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5962 |
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Tuesday, May 21, 2019, Saal Brüssel 5:40 PM Properties of brazed joints 1 |
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Improvement of fatigue strength and structural design in heavy steel constructions through arc brazing |
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Andreas Gericke* / Fraunhofer IGP, Germany Filip Wegener / Fraunhofer IGP, Deutschland Karl Drebenstedt/ Universität Stuttgart, Lehrstuhl für Konstruktion und Entwurf, Deutschland Knuth-Michael Henkel/ Universität Rostock, Lehrstuhl Fügetechnik, Deutschland Ralf Glienke/ Hochschule Wismar, Deutschland Ulrike Kuhlmann/ Universität Stuttgart, Lehrstuhl für Konstruktion und Entwurf, Deutschland |
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Regardless of its advantages, including decreased heat input and the usability on galvanized materials, arc brazing has not been used much in heavy steel constructions. One reason is that arc brazing is not regulated in the European building standards, especially for sheet thicknesses t e 3mm due to the lack of knowledge about the mechanical properties of the joints and little experience for long-term behavior of arc-brazed heavy plate steel structures. Currently for a wide range of steel structures, including tubular steel towers for wind turbines, bridges or cranes, the improvement of fatigue strength is an important concern due to achievable service life, design reasons and materials selection, e.g. for high strength steels. The fatigue strength of those structures can dramatically be reduced through certain weld details, which can´t be left out. Those details are often little stressed and under static loads, like bushings for ladders, cable holders or gutters. This contribution shows the possibility of substituting certain welded seams through arc brazed seams with copper basis filler materials. Based on extensive Wöhler-tests, it will be shown that the life time of cyclically loaded structures can be increased up to 500 % through the usage of arc brazing for certain details. This extends the possibilities in design and material selection for steel structures in different industrial sectors. The reasons of the fatigue improvement will be discussed with the measurement of hardness and residual stresses, investigations on the microstructures and numerical analysis. The whole study including process parameters, materials and static load-bearing capacities of the joints will be shown and the state of standardization, including current activities of certain working groups, as well as the risk of liquid metal induced embrittlement will be discussed. Finally the economic aspects and selected industrial examples will be shown. |