P 744 - Validation and extension of calculation methods for sheet metal forming, fatigue strength and crash design in vehicle construction with steel

P 742 - Shear-hole soffit connections with more than two bolts in series in the direction of force in components made of high-strength steel (S 690) The design rules for the shear and bearing capacity of bolt groups according to Eurocode 3, Part 1-8 are based on theoretical investigations and extensive tests on bolted connections with plates made of common structural steels S235 and S355. Due to the high ductility of these steel grades, bolted joints subjected to shear loads achieve a plastic distribution of the bolt forces in the ultimate limit state. The lower ductility of high-strength structural steel compared to conventional structural steels raises the question of whether the plates have sufficient deformation capacity and whether a plastic distribution of the bolt forces can be achieved. In order to answer this question, a total of 17 ultimate load tests were carried out on shear-loaded bolted connections with three bolts in succession in the direction of force as part of the research project. In accordance with Eurocode 3, Part 1-12, which contains additional rules for the use of steel grades up to S700, plates made of structural steel grade S690 were used for the tests. The test results show that the connection load-bearing capacities determined in accordance with Eurocode 3, Part 1-8 include additional safety factors. In tests with shearing of the bolts as the decisive failure mechanism, the experimentally determined bearing loads agree very well with the connection bearing capacities according to Eurocode 3, Part 1-8, regardless of the edge and hole spacing. With perforated soffits as the decisive failure mechanism, the test results only agree well with the connection load-bearing capacities determined in accordance with Eurocode 3, Part 1-8 for large edge and hole spacings. For small edge and hole spacings, the design rules are conservative and provide up to 27% lower connection load-bearing capacities. Based on the test results and numerical investigations carried out in parallel using the finite element (FE) method, a proposal for the modification of the design rules for the ultimate limit state bearing capacity was developed, which allows the existing bearing capacity reserves to be utilised. The modified design approach was then verified with the aid of FE parameter studies on shear-stressed bolted connections with three bolts in the direction of force one behind the other. Finally, further questions were asked about bolt force distribution in shear-loaded bolted connections with more than three bolts in succession in the direction of force as well as about "unbalanced bolt patterns" and the Authors: D. Ungermann, S. Schneider Publication: 2010

P 746 - Hot laser welding of heat-treatable steels during the induction hardening process In order to extend the range of applications and to ensure faster and safer processing of heat-treatable steels, a process has been developed that combines induction hardening and laser welding in a single process. This combination makes it possible to weld in the area of the component that has been inductively heated to austenitising temperature, so that any stresses that may arise during welding do not occur. Hot welding" reduces the risk of cold cracking in the area of the weld seam and prevents softening of the base material. Once the welding process is complete, the surface of the component can also be heated to a temperature above 900 °C (> Ac3) using the inductor in the feed. A trailing spray quenches the weld seam and the entire inductively heated area. This results in a homogeneous hardness distribution in these areas. To investigate the process, a combined hardening welding process was first designed with the aid of FEM simulations and by selecting a suitable sample geometry. The test technology required for the process was developed and set up. As part of the investigations, samples were produced by systematically varying the process parameters, which were validated with regard to their hardness, microstructure and optical properties. The results of the practical tests were compared with the simulation results so that the numerical model could be adapted. It was shown that this method makes it possible to significantly shorten the process duration when processing heat-treatable steels and to simplify the process sequence. The weld seams produced using this method exhibit a homogeneous distribution of hardness in the area of the weld seam and the HAZ. In these two areas of the test piece, metallographic analyses were able to demonstrate a martensitic microstructure. With the help of the simulation, a very precise prediction of the process can be made. The research project was carried out at the Laser Zentrum Hannover e. V. and the Institute of Electroprocess Technology, Leibniz Universität Hannover with technical support and financial assistance from the Forschungsvereinigung Stahlanwendung e. V., Düsseldorf, with funds from the Stiftung Stahlanwendungsforschung, Essen. Authors: D. Kracht, D. Herzog, P. Kallage, R. Rosenfeld, B. Nacke, H. Schülbe, M. Mach Publication: 2009

P747 - Technical and economic comparison of Slim-Floor ceilings and conventional construction methods for flat ceiling constructions Flat slabs offer many advantages over beamed floor systems due to the free floor plan design, reduced storey heights, simple and fast formwork and easier routing of installation lines. The flat ceilings can be constructed in reinforced concrete or in reinforced concrete composite construction (slim-floor ceilings). However, slim-floor ceilings in composite construction currently only play a minor role in Germany. The aim of the study is therefore to compare the cost-effectiveness of slim-floor ceilings with conventional reinforced concrete flat slabs. In addition to a mass and cost analysis, the construction times are also compared using various flat slab systems and the advantages of the individual construction methods are worked out. Publication: 2008 Authors: Prof. Dr.-Ing. U. Kuhlmann, Dipl.-Ing. G. Hauf, Dr.-Ing. N. Sauerborn

P 740 - Partially transparent load-bearing composite components made of steel and glass Due to its high chemical resistance, its low specific weight and, not least, its transparency, glass is an ideal material for a wide range of applications in the construction industry. Due to the brittleness and high notch sensitivity of glass, mechanical fasteners are less suitable for joining. However, glass can be joined to itself or to other materials particularly favourably using adhesive bonding technology. Furthermore, visible mechanical fasteners in the edge area such as screws, point fasteners fixed in holes or clamps can be largely dispensed with. The aim of the research work is the applicability of structural adhesive bonds to large, partially transparent composite components, such as those commonly used in the construction industry, and frame corners. In addition to their partial transparency, these bonded composite components should be able to bear the loads commonly encountered in the construction industry. Publication: 2009 Authors: Prof. Dr.-Ing. Ö. Bucak, Dipl.-Ing. M. Bues, Dipl.-Ing. M. Illguth, Univ.-Prof. Dr-Ing. P. L. Geiß, Dipl.-wirt.-Ing. M. P. Kötter