P 1561 - Modelling and evaluation of logistics chains for hydrogen transport for the steel industry with special consideration of transport-related energy losses

P 1560 - Influence of corrosive media on the fatigue strength of offshore wind turbines Offshore steel structures are sometimes exposed to harsh environmental conditions. At the same time, they are at risk of fatigue due to cyclic loads from wind, waves and operational or traffic loads. Both the steel structure, which is at risk of fatigue, and the corrosion protection, which degrades over the years, have a limited service life. When the corrosion protection has reached the end of its service life and fails, the steel is exposed to free corrosion. In order to continue operating the structures in this condition, it is necessary to investigate the influence of corrosion on fatigue strength. For this purpose, new methods must be developed with which the actual condition of corroded components of the load-bearing structures can be recorded and integrated into predictions for a (remaining) service life. Steel structures generally have numerous welded joints. These behave differently to the base material due to the existing stress concentrations caused by the weld seam geometry and the residual stresses from the welding process. Fatigue tests were therefore carried out on corroded base material, fillet weld and butt weld samples. In addition, 3D scans and residual stress measurements were carried out. The fatigue tests were then recalculated using local fatigue concepts, taking into account the real specimen geometry from the 3D scans and the measured residual stresses. It was shown that the notch stresses have a major influence on the prediction of the service life. In addition, it was found that the residual stresses play an important role and must be taken into account when assessing the remaining service life of corroded steel components. By applying local methods, the scatter in the Wöhler curves could be minimised, thus increasing reliability. It was shown for welded specimens that it is possible to take into account the real condition of corroded components in the calculation of fatigue strength. Using the replica technique, in which impressions of corroded components are created as part of structural inspections, it was shown that the results from the previous investigations based on notch stresses can be transferred to real structures. Further investigations with a total of 12 months of corrosive exposure have shown that the fatigue strength does not fall continuously and equally for all sample geometries. The reduction in fatigue strength for base material samples, for example, is greater than for welded samples, which can be attributed to a lower notch effect in the initial state prior to corrosive exposure. It has also been shown that there is an equalisation effect over a long corrosion period, which leads to different specimen geometries with different fatigue strengths in the uncorroded state having similar fatigue strengths after exposure to corrosion. This is due to the different interaction of corrosion and weld notches. Sharp initial notches become milder due to corrosion and milder initial notches become sharper due to corrosion. The aim of the research project was achieved. Publication: February 2025 Authors: S. Shojai, P. Schaumann, E. Ghafoori, Ch. Woitzik, R. and F. von Bock and Polach

P 1562 - Increasing the storage and transport efficiency of liquid hydrogen in steel fibre composite tanks by thermally sprayed TBC layers Wind power-to-gas concepts have great potential to sustainably meet the increasing demand for green hydrogen as an energy carrier and raw material. It has been shown in the past that there is an enormous level of energy overproduction, which currently remains unutilised due to the shutdown of wind power plants. This is due to the nascent market and therefore a lack of experience in transporting large quantities of liquid hydrogen (LH2). Current tank designs are based on standard applications for storage and transport on land with vacuum-insulated, double-walled constructions made of austenitic stainless steel, which have comparatively high thermal diffusivity and conductivity as well as increased weight. This currently reduces efficiency due to the increased boil-off and the unfavourable gravimetric storage density. New tank concepts are therefore required for the maritime production and transport of LH2. In order to meet these requirements, the focus initially shifted to special fibre-reinforced plastic composite (FRP) steel hybrid tank concepts, which guarantee high mass-specific strength and increased protection against corrosion and have become established in the aerospace industry. In the course of the project, questions relating to interactions with coatings, production, material, temperature resistance and design for commercial utilisation were investigated in particular. A further requirement is the necessary increase in the insulation effect in relation to evaporation losses (boil-off). With current double-walled and vacuum-insulated tanks, the boil-off is approx. 2 % of the storage volume per day, which leads to large storage losses and inefficiency in the case of longer storage and transport times, e.g. over several days. In order to counteract the boil-off and to additionally protect the tank shell from dynamic sloshing forces, thermal barrier coatings (TBC) applied by thermal spraying have come into focus due to their high insulating effect and wear resistance. However, the application of TBC was previously limited to use at high temperatures and was extended to the cryogenic temperature range during the project. The investigations focussed on the validation of standard MCrAlY alloys and innovative (partially) amorphous iron-based coatings with regard to mechanical-technological and insulating properties in the low temperature range by varying different spraying processes and parameters. In the course of the project, it was shown that a combination of the two approaches is possible and easy to realise in terms of production technology. This meant that both the TBC layers and the fibre windings could be applied in sufficient thickness and in a defined sequence. These successful investigations formed the basis for the complete coating, fibre composite winding and subsequent testing of a small prototype tank. The objective of the research project was achieved. Publication: February 2025 Authors: M. Hauer, S. Schmidt, A. Gericke, N. Stroetmann, L. Sattler, W. Flügge