Mode-III fatigue of welded joints in steel maritime structures: Weld notch shear stress distributions and effective notch stress based resistance

The predominant mode-I response of maritime structures can be multiaxial, involving out-of-plane mode -III shear components. Semi-analytical mode-III notch stress distribution formulations have been established for critical details like welded T-joints and cruciform joints, reflecting (non-)symmetry with respect to half the plate thickness. Using a stress distribution formulation based effective notch stress as fatigue strength criterion, the mode-III welded joint mid-cycle fatigue resistance characteristics have been investigated. In comparison to mode-I, the material characteristic length and resistance curve slope estimate suggest the fatigue damage process to be even more an initiation related near-surface phenomenon. Mean shear stress effects seem insignificant.

Automated summary

The dominant response mode of maritime structures can be multi-axial, including out-of-plane mode-III shear components. Semi-analytical mode-III notch stress distribution formulations have been established for critical details such as welded T-joints and cruciform joints, reflecting (non-)symmetry with respect to half the plate thickness. By using an effective notch stress based on the stress distribution formulation as a fatigue strength criterion, the mid-cycle fatigue resistance characteristics of mode-III welded joints were investigated. Compared to mode-I, the results suggest that the fatigue damage process for mode-III is even more surface initiation-related.