Fatigue strength evaluation of non-continuous incomplete penetration fillet-welded joints transferring stress flow by the S-N criteria incorporating the «Hot-spot stress» or «Notch-stress» approaches is dubious since the characteristic stress at the crack initiation location is not established by the rules for fatigue design. Application of the linear fracture mechanics (LMF) technique meets a problem of numerical modeling the crack three-dimensional shape and front extension, which becomes insoluble when the crack approaches the outer surface of weld bead and propagates along the seam. Apart from that, considering material plasticity beyond the initial phase of crack extensions from the cavity is off the frames of the principles of the LMF.

An approach based on the FEA simulation of fatigue damage accumulation is suggested and applied to evaluate the crack initiation at the cavity and propagation in the non-continuous fillet-welded joint. The crack initiation at the cavity, its three-dimensional shape formation and evolution are simulated taking into account the elastic-plastic cyclic deformation of weld material until almost complete failure of the joint. The results of analysis are in good agreement with published experimental data.