The peak stress method to estimate the mode I notch stress intensity factor in welded joints using three-dimensional finite element models

•The peak stress method enables one to readily estimate the Notch Stress Intensity Factors (NSIFs).•The peak stress method has been used with three-dimensional (3D) finite element (FE) analyses.•Approximate and exact values of the mode I NSIF have been compared successfully.•The peak stress method can be used to assess the fatigue strength of fillet-welded using 3D FE analyses.

The peak stress method is a simplified, FE-based technique to estimate the mode I and mode II Notch Stress Intensity Factors (NSIFs) at the tip of sharp V-notches or cracks. Then it is useful to readily assess the fatigue strength of fillet-welded joints failing from the weld toe or the weld root according to the local approach based on the NSIFs. Originally based on two-dimensional FE models, the PSM is extended here to be used with three-dimensional FE models, which are increasingly adopted in practical applications. Exact and approximate values of the mode I NSIF at the toe of cruciform and T butt- or fillet-welded tubular joints are calculated and compared successfully.