Schweißnahtnachbehandlung mit höherfrequenten Hämmerverfahren – Ermüdungsfestigkeit,Qualitätssicherung,Bemessung

Im Rahmen des Forschungsprojekts REFRESH wurden umfangreiche systematische Untersuchungen zur Ermüdungsfestigkeit mit höherfrequenten Hämmerverfahren nachbehandelter Schweißnähte durchgeführt. Die statistisch abgesicherten Ergebnisse belegen die hohe ermüdungsfestigkeitssteigernde Wirksamkeit der Verfahren und ermöglichten die Entwicklung eines experimentell abgesicherten Bemessungskonzeptes. Um die Anwendung überwachen zu können und die Behandlungsqualität sicherzustellen, wurde ein Qualitätssicherungssystem und ein Anforderungskatalog an das Fachpersonal erarbeitet. Die Zertifizierung der Verfahren erfolgt auf Basis eines gemeinsam von der Bundesanstalt für Materialforschung und ‐prüfung und der Versuchsanstalt für Stahl, Holz und Steine der Universität Karlsruhe erarbeiteten Zertifizierungssystems. Postweld treatment by high frequency hammer peening methods – fatigue resistance, quality control, design. In the range of the research project REFRESH comprehensive, systematic investigations regarding the fatigue resistance of welds treated with high frequency peening methods have been conducted. The statistically confirmed results prove the high beneficial effect of the methods and allowed to develop an experimentally verified design concept. In order to control the application quality and to ensure the desired effects a quality assurance system and a catalogue of requirements for specialists has been worked out. The certification of the methods is performed on the base of a common certification system, developed by the German Federal Institute for Material Research and Testing (BAM) and the Research Centre for Steel, Timber and Masonry, University of Karlsruhe.     

Eine Methode zur Bewertung von Restspalten in Schweißnähten an T‐ und Kreuzstoßverbindungen

A method to assess root gaps in welded seams of T‐ and Cross joints. Design and welding codes require full penetration in case of complete butt splices. This often ends up to time‐ and cost‐intensive repair work for the executing steel work company. Quite recently, classification methods and along with these, a method of tolerating such partial penetrations (here: root gaps) to be considered right from the weld design or planning stage were actually missing, so that additional manufacturing work was preassigned from the outset. Within an AiF‐DASt‐research project [1] an assessment method has been developed basing on an accurate detection of root gaps by non‐destructive testing methods. That method guarantees the demanded structural reliability of a steel structure despite of leaving a weld that actually is to be rejected due to insufficient penetration according to the conventional codes.     

Numerische Analyse geschweißter Verbindungen von Duplexstahl und Quarzglas

Numerical analysis of welded joints between duplex steel and quartz glass. Welded joints are a vital element in structural engineering. Originating from conventional carbon steel welding in construction, recent advancements in welding technology now allow the joint of modern high‐strength steel and glass materials. With today's methods, an analysis of the welded joints' structural behaviour can be conducted by experiment, as well as by numerical analysis. Particularly for the numeric analysis, capturing the non‐linear thermal and mechanical properties of the materials is important, in order to allow a realistic determination of temperature, microstructure and residual stresses for different types of joints. Simulations of multi‐layered weld joint on duplex steel show, that a targeted heat treatment during MAG‐welding by variation of the welding parameters achieves a beneficial ratio between ferrite and austenite which, for example, ensures a high resistance of the weld to corrosion. The material quartz glass can generally be welded as butt‐weld with a CO₂‐laser. The simulations of a welded joint of a plate and a pipe show, that an optimization of the welding technology of preheat laser beam and welding laser beam is necessary, in order to reduce the thermal impact during the welding process, as well as residual stress in the joint. At the Department of Steel Structures at the Bauhaus‐Universität Weimar, numerical simulations of welded joints between steel and glass materials are a current and topical research focus.