P 540 - Flanging thin-walled sheet steel components

P 546 - Development of a spur gear differential with internal gearing in sheet metal construction The most common type of axle differential for vehicles to date is the bevel gear differential. With this differential, the torque is transmitted over a relatively small diameter with correspondingly high component stresses. In order to increase the load-bearing capacity, the bevel gears are sometimes made from materials with particularly high strength. The high axial forces from the bevel gear teeth also require a solid and heavy cast housing. As part of the research project, a spur gear differential with internal gearing was developed and investigated as an alternative to the bevel gear differential. In this type of differential, the torque is transmitted over a relatively large diameter. This results in relatively small gear forces with correspondingly low component stresses. This type of differential therefore allows either a higher transmissible torque with the same installation space requirement, or a lower installation space requirement and lower weight with the same transmissible torque as a comparable bevel gear differential. Prototypes were produced with the same load capacity and a more compact and lighter design compared to a reference bevel gear differential. A total of four prototypes were built for testing. Two of these were designed as lightweight variants with a sheet metal web. These variants are around 17% lighter than the bevel gear differential. For the tests on the basic operating behaviour of the spur gear differential, two further differentials with a solid web were built, which are still around 4% lighter than the reference differential. The investigations into the function of the differential show a locking value curve that increases with the load. The differential behaves symmetrically in left and right curves. The measured blocking values are between 13% and 18%. In contrast, the locking value on the reference differential remains constant at approx. 9% as the load increases. The locking value behaviour of the spur gear differential can be assessed as favourable for the driving behaviour based on the test bench tests. The tests on the load-bearing capacity of the differential revealed an insufficient scuffing load-bearing capacity of the planetary bearing, which could not be eliminated within the scope of the project. As the bearing of the bevel gears in the reference differential functions with a similarly high load, it is assumed that the problems in the spur gear differential can be solved. Authors: B. R. Höhn, K. Michaelis, M. Heizenröther Publication: 2005

P 547 - Manufacture of a flangeless fuel tank with complex geometry The aim of the research project was the production of a package-optimised fuel tank made of steel. This was based on the results of research project P 410 "Production of a fuel tank with complex geometry made of steel using hydroforming". The package optimisation aimed for in this research project was achieved by designing the tank as a flangeless (laser) welded tank using forming and joining technology. A major problem in the production of a flangeless tank made of stainless steel is the uneven, moulding-related spring-up and spring-back, particularly in the frame areas. This makes the positioning and orientation of the tank halves required for joining very difficult. In this project, the residual stress state in the formed sheet metal half-shells was therefore first analysed using the drill hole method and the disassembly method. From this, design and tooling measures (increasing the rigidity through appropriate embossing) were derived in order to minimise the forming-related springback. In the field of joining technology, a special welding process (based on the use of a special robot head) and a corresponding clamping device were developed and realised, which was able to achieve precise trimming and joining. However, it turned out that the shape deviations caused by springback could not be fully compensated for by increasing the rigidity and by the clamping technology used. For this reason, the tank half-shells were ultimately successfully joined using piece-by-piece laser welding and manual TIG welding. Finally, the manufactured tanks were subjected to component tests in accordance with the VW factory standard. The knowledge gained can initially make the manufacture of modern tank systems with complex geometries from steel materials considerably easier. In addition, the findings can also be transferred to other potential areas of application, for example in rail and aircraft construction, apparatus engineering, sanitary engineering or the household appliance industry. Authors: M. Kleiner, W. Homberg, A. Wellendorf, M. Gösling, F. Trösken, F. Behr, T. Langhammer Publication: 2006

P 549 - Material flow control through optimised design of a burr geometry that varies in circulation Components with good mechanical properties can be produced relatively cost-effectively in large quantities using the forging manufacturing process. Nevertheless, this manufacturing process is also subject to the economic pressure of a large number of competing processes. This is because, apart from the quality of the component, costs are the decisive factor for the customer when placing production orders. It is therefore important to pursue the goal of producing high-quality components even more cost-effectively. In order to improve the economic boundary conditions, the reduction of forming force and input mass is particularly suitable in the forging process, as these factors are ultimately reflected to a large extent in the overall costs of the components. Although the precision forging process makes it possible to produce forged parts without excess material, this is difficult to realise for many components. Due to the combination of technological and economic factors, the majority of forged components are produced with excess material. This excess material must flow between the moulding dies via the so-called flash path. The design of the shape of this flash path has a significant influence on the tool stress, the flow behaviour within the engraving and the required excess material. As the flow behaviour of complex forged parts is not constant, it is advisable to design the flash path variably according to the flow conditions. At present, the design is mainly based on individual empirical values. Systematic design methods and solutions to support the design process within CAD systems do not yet exist. As part of this project, various methods for designing variable burr geometries were developed. In order to compensate for the higher design effort of variable burr geometries modelling concepts were also developed in various CAD systems to simplify and partially automate the design of burr paths. To verify the positive effects of variable flash paths on the insertion mass or forming force, variable flash paths for forging tools were designed iteratively, checked with the aid of FEM simulation (finite element method) and the analysed improvements verified by means of test forging operations. RESEARCH ASSOCIATION FOR STAHLANWENDUNG e.V. Publication: 2004 Authors: Prof. Dr.-Ing. E. Doege, Prof. Dr.-Ing. B.-A. Behrens, Dipl.-Ing. G. Klawitter