P 566 - Use of near-net-shape semi-finished steel products with variable diameters for hydroforming in the spinning - bending - hydroforming process chain

P 567 - Simulation-based optimisation of the forming - laser beam welding process chain Innovative production technologies in the field of forming technology, e.g. hydroforming (hydroforming), and in the field of joining technology, e.g. laser beam welding, enable the production of functional structural elements in lightweight construction. The advantages of these processes, such as an increase in rigidity despite a reduction in weight, are particularly evident when using high-strength and higher-strength steels. The industry's requirements in terms of manufacturing efficiency, load-bearing capacity and weight reduction of component structures require further innovations in the field of manufacturing technologies. In this context, the combination of the aforementioned processes offers the possibility of utilising the specific advantages of the individual production steps, such as the high level of automation, within a process chain. Numerical simulation based on the finite element method (FEM) serves as a tool for analysing the effects of the process on the machined component. The main objective of forming simulation is to investigate the process parameters and analyse the feasibility of the individual forming steps. Welding simulation is used to determine component distortion as a result of heat input into the component. Up to now, there have been no integration possibilities due to the different objectives and methods of the respective process simulations, making it difficult to take a holistic view in the simulation. The high stresses that are present as residual stresses in a formed semi-finished product after the forming process have a considerable influence on the behaviour of the component in the further course of the production chain. During laser beam welding, the internal equilibrium of the residual stresses is disturbed by the beam-substance interaction of the component with the laser beam. As a result, the internal energy is partially converted into a deformation of the material. This deformation has a major influence on the distortion caused by welding. As part of this research project, a methodology was developed to transfer the results of the simulation of the hydroforming process to the simulation of laser beam welding. For this purpose, the result of the forming simulation is implemented as the initial state in the welding simulation. In order to obtain a stable stress state as the initial state in the welding simulation, a strain tensor was generated based on the stress state in the last step of the forming simulation, which produces the required stress state. The results of exemplary simulation calculations show a significant improvement in accuracy through the integrated consideration of the two processes of hydroforming and laser beam welding in contrast to a mere distortion simulation of welding. In the case of complex structures, some tendencies only become apparent when the integration method is used. However, quantitative statements on the deformation of the structure due to the laser energy applied using numerical methods and highly abstracted models, such as modelling the clamping or the heat source, are not yet possible. Authors: M. F. Zäh, F. Auer, S. Roeren, H. Hoffmann, S. Häußinger Publication: 2004

P 568 - Possible applications of dry cutting and minimum quantity cooling lubrication in the machining of high-alloy, corrosion-resistant steel materials In the machining of steel materials, the use of conventional cooling lubricants is increasingly being replaced by the technologies of dry machining and minimum quantity cooling lubrication. While standardised solutions exist for numerous, easily machinable materials, the machining of high-alloy, corrosion-resistant steels places the highest demands on the design of the production processes. As part of the research project, experimental investigations were carried out into the turning and drilling of high-alloy, corrosion-resistant steels with different cooling lubricant concepts. The aim of the project was to highlight the possible applications of dry machining and minimum quantity cooling lubrication and to develop new solutions. The knowledge gained from the investigations allows easy transferability to other materials and related manufacturing processes. The results show that dry machining of corrosion-resistant steels is technologically feasible and economically viable in many cases. The performance of wet machining can be clearly surpassed if the processes are analysed in detail and the cutting parameters and tools are adapted. The reduction of cooling lubricant only poses major problems when machining heat-resistant materials with high toughness. Examples of this are high-alloyed austenitic-ferritic or nitrogen-alloyed austenitic steels. In order to ensure that the results obtained can be transferred to industrial practice, the production of a hexagon fitting screw was verified. It became clear that the process design, especially under the boundary conditions of dry machining, is of great importance. If the necessary process adjustments are made, economical machining is possible without any problems while maintaining the required quality characteristics. RESEARCH ASSOCIATION FOR STAHLANWENDUNG e.V. Publication: 2003 Authors: Prof. Dr.-lng. Dr. h.c. K. Weinert, Dipl.-Ing. S.Hesterberg, M.Sc., Dipl.-Ing. S. Wittkop

P 561 - Forming-based joining for stainless steel façade elements Due to its typical properties, such as good formability combined with high component strength, steel offers excellent potential for architectural expression. As part of this project, the Chair of Forming Technology at the University of Dortmund used a new type of stainless steel façade system as an example for a new test hall, focussing in particular on questions relating to assembly technology, corrosion resistance and design. A key focus was the development and optimisation of the element geometry for this façade cladding. The individual elements had to be installed in such a way as to minimise surface damage and ensure all the relevant structural properties. At the same time, cost-effectiveness was to be improved through a quick, simple and functional installation technique. This objective was to be achieved through an assembly system with a high degree of prefabrication in the workshop to minimise on-site assembly times and the on-site use of a forming joining technique such as clinching. Construction and assembly of the realised stainless steel façade ultimately had to be carried out in a more conventional manner, as hand-guided setting equipment was not available for use on site during the construction phase. This restriction was primarily due to the system dimensions, which precluded the use of a non-stationary, hand-guided setting unit. With the specified geometric dimensions of the parts to be joined - especially the panels - accessibility to all the required joining points would only be possible with increased design and technical equipment - and therefore only with increasing mould masses. This meant that the use of a forming joining process was only possible to a limited extent in terms of the objective. As an alternative, the assembly technique - adapted to the selected panel geometry - was modified in such a way that concealed assembly points were used to prevent penetration of the façade surface. This surface-friendly installation technique is based on internal clamping elements that fulfil all the necessary static boundary conditions. It fulfils the requirement for shorter installation times on the construction site. The clamping elements are fastened quickly and easily using riveting technology with lightweight hand-held tools. The concealed mounting points significantly characterise the sophisticated visual appearance of the façade, especially in the stainless steel version presented here. The investigations show extended possibilities for the use of large-area elements as façade cladding. The assembly technique presented here was developed as an example for the construction of an external façade cladding made of stainless steel and can be transferred to other sheet materials with corresponding formability. This development work thus characterises the outstanding properties of steel as a material. In addition to the mechanical and technical requirements, the use of stainless steel also fulfils further requirements in terms of appearance and design. RESEARCH ASSOCIATION FOR STAHLANWENDUNG e.V. Publication: 2004 Authors: Prof. Dr.-Ing. M. Kleiner, Dr.-Ing. F.-J.Kleiner