Effect of angular distortion and axial misalignment on the fatigue strength of welded and grinded mild steel cruciform joints.

Abstract The focus of this work is to investigate the fatigue strength of a cruciform joint one-sided through-welded by a VH seam with a backing layer made of a 10 mm thick S355 mild steel. The aim is, firstly to analyse the effect of the deformation state incorporating angular distortion and axial misalignment on the fatigue strength of the tested specimens. Secondly, the analysis of the benefit by grinding as post-treatment method on the resulting fatigue performance. The deformation impact is numerically investigated utilizing geometry measurements of the specimens as well as strain gauge measurements for validation. Thereby, the near notch stress under clamping condition without any load and under an additional static nominal load is analysed. Based on these investigations, the applied stress range for each tested specimen is converted to a “deformation-free” condition by means of the IIW-recommended km-factor. The statistical analyses of the data points with and without this modification reveals a significant impact by the deformation state on both, the evaluated fatigue strength and the scatter band. Moreover, this affects the evaluated benefit by grinding as post-treatment, whereas an increase of more than 40% in the fatigue strength at two million cycles is observed using the modified data points.