Fatigue assessment of steel load-carrying cruciform welded joints by means of local approaches

In this paper, local approaches are employed to analyse stress distributions, local fatigue indicators of weld toe, and weld root in load-carrying cruciform welded joints (LCWJs). An extension of previous available equations is applied herein to calculate the approximate notch strain energy density (SED) based on the notch stress intensity factors (NSIFs) of LCWJ. The extending range of applicability is useful to explain various geometry effects comprehensively of LCWJ under cyclic tension and bending. By employing these extended equations, SED values can be rapidly evaluated without any finite element calculations. The NSIF and SED values obtained according to proposed analytical solutions are first validated by comparing finite element data from several stimulations in LCWJ models, resulting in a good agreement. Moreover, the failure transition relationship between weld toe and weld root is assured by SED values considering variations of notch angles. As a preliminary validation, the accuracy and reliability of proposed analytical model in this paper are checked by several experimental data generated from testing under fatigue loading. The good agreements between the experimental results and existing scatter bonds based on local NSIF, SED, and peak stress method fatigue design standards establish reliable basis for validation of the present analytical equations.