Residual stress relaxation in welded large components

Majid Farajian; Thomas Nitschke-Pagel

doi:10.3139/120.110773

Article

Residual stress relaxation in welded large components

Majid Farajian and Thomas Nitschke-Pagel

Published/Copyright: August 31, 2015

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From the journal Materials Testing Volume 57 Issue 9

Abstract

Residual stress relaxation of butt-welded large components under cyclic mechanical loading was investigated. The experiments were carried out on different types of steel with yield strengths between 300 and 800 MPa. X-ray diffraction technique was applied for the residual stresses analysis. High tensile residual stresses as high as the yield strength could be measured in large components. However, a fraction of maximum residual stress accommodated in the weld bead centerline is available at the weld toe. Under four-point bending of the large scale weldments, a considerable relaxation of residual stresses in the weld and its vicinity was observed during the first loadings. This behavior could be observed regardless wether the weld was under tensile or compressive loading.

Kurzfassung

Der Eigenspannungsabbau von stumpfgeschweißten Großkomponenten unter zyklischer mechanischer Beanspruchung wurde untersucht. Die Versuche wurden an Stählen mit Streckgrenzen von 300 bis 800 MPa durchgeführt. Für die Eigenspannungsermittlung wurde das Röntgenbeugungsverfahren eingesetzt. Es wurde festgestellt, dass sehr hohe Zugeigenspannungen in Höhe der Streckgrenze der Grundwerkstoffe in geschweißten Großkomponenten vorliegen können. Allerdings ist nur ein Bruchteil der maximalen Zugeigenspannung an den Schweißnahtübergängen vorhanden. Unter Vierpunkt- Biegung der Schweißverbindungen wurde ein beträchtlicher Eigenspannungsabbau in der Schweißnaht und deren Umgebung während des ersten Belastungszyklus beobachtet. Dieses Verhalten war unabhängig davon, ob die Schweißnaht Zug- oder Druckbelastung erfuhr.

§Correspondence Address, Dr. -Ing. Majid Farajian, Gruppe Ermüdungsverhalten, Bruchmechanik, Geschäftsfeld Bauteilsicherheit und Leichtbau, Fraunhofer-Institut für Werkstoffmechanik IWM, Wöhlerstr. 11, 79108 Freiburg, Deutschland. E-mail: majid.farajian@iwm.fraunhofer.de

Dr.-Ing. Majid Farajian, born in 1976, received his BSc in Mechanical Engineering from the Tehran Polytechnic, Iran, and his MSc in Materials Processing from the Royal Institute of Technology in Stockholm, Sweden. He received his PhD from the Faculty of Mechanical Engineering of the University of Braunschweig, Germany in 2011. After two years post-doctoral research activities, he continued his work in the field of fatigue and residual stresses at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg, Germany. Since then, he is the head of the team “Component Strength” at the Fraunhofer IWM.

Dr.-Ing. Thomas Nitschke-Pagel, born in 1958, completed his studies of General Engineering at the University of Kassel, Germany. From 1987 to 1991, he was employed as a research associate at the Institut für Werkstofftechnik at the same university. He has been a research associate at the Institute of Welding of the Technical University of Braunschweig, Germany since 1992 and is currently the head of the working groups “Welded Components Behavior” and “Welding Processes”. He received his doctorate at the Institute of Joining and Welding in 1994.

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Published Online: 2015-08-31

Published in Print: 2015-09-01

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https://doi.org/10.3139/120.110773