Numerical and Experimental Investigations on the Defect Tolerance of Brazed Steel Joints

Adrian Lis; Michael Koster; Christian Leinenbach

doi:10.3139/120.110372

Article

Numerical and Experimental Investigations on the Defect Tolerance of Brazed Steel Joints

Adrian Lis , Michael Koster and Christian Leinenbach

Published/Copyright: May 26, 2013

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From the journal Materials Testing Volume 54 Issue 9

Abstract

Based on the combination of FE-calculations and experimental results a defect assessment procedure for brazed steel joints was developed in the present work, which reliably takes into account the effect of different steel heat treatments and defined artificial defects in the braze layer. Tensile tests with defect free joints consisting of X3CrNiMo13-4 as substrate material and of Au-18wt.-%Ni as filler metal serve as a basis to simulate the elastic-plastic material behaviour. By correlating experimental and numerical methods, failure criteria could be derived which indicate and predict failure of brazed components. These failure criteria were also presumed to calculate the maximum tolerable loads for specimens containing different defects. The results show that the simulations correlate very well with the experimental results. Furthermore, they provide a possibility to analyze the failure behaviour for different defect types and the influence of different heat treatments on the joint strength.

Kurzfassung

Im Rahmen der vorliegenden Arbeit wurde basierend auf der Kombination aus FE-Berechnungen und experimentellen Ergebnissen eine Methode der Fehlerbeurteilung für Stahllötverbindungen entwickelt, wobei der Einfluss verschiedener Wärmebehandlungen und definiert künstliche Defekte der Lötschicht berücksichtigt werden. Das elastisch-plastische Materialverhalten wurde mittels Zugfestigkeits-prüfungen von hartgelöteten, defektfreien Verbunden aus Stahl X3CrNiMo13-4 und Lot Au-18wt.-%Ni untersucht. Durch Korrelation von experimentellen und numerischen Methoden konnten Versagenskriterien von hartgelöteten Verbindungen abgeleitet, sowie auch auf fehlerhafte T-Stoß-Proben, übertragen werden. Die Untersuchungen zeigen eine sehr gute Übereinstimmung der experimentellen Ergebnisse mit den Simulationsergebnissen. Somit können FE-Simulationen neben der Abschätzung des Einflusses von Lötfehlern auch zur Berücksichtigung verschiedener Wärmebehandlungsverfahren eingesetzt werden.

Dipl.-Ing. Adrian Lis, born in 1986, studied mechanical engineering at the Technical University of Kaiserslautern, Germany, and at the University of Technology Luleå, Sweden. After finishing his diploma thesis in 2011 at the Swiss Federal Laboratories for Materials Science and Technology, Empa, Switzerland, he started to work there on his PhD thesis.

Dr.-Ing. Michael Koster, born in 1978, studied at the University of Kaiserslautern. In collaboration with the ENI Metz and the German-French University in Saarbrücken he finished his studies with a german-french double diploma in mechanical engineering. During his PhD at the Institute of Materials Science and Engineering at the University of Kaiserslautern from 2005–2010, M. Koster studied the very-high cycle fatigue behaviour of railway wheel steels. Since 2010 he is working at the Swiss Federal Laboratories for Materials Science and Technology (Empa) on the integrity of brazed steel joints.

Dr.-Ing. Christian Leinenbach, born in 1974, studied Physics and Materials Science and Engineering at Saarland University, Saarbrücken, Germany, and at Luleå University of Technology, Sweden. In 2000, he graduated (Dipl.-Ing.) at Saarland University. In the same year, he transferred to the Institute of Materials Science and Engineering at the University of Kaiserslautern, Germany, where completed his dissertation on the cyclic deformation behaviour of surface modified titanium alloys in 2004. In 2005, he moved to the Swiss Federal Laboratories for Materials Science and Technology (Empa), where he is currently Head of the Advanced Joining Technologies Group.

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Published Online: 2013-05-26

Published in Print: 2012-09-01

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https://doi.org/10.3139/120.110372