Title: Relaxation of welding residual stresses – Part I: under quasi-static loading

Authors: Majid Farajian; Thomas Nitschke-Pagel; Klaus Dilger

Addresses: Institute of Joining and Welding, University of Braunschweig, Langer Kamp 8, D-38106 Braunschweig, Germany. ' Institute of Joining and Welding, University of Braunschweig, Langer Kamp 8, D-38106 Braunschweig, Germany. ' Institute of Joining and Welding, University of Braunschweig, Langer Kamp 8, D-38106 Braunschweig, Germany

Abstract: The influence of welding residual stress on fatigue performance depends strongly on how stable these stresses are during cyclic loading. If the tensile residual stresses at the fatigue crack initiation sites relax, their influence on service life decreases and if they stay stable their influence on life assessments should be taken into consideration. The relaxation of residual stresses under cyclic loading is most considerable during the very first load cycle which could be considered as relaxation under quasi-static loading. It was shown here that the von Mises failure criterion describes the relaxation mechanisms in welded S355J2G3 and S690QL specimens under quasi-static tensile and compressive loading. By increasing the tensile load a continuous relaxation of residual stresses occurs. Under compression the relaxation sets in with delay which is an evidence of stability of tensile residual stresses under compression. The residual stresses were determined by means of X-ray diffraction.

Keywords: fatigue strength; butt welding; residual stress; welded joints; relaxation; crack propagation; crack initiation; quasi-static loading.

DOI: 10.1504/IJMMP.2012.045800

International Journal of Microstructure and Materials Properties, 2012 Vol.7 No.1, pp.3 - 15

Published online: 12 Mar 2012 *

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