P 1234 - Surface structures made of curved sandwich elements

P 1232 - Laser beam welding of ultra-high strength steels 22MnB5 and DP1000 - Generation and validation of material parameters in heat affected zones (HAZ) for a closed simulation chain from temperature field simulation of the joining technology to loading The aim of the research project is to close the simulation chain from joining technology to crash simulation for ultra-high-strength steels (UHSS). A deeper understanding of the temperature-dependent change in material properties in the heat-affected zone (HAZ) caused by the welding process is to be gained and transferred to simulation approaches. For this purpose, the temperature curves occurring in the various areas of the HAZ during laser beam welding are simulated in material samples. The mechanical-technological properties of these areas are then determined and implemented in the finite element model (FEM) for the load simulation. The simulation approach developed in this way is initially used for tensile tests and component-like geometries and later simplified for use in complete vehicle simulations and implemented using a component concept as an example. The intended results are the correlation of heating rate and transformation temperatures and the determination of the influence on the microstructure formation, the generation of temperature-dependent mechanical-technological properties in the HAZ of laser beam welds and the determination of the necessary level of detail of the joining zone depicted in the FEM model to improve crash simulation results. The results can be implemented in FEM models at short notice and utilised economically. This enables simulation service providers to expand their portfolio with a valuable area of work. For manufacturers and processors of UHSS components, the improved prediction of the load behaviour of ultra-high-strength steels can open up new lightweight construction potential and reduce the costs of complex tests and prototypes. In addition, material technology companies have the opportunity to adapt a methodology that opens up a new field for generating material data. Publication: 2020 Authors: Prof. Dr.-Ing. U. Reisgen, Prof. Dr. St. Eckstein

P 1236 - Quantitative description of the influence of toughness on the residual cracking properties of modern pipeline steels Resistance to long-running cracks while ensuring crack arrest is one of the most important safety requirements for gas transport pipelines. Pipeline steels with excellent toughness properties have been developed to fulfil these requirements. However, due to the fracture phenomena occurring during experimental toughness characterisation in notched bar impact bending tests and Battelle drop weight tests to rule out brittle crack initiation, the conventional design methods for extensive use of these outstanding properties must be questioned. The phenomena include so-called separations and inverse fracture behaviour. In addition to the exclusion of brittle crack initiation, ductile crack arrest must be ensured. Sufficient material resistance to crack propagation is defined as the high layer energy value from notched bar impact tests. Studies in the past have shown non-conservative design results for modern pipeline steels, which are countered with corresponding safety factors. In this project, damage mechanics modelling approaches were therefore developed and parameterised on the basis of extensive experimental work in the low position and at RT. The ductile and brittle damage models were verified by simulating notched bar impact bending tests and Battelle drop weight tests and then used to predict the pipe behaviour. Separation and inverse fracture behaviour were simulated for the first time in the Battelle drop weight test. At component level, the simulations showed an increase in the crack propagation velocity as a result of the separations, but in the laboratory tests and in the pipe, less critical stress conditions in the area in front of the crack front with regard to the initiation of the split fracture. With regard to the inverse fracture behaviour, it could be concluded that this is due to the stress conditions in the laboratory samples in the high position and is not to be expected in the pipe. In parallel, a coupled FSI pipe model was developed to estimate the interactions between the crack propagation in the pipe wall, the fluid decompression inside the pipe and the soil backfill in onshore applications. During the simulation of the bursting process, the three-dimensional FSI model is used to calculate the pressure fields inside the pipeline, which differ greatly depending on the fluid. In comparison with measurements from bursting tests, accurate predictions were achieved and the approach verified for single-phase and two-phase natural gases and CO2 mixtures. The project results obtained support the safe handling of ultra-high-toughness piping materials and extend their range of applications. Based on the numerical predictions, sometimes applied correlations between the material behaviour at laboratory and component level can be evaluated. Furthermore, the damage-mechanical and multi-physical modelling concepts represent innovative tools for the design of other pressurised components. Publication: January 2021 Authors: Prof. Dr.-Ing. S. Münstermann, David Lenz, M.Sc., Prof. Dr.-Ing. A. Nonn, V.Keim, M.Sc.

