P 1322 - Development of a design concept for multi-axis stressed tools made of carbide-rich tool steel for cold work applications

P 1323 - Extension of the constitution diagrams for high Mn-containing steels in dissimilar welded joints by hazard zones The primary aim of the research project was to determine the hazard ranges for the newly developed Constitution of High Manganese Steel Welds (COHMS) constitution diagram in order to enable low-hazard welding of high-manganese steels in dissimilar joints with ferritic joining partners. Three economically relevant austenitic iron-manganese steels (Fe-Mn) with different alloying concepts, two ferritic body steels and various welding consumables were used as test materials. This allowed all microstructural areas in the COHMS diagram to be covered. Seam irregularities, such as impermissible hardening due to unwanted martensite formation and weld-related hot or cold cracking, can occur in the mixed weld metal of weld seams of these joining partners. In order to determine the location of the risk areas, dissimilar weld metals had to be produced with defined mixtures and then tested using suitable test methods such as 4-point bending, shear and impact tensile tests and hardness tests (hardening crack tendency) as well as programmed deformation crack (PVR) and cast pin tear (CPT) tests (hot crack tendency). Testing these dissimilar weld metals required a modification of the test sequence for the PVR test and the construction of a suitable crucible induction melting furnace for the CPT test. The construction of this induction melting furnace went through several iteration loops and was significantly delayed due to the pandemic. As the final prototype could not be finalised on the hardware side until the end of the project, it was no longer possible to carry out CPT hot tear tests with the mixed welding materials. In addition, the furnace is currently being supplemented by a SIMATIC S7-1200 controller, which serves to automate the entire process. The final induction melting furnace currently enables the casting of a maximum of 33 g of metallic sample material in an inert atmosphere in gravity casting or suction casting in addition to the casting of hot crack samples. Tensile, compression and impact test specimens can be produced from these cast samples. Although the solidification cracking tendency of dissimilar weld metal could not be determined using the CPT test, the results of the other work packages in the research project made it possible to extend the COHMS diagram to include the hazard ranges. It was also possible to determine a low-hazard area. The objective of the research project was achieved. Publication: March 2025 Authors: F. Urban, N. Kauss, M. Kuhlmann, M. Zinke

P 1320 - Preparation of a test specification for the plane torsion test The aim of this research project was to prepare a test specification for the plane torsion test. For this purpose, different influences on the test results in the plane torsion test were analysed. On the one hand, the influences on the machine side, for example the torque sensor, the optical strain measurement, a height difference between the inner and outer clamping on the measurement results were analysed. The influences of the clamping geometry and structuring on the process limits of slippage and wrinkling were also analysed. These findings were used to adapt the testing machine to the materials to be tested. Further investigations into the specimen-side influences on the test showed that the shape of the groove specimen has an influence on the strain inhomogeneity in the sheet thickness direction. A suitable specimen shape for determining flow curves was derived from this. It was also shown that although the determination of elongation at break in the plane torsion test with a groove specimen is dependent on the manufacturing process of the specimen, the surface quality is not the only influencing factor that leads to an increase in the elongation achieved. The technological challenge in the plane torsion test was to ensure a quasi-static test during the entire test. For this purpose, an analytical approach was determined that describes the maximum strain rate on full specimens. From this, a guideline for the maximum rotation speed as a function of the strain hardening exponent and a geometric ratio of the testing machine for a quasi-static test could be created. It was possible to define a test sequence that enables the reproducible determination of flow curves in the plane torsion test. The validity of the determined flow curves was confirmed by comparative tests with established tests. In order to categorise the economic efficiency of the plane torsion test, an economic efficiency analysis was carried out in comparison with established test methods. This showed that the plane torsion test represents an economical alternative to the established test methods. Based on the findings of the previous investigations, a proposal was drawn up for a test specification that enables the reproducible determination of flow curves. Publication: June 2023 Authors: Prof. Dr.-Ing. A. Erman Tekkaya, Dr.-Ing. T. Clausmeyer, Dr.-Ing. H. Traphöner, M. Sc. F. Stiebert

