P 363 - Flexural lateral-torsional buckling of composite beams without concrete chord

P 367: Investigation and testing of a steel spaceframe structure made of hydroformed and roll-formed components In today's car body construction, the multi-shell design in steel is leading. The main advantages here are the low costs and the proven suitability for mass production. In view of the level of maturity achieved today, there are only a few opportunities left to realise further optimisation potential. Due to the differential shell design and the sub-optimal properties of some structural bodywork components as a result of the joining technology required, an approach to saving weight with the same or better performance is seen in the steel sector with a body structure in the form of a spaceframe, as previously known from the aluminium sector. Theoretically, the conceptual advantages that can be achieved from the closed profiles used there - low weight with good rigidity and crash properties - can be partially transferred to steel bodies. A promising approach here is to use rolled profiles instead of extruded aluminium spaceframes and to replace cast nodes with hydroformed (hydroformed) parts. The stiffening sheet metal panels are usually produced as deep-drawn sheet metal mouldings. The aim of this project was therefore to provide and verify statements on the suitability of rolled and hydroformed body components as well as information on the weight-saving potential and suitable joining processes. In a previous feasibility study, a complex car body node from the rear end of the vehicle was examined for its manufacturability by hydroforming. The result showed that the component could be designed to be suitable for hydroforming by making minor adjustments - caused by the high degree of forming. Appropriately designed initial tubes were then formed into hydroformed parts in practical trials. Critical design areas were iteratively minimised in the course of the tests. These were, for example, sharp radii, strong cross-sectional jumps or secondary moulding elements that hinder the flow of the material. In parallel, different materials were used to determine the most favourable potentials from this point of view. The prototypes produced were installed in a car body with an adapted rear end and measured. The measurement results show good agreement with the originally determined FEM results. Due to the complexity of the component, the existing geometry could only be produced in one forming step using one of the materials investigated, 1.4303. For other steel grades, further design steps were necessary. For other steel grades, further design changes to the component or additional production steps were necessary, resulting in a lower degree of integration. A detailed profitability analysis is required here. The selected concept of hydroforming nodes and rolled profiles made it possible to reduce the number of components for the rear carriage from 44 to 35 and the weight by 10% (5870 g). The stiffness values determined for the installed rear carriage were in good agreement with the calculated predictions. The project also provided valuable insights into the design and material selection of complex body components adapted to the hydroforming process, as well as their integration into an existing self-supporting, multi-shell vehicle body. STUDIENGESELLSCHAFT STAHLANWENDUNG e.V. Publication: 2000 Authors: Dr.-Ing. T. Krusche, Dipl.-Ing. H. Walter, Dr.-Ing. K.-U. Dudziak

P 368: Characterisation of sandwich components made of steel cover sheets with a core of fused metallurgically produced foamed aluminium In the preceding project P 281.1 "Industrial use of sheet steel composites with foamed aluminium Project 1 Sandwich constructions made of sheet steel with foamed aluminium" of the Studiengesellschaft Stahlanwendung e.V., a new type of sandwich composite made of steel cover sheets and an aluminium foam core with a metallic bond between the components was developed. This sandwich composite combines a low weight per unit area with the good strength and surface properties of steel and the functional properties of the foam core layer (energy absorption, reduced thermal conductivity, etc.). The P 368 research project, which has now been completed, was designed to test whether a similar bond between steel cover sheets and aluminium foam core is possible by bonding the two metals. Experiments with various adhesive systems showed that a durable, shear-resistant bond between the aluminium foam core layer and steel cover sheets can be achieved by bonding with a viscous epoxy resin adhesive to produce a sandwich composite. By roughening the surfaces and heat-curing the adhesive, reproducible sandwiches can be produced in which the foam core layer is the weakest link. Bonding the sandwich partners also enables sandwiches with steel cover sheets of more than 2 mm (here 3 and 5 mm) and corresponding foam core layers (30 and 50 mm), which cannot be produced using the method developed in P 281.1. The testing of bonded sandwich panels in shear, tensile and bending tests shows that, depending on the selected foam core alloy, similarly good properties can be achieved as with material with a metallic bond. The peel strengths determined for bonded sandwiches are also acceptable despite the rather hard and brittle epoxy resin adhesive. Uncoated steel sheets have slightly lower peel strengths than roll-aluminised cover sheets, but these should also be fully adequate for use. It should be noted that due to the low thermal resistance of the resin adhesive, high-temperature applications are not possible and joining by welding has not yet been realised experimentally. Three-dimensional moulded parts are also not yet feasible. STUDIENGESELLSCHAFT STAHLANWENDUNG e.V. Publication: 1998 Authors: Prof. D.-Ing. W. Bleck, Dipl.-Ing. H. von Hagen

P 336: Determination of application and decision criteria for an efficient application of multi-point drawing technology in the series operation of pressing plants Multi-point drawing equipment in press shops can be used to increase the drawing depths of deep-drawn components, especially those made of high-strength materials, and to improve the quality level and productivity. The aim of this research work was to demonstrate the technological advantages and to develop process-specific knowledge about initial settings and parameter influences. The research results should provide decision criteria for the introduction and industrial implementation of this technology. A computer programme for realistic finite element process simulation was developed to illustrate the technological relationships. A special feature is the elastic modelling of the hold-down device. It allows modelling of the deformation under the effect of force during the sheet metal run-in. Corresponding practical tests were carried out on a hydraulic press with 16-point drawing systems. These included conventional deep drawing without and with an elastic hold-down plate as well as multi-point drawing with the elastic hold-down plate. Sheet thickness distribution, flange tightening, contact conditions and blank holder deformations in the process were monitored and quantitatively evaluated as comparative criteria. The test materials were the soft deep-drawing steel DC 04 as a reference and ZStE 220i and H340 as isotropic or higher-strength steel grades. The investigations demonstrated in simulation and practice that the use of multi-point drawing technology can increase process reliability and at the same time extend the technological limits. Unfavourable distributions of the actually prevailing local surface pressures between the blank holder, sheet and die proved to be the cause of failures. It was shown that the use of an elastic hold-down device is a prerequisite for a functional multi-point drawing system and technologically optimised results. Advice is given on the effective initial setting of the quill forces with the aid of FEM simulation for various applications. This work contains valuable information for the technological design of multi-point drawing presses and provides new arguments for the use of this technology by steel processors. STUDIENGESELLSCHAFT STAHLANWENDUNG e.V. Publication: 2000 Authors: Dipl.-Ing. L. Klose, Dipl.-Ing. H. Bräunlich