P 1237 - Extension of the process limits for wrinkle-free sealing of lids made of high-strength thin packaging steel Against the background of constantly dwindling resources and very high production volumes in the billions, the issue of material savings is of central importance in the packaging steel industry. The entire packaging steel processing industry is therefore faced with the economic and technical challenge of having to process high-strength tinplate alloys reliably. This research project investigated the extent to which thinner, higher-strength metal packaging materials can be reliably processed and used to increase the functionality of cans (in this case, three-piece food cans). Based on extensive research into the seaming technology of metal packaging and the expert discussion (interview) within the project-accompanying industrial working group, the main influences on the seaming process were analysed, weighted and evaluated. The main influences were analysed with the aid of an FEM process model for the roll capping technology and then an optimisation was carried out for the main parameters. Using a derived criterion for crease assessment (waviness and maximum crease height) in the FEM results, comparability was established and made assessable. As part of the process optimisation, the profile geometry of the OP1 capping roller was changed in particular. The profile height and the profile radii proved to be significant influences. The values achieved for these parameters within the optimisation showed significantly better wrinkle behaviour in the FEM model and were subsequently verified in experimental tests on industrial machines. Within the experimental tests at three machine manufacturers and one can manufacturer, the improvement of the crease behaviour with the new tool geometries for the OP1 seaming operation could be practically proven. The cans produced by the industrial participants were sent in small quantities to the industrial measuring partner, who analysed them in terms of wrinkling using a new non-destructive measuring principle. The analysis of the results for all the materials investigated showed that the optimised process settings and tool geometries resulted in a significant improvement in wrinkling for all manufacturers. The dent test was carried out on a random basis as part of investigations into the functionality of the sealed cans. From this sample it can be deduced that all materials with a higher strength have the potential to improve functionality. However, it can also be emphasised that materials with a high strength and a high elongation have a greater potential for improving the component function than materials with a pure increase in strength. Publication date: August 2020 Authors: Prof. Dr.-Ing. W.-G. Drossel Dipl.-Ing. T. Lieber Dipl.-Ing. Dipl.-Wirtsch.-Ing. M. Nagel

P 1238 - Local material influence during mould hardening to improve the joinability of components made of 22MnB5 The aim of the research project was to improve the joinability of mould-hardened components made of 22MnB5 through the targeted introduction of local thinning with the associated formation of deformation-induced ferrite (DIF). In addition to the localised reduction in material thickness, the material properties were also influenced by the targeted introduction of DIF. To this end, the IFUM Hannover carried out investigations into the mould hardening of locally softened blanks. The IWF Magdeburg focussed on expanding the joinability of material combinations with 22MnB5 through resistance spot welding and semi-tubular punch riveting. At the beginning of the project, extensive tests were carried out on the forming dilatometer to determine the process window for the formation of DIF. The findings from the dilatometer tests were then validated by means of experimental thinning tests. For this purpose, tests were carried out on a hydraulic double-column press in which embossing was applied to the blanks using a deformation plate during a conventional mould hardening process. The tests carried out showed that it was not possible to produce sufficient embossing points with the formation of DIF using conventional mould hardening due to the long contact time of the deformation tools with the blanks used. For this reason, model tests were carried out on a spindle press from Weingarten, in which very short contact times were possible due to the abrupt punch movement. The tests on the screw press were used to investigate the generation of DIF in a forming process. As it was not possible to transfer the objective pursued to a mould hardening process, the potential of DIF generation was finally investigated in a numerical simulation. Publication: May 2021 Authors: Prof. Dr.-Ing. B.-A. Behrens, Prof. Dr.-Ing. S. Jüttner