a model and the simulation of reinforced composites profiles were set up, that can be used to predict the elastic and strength behavior of heterogeneous reinforced composite profiles in an early design stage. By the use of cruciform specimens, whose geometry was optimized for the reinforced material, the failure criterion and the consideration of the homogenized material for strength analysis could be verified. Fracture mechanics and high dynamic impact loads were considered as well.

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