P 1065 - Tool-integrated temperature measurement for press hardening

P 1064 - Economical production of weight- and property-optimised functional components by means of incremental sheet metal forming The objective of the research project is the economic production of industrially relevant functional components using incremental sheet metal forming. A defined edge thickening of sheet metal blanks and subsequent embossing of serrations are to be investigated. By using suitable materials, the work will focus on the targeted utilisation and maximisation of work hardening. In co-operation with the partners, the aim is to significantly reduce the machining time. Based on the current status of the incremental approach, this must be greatly reduced and brought closer to realistic cycle times. The process acceleration required for this involves changes to the thermal process conditions, which are to be investigated as part of this research project. Using new strategies, the effects on the specifically adjustable component properties are to be determined experimentally and numerically so that subsequent heat treatment can be dispensed with in order to save costs and avoid the associated negative aspects. The challenge is to maximise the material-dependent effect of work hardening and to optimise it for a possible industrial application. The disadvantageous aspects of conventional production are to be avoided by shaping close to the final contour and optimising the use of the material and its work hardening. There are fundamental challenges for the complex process with cyclical loading and unloading with mutual influence of the process parameters. These relate to the prevailing tool load, the process parameters to be set and the entire tribological system, which requires the use of new tool steels and suitable lubricant technology. The main focus of the investigations is to determine and control the resulting conflict of objectives with regard to the forming temperature due to the accelerated process control and the targeted work hardening. Publication date: August 2020 Authors: Prof. Dr.-Ing. Dr.-Ing. E.h. A. E. Tekkaya, Dr.-Ing. P. Sieczkarek, Dr.-Ing. S. Gies, S. Wernicke M. Sc.

P 1063 - Tribosystem optimisation in the forming of complex components made of iron-manganese steels with TWIP effect Iron-manganese steels with TWIP effect have been proven to have a very advantageous property profile, especially with regard to mechanical properties and forming behaviour. The special properties make this new class of materials very attractive in industrial terms. Due to the high level of strength combined with high ductility, iron-manganese steels are extremely interesting not only for non-automotive applications but also for applications in crash-relevant automotive body structures.Modern lightweight construction concepts can benefit greatly from iron-manganese steels (FeMn), as component consolidation can save a considerable amount of vehicle mass and therefore fuel. Furthermore, cold-formable FeMn steels offer potential as an alternative to hot-formed components. The aim of this research project was to make the forming potential of iron-manganese steels with TWIP effect accessible to users in practice for the production of geometrically complex, high-strength components. The aim of the research project was to expand the process window. This objective was to be achieved by optimising the tribological conditions of both forming processes, with strip drawing tests in various designs representing different contact conditions and process temperatures forming an essential part of the experimental investigations. The corresponding test equipment was modified for this purpose, in particular to reproduce a temperature field similar to that in series production. In the test series, a dependency on the oiling condition was determined, which differs in part from the behaviour of conventional steel grades. In further deep-drawing tests, in addition to a clear dependence of deep-drawing properties on the forming lubricant used, the optimisation potential of tool cooling was also validated. The deep drawability of test components made of FeMn was positively influenced by lowering the mould temperature, almost independently of the lubricant used. Authors: B.-A. Behrens, C. Gaebel, M. Micke-Camus, D. Yilkiran, C. Pfeffer Publication: 2018