P 1326 - Inspection, monitoring and documentation of steel structures Infrastructure structures and hall buildings are planned for long-term use and are subject to degradation in the course of their planned utilisation. Due to the high and varied use of these structures, damage caused by use is inevitable. If defects and damage are detected promptly and repaired immediately, the good condition of the structures can be maintained for their entire service life. Structural inspections at regular intervals, which are usually time-consuming and labour-intensive and involve restrictions on the use of the structure during the inspection, help to achieve this. In this research project, the idea of an automated condition survey by flying over structures with unmanned aerial vehicles (UAV) was developed. Subsequent automated 2D/3D image processing and image evaluation through to supplementing the digital building file with damage and defect reports as well as instructions for action complement a digitised and automated building inspection. In future, this should enable efficient and closely spaced inspections of structures, allowing damage and defects to be detected and repaired at an early stage. To this end, steel structures (halls and bridges), airworthy areas and any visible damage were examined. This was followed by a damage catalogue as a basis for the inspection of steel structures with assessments for different types of damage occurring on steel. From the point of view of automated image data processing, an analysis of the damage description and deviation from the normal condition as well as a definition of this took place. Methods for the automated evaluation and classification of damage structures based on image data were developed for this purpose. Based on this, it was possible to develop a procedure for evaluating individual damage as well as the entire structure. At the same time, the UAV system, a navigation solution based on 3D route planning and a multi-sensor system were developed. Suitable sensors were analysed and integrated to carry out the inspection and a safety concept was integrated. The finally developed procedure for the traceability and visualisation of the results in a 3D model provides the inspector with a tool for the inspection of steel structures. The above-mentioned research objective was thus achieved. The economic damage to the Federal Republic of Germany caused by bridges in need of renovation and the associated congestion caused by (partial) road closures can thus be reduced. This problem can be counteracted by inspecting bridges using UAVs, as damage can be recognised at an earlier stage and thus counteracted more quickly (preventive strategy). For the inspection engineers, always represented as SMEs, such a supported inspection process of a bridge or transport structure would also simplify and speed up the inspection process. The inspection process would no longer take several employees several days, and the profitability and productivity of the SME could therefore increase. The otherwise necessary use of makeshift equipment such as cherry pickers or under-bridge inspection devices is reduced and therefore also the hazardous work for personnel. It is also a new product portfolio that the inspection engineer can offer to the numerous bridge construction clients. This also appeals to the clients of hall constructions, where a structural inspection is currently not mandatory. Thanks to a faster and therefore more favourable inspection by aerial survey, some hall owners will have their buildings inspected more frequently or at all than is currently the case. Overall, this process contributes to a completely new type of building assessment in the construction industry and links the construction industry with its primarily SME companies with state-of-the-art technology and Industry 4.0. Publication: 2021 Authors: Prof. Dr.-Ing. W. Flügge, Dipl.-Ing. F. Gierschner, M.Sc. T. Ambrosat, M.Sc. A. Hundrup, Priv.-Doz. Dr F. Weichert

P 1327 - Optimised design of combined steel sheet pile walls for the installation process and the final state The overall objective of the research project is the optimisation of design methods for combined steel sheet pile walls used in quay wall construction to secure the ground jumps. The following objectives are defined for this purpose: - The design is carried out without taking the installation process into account. The influence on the final position and thus also on the design must be checked (objective 1). - Furthermore, the surrounding soil is not taken into account as resistance in the combined verification against buckling and lateral-torsional buckling, so that the load-bearing behaviour in the final state is underestimated. Approaches must be developed to take soft soils and stratified subsoil structures into account. (Objective 2). - For the flanges of the load-bearing piles, global internal forces and local influences from the flange bending are currently only taken into account in a generalised manner by reducing the yield strength. Possible load-bearing capacity reserves with separate consideration are to be examined (objective 3). - When determining the load-bearing capacity, either only plastic or only elastic resistance values are assigned to the intermediate piles. The use of partially plastic resistances should be investigated (objective 4). Firstly, the basics were determined in the research project in a parameter identification. For this purpose, common quay wall projects were analysed with regard to the subsoil stratification of load-bearing piles. The valid design methods were also compiled. This was followed by a metrological investigation of the installation during heavy pile driving in order to identify the dynamic influences of the installation method on the final position. The results show the influence of pile driving during installation and serve as a basis for numerical analyses. The numerical replacement model for the installation of the soldier pile was used to identify individual influencing variables on the position in the final position and recommendations were made for accurate installation. The model can be used to predict the final position after installation. To take into account the bedding of soldier piles in cohesive and layered soils, model tests as well as full-scale tests were carried out and spring stiffnesses were derived. Generally valid approaches were then determined with the aid of a numerical model. Together, these serve as the basis for further investigations into the buckling and lateral-torsional buckling of I-shaped soldier piles in layered soils. The lateral-torsional buckling investigations took into account common quay wall structures and soil layers in North German deep-sea harbours. Extensive parameter analyses were carried out for these and the buckling length coefficients were evaluated. Approximation functions were derived and statistically evaluated. With the help of these results, it is now possible to check against flexural buckling and lateral-torsional buckling with indirect consideration of the resistance in the soil. Investigations show an optimisation of the verification for a typical quay wall of up to 40 %. Furthermore, limit criteria for the necessity of the verification were developed. The results are to be incorporated into the recommendations of the "Embankments" working committee. In addition, parameter analyses were carried out on partially welded bearing piles. This was used to derive formulae for determining the effective torsional moment of inertia. Until now, it was not possible to take partial welding fully into account in the design. The formulae determined were proposed in TC250/SC3/WG18 and incorporated into the draft standard prEN1993 Part 5. Recommendations for determining the resistance were given for the design of load-bearing piles under local stress with an additional global stress. In addition to the water pressure, the resistance model also takes into account other important geometric parameters as well as the material of the bearing and intermediate piles. In order to consider partially plastic conditions in the design of Z-slabs subjected to bending, 4-point bending tests were carried out and an FE model was validated. Parameter analyses were carried out on various profiles from practice, a resistance model was derived and partial safety factors were determined. The results for the partially plastic design were incorporated into the Eurocode 3 Part 5 standard. The experimental and numerical investigations have already been presented in standardisation meetings. Up to 15 % higher load capacities can be taken into account. Publication: 2021 Authors: Prof. Dr.-Ing. U. Kuhlmann, A. Enders, M.Eng, Prof. Dr.-Ing. J. Grabe, J. Beuße, M.Sc.