Fatigue strength of cruciform joints with weld imperfections: A comprehensive numerical study

The paper presents an investigation into the fatigue resistance of load-carrying cruciform joints that exhibit weld imperfections. To accomplish this, a finite-element model of the joint is validated by a comparison to experimental investigations. The model includes both a global and a submodel that integrates the effective notch stress concept into its design. This enables the simulation of various types of weld imperfections, such as lack of penetration, lack of root fusion, undercut, excessive convexity, incorrect weld toe, excessive asymmetry of fillet welds and linear misalignment, to assess their impact on the fatigue strength of the cruciform joint. The analysis reveals that these imperfections lead to an increase in stress at the notches of the cruciform joint, which can be characterized as a function of the joint's geometrical properties. Global geometry influences on the fatigue strength of different cruciform join geometries can be regarded independently from the influence of the weld imperfections that is given by stress concentration factors. The normalised stress concentration factor enables a comparison between imperfection influences and shows, that the notch-softer design with full penetration welding at the cruciform joint is in a relative relation more strongly influenced by imperfections than the design with fillet welds. Also, the undercut represents the imperfection with the strongest effect in a relative relation within the sizes considered. Being able to evaluate the fatigue strength values of steel components with weld imperfections eliminates the need for costly repairs and new fabrications, which would otherwise result in a loss of resources and economic efficiency.