P 1067 - Determination of high toughness requirements for steel using hybrid damage mechanics methods In addition to the safety verification in the ultimate limit state, which is performed with the basic assumption of ductile material behaviour, the ultimate limit state verification for steel structures in Eurocode 3 also requires the selection of steel grades in accordance with DIN EN 1993-1-10 or DASt-RiLi 009 in order to avoid brittle fracture. The choice of steel grade, together with the requirements from the tensile test, is also regarded as a guarantee for ductile material behaviour. In Germany, the weld-on bending test (AUBI) in accordance with SEP 1390 for assessing the qualitative crack arresting capacity of the steel base material, which is currently generally required for welded steel structures for steel grades up to S355J2 with plate thicknesses greater than 30 mm, is another proof of toughness in the high position. However, in the course of harmonising European standards, the AUBI was not accepted by the other EU member states. Instead, a depth-oriented replacement criterion was introduced, utilising the better properties of fine-grained structural steels resulting from more modern production technology. In the past, investigations were carried out to correlate the AUBI with notched bar impact results; an endeavour that did not lead to satisfaction due to its strongly empirical character and left questions unanswered as a result. The unsatisfactory situation is that the AUBI is only used as a special substitute test for compliance with a special delivery condition, but is difficult to justify from a material-mechanical point of view as a high-strength criterion with regard to the safety requirements for load-bearing structures and can only be used to a limited extent. In any case, it was not designed for the increasingly required use of higher-strength steels and deviating geometric shapes. In the European product standards, toughness is tested in the notched bar impact test. There is therefore a desire to cover the remaining areas, for which the AUBI is still required in Germany, with formulations of minimum values from the notched bar impact test, especially for the high position. This applies to ranges up to S355J2 as well as to higher-strength steels and other product forms based on the nominal values of the materials. This is where the present research project comes in. Innovative scientific methods based on hybrid damage mechanics models are used, which allow the numerically supported simulation of the AUBI, taking into account both the cleavage fracture (low position) and toughening fracture (high position) failure modes. As a result, the correlation of the toughness high position of the notched bar impact test with the AUBI could be consistently demonstrated and numerically determined for all steel grades and thicknesses. This has created a general criterion that overcomes the material and product shape-related restrictions of the AUBI. Publication date: April 2019 Institute for Steel Construction, RWTH Aachen University Prof. Dr Markus Feldmann, Sandro Citarelli M.Sc. Institute of Ferrous Metallurgy, RWTH Aachen University Prof. Dr.-Ing. Sebastian Münstermann Markus Könemann M.Sc.

P 1062 - Load-bearing capacity of mixed connections of normal-strength and higher-strength steels in steel construction The requirement for filigree constructions with high stresses consequently leads to the use of higher-strength steels. In addition to questions of stability and fatigue, the connection and joining options are also decisive for their use. The procedure for mixed connections is open, i.e. when higher-strength S690 steels are connected to normal-strength S355 steels, for example. This is a situation that occurs as standard in practice because the choice of steel is usually adapted to the utilisation and there are always attachments with lower stresses. Current design concepts in EN 1993-1-8 for fillet welded joints do not take the strength of the weld metal into account. Also, mixed joints are currently to be designed according to the higher-strength steel with regard to the weld material, but may only be calculated with the values of the normal-strength base material. The aim of the research project is to check the applicability of the already adapted design model for fillet welds of the same base materials and to develop a realistic and comprehensible design model to determine the load-bearing capacity of hybrid welded joints with fillet welds made of normal-strength and higher-strength structural steels for use in steel construction and related areas (plant and crane construction). The aim is to improve the load-bearing capacity of fillet welds in hybrid joints in the current steel construction standards. Future consideration of the welding filler material in combination with the different base materials to be joined should enable a suitable selection of the optimum combination of load-bearing capacity, toughness and deformability. Component tests are carried out to characterise the load-bearing capacity and deformation of mixed joints and comprehensive material tests to determine the mechanical properties. Based on the correlation between component tests and mechanical properties, a detailed statistical analysis of the results was carried out. Based on the evaluation of the experimental test results and the results of the statistical analysis, the applicability of the adapted design model according to Rasche [7] was confirmed. The results were summarised in recommendations which, on the one hand, cover the design and welding of dissimilar joints for practical use and, on the other hand, provide design rules which can be forwarded to the CEN committees as a proposed standard via the German mirror committee. Publication date: April 2019 Authors: Prof. Dr.-Ing. U. Kuhlmann, J. Spiegler, M.Sc.