Fatigue reliability analysis of butt welded joints with misalignments based on hotspot stress approach

Abstract

Fatigue reliability of butt welded joints with misalignments is assessed, based on the structural hotspot stress approach. The unsymmetrical weld profile induced stress concentration is evaluated using the finite element and Monte Carlo methods based on a series of simulated weld profiles from published statistical data. The Monte Carlo method is also used to assess the uncertainty on the critical stress magnification factor proposed to represent the margin left for the misalignment effect to trigger fatigue failure. A limit state function is formulated based on the critical and actual stress magnification factors. The first order reliability method is applied to evaluate the reliability levels of different welding processes, reliability levels of standards and the lateral distortion limits for a target reliability index. The results show the advantage of the laser welding over the conventional arc welding regarding fatigue reliability. The tolerance limits of misalignments specified by standards lead to different reliability levels for different welded joint plate thicknesses. The thin-plate joints show a low reliability level and the reliability index increases with the plate thickness.