P 1007 - Method for characterising the failure behaviour of high-strength sheet steel materials in a wide range of stress states using uniaxial tensile testing machines

P 1008 - Application-oriented simulation of thermal straightening Particularly in the case of large structures, such as those welded in ship and rail vehicle construction, the remaining distortions are very critical due to their enormous dimensions of up to several centimetres. Post-treatment must therefore be included in the work planning just as much as the welding itself. Thermal straightening has been an established process for decades. The straightening process parameters are currently selected on the basis of practical experience. However, the influence of design conditions, the material and the different straightening processes are extremely difficult to determine in this way. The basics of the analytical model, the realisation for practical application and the coupling with the numerical calculation are presented. The coupled analytical-numerical hybrid model is designed to capture the welding process chain and the subsequent thermal straightening. The analytical model is used to determine the equivalent shrinkage strain for the thermomechanical load of each straightening point, taking into account the significant influencing factors. This is transferred to an FE model of the structure and the deformation of the entire structure is calculated using an elastic analysis. The mutual influence of the existing residual welding stresses and individual alignment points is taken into account iteratively by means of feedback. The calculation is based on the application of the analytical numerical hybrid model for welding distortion simulation. The methodological approach is explained in detail in the report. In addition to the fundamentals of the hybrid model, other important aspects such as the recording of different straightening processes, process conditions and industry-relevant materials are also discussed. In addition, the qualitative interaction between thermal levelling and the welding process was investigated and integrated into the calculation procedure. The hybrid model was initially applied and validated on simple sheet metal specimens. Based on a structure joined by means of eight seams, the consideration of the welding sequence and the straightening sequence in the hybrid model was investigated. in the hybrid model was analysed. This was then applied to a test structure from the railway vehicle construction industry. Four 2 mm thick profiles were joined to a base plate measuring 500 x 400 mm using 16 weld seams and then straightened using two independent scenarios. The CPU time of the numerical calculation on the structures was less than 10 minutes in each case. The validity of the calculations was thus verified experimentally. Publication: 2016 Authors: V. Mikhailov, N. Doynov, F. Kuke

P 1005 - Investigations into the load-bearing behaviour and service life of bonded joints in steel structures under cyclic loading The use of innovative adhesive bonding technology increases the productivity, quality and efficiency of German steel construction. It also represents an alternative to conventional joining methods, which have fundamental disadvantages for steel structures. For example, the bonding joining process can avoid welding-related component distortion and cross-sectional weakening due to bolt holes. Due to the high degree of prefabrication, steel construction is predestined for the use of adhesive bonding, as load-bearing, serviceable and durable bonded joints can be produced under workshop conditions. However, it is not possible to verify such bonded steel joints on the basis of current standards. Time-consuming and expensive approval procedures would be necessary, which is why small and medium-sized enterprises (SMEs) decide against adhesive bonding technology. The inclusion of bonded steel joints in standardisation would provide a remedy here. For this reason, the first step is to develop basic principles for the verification of load-bearing capacity using two application cases from steel façade construction, which relate exclusively to short-term, one-off and quasi-static loads. A further aim of the project is to supplement these findings by investigating the long-term load-bearing behaviour of bonded joints under cyclic loading. The results of the analyses provide input parameters for the development of verification concepts for bonded steel joints. Publication: 2018 Authors: Prof Pasternak, Prof Dilger

P 1004 - Hybrid forging - Combined forming and joining This study investigated the feasibility and potential of a hot Hyrid forging process for a pressure flange. This process is characterised by the simultaneous forming and joining of a thick plate and a shaft in one step. Firstly, the process was designed using FEM software. Compared to a reference process, significant reductions in the press force were achieved, making it possible to forge larger flanges on smaller forming units. The stainless steel X6CrNiMoTi17-12-2 (1.4571) was used as the material. Tests were then carried out on an industrially used eccentric press. The key feature was to ensure a positive fit between the two components, as it was not possible to achieve a material bond. For this purpose, the sheets were provided with a chamfer and recesses, which were filled with the material of the shaft during the forming process to prevent axial and radial displacement. This goal was achieved. To achieve this, however, the sheet metal had to be heated more than the shaft material, as otherwise gaps would have formed after cooling due to thermal shrinkage. The pressing forces could also be reduced in reality. Normally, the real process requires press forces of approx. 800 tonnes for forging with burrs. These forces are higher with burrless forging. A significant reduction in pressing forces has therefore been achieved. Forging companies can now manufacture rotationally symmetrical parts in a manual production process using hybrid forging. This means that parts can be produced without burrs with a low forming force. This leads to a reduction in tool stress and thus to an increase in tool life. Smaller presses can be used for comparable parts. Automation including feeding technology is still to be developed. This means that long parts can also be produced, which make up a larger proportion of solid moulded components in industry. The research project P 1004 of the Forschungsvereinigung Stahlanwendung e.V., Düsseldorf was carried out by the IPH - Institut für Integrierte Produktion Hannover GmbH with technical support and financial assistance from the Forschungsvereinigung Stahlanwendung e. V., Düsseldorf. Publication: 2015 Authors: J. Langner, M. Stonis

P 1010 - Pre-hole-free joining of steel-intensive lightweight structures by resistance element welding with prefabrication In recent years, due to legal requirements, the automotive industry has increasingly focussed on lightweight construction measures, particularly in the body structure through the load-appropriate use of various lightweight materials. A mixed construction method, in which high-strength and ultra-high-strength, press-hardened sheet steel parts are combined with aluminium materials, is particularly suitable for large-scale production in order to create lightweight, yet rigid and crash-resistant body structures in shell construction. The thermal-mechanical joining processes developed in recent years for series production and not exclusively for this application offer a high application potential and the first series applications have already been realised. Due to the novelty of resistance element welding, the process-related properties and characteristics have so far been insufficiently investigated, so that there is a lack of sufficient knowledge on the welding, strength and failure behaviour of corresponding joints and material combinations. The aim of the research project was to develop and qualify resistance element welding with prefabrication of an aluminium or FRP composite partner as an economical joining process for joining these lightweight construction materials with high-strength and ultra-high-strength steel materials. As resistance element welding is still a relatively new joining process, the requirements were initially adapted on the basis of the investigations carried out to date. This involved analysing the special process-related features of resistance element welding of prefabricated composite partners and characterising the properties of the resulting joints. By analysing the joining process and the joint formation, taking into account the properties of the rivet elements, it was possible to gain important insights into the design of the rivet elements and processes as well as their reliable use. The evaluation of the performance characteristics in terms of joint and handling strength was also part of the project. As a result, industrial users were provided with information on the use of a flexible joining process for the realisation of future lightweight structures. The implementation of the optimisation derived from the results obtained marks an important contribution to the development of resistance element welding and the economic production of future lightweight structures in mixed steel construction. Publication: December 2020 Authors: Prof. Dr.-Ing. G. Meschut , Dipl.-Wirt.-Ing. V. Janzen