Due to the additional local stress concentration caused by undercut and misaligned defects, welded joints own less fatigue strength. This work uses probabilistic technique and fracture mechanics theory to quantitatively investigate the impacts of undercuts and misalignments on fatigue performance and reliability of Load-carrying Cruciform Welded Joint (LCWJ). Firstly, the geometrical characteristics summary of the size and type of undercuts and misalignments are provided from researches and experiments. Subsequently. Evaluations of the stress levels are combined with the nominal loadings in LCWJs, probabilistic distributions of material fracture properties, and various configurations of geometries and flaws. Meanwhile, the estimations of fatigue strengths are conducted by the probabilistic reliability theory by taking into account the distributions of the actual fatigue data. The findings reveal a clear disparity between the base metal and weldment test results. Different reliability levels for various defect types and sizes and in LCWJs are caused by the tolerance limits.

Fatigue experiments and numerical simulations based on the Linear Elastic Fracture Mechanics (LEFM) theory were conducted on the Even-Matched (EM) and Under-Matched (UM) 10CrNi3MoV Load-carrying Cruciform Welded Joints (LCWJs). The study firstly experimentally investigated the Fatigue Crack Growth Rate (FCGR) of base metal, EM, and UM weldments. The corresponding Paris parameters as essential input data are provided to assess the fatigue crack propagation behavior for weld toe and weld root failure of LCWJs. On the one hand, the Stress Intensity Factors (SIFs) at weld toe and weld root were calculated considering the effects of LCWJ specimen geometries, initial crack types, and sizes. The comparisons between simulated results and standards analytical solutions were executed, which exhibit good accordance. It proved that the fatigue fracture simulation procedure based on LEFM is appropriate for the fatigue assessment of LCWJs. Eventually, it conducted the parametric analysis by predicted S-N curves, which included in the weld length, initial crack shape, initial crack size, penetration length, and materials fracture parameter, to explore some safety assessment reference lines for both failure modes of LCWJ.

Fatigue experiments and numerical simulations based on the Linear Elastic Fracture Mechanics (LEFM) theory were conducted on the Even-Matched (EM) and Under-Matched (UM) 10CrNi3MoV Load-carrying Cruciform Welded Joints (LCWJs). The study firstly experimentally investigated the Fatigue Crack Growth Rate (FCGR) of base metal, EM, and UM weldments. The corresponding Paris parameters as essential input data are provided to assess the fatigue crack propagation behavior for weld toe and weld root failure. On the one hand, the Stress Intensity Factors (SIFs) at weld toe and weld root were calculated considering the effects of LCWJ specimen geometries, initial crack types, and sizes. The comparisons between simulated results and standards analytical solutions were executed, which exhibit good accordance. It proved that the fatigue fracture simulation procedure based on LEFM is appropriate for the fatigue assessment of LCWJs. Eventually, it conducted the parametric analysis by predicted S-N curves, which included in the weld length, initial crack shape, initial crack size, penetration length, and materials fracture parameter, to explore some safety assessment reference lines for both failure modes of LCWJ.